# 1998 MRS Fall Meeting & Exhibit

November 30 - December 4, 1998 | Boston
Meeting Chairs:
Clyde L. Briant, Eric H. Chason, Howard E. Katz, Yuh Shiohara

## Symposium U—Organics with Supramolecular Structure and Function

-MRS-

### Chairs

Martin Bryce, Univ of Durham
Christopher Ober, Cornell Univ
Michael Ward, Univ of Minnesota

### Symposium Support

• Army Research Office

* Invited paper

SESSION U1: MOLECULAR RECOGNITION IN SUPRAMOLECULAR SOLIDS
Chair: Bruce M. Foxman
Monday Morning, November 30, 1998
America South (W)
8:30 AM U1.1
CRYSTAL ENGINEERING OF DIAMONDOID NETWORKS FOR SECOND-ORDER NONLINEAR OPTICAL APPLICATIONS. Wenbin Lin , Zhiyong Wang, Ren-Gen Xiong, Department of Chemistry, Brandeis University, Waltham, MA.

The design of organic and metal-organic diamondoid frameworks has received considerable attention over the past decade, in part, because of the recognition that daimondoid networks have high propensity to pack in acentric space groups as a result of the lack of an inversion center. Acentric solids and thin films are of great interest owing to their potential applications as second-order nonlinear optical (NLO) materials. In fact, one of the best known inorganic second-order nonlinear optical materials, potassium dideuterophosphate (KDP), crystallizes as a diamondoid network. Despite the intense search over the past decade, acentric organic and metal-organic diamondoid frameworks have not been rationally synthesized to date. We have designed a novel approach to crystal engineering of acentric metal-organic diamondoid frameworks for second-order NLO applications. Our strategy relies on the use of four- or six- coordinate metal centers in combination with unsymmetrical, bifunctional linker groups. For example, both bis(isonicotinato)zinc and cadmium bis(4-pyridylacrylic acid) have been prepared hydrothermally. They both crystallize in acentric space groups, and possess a three-fold and five-fold interpenetrated diamondoid structure, respectively. Preliminary second harmonic generation measurements showed that these diamondoid networks exhibit second-order NLO efficiencies comparable to technologically important lithium niobate.

8:45 AM U1.2
ENGINEERING MIXED CRYSTALS. Bart Kahr , Loyd Bastin, Anand Subramony, Rich Gurney, Christine Mitchell.

While a great deal of effort recently has been directed at the design of molecular crystalline materials, especially by exploiting hydrogen bonds, little attention has been paid to the design of dilute solid solutions even though for some optical and spectroscopic applications molecules that are oriented and isolated from one another are requisite. We have been seeking to identify the prevailing intermolecular forces that determine for formation of dye inclusion crystals (DICs), simple crystalline substances that contain organic chromophores oriented and isolated in particular sectors during growth from solution. In this paper, we focus on orienting organic dyes within otherwise single crystals of inorganic salts such as potassium sulfate, potassium dihydrogen phosphate, and barium acetate. We emphasize the use of such crystals in chemical analysis, the determination of crystal growth mechanisms, and in the stabilization of reactive intermediates and electronically excited states.

9:00 AM *U1.3
SUPRAMOLECULAR CONTROL OF THE BULK MAGNETIC PROPERTIES OF MANGANOPORPHRYIN-BASED MAGNETS. Joel S. Miller , University of Utah, Dept. of Chemistry, Salt Lake City, UT; Arthur J. Epstein, The Ohio State University, Dept. of Physics and Dept. of Chemistry, Columbus, OH.

Coordination polymer-based magnets comprised of alternating [Mn(III)(porphryrin)]+ and [A]- (A = TCNE, TCNQ, C4(CN)6, chloranil) have been prepared and structurally and magnetically characterized. The [A]- is trans-$\mu$-bound to two adjacent Mn(III) sites in the chain. Adjacent sites exhibit antiferromagnetic coupling between the S = 1/2 [A]- quantum spin and the S = 2 Mn(III) classical spin and magnetic order occurs below 25 K. The intrachain coupling, as evidence by increasing Tmin, and fits to the Seiden expression for isolated chains comprised of alternating quantum {S = 1/2; [A].-} and classical {S = 2; [Mn(III)porphryrin)]+} spins is correlated with decreasing MnN4 - [TCNE]- dihedral angles. MO calculations identify the key overlap due to the sigma-dz2/pz on the [TCNE]- N bound to the Mn(III). Use of octaethylporphyrin leads to a antiferromagnet whereas use of tetraphenylporphryin and substituted tetraphenylporphryin leads to magnets with interchain ferromagnetic coupling and ferrimagnetic behavior. The differing magnetic behavior is attributed to enhanced ferromagnetic dipolar interactions for the latter class of magnets. The magneto-structure correlation as well as recent developments in this class of materials will be discussed.

9:30 AM U1.4
SOLID-STATE STRUCTURAL ORDERING IN STABLE ORGANIC RADICALS. Paul M. Lahti , Jacqueline Ferrer, Univ of Massachusetts, Dept of Chemistry, Amherst, MA; Clifford George, Naval Research Laboratory, Washington, DC.

Recent work in organic molecular magnetic materials has included efforts to design specific hydrogen-bonded and dipolar solid state interactions, which will act to assemble stable radicals into relative orientations that favor intermolecular ferromagnetic exchange interactions. We describe work aimed at design of such systems, with primary focus on one example, benzimidazole-2-tert-butyl-nitroxide (BIm-tBN). BIm-tBN forms stacks of molecules that are H-bonded together to produce a highly organized, centrosymmetric crystal structure. The relationship of isolated-molecule properties such as spin density distribution (investigated by ESR spectroscopy and DFT computations) to typical models for intermolecular exchange in the solid state will be outlined for this example, as well as prospects for extensions to related systems.

9:45 AM U1.5
SELF-ASSEMBLY OF LAYERED COORDINATION NETWORKS WITH CLAY-LIKE PROPERTIES. George K. H. Shimizu , Univ of Calgary, Dept of Chemistry, Calgary, Alberta, CANADA; Gary D. Enright, Chris I. Ratcliffe, Gabriela S. Rego, John A. Ripmeester, Dan D. M. Wayner, National Research Council of Canada, Steacie Institute for Molecular Sciences, Ottawa, Ontario, CANADA.

Clays and zeolites are rigid framework aluminosilicates with layered and channel motifs, respectively. From a metal coordination chemistry standpoint, these networks provide attractive model compounds owing to their robust nature, porousity and functionality. This presentation will discuss a family of lamellar metal coordination compounds, generated from fundamental design principles, and it's analogy to clay-like materials. A novel dithia ligand, designed to favor the formation of infinite frameworks, was synthesized and found to form a layered solid with silver(I). The observed structure is versatile as it can be tuned by changing the anion, ancillary ligands on the metals, or, significantly, by functionalizing the ligand itself. The prospect of organic derivatization offers a wide range of structural options and hence, variation in the physical properties of these complexes. Studies to date show interlayer swelling in the presence of solvent, selectivity in inclusion behavior and ion exchange ability.

10:15 AM U1.6
ETHYNYL-SUBSTITUTED TETRAHEDRAL MOLECULES: BUILDING BLOCKS FOR 3D-NETWORKS. Elena Galoppini , Wenzhuo Guo, Quiongying Fu, Rutgers University, Department of Chemistry, Newark, NJ; Richard Gilardi, Laboratory for the Structure of Matter, The Naval Research Laboratory, Washington, DC.

The ability to design organic crystals or polymers with large and dimensionally-fixed cavities may lead to materials exhibiting unprecedented and possibly useful properties. As part of this interest, we are studying molecules capable of selective and strongly directional intermolecular interactions (such as hydrogen bonds) and which may pack in a predictable manner. We present the synthesis and crystal structure of molecules with a tetrahedral core, such as methane and adamantane, substituted at the four vertices with phenylacetylenic units or phenylboronic esters. The tetrahedral core provides a rigid scaffold, which maintains fixed the orientation of the rod-like functional groups. Hydrogen bonding, metal-ligand coordination, polymerization reactions were used to connect the building blocks. Such molecules form diamondoid' crystals, three-dimensional networks obtained by connecting the four vertices of tetrahedra and which resemble the diamond structure.

10:30 AM *U1.7
MOLECULAR ENGINEERING OF NON-CENTROSYMMETRIC FILMS FOR NONLINEAR OPTICAL APPLICATIONS. Geoffrey J. Ashwell , Cranfield University, Molecular Electronics, Cranfield, UNITED KINGDOM.

Interest in Langmuir-Blodgett (LB) films for second-harmonic generation (SHG) stems from the requirement that the structure must be non-centrosymmetric and from the fact that the LB technique allows control of the packing at the molecular level. Amphiphilic materials, those with a hydrophilic head and a hydrophobic tail, may be aligned at the air-water interface but, when deposited, the layers tend to pack centrosymmetrically with the interfaces being alternately hydrophilic (head-to-head) and hydrophobic (tail-to-tail). This may be overcome by considering the molecular criteria for non-centrosymmetric deposition and, at Cranfield, Z-type structures have been routinely obtained by rendering the chromophore hydrophobic at both ends. This causes the LB film surface to be invariably hydrophobic and suppresses the natural tendency of the molecules to invert during deposition. There is a narrow range of alkyl chain lengths which allows the films to be non-centrosymmetric but long-term stability has been realised by considering the compatibility of the end groups within the multilayer. When carefully selected, non-centrosymmetric alignment arises and the second-harmonic intensity increases quadratically with the number of layers, i.e. as I(N)2w= I(1)2w N2, to thicknesses suitable for waveguiding. The lecture will focus on the optimisation of the nonlinear optical properties of LB films of a novel dye, E-4-[(N-octadecyl-6,7,8-trihydro-5-isoquinolylidene)methyl]-N,N-dibutylaniline octadecylsulfate. The films are transparent at the fundamental frequency and only slightly absorbing at the second-harmonic. Nonetheless, the susceptibility is high ($\chi$zzz(2) = 76 pm V-1 at 1.064 $\mu$m for I = 3.15 nm layer-1) and the second-harmonic intensity is the strongest to date from a weakly absorbing film.

11:00 AM *U1.8
GAS SORPTION ISOTHERMS FOR DESIGNED MICROPOROUS METAL-ORGANIC MATERIALS. O.M. Yaghi , Hailian Li, and Mohamed Eddaoudi, Arizona State University, Department of Chemistry and Biochemistry, Tempe, AZ.

Despite the exponential growth in the number of reports on crystalline metal-organic materials with open-framework structures, studies focusing on establishing their gas sorption isotherms and thus microporosity, remain largely unknown. This presentation will show that permanent micrOporosity, similar to that commonly observed in zeolites, can be achieved with metal-organic open frameworks. Gas sorption isotherm, surface area, and pore volume measurements for materials such as Zn(BDC)$\cdot$(DMF)(H20) having 5-15 $\AA$ diameter apertures will be presented. Key aspects to developing strategies for producing rigid and stable metal-organic frameworks with extended channels will be outlined.

11:30 AM *U1.9
TETRATHIAFULVALENES: VERSATILE BUILDING BLOCKS IN MACROCYCLIC AND SUPRAMOLECULAR CHEMISTRY. Jan Becher , Department of Chemistry, Odense University, Odense M, DENMARK.

The effective syntheses of a variety of tetrathiafulvalene building blocks, including pyrrolo- and 2,5-dihydropyrrolo-fused tetrathiafulvalenes have been developed, allowing easy construction and preparation of complex molecular assemblies. The facile deprotection of the 2-cyanoethyl group, a versatile protecting group for 1,3-dithiolium-2-thione-4,5-dithiolates and tetrathiafulvalene-thiolates (1), is an excellent method for the incorporation of tetrathiafulvalene units into macrocyclic and supramolecular compounds. The selective and stepwise protection-deprotection methodology have been used extensively by our group for the preparation of two and three dimensional macrocyclic (mono-, bis- and tricyclic) as well as tetrathiafulvalene-based supramolecular systems (2). Utilization of the thiolates generated by the new methodology are illustrated by recent examples of oligomeric and supramolecular tetrathiafulvalene-based systems, such as: Dendritic (3) and oligo-tetrathiafulvalenes, three dimensional tetrathiafulvalenophanes, tetrathiafulvalene-containing catenanes (4) or rotaxanes (5) as well as donor acceptor systems based on tetrathiafulvalene as the donating group.
References
1.    M. B. Nielsen, S. B. Nielsen and J. Becher, Self complexing Tetrathiafulvalene Macrocycles, a Tetrathiafulvalene Switch'', Chem. Commun., 1998, 475.
2.    M. B. Nielsen, N. Thorup and J. Becher, Synthesis of a criss-cross overlapped Tetrathiafulvalenophane and a topologically new [2]catenane'', J. Chem. Soc. Perkin 1, 1998, 1305.
3.    C. A. Christensen, L. M. Goldenberg, M. R. Bryce and J. Becher, Synthesis and electrochemistry of a tetrathiafulvalene (TTF)21-glycol dendrimer'', Chem. Commun., 1998, 509.
4.    K. B. Simonsen and J. Becher, Tetrathiafulvalene Thiolates'', Synlett, 1997, 1211. 5.    M. B. Nielsen and J. Becher, Two- and Three-Dimensional Tetrathiafulvalene Macrocycles'', Liebigs Ann/Recueil, 1997, 2177.

SESSION U2: MOLECULAR RECOGNITION IN SUPRAMOLECULAR SOLIDS (continued)
Chair: Omar M. Yaghi
Monday Afternoon, November 30, 1998
America South (W)
1:30 PM *U2.1
SYNTHESIS AND PROPERTIES OF HELICAL AROMATIC MOLECULES THAT SELF-ASSEMBLE INTO COLUMNS. Thomas J. Katz , Colin Nuckolls, Joseph M. Fox, Columbia Univ, Dept of Chemistry, New York, NY; Thierry Verbiest, Sven Van Elschocht, and André Persoons, K.U. Leuven, Laboratory of Chemical and Biological Dynamics, Leuven, BELGIUM; Andrew J. Lovinger, Bell Labs, Lucent Technologies, Murray Hill, NJ.

Molecules that resemble those forming chiral discotic mesophases, but whose core ring systems are twisted helically, have been synthesized in nonracemic form. Some self-assemble into columnar structures in solution, as do the pure materials in bulk and in Langmuir-Blodgett films. When they assemble, the circular dichroisms, specific rotations, and second harmonic generating ability all greatly increase. The circular dichroisms of one of the self-assembling materials is sufficiently large that it can be measured easily from a single monolayer. The long wavelength circular dichroisms of the synthesized helical metal-phthalocyanines split.
Unlike the nonracemic self-assembling molecules, the racemic ones do not organize into similarly large structures, and their second-harmonic generating ability is small. Among the materials prepared is the first columnar mesophase that has a nonracemic helical core.

2:00 PM *U2.2
FUNCTIONAL SUPRAMOLECULAR AND MACROMOLECULAR DENDRIMERS ON A LATTICE. V. Percec , The W.M. Keck Laboratories for Organic Synthesis, Department of Macromolecular Science, Case Western Reserve University, Cleveland, OH.

This presentation will discuss the elaboration of the first library of functional dendrons that self-assemble into cylindrical and spherical supramolecular dendrimers which subsequently self-organize into various cubic or columnar hexagonal lattices. Retrosynthetic analyses of these lattices by XRD allows the design of various classes of monomeric dendrons which after polymerization produce polymers with various architectures and shapes that self-organize in similar lattices with those of the parent supramolecular dendritic synthons. Applications in various areas of material science will be discussed.

2:30 PM U2.3
TEMPLATE DIRECTED ARCHITECTURAL ISOMERISM IN OPEN MOLECULAR FRAMEWORKS. Jennifer A. Swift , Adam M. Pivovar, Michael D. Ward, University of Minnesota, Department of Chemical Engineering and Materials Science, Minneapolis, MN.

Highly porous host lattices based on resilient 2-dimensional guanidinium-sulfonate hydrogen bonded networks that are connected continuously in the third dimension by 4,4'-biphenyldisulfonate pillars to generate a brick-like framework are described. The brick framework is a predictable architectural isomer of a previously observed guanidinium-sulfonate host lattice consisting of discrete bilayers. The amount of void space in the brick framework is nominally twice that of the bilayer form, with the framework occupying only 30% of the total volume. The host framework conforms to the different steric demands and occupancies of various aromatic guests by puckering of the flexible, yet resilient, hydrogen bonded network and by rotation (and/or twisting) of the pillars about their long axes, the latter also governing the width of the pores in the framework. The formation of the brick architecture can be attributed to steric templating by the included molecular guests and host-guest interactions that favor assembly of this framework over its bilayer counterpart. Inclusion of select guest molecules in brick frameworks yields polar crystals. Formation of such polar materials may be attributed to correlated guest-host-guest interactions, mediated through the corrugated guanidinium-sulfonate sheets. Development of these materials may yield a new class of NLO materials.

2:45 PM U2.4
NANOPARTICLE ENCAPSULATION USING RESORCINARENE-BASED SYSTEMS. Kevin B. Stavens, Stephen V. Pusztay, Ronald P. Andres, Alexander Wei , Purdue University, Depts. of Chemistry and Chemical Engineering, West Lafayette, IN.

Resorcinol-based calix[4]arenes (resorcinarenes) have demonstrated excellent potential for encapsulating and stabilizing nanosized particles. Gold clusters 2-5 nm in diameter were generated by vapor- and solution-phase techniques and were captured in millimolar hydrocarbon solutions of resorcinarenes and other surfactants. The capture efficiency of Au nanoparticles using resorcinarenes was several times greater relative to alkanethiols. Nanoparticles stabilized by several resorcinarene and binary resorcinarene-thiol systems were characterized by absorption spectroscopy and transmission electron microscopy. It was found that hydrogen bonding is an important factor in both capture efficiency and aggregate stability. The potential of resorcinarene-based encapsulation systems for creating ordered nanostructures will be discussed.

3:15 PM *U2.5
DESIGN, DISCOVERY AND SYNTHESIS OF REACTIVE SUPRAMOLECULAR ARRAYS. Bruce M. Foxman , Brandeis University, Dept. of Chemistry, Waltham, MA.

A supramolecular organic array, with an organized set of reactive groups, provides an opportunity to carry out either stereospecific or regiospecific chemical reactions, and/or reactions that cannot be performed in solution. Of course, not every array affords such an opportunity, and we must consider both the principles required for successful assembly, as well as experience-based procedures, to ensure success. While there is a considerable database of solid-state reactions, the number of new reaction classes has increased only slowly, with a consequent slow growth in design principles. As part of the concept of crystal engineering we can use our knowledge of molecular solid-state chemistry, crystal packing, and chemical reactivity to produce reactive materials. In recent years, we have designed several solid-state reactions by using structural analogies derived from the Cambridge Structural Database (three examples from organic and metal-organic chemistry will be discussed). Following the initial design work, we developed two new series of metal salts and complexes with unique reactivity properties. Solid metal alkynoates and alkenoates undergo oligomerization and polymerization reactions when exposed to Co-60 gamma-rays. For example, irradiation of solid sodium trans-2-butenoate leads to a linear trimer, one of eight possible diastereomers, in high yield. Studies of crystalline metal complexes containing such unsaturated ligands provide new insight into solid-state reactivity. In addition to the use of hydrogen bonding and bilayer interactions as agents for the production of reactive phases, changes in metal ion within an isomorphous set of structures may have profound effects on reactivity. The discussion will include a review of our expanding database of engineered reactive molecular crystals, and the implications of recent results on design criteria.

3:45 PM *U2.6
THE HYDROGEN BOND AND CRYSTAL ENGINEERING: CONSTRUCTING PREDICTABLE MOLECULAR ARCHITECTURES. Christer B. Aakeroy , Department of Chemistry, Kansas State University, Manhattan, KS.

Crystal engineering is governed by the nature and structural consequences of intermolecular forces, and the way in which such interactions are utilized for controlling the assembly of molecules into predictable structural motifs. A vital part of crystal engineering is therefore dedicated to the identification of robust intermolecular synthons that can be used as reliable connectors (microscopic ÎglueÌ) between molecules.
We have demonstrated that certain organic molecular building blocks have a propensity to form low-dimensional assemblies (chains, ribbons, layers) via complementary N-H...O, C-H...O and O-H...O hydrogen bonds. Through systematic structural studies of closely related compounds, we have been able to derive some guidelines for how we can design and build robust molecular scaffolding that can form the structural backbone in new functional solids. Furthermore, in an effort to design new transition-metal containing materials, we have combined the geometric features of well-known coordination chemistry (notably of silver(I)) with intermolecular connectors with a view to examining how the structural balance in such materials is determined by competition and/or collaboration between intermolecular synthons and the spatial requirements of transition-metal complexes.

4:15 PM U2.7
THE BINARY APPROACH TO SUPRAMOLECULAR STRUCTURE AND FUNCTION. Joseph W. Lauher , Frank W. Fowler, State University of New York, Department of Chemistry, Stony Brook, NY.

The function of a supramolecular entity depends upon the chemical composition and nature of the constituent molecules, as well as the symmetry and spatial properties of the assembly of molecules. Since one has little control over the actual supramolecular properties of a given molecule, one must approach a synthesis with a focus on the final supramolecular goal, as opposed to a focus on the identity of the individual molecules. A realization of the final goal may require the achievement of a specific structure, a specific function or both, since function often depends upon structure.
We have developed a binary approach to this problem, using one molecule to control the structure of a supramolecular assembly, while the second provides the function. Our approach is based upon a library of chemical functionalities that lead to predictable structural patterns based upon persistent patterns of hydrogen bonds. Molecules possessing these functionalities can be synthesized and used to control and determine supramolecular structure. A second functionality is added as a handle to control the second molecular entity, the one that provides the function or completes the structure of the final product. For this we have used a variety of interactions, including hydrogen bonds, metal-ligand coordination and halide-nitrogen interactions. Successful applications of the technique include the synthesis of a wide variety of layered structures, designed diacetylene polymerizations and the controlled spacing of metal atoms.

4:30 PM *U2.8
Wais Hosseini , Univ Louis Pasteur, Strasbourg, FRANCE.

Abstract Not Available

SESSION U3: THIN FILMS AND LAYERED STRUCTURES
Chair: Neal R. Armstrong
Tuesday Morning, December 1, 1998
America South (W)
8:30 AM *U3.1
SUPRAMOLECULAR LAMINATES WITH AFFINITY FOR AROMATIC GUESTS. Mike Zaworotko , Kumar S. Biradha, Department of Chemistry, The University of Winnipeg, Winnipeg, Manitoba, CANADA.

That solid state architecture profoundly influences bulk physical properties and therefore function of solids has provided impetus for recent activity in the field of crystal engineering. The nature of crystal engineering means that chemists can design new crystal structures without the need to develop new molecular structures. Rather, the chemist simply has to focus upon multifunctional exodentate moieties and the concept of supramolecular synthons . This presentation will focus upon the development of new classes of layered solid1 that might be of general interest for materials or separations applications. We shall present recent results involving organic solids based upon simple acids such as trimesic acid and trimellitic acid and discuss their significance in the following contexts: 1) what impact will crystal engineering have upon design and synthesis of covalent polymers?; 2) what opportunities might there be for applications of the new materials?
1. Sharma, C.V.K.; Zaworotko, M.J.; Rogers, R.D., 1997. Supramolecular Laminates'' Chem. Commun. , 1559-1560, 1997.

9:00 AM *U3.2
MOLECULAR SCAFFOLDS FROM DERIVATIVES OF 2,5-DIKETOPIPERAZINE. G. Tayhas R. Palmore , Tzy-Jiun Luo, Mary T. McBride, University of California, Department of Chemistry, Davis, CA; Terry A. Land, James J. DeYoreo, Lawrence Livermore National Laboratory, Livermore, CA.

Derivatives of 2,5-diketopiperazine (DKP) are known to assemble into hydrogen-bonded tapes in their crystalline solids. Hydrogen-bonded tapes can function as scaffolds for positioning guest molecules within the crystalline lattice, and depending on what substituents or guest molecules are chosen, there is the potential for creating solids with new bulk properties. We will describe our efforts at elucidating physical-organic trends between the molecular constituents and their assembly into crystalline solids using several methods of analysis: X-ray diffraction, NMR and IR spectroscopies, in situ atomic force microscopy, co-crystallization techniques and computer modeling.

9:30 AM *U3.3
FROM BENZENE TO 2D- AND 3D-NANOPARTICLES. Klaus Müllen, Max-Planck-Institute for Polymer Research, Mainz, GERMANY.

The benzene ring serves as versatile building block of carbon-rich 2D- and 3D-macromolecules. A novel cycloaddition-deprotection protocol provides dendritic polyphenylenes which are shape persistent 3D-nanoparticles. Suitably designed oligo- and polyphenylenes are transformed into giant polycyclic aromatic hydrocarbons (PAHs) by mild intramolecular cyclodehydrogenation. These PAHs constitute molecular (2D)-models of graphite. Their supramolecular ordering is a key prerequisite when elucidating their role as media for charge carrier transport in molecular electronics. Current-potential curves recorded by scanning tunneling microscopy for single PAH discs and the drastic increase of charge mobility as a result of their liquid-crystalline order in $\pi$-stacked columnar arrays are typical results of their physical characterization.

10:15 AM U3.4
THE EVOLUTION OF ORDERED POLYCRYSTALLINE FILMS DURING VAPOR DEPOSITION OF 4-AMINOBENZOPHENONE AND 4-(N,N-DIMETHYLAMINO)-3-ACETAMIDONITROBENZENE ON ALKALI HALIDE SUBSTRATES. John McAleese, David Sheen , John Sherwood and Qingwu Wang, University of Strathclyde, Department of Pure and Applied Chemistry, Glasgow, Scotland, UNITED KINGDOM.

The polycrystalline films which develop during the vapor deposition of the non-linear optical materials 4-aminobenzophenone (ABP) and 4-(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN) on prebaked KCL or KBr (001) faces show biaxial orientation along [110] and [$\bar{1}$10] directions, in common with many organic materials deposited on these substrates. During deposition, some interesting changes in film morphology have

SYMPOSIUM U Organics with Supramolecular Structure and Function November 30 - December 3, 1998 Chairs

Martin Bryce          Christopher Ober

Dept of Chemistry        Dept of MS&E

Univ of Durham          Cornell Univ

Durham,  DH1 3LE UNITED KINGDOM        327 Bard Hall

44-191-374-3118          Ithaca, NY 14853

607-255-8417

Michael Ward
Chemical Engineering and Materials Science
Univ of Minnesota
151 Amundson Hall
Minneapolis, MN 55455
612-625-3062

Symposium Support
*Army Research Office

* Invited paper

SESSION U1: MOLECULAR RECOGNITION IN SUPRAMOLECULAR SOLIDS
Chair: Bruce M. Foxman
Monday Morning, November 30, 1998
America South (W)
8:30 AM U1.1
CRYSTAL ENGINEERING OF DIAMONDOID NETWORKS FOR SECOND-ORDER NONLINEAR OPTICAL APPLICATIONS. Wenbin Lin , Zhiyong Wang, Ren-Gen Xiong, Department of Chemistry, Brandeis University, Waltham, MA.

The design of organic and metal-organic diamondoid frameworks has received considerable attention over the past decade, in part, because of the recognition that daimondoid networks have high propensity to pack in acentric space groups as a result of the lack of an inversion center. Acentric solids and thin films are of great interest owing to their potential applications as second-order nonlinear optical (NLO) materials. In fact, one of the best known inorganic second-order nonlinear optical materials, potassium dideuterophosphate (KDP), crystallizes as a diamondoid network. Despite the intense search over the past decade, acentric organic and metal-organic diamondoid frameworks have not been rationally synthesized to date. We have designed a novel approach to crystal engineering of acentric metal-organic diamondoid frameworks for second-order NLO applications. Our strategy relies on the use of four- or six- coordinate metal centers in combination with unsymmetrical, bifunctional linker groups. For example, both bis(isonicotinato)zinc and cadmium bis(4-pyridylacrylic acid) have been prepared hydrothermally. They both crystallize in acentric space groups, and possess a three-fold and five-fold interpenetrated diamondoid structure, respectively. Preliminary second harmonic generation measurements showed that these diamondoid networks exhibit second-order NLO efficiencies comparable to technologically important lithium niobate.

8:45 AM U1.2
ENGINEERING MIXED CRYSTALS. Bart Kahr , Loyd Bastin, Anand Subramony, Rich Gurney, Christine Mitchell.

While a great deal of effort recently has been directed at the design of molecular crystalline materials, especially by exploiting hydrogen bonds, little attention has been paid to the design of dilute solid solutions even though for some optical and spectroscopic applications molecules that are oriented and isolated from one another are requisite. We have been seeking to identify the prevailing intermolecular forces that determine for formation of dye inclusion crystals (DICs), simple crystalline substances that contain organic chromophores oriented and isolated in particular sectors during growth from solution. In this paper, we focus on orienting organic dyes within otherwise single crystals of inorganic salts such as potassium sulfate, potassium dihydrogen phosphate, and barium acetate. We emphasize the use of such crystals in chemical analysis, the determination of crystal growth mechanisms, and in the stabilization of reactive intermediates and electronically excited states.

9:00 AM *U1.3
SUPRAMOLECULAR CONTROL OF THE BULK MAGNETIC PROPERTIES OF MANGANOPORPHRYIN-BASED MAGNETS. Joel S. Miller , University of Utah, Dept. of Chemistry, Salt Lake City, UT; Arthur J. Epstein, The Ohio State University, Dept. of Physics and Dept. of Chemistry, Columbus, OH.

Coordination polymer-based magnets comprised of alternating [Mn(III)(porphryrin)]+ and [A]- (A = TCNE, TCNQ, C4(CN)6, chloranil) have been prepared and structurally and magnetically characterized. The [A]- is trans-$\mu$-bound to two adjacent Mn(III) sites in the chain. Adjacent sites exhibit antiferromagnetic coupling between the S = 1/2 [A]- quantum spin and the S = 2 Mn(III) classical spin and magnetic order occurs below 25 K. The intrachain coupling, as evidence by increasing Tmin, and fits to the Seiden expression for isolated chains comprised of alternating quantum {S = 1/2; [A].-} and classical {S = 2; [Mn(III)porphryrin)]+} spins is correlated with decreasing MnN4 - [TCNE]- dihedral angles. MO calculations identify the key overlap due to the sigma-dz2/pz on the [TCNE]- N bound to the Mn(III). Use of octaethylporphyrin leads to a antiferromagnet whereas use of tetraphenylporphryin and substituted tetraphenylporphryin leads to magnets with interchain ferromagnetic coupling and ferrimagnetic behavior. The differing magnetic behavior is attributed to enhanced ferromagnetic dipolar interactions for the latter class of magnets. The magneto-structure correlation as well as recent developments in this class of materials will be discussed.

9:30 AM U1.4
SOLID-STATE STRUCTURAL ORDERING IN STABLE ORGANIC RADICALS. Paul M. Lahti , Jacqueline Ferrer, Univ of Massachusetts, Dept of Chemistry, Amherst, MA; Clifford George, Naval Research Laboratory, Washington, DC.

Recent work in organic molecular magnetic materials has included efforts to design specific hydrogen-bonded and dipolar solid state interactions, which will act to assemble stable radicals into relative orientations that favor intermolecular ferromagnetic exchange interactions. We describe work aimed at design of such systems, with primary focus on one example, benzimidazole-2-tert-butyl-nitroxide (BIm-tBN). BIm-tBN forms stacks of molecules that are H-bonded together to produce a highly organized, centrosymmetric crystal structure. The relationship of isolated-molecule properties such as spin density distribution (investigated by ESR spectroscopy and DFT computations) to typical models for intermolecular exchange in the solid state will be outlined for this example, as well as prospects for extensions to related systems.

9:45 AM U1.5
SELF-ASSEMBLY OF LAYERED COORDINATION NETWORKS WITH CLAY-LIKE PROPERTIES. George K. H. Shimizu , Univ of Calgary, Dept of Chemistry, Calgary, Alberta, CANADA; Gary D. Enright, Chris I. Ratcliffe, Gabriela S. Rego, John A. Ripmeester, Dan D. M. Wayner, National Research Council of Canada, Steacie Institute for Molecular Sciences, Ottawa, Ontario, CANADA.

Clays and zeolites are rigid framework aluminosilicates with layered and channel motifs, respectively. From a metal coordination chemistry standpoint, these networks provide attractive model compounds owing to their robust nature, porousity and functionality. This presentation will discuss a family of lamellar metal coordination compounds, generated from fundamental design principles, and it's analogy to clay-like materials. A novel dithia ligand, designed to favor the formation of infinite frameworks, was synthesized and found to form a layered solid with silver(I). The observed structure is versatile as it can be tuned by changing the anion, ancillary ligands on the metals, or, significantly, by functionalizing the ligand itself. The prospect of organic derivatization offers a wide range of structural options and hence, variation in the physical properties of these complexes. Studies to date show interlayer swelling in the presence of solvent, selectivity in inclusion behavior and ion exchange ability.

10:15 AM U1.6
ETHYNYL-SUBSTITUTED TETRAHEDRAL MOLECULES: BUILDING BLOCKS FOR 3D-NETWORKS. Elena Galoppini , Wenzhuo Guo, Quiongying Fu, Rutgers University, Department of Chemistry, Newark, NJ; Richard Gilardi, Laboratory for the Structure of Matter, The Naval Research Laboratory, Washington, DC.

The ability to design organic crystals or polymers with large and dimensionally-fixed cavities may lead to materials exhibiting unprecedented and possibly useful properties. As part of this interest, we are studying molecules capable of selective and strongly directional intermolecular interactions (such as hydrogen bonds) and which may pack in a predictable manner. We present the synthesis and crystal structure of molecules with a tetrahedral core, such as methane and adamantane, substituted at the four vertices with phenylacetylenic units or phenylboronic esters. The tetrahedral core provides a rigid scaffold, which maintains fixed the orientation of the rod-like functional groups. Hydrogen bonding, metal-ligand coordination, polymerization reactions were used to connect the building blocks. Such molecules form diamondoid' crystals, three-dimensional networks obtained by connecting the four vertices of tetrahedra and which resemble the diamond structure.

10:30 AM *U1.7
MOLECULAR ENGINEERING OF NON-CENTROSYMMETRIC FILMS FOR NONLINEAR OPTICAL APPLICATIONS. Geoffrey J. Ashwell , Cranfield University, Molecular Electronics, Cranfield, UNITED KINGDOM.

Interest in Langmuir-Blodgett (LB) films for second-harmonic generation (SHG) stems from the requirement that the structure must be non-centrosymmetric and from the fact that the LB technique allows control of the packing at the molecular level. Amphiphilic materials, those with a hydrophilic head and a hydrophobic tail, may be aligned at the air-water interface but, when deposited, the layers tend to pack centrosymmetrically with the interfaces being alternately hydrophilic (head-to-head) and hydrophobic (tail-to-tail). This may be overcome by considering the molecular criteria for non-centrosymmetric deposition and, at Cranfield, Z-type structures have been routinely obtained by rendering the chromophore hydrophobic at both ends. This causes the LB film surface to be invariably hydrophobic and suppresses the natural tendency of the molecules to invert during deposition. There is a narrow range of alkyl chain lengths which allows the films to be non-centrosymmetric but long-term stability has been realised by considering the compatibility of the end groups within the multilayer. When carefully selected, non-centrosymmetric alignment arises and the second-harmonic intensity increases quadratically with the number of layers, i.e. as I(N)2w= I(1)2w N2, to thicknesses suitable for waveguiding. The lecture will focus on the optimisation of the nonlinear optical properties of LB films of a novel dye, E-4-[(N-octadecyl-6,7,8-trihydro-5-isoquinolylidene)methyl]-N,N-dibutylaniline octadecylsulfate. The films are transparent at the fundamental frequency and only slightly absorbing at the second-harmonic. Nonetheless, the susceptibility is high ($\chi$zzz(2) = 76 pm V-1 at 1.064 $\mu$m for I = 3.15 nm layer-1) and the second-harmonic intensity is the strongest to date from a weakly absorbing film.

11:00 AM *U1.8
GAS SORPTION ISOTHERMS FOR DESIGNED MICROPOROUS METAL-ORGANIC MATERIALS. O.M. Yaghi , Hailian Li, and Mohamed Eddaoudi, Arizona State University, Department of Chemistry and Biochemistry, Tempe, AZ.

Despite the exponential growth in the number of reports on crystalline metal-organic materials with open-framework structures, studies focusing on establishing their gas sorption isotherms and thus microporosity, remain largely unknown. This presentation will show that permanent micrOporosity, similar to that commonly observed in zeolites, can be achieved with metal-organic open frameworks. Gas sorption isotherm, surface area, and pore volume measurements for materials such as Zn(BDC)$\cdot$(DMF)(H20) having 5-15 $\AA$ diameter apertures will be presented. Key aspects to developing strategies for producing rigid and stable metal-organic frameworks with extended channels will be outlined.

11:30 AM *U1.9
TETRATHIAFULVALENES: VERSATILE BUILDING BLOCKS IN MACROCYCLIC AND SUPRAMOLECULAR CHEMISTRY. Jan Becher , Department of Chemistry, Odense University, Odense M, DENMARK.

The effective syntheses of a variety of tetrathiafulvalene building blocks, including pyrrolo- and 2,5-dihydropyrrolo-fused tetrathiafulvalenes have been developed, allowing easy construction and preparation of complex molecular assemblies. The facile deprotection of the 2-cyanoethyl group, a versatile protecting group for 1,3-dithiolium-2-thione-4,5-dithiolates and tetrathiafulvalene-thiolates (1), is an excellent method for the incorporation of tetrathiafulvalene units into macrocyclic and supramolecular compounds. The selective and stepwise protection-deprotection methodology have been used extensively by our group for the preparation of two and three dimensional macrocyclic (mono-, bis- and tricyclic) as well as tetrathiafulvalene-based supramolecular systems (2). Utilization of the thiolates generated by the new methodology are illustrated by recent examples of oligomeric and supramolecular tetrathiafulvalene-based systems, such as: Dendritic (3) and oligo-tetrathiafulvalenes, three dimensional tetrathiafulvalenophanes, tetrathiafulvalene-containing catenanes (4) or rotaxanes (5) as well as donor acceptor systems based on tetrathiafulvalene as the donating group.
References
1.    M. B. Nielsen, S. B. Nielsen and J. Becher, Self complexing Tetrathiafulvalene Macrocycles, a Tetrathiafulvalene Switch'', Chem. Commun., 1998, 475.
2.    M. B. Nielsen, N. Thorup and J. Becher, Synthesis of a criss-cross overlapped Tetrathiafulvalenophane and a topologically new [2]catenane'', J. Chem. Soc. Perkin 1, 1998, 1305.
3.    C. A. Christensen, L. M. Goldenberg, M. R. Bryce and J. Becher, Synthesis and electrochemistry of a tetrathiafulvalene (TTF)21-glycol dendrimer'', Chem. Commun., 1998, 509.
4.    K. B. Simonsen and J. Becher, Tetrathiafulvalene Thiolates'', Synlett, 1997, 1211. 5.    M. B. Nielsen and J. Becher, Two- and Three-Dimensional Tetrathiafulvalene Macrocycles'', Liebigs Ann/Recueil, 1997, 2177.

SESSION U2: MOLECULAR RECOGNITION IN SUPRAMOLECULAR SOLIDS (continued)
Chair: Omar M. Yaghi
Monday Afternoon, November 30, 1998
America South (W)
1:30 PM *U2.1
SYNTHESIS AND PROPERTIES OF HELICAL AROMATIC MOLECULES THAT SELF-ASSEMBLE INTO COLUMNS. Thomas J. Katz , Colin Nuckolls, Joseph M. Fox, Columbia Univ, Dept of Chemistry, New York, NY; Thierry Verbiest, Sven Van Elschocht, and André Persoons, K.U. Leuven, Laboratory of Chemical and Biological Dynamics, Leuven, BELGIUM; Andrew J. Lovinger, Bell Labs, Lucent Technologies, Murray Hill, NJ.

Molecules that resemble those forming chiral discotic mesophases, but whose core ring systems are twisted helically, have been synthesized in nonracemic form. Some self-assemble into columnar structures in solution, as do the pure materials in bulk and in Langmuir-Blodgett films. When they assemble, the circular dichroisms, specific rotations, and second harmonic generating ability all greatly increase. The circular dichroisms of one of the self-assembling materials is sufficiently large that it can be measured easily from a single monolayer. The long wavelength circular dichroisms of the synthesized helical metal-phthalocyanines split.
Unlike the nonracemic self-assembling molecules, the racemic ones do not organize into similarly large structures, and their second-harmonic generating ability is small. Among the materials prepared is the first columnar mesophase that has a nonracemic helical core.

2:00 PM *U2.2
FUNCTIONAL SUPRAMOLECULAR AND MACROMOLECULAR DENDRIMERS ON A LATTICE. V. Percec , The W.M. Keck Laboratories for Organic Synthesis, Department of Macromolecular Science, Case Western Reserve University, Cleveland, OH.

This presentation will discuss the elaboration of the first library of functional dendrons that self-assemble into cylindrical and spherical supramolecular dendrimers which subsequently self-organize into various cubic or columnar hexagonal lattices. Retrosynthetic analyses of these lattices by XRD allows the design of various classes of monomeric dendrons which after polymerization produce polymers with various architectures and shapes that self-organize in similar lattices with those of the parent supramolecular dendritic synthons. Applications in various areas of material science will be discussed.

2:30 PM U2.3
TEMPLATE DIRECTED ARCHITECTURAL ISOMERISM IN OPEN MOLECULAR FRAMEWORKS. Jennifer A. Swift , Adam M. Pivovar, Michael D. Ward, University of Minnesota, Department of Chemical Engineering and Materials Science, Minneapolis, MN.

Highly porous host lattices based on resilient 2-dimensional guanidinium-sulfonate hydrogen bonded networks that are connected continuously in the third dimension by 4,4'-biphenyldisulfonate pillars to generate a brick-like framework are described. The brick framework is a predictable architectural isomer of a previously observed guanidinium-sulfonate host lattice consisting of discrete bilayers. The amount of void space in the brick framework is nominally twice that of the bilayer form, with the framework occupying only 30% of the total volume. The host framework conforms to the different steric demands and occupancies of various aromatic guests by puckering of the flexible, yet resilient, hydrogen bonded network and by rotation (and/or twisting) of the pillars about their long axes, the latter also governing the width of the pores in the framework. The formation of the brick architecture can be attributed to steric templating by the included molecular guests and host-guest interactions that favor assembly of this framework over its bilayer counterpart. Inclusion of select guest molecules in brick frameworks yields polar crystals. Formation of such polar materials may be attributed to correlated guest-host-guest interactions, mediated through the corrugated guanidinium-sulfonate sheets. Development of these materials may yield a new class of NLO materials.

2:45 PM U2.4
NANOPARTICLE ENCAPSULATION USING RESORCINARENE-BASED SYSTEMS. Kevin B. Stavens, Stephen V. Pusztay, Ronald P. Andres, Alexander Wei , Purdue University, Depts. of Chemistry and Chemical Engineering, West Lafayette, IN.

Resorcinol-based calix[4]arenes (resorcinarenes) have demonstrated excellent potential for encapsulating and stabilizing nanosized particles. Gold clusters 2-5 nm in diameter were generated by vapor- and solution-phase techniques and were captured in millimolar hydrocarbon solutions of resorcinarenes and other surfactants. The capture efficiency of Au nanoparticles using resorcinarenes was several times greater relative to alkanethiols. Nanoparticles stabilized by several resorcinarene and binary resorcinarene-thiol systems were characterized by absorption spectroscopy and transmission electron microscopy. It was found that hydrogen bonding is an important factor in both capture efficiency and aggregate stability. The potential of resorcinarene-based encapsulation systems for creating ordered nanostructures will be discussed.

3:15 PM *U2.5
DESIGN, DISCOVERY AND SYNTHESIS OF REACTIVE SUPRAMOLECULAR ARRAYS. Bruce M. Foxman , Brandeis University, Dept. of Chemistry, Waltham, MA.

A supramolecular organic array, with an organized set of reactive groups, provides an opportunity to carry out either stereospecific or regiospecific chemical reactions, and/or reactions that cannot be performed in solution. Of course, not every array affords such an opportunity, and we must consider both the principles required for successful assembly, as well as experience-based procedures, to ensure success. While there is a considerable database of solid-state reactions, the number of new reaction classes has increased only slowly, with a consequent slow growth in design principles. As part of the concept of crystal engineering we can use our knowledge of molecular solid-state chemistry, crystal packing, and chemical reactivity to produce reactive materials. In recent years, we have designed several solid-state reactions by using structural analogies derived from the Cambridge Structural Database (three examples from organic and metal-organic chemistry will be discussed). Following the initial design work, we developed two new series of metal salts and complexes with unique reactivity properties. Solid metal alkynoates and alkenoates undergo oligomerization and polymerization reactions when exposed to Co-60 gamma-rays. For example, irradiation of solid sodium trans-2-butenoate leads to a linear trimer, one of eight possible diastereomers, in high yield. Studies of crystalline metal complexes containing such unsaturated ligands provide new insight into solid-state reactivity. In addition to the use of hydrogen bonding and bilayer interactions as agents for the production of reactive phases, changes in metal ion within an isomorphous set of structures may have profound effects on reactivity. The discussion will include a review of our expanding database of engineered reactive molecular crystals, and the implications of recent results on design criteria.

3:45 PM *U2.6
THE HYDROGEN BOND AND CRYSTAL ENGINEERING: CONSTRUCTING PREDICTABLE MOLECULAR ARCHITECTURES. Christer B. Aakeroy , Department of Chemistry, Kansas State University, Manhattan, KS.

Crystal engineering is governed by the nature and structural consequences of intermolecular forces, and the way in which such interactions are utilized for controlling the assembly of molecules into predictable structural motifs. A vital part of crystal engineering is therefore dedicated to the identification of robust intermolecular synthons that can be used as reliable connectors (microscopic ÎglueÌ) between molecules.
We have demonstrated that certain organic molecular building blocks have a propensity to form low-dimensional assemblies (chains, ribbons, layers) via complementary N-H...O, C-H...O and O-H...O hydrogen bonds. Through systematic structural studies of closely related compounds, we have been able to derive some guidelines for how we can design and build robust molecular scaffolding that can form the structural backbone in new functional solids. Furthermore, in an effort to design new transition-metal containing materials, we have combined the geometric features of well-known coordination chemistry (notably of silver(I)) with intermolecular connectors with a view to examining how the structural balance in such materials is determined by competition and/or collaboration between intermolecular synthons and the spatial requirements of transition-metal complexes.

4:15 PM U2.7
THE BINARY APPROACH TO SUPRAMOLECULAR STRUCTURE AND FUNCTION. Joseph W. Lauher , Frank W. Fowler, State University of New York, Department of Chemistry, Stony Brook, NY.

The function of a supramolecular entity depends upon the chemical composition and nature of the constituent molecules, as well as the symmetry and spatial properties of the assembly of molecules. Since one has little control over the actual supramolecular properties of a given molecule, one must approach a synthesis with a focus on the final supramolecular goal, as opposed to a focus on the identity of the individual molecules. A realization of the final goal may require the achievement of a specific structure, a specific function or both, since function often depends upon structure.
We have developed a binary approach to this problem, using one molecule to control the structure of a supramolecular assembly, while the second provides the function. Our approach is based upon a library of chemical functionalities that lead to predictable structural patterns based upon persistent patterns of hydrogen bonds. Molecules possessing these functionalities can be synthesized and used to control and determine supramolecular structure. A second functionality is added as a handle to control the second molecular entity, the one that provides the function or completes the structure of the final product. For this we have used a variety of interactions, including hydrogen bonds, metal-ligand coordination and halide-nitrogen interactions. Successful applications of the technique include the synthesis of a wide variety of layered structures, designed diacetylene polymerizations and the controlled spacing of metal atoms.

4:30 PM *U2.8
Wais Hosseini , Univ Louis Pasteur, Strasbourg, FRANCE.

Abstract Not Available

SESSION U3: THIN FILMS AND LAYERED STRUCTURES
Chair: Neal R. Armstrong
Tuesday Morning, December 1, 1998
America South (W)
8:30 AM *U3.1
SUPRAMOLECULAR LAMINATES WITH AFFINITY FOR AROMATIC GUESTS. Mike Zaworotko , Kumar S. Biradha, Department of Chemistry, The University of Winnipeg, Winnipeg, Manitoba, CANADA.

That solid state architecture profoundly influences bulk physical properties and therefore function of solids has provided impetus for recent activity in the field of crystal engineering. The nature of crystal engineering means that chemists can design new crystal structures without the need to develop new molecular structures. Rather, the chemist simply has to focus upon multifunctional exodentate moieties and the concept of supramolecular synthons . This presentation will focus upon the development of new classes of layered solid1 that might be of general interest for materials or separations applications. We shall present recent results involving organic solids based upon simple acids such as trimesic acid and trimellitic acid and discuss their significance in the following contexts: 1) what impact will crystal engineering have upon design and synthesis of covalent polymers?; 2) what opportunities might there be for applications of the new materials?
1. Sharma, C.V.K.; Zaworotko, M.J.; Rogers, R.D., 1997. Supramolecular Laminates'' Chem. Commun. , 1559-1560, 1997.

9:00 AM *U3.2
MOLECULAR SCAFFOLDS FROM DERIVATIVES OF 2,5-DIKETOPIPERAZINE. G. Tayhas R. Palmore , Tzy-Jiun Luo, Mary T. McBride, University of California, Department of Chemistry, Davis, CA; Terry A. Land, James J. DeYoreo, Lawrence Livermore National Laboratory, Livermore, CA.

Derivatives of 2,5-diketopiperazine (DKP) are known to assemble into hydrogen-bonded tapes in their crystalline solids. Hydrogen-bonded tapes can function as scaffolds for positioning guest molecules within the crystalline lattice, and depending on what substituents or guest molecules are chosen, there is the potential for creating solids with new bulk properties. We will describe our efforts at elucidating physical-organic trends between the molecular constituents and their assembly into crystalline solids using several methods of analysis: X-ray diffraction, NMR and IR spectroscopies, in situ atomic force microscopy, co-crystallization techniques and computer modeling.

9:30 AM *U3.3
FROM BENZENE TO 2D- AND 3D-NANOPARTICLES. Klaus Müllen, Max-Planck-Institute for Polymer Research, Mainz, GERMANY.

The benzene ring serves as versatile building block of carbon-rich 2D- and 3D-macromolecules. A novel cycloaddition-deprotection protocol provides dendritic polyphenylenes which are shape persistent 3D-nanoparticles. Suitably designed oligo- and polyphenylenes are transformed into giant polycyclic aromatic hydrocarbons (PAHs) by mild intramolecular cyclodehydrogenation. These PAHs constitute molecular (2D)-models of graphite. Their supramolecular ordering is a key prerequisite when elucidating their role as media for charge carrier transport in molecular electronics. Current-potential curves recorded by scanning tunneling microscopy for single PAH discs and the drastic increase of charge mobility as a result of their liquid-crystalline order in $\pi$-stacked columnar arrays are typical results of their physical characterization.

10:15 AM U3.4
THE EVOLUTION OF ORDERED POLYCRYSTALLINE FILMS DURING VAPOR DEPOSITION OF 4-AMINOBENZOPHENONE AND 4-(N,N-DIMETHYLAMINO)-3-ACETAMIDONITROBENZENE ON ALKALI HALIDE SUBSTRATES. John McAleese, David Sheen , John Sherwood and Qingwu Wang, University of Strathclyde, Department of Pure and Applied Chemistry, Glasgow, Scotland, UNITED KINGDOM.

The polycrystalline films which develop during the vapor deposition of the non-linear optical materials 4-aminobenzophenone (ABP) and 4-(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN) on prebaked KCL or KBr (001) faces show biaxial orientation along [110] and [$\bar{1}$10] directions, in common with many organic materials deposited on these substrates. During deposition, some interesting changes in film morphology have

SYMPOSIUM U Organics with Supramolecular Structure and Function November 30 - December 3, 1998 Chairs

Martin Bryce          Christopher Ober

Dept of Chemistry        Dept of MS&E

Univ of Durham          Cornell Univ

Durham,  DH1 3LE UNITED KINGDOM        327 Bard Hall

44-191-374-3118          Ithaca, NY 14853

607-255-8417

Michael Ward
Chemical Engineering and Materials Science
Univ of Minnesota
151 Amundson Hall
Minneapolis, MN 55455
612-625-3062

Symposium Support
*Army Research Office

* Invited paper

SESSION U1: MOLECULAR RECOGNITION IN SUPRAMOLECULAR SOLIDS
Chair: Bruce M. Foxman
Monday Morning, November 30, 1998
America South (W)
8:30 AM U1.1
CRYSTAL ENGINEERING OF DIAMONDOID NETWORKS FOR SECOND-ORDER NONLINEAR OPTICAL APPLICATIONS. Wenbin Lin , Zhiyong Wang, Ren-Gen Xiong, Department of Chemistry, Brandeis University, Waltham, MA.

The design of organic and metal-organic diamondoid frameworks has received considerable attention over the past decade, in part, because of the recognition that daimondoid networks have high propensity to pack in acentric space groups as a result of the lack of an inversion center. Acentric solids and thin films are of great interest owing to their potential applications as second-order nonlinear optical (NLO) materials. In fact, one of the best known inorganic second-order nonlinear optical materials, potassium dideuterophosphate (KDP), crystallizes as a diamondoid network. Despite the intense search over the past decade, acentric organic and metal-organic diamondoid frameworks have not been rationally synthesized to date. We have designed a novel approach to crystal engineering of acentric metal-organic diamondoid frameworks for second-order NLO applications. Our strategy relies on the use of four- or six- coordinate metal centers in combination with unsymmetrical, bifunctional linker groups. For example, both bis(isonicotinato)zinc and cadmium bis(4-pyridylacrylic acid) have been prepared hydrothermally. They both crystallize in acentric space groups, and possess a three-fold and five-fold interpenetrated diamondoid structure, respectively. Preliminary second harmonic generation measurements showed that these diamondoid networks exhibit second-order NLO efficiencies comparable to technologically important lithium niobate.

8:45 AM U1.2
ENGINEERING MIXED CRYSTALS. Bart Kahr , Loyd Bastin, Anand Subramony, Rich Gurney, Christine Mitchell.

While a great deal of effort recently has been directed at the design of molecular crystalline materials, especially by exploiting hydrogen bonds, little attention has been paid to the design of dilute solid solutions even though for some optical and spectroscopic applications molecules that are oriented and isolated from one another are requisite. We have been seeking to identify the prevailing intermolecular forces that determine for formation of dye inclusion crystals (DICs), simple crystalline substances that contain organic chromophores oriented and isolated in particular sectors during growth from solution. In this paper, we focus on orienting organic dyes within otherwise single crystals of inorganic salts such as potassium sulfate, potassium dihydrogen phosphate, and barium acetate. We emphasize the use of such crystals in chemical analysis, the determination of crystal growth mechanisms, and in the stabilization of reactive intermediates and electronically excited states.

9:00 AM *U1.3
SUPRAMOLECULAR CONTROL OF THE BULK MAGNETIC PROPERTIES OF MANGANOPORPHRYIN-BASED MAGNETS. Joel S. Miller , University of Utah, Dept. of Chemistry, Salt Lake City, UT; Arthur J. Epstein, The Ohio State University, Dept. of Physics and Dept. of Chemistry, Columbus, OH.

Coordination polymer-based magnets comprised of alternating [Mn(III)(porphryrin)]+ and [A]- (A = TCNE, TCNQ, C4(CN)6, chloranil) have been prepared and structurally and magnetically characterized. The [A]- is trans-$\mu$-bound to two adjacent Mn(III) sites in the chain. Adjacent sites exhibit antiferromagnetic coupling between the S = 1/2 [A]- quantum spin and the S = 2 Mn(III) classical spin and magnetic order occurs below 25 K. The intrachain coupling, as evidence by increasing Tmin, and fits to the Seiden expression for isolated chains comprised of alternating quantum {S = 1/2; [A].-} and classical {S = 2; [Mn(III)porphryrin)]+} spins is correlated with decreasing MnN4 - [TCNE]- dihedral angles. MO calculations identify the key overlap due to the sigma-dz2/pz on the [TCNE]- N bound to the Mn(III). Use of octaethylporphyrin leads to a antiferromagnet whereas use of tetraphenylporphryin and substituted tetraphenylporphryin leads to magnets with interchain ferromagnetic coupling and ferrimagnetic behavior. The differing magnetic behavior is attributed to enhanced ferromagnetic dipolar interactions for the latter class of magnets. The magneto-structure correlation as well as recent developments in this class of materials will be discussed.

9:30 AM U1.4
SOLID-STATE STRUCTURAL ORDERING IN STABLE ORGANIC RADICALS. Paul M. Lahti , Jacqueline Ferrer, Univ of Massachusetts, Dept of Chemistry, Amherst, MA; Clifford George, Naval Research Laboratory, Washington, DC.

Recent work in organic molecular magnetic materials has included efforts to design specific hydrogen-bonded and dipolar solid state interactions, which will act to assemble stable radicals into relative orientations that favor intermolecular ferromagnetic exchange interactions. We describe work aimed at design of such systems, with primary focus on one example, benzimidazole-2-tert-butyl-nitroxide (BIm-tBN). BIm-tBN forms stacks of molecules that are H-bonded together to produce a highly organized, centrosymmetric crystal structure. The relationship of isolated-molecule properties such as spin density distribution (investigated by ESR spectroscopy and DFT computations) to typical models for intermolecular exchange in the solid state will be outlined for this example, as well as prospects for extensions to related systems.

9:45 AM U1.5
SELF-ASSEMBLY OF LAYERED COORDINATION NETWORKS WITH CLAY-LIKE PROPERTIES. George K. H. Shimizu , Univ of Calgary, Dept of Chemistry, Calgary, Alberta, CANADA; Gary D. Enright, Chris I. Ratcliffe, Gabriela S. Rego, John A. Ripmeester, Dan D. M. Wayner, National Research Council of Canada, Steacie Institute for Molecular Sciences, Ottawa, Ontario, CANADA.

Clays and zeolites are rigid framework aluminosilicates with layered and channel motifs, respectively. From a metal coordination chemistry standpoint, these networks provide attractive model compounds owing to their robust nature, porousity and functionality. This presentation will discuss a family of lamellar metal coordination compounds, generated from fundamental design principles, and it's analogy to clay-like materials. A novel dithia ligand, designed to favor the formation of infinite frameworks, was synthesized and found to form a layered solid with silver(I). The observed structure is versatile as it can be tuned by changing the anion, ancillary ligands on the metals, or, significantly, by functionalizing the ligand itself. The prospect of organic derivatization offers a wide range of structural options and hence, variation in the physical properties of these complexes. Studies to date show interlayer swelling in the presence of solvent, selectivity in inclusion behavior and ion exchange ability.

10:15 AM U1.6
ETHYNYL-SUBSTITUTED TETRAHEDRAL MOLECULES: BUILDING BLOCKS FOR 3D-NETWORKS. Elena Galoppini , Wenzhuo Guo, Quiongying Fu, Rutgers University, Department of Chemistry, Newark, NJ; Richard Gilardi, Laboratory for the Structure of Matter, The Naval Research Laboratory, Washington, DC.

The ability to design organic crystals or polymers with large and dimensionally-fixed cavities may lead to materials exhibiting unprecedented and possibly useful properties. As part of this interest, we are studying molecules capable of selective and strongly directional intermolecular interactions (such as hydrogen bonds) and which may pack in a predictable manner. We present the synthesis and crystal structure of molecules with a tetrahedral core, such as methane and adamantane, substituted at the four vertices with phenylacetylenic units or phenylboronic esters. The tetrahedral core provides a rigid scaffold, which maintains fixed the orientation of the rod-like functional groups. Hydrogen bonding, metal-ligand coordination, polymerization reactions were used to connect the building blocks. Such molecules form diamondoid' crystals, three-dimensional networks obtained by connecting the four vertices of tetrahedra and which resemble the diamond structure.

10:30 AM *U1.7
MOLECULAR ENGINEERING OF NON-CENTROSYMMETRIC FILMS FOR NONLINEAR OPTICAL APPLICATIONS. Geoffrey J. Ashwell , Cranfield University, Molecular Electronics, Cranfield, UNITED KINGDOM.

Interest in Langmuir-Blodgett (LB) films for second-harmonic generation (SHG) stems from the requirement that the structure must be non-centrosymmetric and from the fact that the LB technique allows control of the packing at the molecular level. Amphiphilic materials, those with a hydrophilic head and a hydrophobic tail, may be aligned at the air-water interface but, when deposited, the layers tend to pack centrosymmetrically with the interfaces being alternately hydrophilic (head-to-head) and hydrophobic (tail-to-tail). This may be overcome by considering the molecular criteria for non-centrosymmetric deposition and, at Cranfield, Z-type structures have been routinely obtained by rendering the chromophore hydrophobic at both ends. This causes the LB film surface to be invariably hydrophobic and suppresses the natural tendency of the molecules to invert during deposition. There is a narrow range of alkyl chain lengths which allows the films to be non-centrosymmetric but long-term stability has been realised by considering the compatibility of the end groups within the multilayer. When carefully selected, non-centrosymmetric alignment arises and the second-harmonic intensity increases quadratically with the number of layers, i.e. as I(N)2w= I(1)2w N2, to thicknesses suitable for waveguiding. The lecture will focus on the optimisation of the nonlinear optical properties of LB films of a novel dye, E-4-[(N-octadecyl-6,7,8-trihydro-5-isoquinolylidene)methyl]-N,N-dibutylaniline octadecylsulfate. The films are transparent at the fundamental frequency and only slightly absorbing at the second-harmonic. Nonetheless, the susceptibility is high ($\chi$zzz(2) = 76 pm V-1 at 1.064 $\mu$m for I = 3.15 nm layer-1) and the second-harmonic intensity is the strongest to date from a weakly absorbing film.

11:00 AM *U1.8
GAS SORPTION ISOTHERMS FOR DESIGNED MICROPOROUS METAL-ORGANIC MATERIALS. O.M. Yaghi , Hailian Li, and Mohamed Eddaoudi, Arizona State University, Department of Chemistry and Biochemistry, Tempe, AZ.

Despite the exponential growth in the number of reports on crystalline metal-organic materials with open-framework structures, studies focusing on establishing their gas sorption isotherms and thus microporosity, remain largely unknown. This presentation will show that permanent micrOporosity, similar to that commonly observed in zeolites, can be achieved with metal-organic open frameworks. Gas sorption isotherm, surface area, and pore volume measurements for materials such as Zn(BDC)$\cdot$(DMF)(H20) having 5-15 $\AA$ diameter apertures will be presented. Key aspects to developing strategies for producing rigid and stable metal-organic frameworks with extended channels will be outlined.

11:30 AM *U1.9
TETRATHIAFULVALENES: VERSATILE BUILDING BLOCKS IN MACROCYCLIC AND SUPRAMOLECULAR CHEMISTRY. Jan Becher , Department of Chemistry, Odense University, Odense M, DENMARK.

The effective syntheses of a variety of tetrathiafulvalene building blocks, including pyrrolo- and 2,5-dihydropyrrolo-fused tetrathiafulvalenes have been developed, allowing easy construction and preparation of complex molecular assemblies. The facile deprotection of the 2-cyanoethyl group, a versatile protecting group for 1,3-dithiolium-2-thione-4,5-dithiolates and tetrathiafulvalene-thiolates (1), is an excellent method for the incorporation of tetrathiafulvalene units into macrocyclic and supramolecular compounds. The selective and stepwise protection-deprotection methodology have been used extensively by our group for the preparation of two and three dimensional macrocyclic (mono-, bis- and tricyclic) as well as tetrathiafulvalene-based supramolecular systems (2). Utilization of the thiolates generated by the new methodology are illustrated by recent examples of oligomeric and supramolecular tetrathiafulvalene-based systems, such as: Dendritic (3) and oligo-tetrathiafulvalenes, three dimensional tetrathiafulvalenophanes, tetrathiafulvalene-containing catenanes (4) or rotaxanes (5) as well as donor acceptor systems based on tetrathiafulvalene as the donating group.
References
1.    M. B. Nielsen, S. B. Nielsen and J. Becher, Self complexing Tetrathiafulvalene Macrocycles, a Tetrathiafulvalene Switch'', Chem. Commun., 1998, 475.
2.    M. B. Nielsen, N. Thorup and J. Becher, Synthesis of a criss-cross overlapped Tetrathiafulvalenophane and a topologically new [2]catenane'', J. Chem. Soc. Perkin 1, 1998, 1305.
3.    C. A. Christensen, L. M. Goldenberg, M. R. Bryce and J. Becher, Synthesis and electrochemistry of a tetrathiafulvalene (TTF)21-glycol dendrimer'', Chem. Commun., 1998, 509.
4.    K. B. Simonsen and J. Becher, Tetrathiafulvalene Thiolates'', Synlett, 1997, 1211. 5.    M. B. Nielsen and J. Becher, Two- and Three-Dimensional Tetrathiafulvalene Macrocycles'', Liebigs Ann/Recueil, 1997, 2177.

SESSION U2: MOLECULAR RECOGNITION IN SUPRAMOLECULAR SOLIDS (continued)
Chair: Omar M. Yaghi
Monday Afternoon, November 30, 1998
America South (W)
1:30 PM *U2.1
SYNTHESIS AND PROPERTIES OF HELICAL AROMATIC MOLECULES THAT SELF-ASSEMBLE INTO COLUMNS. Thomas J. Katz , Colin Nuckolls, Joseph M. Fox, Columbia Univ, Dept of Chemistry, New York, NY; Thierry Verbiest, Sven Van Elschocht, and André Persoons, K.U. Leuven, Laboratory of Chemical and Biological Dynamics, Leuven, BELGIUM; Andrew J. Lovinger, Bell Labs, Lucent Technologies, Murray Hill, NJ.

Molecules that resemble those forming chiral discotic mesophases, but whose core ring systems are twisted helically, have been synthesized in nonracemic form. Some self-assemble into columnar structures in solution, as do the pure materials in bulk and in Langmuir-Blodgett films. When they assemble, the circular dichroisms, specific rotations, and second harmonic generating ability all greatly increase. The circular dichroisms of one of the self-assembling materials is sufficiently large that it can be measured easily from a single monolayer. The long wavelength circular dichroisms of the synthesized helical metal-phthalocyanines split.
Unlike the nonracemic self-assembling molecules, the racemic ones do not organize into similarly large structures, and their second-harmonic generating ability is small. Among the materials prepared is the first columnar mesophase that has a nonracemic helical core.

2:00 PM *U2.2
FUNCTIONAL SUPRAMOLECULAR AND MACROMOLECULAR DENDRIMERS ON A LATTICE. V. Percec , The W.M. Keck Laboratories for Organic Synthesis, Department of Macromolecular Science, Case Western Reserve University, Cleveland, OH.

This presentation will discuss the elaboration of the first library of functional dendrons that self-assemble into cylindrical and spherical supramolecular dendrimers which subsequently self-organize into various cubic or columnar hexagonal lattices. Retrosynthetic analyses of these lattices by XRD allows the design of various classes of monomeric dendrons which after polymerization produce polymers with various architectures and shapes that self-organize in similar lattices with those of the parent supramolecular dendritic synthons. Applications in various areas of material science will be discussed.

2:30 PM U2.3
TEMPLATE DIRECTED ARCHITECTURAL ISOMERISM IN OPEN MOLECULAR FRAMEWORKS. Jennifer A. Swift , Adam M. Pivovar, Michael D. Ward, University of Minnesota, Department of Chemical Engineering and Materials Science, Minneapolis, MN.

Highly porous host lattices based on resilient 2-dimensional guanidinium-sulfonate hydrogen bonded networks that are connected continuously in the third dimension by 4,4'-biphenyldisulfonate pillars to generate a brick-like framework are described. The brick framework is a predictable architectural isomer of a previously observed guanidinium-sulfonate host lattice consisting of discrete bilayers. The amount of void space in the brick framework is nominally twice that of the bilayer form, with the framework occupying only 30% of the total volume. The host framework conforms to the different steric demands and occupancies of various aromatic guests by puckering of the flexible, yet resilient, hydrogen bonded network and by rotation (and/or twisting) of the pillars about their long axes, the latter also governing the width of the pores in the framework. The formation of the brick architecture can be attributed to steric templating by the included molecular guests and host-guest interactions that favor assembly of this framework over its bilayer counterpart. Inclusion of select guest molecules in brick frameworks yields polar crystals. Formation of such polar materials may be attributed to correlated guest-host-guest interactions, mediated through the corrugated guanidinium-sulfonate sheets. Development of these materials may yield a new class of NLO materials.

2:45 PM U2.4
NANOPARTICLE ENCAPSULATION USING RESORCINARENE-BASED SYSTEMS. Kevin B. Stavens, Stephen V. Pusztay, Ronald P. Andres, Alexander Wei , Purdue University, Depts. of Chemistry and Chemical Engineering, West Lafayette, IN.

Resorcinol-based calix[4]arenes (resorcinarenes) have demonstrated excellent potential for encapsulating and stabilizing nanosized particles. Gold clusters 2-5 nm in diameter were generated by vapor- and solution-phase techniques and were captured in millimolar hydrocarbon solutions of resorcinarenes and other surfactants. The capture efficiency of Au nanoparticles using resorcinarenes was several times greater relative to alkanethiols. Nanoparticles stabilized by several resorcinarene and binary resorcinarene-thiol systems were characterized by absorption spectroscopy and transmission electron microscopy. It was found that hydrogen bonding is an important factor in both capture efficiency and aggregate stability. The potential of resorcinarene-based encapsulation systems for creating ordered nanostructures will be discussed.

3:15 PM *U2.5
DESIGN, DISCOVERY AND SYNTHESIS OF REACTIVE SUPRAMOLECULAR ARRAYS. Bruce M. Foxman , Brandeis University, Dept. of Chemistry, Waltham, MA.

A supramolecular organic array, with an organized set of reactive groups, provides an opportunity to carry out either stereospecific or regiospecific chemical reactions, and/or reactions that cannot be performed in solution. Of course, not every array affords such an opportunity, and we must consider both the principles required for successful assembly, as well as experience-based procedures, to ensure success. While there is a considerable database of solid-state reactions, the number of new reaction classes has increased only slowly, with a consequent slow growth in design principles. As part of the concept of crystal engineering we can use our knowledge of molecular solid-state chemistry, crystal packing, and chemical reactivity to produce reactive materials. In recent years, we have designed several solid-state reactions by using structural analogies derived from the Cambridge Structural Database (three examples from organic and metal-organic chemistry will be discussed). Following the initial design work, we developed two new series of metal salts and complexes with unique reactivity properties. Solid metal alkynoates and alkenoates undergo oligomerization and polymerization reactions when exposed to Co-60 gamma-rays. For example, irradiation of solid sodium trans-2-butenoate leads to a linear trimer, one of eight possible diastereomers, in high yield. Studies of crystalline metal complexes containing such unsaturated ligands provide new insight into solid-state reactivity. In addition to the use of hydrogen bonding and bilayer interactions as agents for the production of reactive phases, changes in metal ion within an isomorphous set of structures may have profound effects on reactivity. The discussion will include a review of our expanding database of engineered reactive molecular crystals, and the implications of recent results on design criteria.

3:45 PM *U2.6
THE HYDROGEN BOND AND CRYSTAL ENGINEERING: CONSTRUCTING PREDICTABLE MOLECULAR ARCHITECTURES. Christer B. Aakeroy , Department of Chemistry, Kansas State University, Manhattan, KS.

Crystal engineering is governed by the nature and structural consequences of intermolecular forces, and the way in which such interactions are utilized for controlling the assembly of molecules into predictable structural motifs. A vital part of crystal engineering is therefore dedicated to the identification of robust intermolecular synthons that can be used as reliable connectors (microscopic ÎglueÌ) between molecules.
We have demonstrated that certain organic molecular building blocks have a propensity to form low-dimensional assemblies (chains, ribbons, layers) via complementary N-H...O, C-H...O and O-H...O hydrogen bonds. Through systematic structural studies of closely related compounds, we have been able to derive some guidelines for how we can design and build robust molecular scaffolding that can form the structural backbone in new functional solids. Furthermore, in an effort to design new transition-metal containing materials, we have combined the geometric features of well-known coordination chemistry (notably of silver(I)) with intermolecular connectors with a view to examining how the structural balance in such materials is determined by competition and/or collaboration between intermolecular synthons and the spatial requirements of transition-metal complexes.

4:15 PM U2.7
THE BINARY APPROACH TO SUPRAMOLECULAR STRUCTURE AND FUNCTION. Joseph W. Lauher , Frank W. Fowler, State University of New York, Department of Chemistry, Stony Brook, NY.

The function of a supramolecular entity depends upon the chemical composition and nature of the constituent molecules, as well as the symmetry and spatial properties of the assembly of molecules. Since one has little control over the actual supramolecular properties of a given molecule, one must approach a synthesis with a focus on the final supramolecular goal, as opposed to a focus on the identity of the individual molecules. A realization of the final goal may require the achievement of a specific structure, a specific function or both, since function often depends upon structure.
We have developed a binary approach to this problem, using one molecule to control the structure of a supramolecular assembly, while the second provides the function. Our approach is based upon a library of chemical functionalities that lead to predictable structural patterns based upon persistent patterns of hydrogen bonds. Molecules possessing these functionalities can be synthesized and used to control and determine supramolecular structure. A second functionality is added as a handle to control the second molecular entity, the one that provides the function or completes the structure of the final product. For this we have used a variety of interactions, including hydrogen bonds, metal-ligand coordination and halide-nitrogen interactions. Successful applications of the technique include the synthesis of a wide variety of layered structures, designed diacetylene polymerizations and the controlled spacing of metal atoms.

4:30 PM *U2.8
Wais Hosseini , Univ Louis Pasteur, Strasbourg, FRANCE.

Abstract Not Available

SESSION U3: THIN FILMS AND LAYERED STRUCTURES
Chair: Neal R. Armstrong
Tuesday Morning, December 1, 1998
America South (W)
8:30 AM *U3.1
SUPRAMOLECULAR LAMINATES WITH AFFINITY FOR AROMATIC GUESTS. Mike Zaworotko , Kumar S. Biradha, Department of Chemistry, The University of Winnipeg, Winnipeg, Manitoba, CANADA.

That solid state architecture profoundly influences bulk physical properties and therefore function of solids has provided impetus for recent activity in the field of crystal engineering. The nature of crystal engineering means that chemists can design new crystal structures without the need to develop new molecular structures. Rather, the chemist simply has to focus upon multifunctional exodentate moieties and the concept of supramolecular synthons . This presentation will focus upon the development of new classes of layered solid1 that might be of general interest for materials or separations applications. We shall present recent results involving organic solids based upon simple acids such as trimesic acid and trimellitic acid and discuss their significance in the following contexts: 1) what impact will crystal engineering have upon design and synthesis of covalent polymers?; 2) what opportunities might there be for applications of the new materials?
1. Sharma, C.V.K.; Zaworotko, M.J.; Rogers, R.D., 1997. Supramolecular Laminates'' Chem. Commun. , 1559-1560, 1997.

9:00 AM *U3.2
MOLECULAR SCAFFOLDS FROM DERIVATIVES OF 2,5-DIKETOPIPERAZINE. G. Tayhas R. Palmore , Tzy-Jiun Luo, Mary T. McBride, University of California, Department of Chemistry, Davis, CA; Terry A. Land, James J. DeYoreo, Lawrence Livermore National Laboratory, Livermore, CA.

Derivatives of 2,5-diketopiperazine (DKP) are known to assemble into hydrogen-bonded tapes in their crystalline solids. Hydrogen-bonded tapes can function as scaffolds for positioning guest molecules within the crystalline lattice, and depending on what substituents or guest molecules are chosen, there is the potential for creating solids with new bulk properties. We will describe our efforts at elucidating physical-organic trends between the molecular constituents and their assembly into crystalline solids using several methods of analysis: X-ray diffraction, NMR and IR spectroscopies, in situ atomic force microscopy, co-crystallization techniques and computer modeling.

9:30 AM *U3.3
FROM BENZENE TO 2D- AND 3D-NANOPARTICLES. Klaus Müllen, Max-Planck-Institute for Polymer Research, Mainz, GERMANY.

The benzene ring serves as versatile building block of carbon-rich 2D- and 3D-macromolecules. A novel cycloaddition-deprotection protocol provides dendritic polyphenylenes which are shape persistent 3D-nanoparticles. Suitably designed oligo- and polyphenylenes are transformed into giant polycyclic aromatic hydrocarbons (PAHs) by mild intramolecular cyclodehydrogenation. These PAHs constitute molecular (2D)-models of graphite. Their supramolecular ordering is a key prerequisite when elucidating their role as media for charge carrier transport in molecular electronics. Current-potential curves recorded by scanning tunneling microscopy for single PAH discs and the drastic increase of charge mobility as a result of their liquid-crystalline order in $\pi$-stacked columnar arrays are typical results of their physical characterization.

10:15 AM U3.4
THE EVOLUTION OF ORDERED POLYCRYSTALLINE FILMS DURING VAPOR DEPOSITION OF 4-AMINOBENZOPHENONE AND 4-(N,N-DIMETHYLAMINO)-3-ACETAMIDONITROBENZENE ON ALKALI HALIDE SUBSTRATES. John McAleese, David Sheen , John Sherwood and Qingwu Wang, University of Strathclyde, Department of Pure and Applied Chemistry, Glasgow, Scotland, UNITED KINGDOM.

The polycrystalline films which develop during the vapor deposition of the non-linear optical materials 4-aminobenzophenone (ABP) and 4-(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN) on prebaked KCL or KBr (001) faces show biaxial orientation along [110] and [$\bar{1}$10] directions, in common with many organic materials deposited on these substrates. During deposition, some interesting changes in film morphology have

SYMPOSIUM U Organics with Supramolecular Structure and Function November 30 - December 3, 1998 Chairs

Martin Bryce          Christopher Ober

Dept of Chemistry        Dept of MS&E

Univ of Durham          Cornell Univ

Durham,  DH1 3LE UNITED KINGDOM        327 Bard Hall

44-191-374-3118          Ithaca, NY 14853

607-255-8417

Michael Ward
Chemical Engineering and Materials Science
Univ of Minnesota
151 Amundson Hall
Minneapolis, MN 55455
612-625-3062

Symposium Support
*Army Research Office

* Invited paper

SESSION U1: MOLECULAR RECOGNITION IN SUPRAMOLECULAR SOLIDS
Chair: Bruce M. Foxman
Monday Morning, November 30, 1998
America South (W)
8:30 AM U1.1
CRYSTAL ENGINEERING OF DIAMONDOID NETWORKS FOR SECOND-ORDER NONLINEAR OPTICAL APPLICATIONS. Wenbin Lin , Zhiyong Wang, Ren-Gen Xiong, Department of Chemistry, Brandeis University, Waltham, MA.

The design of organic and metal-organic diamondoid frameworks has received considerable attention over the past decade, in part, because of the recognition that daimondoid networks have high propensity to pack in acentric space groups as a result of the lack of an inversion center. Acentric solids and thin films are of great interest owing to their potential applications as second-order nonlinear optical (NLO) materials. In fact, one of the best known inorganic second-order nonlinear optical materials, potassium dideuterophosphate (KDP), crystallizes as a diamondoid network. Despite the intense search over the past decade, acentric organic and metal-organic diamondoid frameworks have not been rationally synthesized to date. We have designed a novel approach to crystal engineering of acentric metal-organic diamondoid frameworks for second-order NLO applications. Our strategy relies on the use of four- or six- coordinate metal centers in combination with unsymmetrical, bifunctional linker groups. For example, both bis(isonicotinato)zinc and cadmium bis(4-pyridylacrylic acid) have been prepared hydrothermally. They both crystallize in acentric space groups, and possess a three-fold and five-fold interpenetrated diamondoid structure, respectively. Preliminary second harmonic generation measurements showed that these diamondoid networks exhibit second-order NLO efficiencies comparable to technologically important lithium niobate.

8:45 AM U1.2
ENGINEERING MIXED CRYSTALS. Bart Kahr , Loyd Bastin, Anand Subramony, Rich Gurney, Christine Mitchell.

While a great deal of effort recently has been directed at the design of molecular crystalline materials, especially by exploiting hydrogen bonds, little attention has been paid to the design of dilute solid solutions even though for some optical and spectroscopic applications molecules that are oriented and isolated from one another are requisite. We have been seeking to identify the prevailing intermolecular forces that determine for formation of dye inclusion crystals (DICs), simple crystalline substances that contain organic chromophores oriented and isolated in particular sectors during growth from solution. In this paper, we focus on orienting organic dyes within otherwise single crystals of inorganic salts such as potassium sulfate, potassium dihydrogen phosphate, and barium acetate. We emphasize the use of such crystals in chemical analysis, the determination of crystal growth mechanisms, and in the stabilization of reactive intermediates and electronically excited states.

9:00 AM *U1.3
SUPRAMOLECULAR CONTROL OF THE BULK MAGNETIC PROPERTIES OF MANGANOPORPHRYIN-BASED MAGNETS. Joel S. Miller , University of Utah, Dept. of Chemistry, Salt Lake City, UT; Arthur J. Epstein, The Ohio State University, Dept. of Physics and Dept. of Chemistry, Columbus, OH.

Coordination polymer-based magnets comprised of alternating [Mn(III)(porphryrin)]+ and [A]- (A = TCNE, TCNQ, C4(CN)6, chloranil) have been prepared and structurally and magnetically characterized. The [A]- is trans-$\mu$-bound to two adjacent Mn(III) sites in the chain. Adjacent sites exhibit antiferromagnetic coupling between the S = 1/2 [A]- quantum spin and the S = 2 Mn(III) classical spin and magnetic order occurs below 25 K. The intrachain coupling, as evidence by increasing Tmin, and fits to the Seiden expression for isolated chains comprised of alternating quantum {S = 1/2; [A].-} and classical {S = 2; [Mn(III)porphryrin)]+} spins is correlated with decreasing MnN4 - [TCNE]- dihedral angles. MO calculations identify the key overlap due to the sigma-dz2/pz on the [TCNE]- N bound to the Mn(III). Use of octaethylporphyrin leads to a antiferromagnet whereas use of tetraphenylporphryin and substituted tetraphenylporphryin leads to magnets with interchain ferromagnetic coupling and ferrimagnetic behavior. The differing magnetic behavior is attributed to enhanced ferromagnetic dipolar interactions for the latter class of magnets. The magneto-structure correlation as well as recent developments in this class of materials will be discussed.

9:30 AM U1.4
SOLID-STATE STRUCTURAL ORDERING IN STABLE ORGANIC RADICALS. Paul M. Lahti , Jacqueline Ferrer, Univ of Massachusetts, Dept of Chemistry, Amherst, MA; Clifford George, Naval Research Laboratory, Washington, DC.

Recent work in organic molecular magnetic materials has included efforts to design specific hydrogen-bonded and dipolar solid state interactions, which will act to assemble stable radicals into relative orientations that favor intermolecular ferromagnetic exchange interactions. We describe work aimed at design of such systems, with primary focus on one example, benzimidazole-2-tert-butyl-nitroxide (BIm-tBN). BIm-tBN forms stacks of molecules that are H-bonded together to produce a highly organized, centrosymmetric crystal structure. The relationship of isolated-molecule properties such as spin density distribution (investigated by ESR spectroscopy and DFT computations) to typical models for intermolecular exchange in the solid state will be outlined for this example, as well as prospects for extensions to related systems.

9:45 AM U1.5
SELF-ASSEMBLY OF LAYERED COORDINATION NETWORKS WITH CLAY-LIKE PROPERTIES. George K. H. Shimizu , Univ of Calgary, Dept of Chemistry, Calgary, Alberta, CANADA; Gary D. Enright, Chris I. Ratcliffe, Gabriela S. Rego, John A. Ripmeester, Dan D. M. Wayner, National Research Council of Canada, Steacie Institute for Molecular Sciences, Ottawa, Ontario, CANADA.

Clays and zeolites are rigid framework aluminosilicates with layered and channel motifs, respectively. From a metal coordination chemistry standpoint, these networks provide attractive model compounds owing to their robust nature, porousity and functionality. This presentation will discuss a family of lamellar metal coordination compounds, generated from fundamental design principles, and it's analogy to clay-like materials. A novel dithia ligand, designed to favor the formation of infinite frameworks, was synthesized and found to form a layered solid with silver(I). The observed structure is versatile as it can be tuned by changing the anion, ancillary ligands on the metals, or, significantly, by functionalizing the ligand itself. The prospect of organic derivatization offers a wide range of structural options and hence, variation in the physical properties of these complexes. Studies to date show interlayer swelling in the presence of solvent, selectivity in inclusion behavior and ion exchange ability.

10:15 AM U1.6
ETHYNYL-SUBSTITUTED TETRAHEDRAL MOLECULES: BUILDING BLOCKS FOR 3D-NETWORKS. Elena Galoppini , Wenzhuo Guo, Quiongying Fu, Rutgers University, Department of Chemistry, Newark, NJ; Richard Gilardi, Laboratory for the Structure of Matter, The Naval Research Laboratory, Washington, DC.

The ability to design organic crystals or polymers with large and dimensionally-fixed cavities may lead to materials exhibiting unprecedented and possibly useful properties. As part of this interest, we are studying molecules capable of selective and strongly directional intermolecular interactions (such as hydrogen bonds) and which may pack in a predictable manner. We present the synthesis and crystal structure of molecules with a tetrahedral core, such as methane and adamantane, substituted at the four vertices with phenylacetylenic units or phenylboronic esters. The tetrahedral core provides a rigid scaffold, which maintains fixed the orientation of the rod-like functional groups. Hydrogen bonding, metal-ligand coordination, polymerization reactions were used to connect the building blocks. Such molecules form diamondoid' crystals, three-dimensional networks obtained by connecting the four vertices of tetrahedra and which resemble the diamond structure.

10:30 AM *U1.7
MOLECULAR ENGINEERING OF NON-CENTROSYMMETRIC FILMS FOR NONLINEAR OPTICAL APPLICATIONS. Geoffrey J. Ashwell , Cranfield University, Molecular Electronics, Cranfield, UNITED KINGDOM.

Interest in Langmuir-Blodgett (LB) films for second-harmonic generation (SHG) stems from the requirement that the structure must be non-centrosymmetric and from the fact that the LB technique allows control of the packing at the molecular level. Amphiphilic materials, those with a hydrophilic head and a hydrophobic tail, may be aligned at the air-water interface but, when deposited, the layers tend to pack centrosymmetrically with the interfaces being alternately hydrophilic (head-to-head) and hydrophobic (tail-to-tail). This may be overcome by considering the molecular criteria for non-centrosymmetric deposition and, at Cranfield, Z-type structures have been routinely obtained by rendering the chromophore hydrophobic at both ends. This causes the LB film surface to be invariably hydrophobic and suppresses the natural tendency of the molecules to invert during deposition. There is a narrow range of alkyl chain lengths which allows the films to be non-centrosymmetric but long-term stability has been realised by considering the compatibility of the end groups within the multilayer. When carefully selected, non-centrosymmetric alignment arises and the second-harmonic intensity increases quadratically with the number of layers, i.e. as I(N)2w= I(1)2w N2, to thicknesses suitable for waveguiding. The lecture will focus on the optimisation of the nonlinear optical properties of LB films of a novel dye, E-4-[(N-octadecyl-6,7,8-trihydro-5-isoquinolylidene)methyl]-N,N-dibutylaniline octadecylsulfate. The films are transparent at the fundamental frequency and only slightly absorbing at the second-harmonic. Nonetheless, the susceptibility is high ($\chi$zzz(2) = 76 pm V-1 at 1.064 $\mu$m for I = 3.15 nm layer-1) and the second-harmonic intensity is the strongest to date from a weakly absorbing film.

11:00 AM *U1.8
GAS SORPTION ISOTHERMS FOR DESIGNED MICROPOROUS METAL-ORGANIC MATERIALS. O.M. Yaghi , Hailian Li, and Mohamed Eddaoudi, Arizona State University, Department of Chemistry and Biochemistry, Tempe, AZ.

Despite the exponential growth in the number of reports on crystalline metal-organic materials with open-framework structures, studies focusing on establishing their gas sorption isotherms and thus microporosity, remain largely unknown. This presentation will show that permanent micrOporosity, similar to that commonly observed in zeolites, can be achieved with metal-organic open frameworks. Gas sorption isotherm, surface area, and pore volume measurements for materials such as Zn(BDC)$\cdot$(DMF)(H20) having 5-15 $\AA$ diameter apertures will be presented. Key aspects to developing strategies for producing rigid and stable metal-organic frameworks with extended channels will be outlined.

11:30 AM *U1.9
TETRATHIAFULVALENES: VERSATILE BUILDING BLOCKS IN MACROCYCLIC AND SUPRAMOLECULAR CHEMISTRY. Jan Becher , Department of Chemistry, Odense University, Odense M, DENMARK.

The effective syntheses of a variety of tetrathiafulvalene building blocks, including pyrrolo- and 2,5-dihydropyrrolo-fused tetrathiafulvalenes have been developed, allowing easy construction and preparation of complex molecular assemblies. The facile deprotection of the 2-cyanoethyl group, a versatile protecting group for 1,3-dithiolium-2-thione-4,5-dithiolates and tetrathiafulvalene-thiolates (1), is an excellent method for the incorporation of tetrathiafulvalene units into macrocyclic and supramolecular compounds. The selective and stepwise protection-deprotection methodology have been used extensively by our group for the preparation of two and three dimensional macrocyclic (mono-, bis- and tricyclic) as well as tetrathiafulvalene-based supramolecular systems (2). Utilization of the thiolates generated by the new methodology are illustrated by recent examples of oligomeric and supramolecular tetrathiafulvalene-based systems, such as: Dendritic (3) and oligo-tetrathiafulvalenes, three dimensional tetrathiafulvalenophanes, tetrathiafulvalene-containing catenanes (4) or rotaxanes (5) as well as donor acceptor systems based on tetrathiafulvalene as the donating group.
References
1.    M. B. Nielsen, S. B. Nielsen and J. Becher, Self complexing Tetrathiafulvalene Macrocycles, a Tetrathiafulvalene Switch'', Chem. Commun., 1998, 475.
2.    M. B. Nielsen, N. Thorup and J. Becher, Synthesis of a criss-cross overlapped Tetrathiafulvalenophane and a topologically new [2]catenane'', J. Chem. Soc. Perkin 1, 1998, 1305.
3.    C. A. Christensen, L. M. Goldenberg, M. R. Bryce and J. Becher, Synthesis and electrochemistry of a tetrathiafulvalene (TTF)21-glycol dendrimer'', Chem. Commun., 1998, 509.
4.    K. B. Simonsen and J. Becher, Tetrathiafulvalene Thiolates'', Synlett, 1997, 1211. 5.    M. B. Nielsen and J. Becher, Two- and Three-Dimensional Tetrathiafulvalene Macrocycles'', Liebigs Ann/Recueil, 1997, 2177.

SESSION U2: MOLECULAR RECOGNITION IN SUPRAMOLECULAR SOLIDS (continued)
Chair: Omar M. Yaghi
Monday Afternoon, November 30, 1998
America South (W)
1:30 PM *U2.1
SYNTHESIS AND PROPERTIES OF HELICAL AROMATIC MOLECULES THAT SELF-ASSEMBLE INTO COLUMNS. Thomas J. Katz , Colin Nuckolls, Joseph M. Fox, Columbia Univ, Dept of Chemistry, New York, NY; Thierry Verbiest, Sven Van Elschocht, and André Persoons, K.U. Leuven, Laboratory of Chemical and Biological Dynamics, Leuven, BELGIUM; Andrew J. Lovinger, Bell Labs, Lucent Technologies, Murray Hill, NJ.

Molecules that resemble those forming chiral discotic mesophases, but whose core ring systems are twisted helically, have been synthesized in nonracemic form. Some self-assemble into columnar structures in solution, as do the pure materials in bulk and in Langmuir-Blodgett films. When they assemble, the circular dichroisms, specific rotations, and second harmonic generating ability all greatly increase. The circular dichroisms of one of the self-assembling materials is sufficiently large that it can be measured easily from a single monolayer. The long wavelength circular dichroisms of the synthesized helical metal-phthalocyanines split.
Unlike the nonracemic self-assembling molecules, the racemic ones do not organize into similarly large structures, and their second-harmonic generating ability is small. Among the materials prepared is the first columnar mesophase that has a nonracemic helical core.

2:00 PM *U2.2
FUNCTIONAL SUPRAMOLECULAR AND MACROMOLECULAR DENDRIMERS ON A LATTICE. V. Percec , The W.M. Keck Laboratories for Organic Synthesis, Department of Macromolecular Science, Case Western Reserve University, Cleveland, OH.

This presentation will discuss the elaboration of the first library of functional dendrons that self-assemble into cylindrical and spherical supramolecular dendrimers which subsequently self-organize into various cubic or columnar hexagonal lattices. Retrosynthetic analyses of these lattices by XRD allows the design of various classes of monomeric dendrons which after polymerization produce polymers with various architectures and shapes that self-organize in similar lattices with those of the parent supramolecular dendritic synthons. Applications in various areas of material science will be discussed.

2:30 PM U2.3
TEMPLATE DIRECTED ARCHITECTURAL ISOMERISM IN OPEN MOLECULAR FRAMEWORKS. Jennifer A. Swift , Adam M. Pivovar, Michael D. Ward, University of Minnesota, Department of Chemical Engineering and Materials Science, Minneapolis, MN.

Highly porous host lattices based on resilient 2-dimensional guanidinium-sulfonate hydrogen bonded networks that are connected continuously in the third dimension by 4,4'-biphenyldisulfonate pillars to generate a brick-like framework are described. The brick framework is a predictable architectural isomer of a previously observed guanidinium-sulfonate host lattice consisting of discrete bilayers. The amount of void space in the brick framework is nominally twice that of the bilayer form, with the framework occupying only 30% of the total volume. The host framework conforms to the different steric demands and occupancies of various aromatic guests by puckering of the flexible, yet resilient, hydrogen bonded network and by rotation (and/or twisting) of the pillars about their long axes, the latter also governing the width of the pores in the framework. The formation of the brick architecture can be attributed to steric templating by the included molecular guests and host-guest interactions that favor assembly of this framework over its bilayer counterpart. Inclusion of select guest molecules in brick frameworks yields polar crystals. Formation of such polar materials may be attributed to correlated guest-host-guest interactions, mediated through the corrugated guanidinium-sulfonate sheets. Development of these materials may yield a new class of NLO materials.

2:45 PM U2.4
NANOPARTICLE ENCAPSULATION USING RESORCINARENE-BASED SYSTEMS. Kevin B. Stavens, Stephen V. Pusztay, Ronald P. Andres, Alexander Wei , Purdue University, Depts. of Chemistry and Chemical Engineering, West Lafayette, IN.

Resorcinol-based calix[4]arenes (resorcinarenes) have demonstrated excellent potential for encapsulating and stabilizing nanosized particles. Gold clusters 2-5 nm in diameter were generated by vapor- and solution-phase techniques and were captured in millimolar hydrocarbon solutions of resorcinarenes and other surfactants. The capture efficiency of Au nanoparticles using resorcinarenes was several times greater relative to alkanethiols. Nanoparticles stabilized by several resorcinarene and binary resorcinarene-thiol systems were characterized by absorption spectroscopy and transmission electron microscopy. It was found that hydrogen bonding is an important factor in both capture efficiency and aggregate stability. The potential of resorcinarene-based encapsulation systems for creating ordered nanostructures will be discussed.

3:15 PM *U2.5
DESIGN, DISCOVERY AND SYNTHESIS OF REACTIVE SUPRAMOLECULAR ARRAYS. Bruce M. Foxman , Brandeis University, Dept. of Chemistry, Waltham, MA.

A supramolecular organic array, with an organized set of reactive groups, provides an opportunity to carry out either stereospecific or regiospecific chemical reactions, and/or reactions that cannot be performed in solution. Of course, not every array affords such an opportunity, and we must consider both the principles required for successful assembly, as well as experience-based procedures, to ensure success. While there is a considerable database of solid-state reactions, the number of new reaction classes has increased only slowly, with a consequent slow growth in design principles. As part of the concept of crystal engineering we can use our knowledge of molecular solid-state chemistry, crystal packing, and chemical reactivity to produce reactive materials. In recent years, we have designed several solid-state reactions by using structural analogies derived from the Cambridge Structural Database (three examples from organic and metal-organic chemistry will be discussed). Following the initial design work, we developed two new series of metal salts and complexes with unique reactivity properties. Solid metal alkynoates and alkenoates undergo oligomerization and polymerization reactions when exposed to Co-60 gamma-rays. For example, irradiation of solid sodium trans-2-butenoate leads to a linear trimer, one of eight possible diastereomers, in high yield. Studies of crystalline metal complexes containing such unsaturated ligands provide new insight into solid-state reactivity. In addition to the use of hydrogen bonding and bilayer interactions as agents for the production of reactive phases, changes in metal ion within an isomorphous set of structures may have profound effects on reactivity. The discussion will include a review of our expanding database of engineered reactive molecular crystals, and the implications of recent results on design criteria.

3:45 PM *U2.6
THE HYDROGEN BOND AND CRYSTAL ENGINEERING: CONSTRUCTING PREDICTABLE MOLECULAR ARCHITECTURES. Christer B. Aakeroy , Department of Chemistry, Kansas State University, Manhattan, KS.

Crystal engineering is governed by the nature and structural consequences of intermolecular forces, and the way in which such interactions are utilized for controlling the assembly of molecules into predictable structural motifs. A vital part of crystal engineering is therefore dedicated to the identification of robust intermolecular synthons that can be used as reliable connectors (microscopic ÎglueÌ) between molecules.
We have demonstrated that certain organic molecular building blocks have a propensity to form low-dimensional assemblies (chains, ribbons, layers) via complementary N-H...O, C-H...O and O-H...O hydrogen bonds. Through systematic structural studies of closely related compounds, we have been able to derive some guidelines for how we can design and build robust molecular scaffolding that can form the structural backbone in new functional solids. Furthermore, in an effort to design new transition-metal containing materials, we have combined the geometric features of well-known coordination chemistry (notably of silver(I)) with intermolecular connectors with a view to examining how the structural balance in such materials is determined by competition and/or collaboration between intermolecular synthons and the spatial requirements of transition-metal complexes.

4:15 PM U2.7
THE BINARY APPROACH TO SUPRAMOLECULAR STRUCTURE AND FUNCTION. Joseph W. Lauher , Frank W. Fowler, State University of New York, Department of Chemistry, Stony Brook, NY.

The function of a supramolecular entity depends upon the chemical composition and nature of the constituent molecules, as well as the symmetry and spatial properties of the assembly of molecules. Since one has little control over the actual supramolecular properties of a given molecule, one must approach a synthesis with a focus on the final supramolecular goal, as opposed to a focus on the identity of the individual molecules. A realization of the final goal may require the achievement of a specific structure, a specific function or both, since function often depends upon structure.
We have developed a binary approach to this problem, using one molecule to control the structure of a supramolecular assembly, while the second provides the function. Our approach is based upon a library of chemical functionalities that lead to predictable structural patterns based upon persistent patterns of hydrogen bonds. Molecules possessing these functionalities can be synthesized and used to control and determine supramolecular structure. A second functionality is added as a handle to control the second molecular entity, the one that provides the function or completes the structure of the final product. For this we have used a variety of interactions, including hydrogen bonds, metal-ligand coordination and halide-nitrogen interactions. Successful applications of the technique include the synthesis of a wide variety of layered structures, designed diacetylene polymerizations and the controlled spacing of metal atoms.

4:30 PM *U2.8
Wais Hosseini , Univ Louis Pasteur, Strasbourg, FRANCE.

Abstract Not Available

SESSION U3: THIN FILMS AND LAYERED STRUCTURES
Chair: Neal R. Armstrong
Tuesday Morning, December 1, 1998
America South (W)
8:30 AM *U3.1
SUPRAMOLECULAR LAMINATES WITH AFFINITY FOR AROMATIC GUESTS. Mike Zaworotko , Kumar S. Biradha, Department of Chemistry, The University of Winnipeg, Winnipeg, Manitoba, CANADA.

That solid state architecture profoundly influences bulk physical properties and therefore function of solids has provided impetus for recent activity in the field of crystal engineering. The nature of crystal engineering means that chemists can design new crystal structures without the need to develop new molecular structures. Rather, the chemist simply has to focus upon multifunctional exodentate moieties and the concept of supramolecular synthons . This presentation will focus upon the development of new classes of layered solid1 that might be of general interest for materials or separations applications. We shall present recent results involving organic solids based upon simple acids such as trimesic acid and trimellitic acid and discuss their significance in the following contexts: 1) what impact will crystal engineering have upon design and synthesis of covalent polymers?; 2) what opportunities might there be for applications of the new materials?
1. Sharma, C.V.K.; Zaworotko, M.J.; Rogers, R.D., 1997. Supramolecular Laminates'' Chem. Commun. , 1559-1560, 1997.

9:00 AM *U3.2
MOLECULAR SCAFFOLDS FROM DERIVATIVES OF 2,5-DIKETOPIPERAZINE. G. Tayhas R. Palmore , Tzy-Jiun Luo, Mary T. McBride, University of California, Department of Chemistry, Davis, CA; Terry A. Land, James J. DeYoreo, Lawrence Livermore National Laboratory, Livermore, CA.

Derivatives of 2,5-diketopiperazine (DKP) are known to assemble into hydrogen-bonded tapes in their crystalline solids. Hydrogen-bonded tapes can function as scaffolds for positioning guest molecules within the crystalline lattice, and depending on what substituents or guest molecules are chosen, there is the potential for creating solids with new bulk properties. We will describe our efforts at elucidating physical-organic trends between the molecular constituents and their assembly into crystalline solids using several methods of analysis: X-ray diffraction, NMR and IR spectroscopies, in situ atomic force microscopy, co-crystallization techniques and computer modeling.

9:30 AM *U3.3
FROM BENZENE TO 2D- AND 3D-NANOPARTICLES. Klaus Müllen, Max-Planck-Institute for Polymer Research, Mainz, GERMANY.

The benzene ring serves as versatile building block of carbon-rich 2D- and 3D-macromolecules. A novel cycloaddition-deprotection protocol provides dendritic polyphenylenes which are shape persistent 3D-nanoparticles. Suitably designed oligo- and polyphenylenes are transformed into giant polycyclic aromatic hydrocarbons (PAHs) by mild intramolecular cyclodehydrogenation. These PAHs constitute molecular (2D)-models of graphite. Their supramolecular ordering is a key prerequisite when elucidating their role as media for charge carrier transport in molecular electronics. Current-potential curves recorded by scanning tunneling microscopy for single PAH discs and the drastic increase of charge mobility as a result of their liquid-crystalline order in $\pi$-stacked columnar arrays are typical results of their physical characterization.

10:15 AM U3.4
THE EVOLUTION OF ORDERED POLYCRYSTALLINE FILMS DURING VAPOR DEPOSITION OF 4-AMINOBENZOPHENONE AND 4-(N,N-DIMETHYLAMINO)-3-ACETAMIDONITROBENZENE ON ALKALI HALIDE SUBSTRATES. John McAleese, David Sheen , John Sherwood and Qingwu Wang, University of Strathclyde, Department of Pure and Applied Chemistry, Glasgow, Scotland, UNITED KINGDOM.

The polycrystalline films which develop during the vapor deposition of the non-linear optical materials 4-aminobenzophenone (ABP) and 4-(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN) on prebaked KCL or KBr (001) faces show biaxial orientation along [110] and [$\bar{1}$10] directions, in common with many organic materials deposited on these substrates. During deposition, some interesting changes in film morphology have

SYMPOSIUM U Organics with Supramolecular Structure and Function November 30 - December 3, 1998 Chairs

Martin Bryce          Christopher Ober

Dept of Chemistry        Dept of MS&E

Univ of Durham          Cornell Univ

Durham,  DH1 3LE UNITED KINGDOM        327 Bard Hall

44-191-374-3118          Ithaca, NY 14853

607-255-8417

Michael Ward
Chemical Engineering and Materials Science
Univ of Minnesota
151 Amundson Hall
Minneapolis, MN 55455
612-625-3062

Symposium Support
*Army Research Office

* Invited paper

SESSION U1: MOLECULAR RECOGNITION IN SUPRAMOLECULAR SOLIDS
Chair: Bruce M. Foxman
Monday Morning, November 30, 1998
America South (W)
8:30 AM U1.1
CRYSTAL ENGINEERING OF DIAMONDOID NETWORKS FOR SECOND-ORDER NONLINEAR OPTICAL APPLICATIONS. Wenbin Lin , Zhiyong Wang, Ren-Gen Xiong, Department of Chemistry, Brandeis University, Waltham, MA.

The design of organic and metal-organic diamondoid frameworks has received considerable attention over the past decade, in part, because of the recognition that daimondoid networks have high propensity to pack in acentric space groups as a result of the lack of an inversion center. Acentric solids and thin films are of great interest owing to their potential applications as second-order nonlinear optical (NLO) materials. In fact, one of the best known inorganic second-order nonlinear optical materials, potassium dideuterophosphate (KDP), crystallizes as a diamondoid network. Despite the intense search over the past decade, acentric organic and metal-organic diamondoid frameworks have not been rationally synthesized to date. We have designed a novel approach to crystal engineering of acentric metal-organic diamondoid frameworks for second-order NLO applications. Our strategy relies on the use of four- or six- coordinate metal centers in combination with unsymmetrical, bifunctional linker groups. For example, both bis(isonicotinato)zinc and cadmium bis(4-pyridylacrylic acid) have been prepared hydrothermally. They both crystallize in acentric space groups, and possess a three-fold and five-fold interpenetrated diamondoid structure, respectively. Preliminary second harmonic generation measurements showed that these diamondoid networks exhibit second-order NLO efficiencies comparable to technologically important lithium niobate.

8:45 AM U1.2
ENGINEERING MIXED CRYSTALS. Bart Kahr , Loyd Bastin, Anand Subramony, Rich Gurney, Christine Mitchell.

While a great deal of effort recently has been directed at the design of molecular crystalline materials, especially by exploiting hydrogen bonds, little attention has been paid to the design of dilute solid solutions even though for some optical and spectroscopic applications molecules that are oriented and isolated from one another are requisite. We have been seeking to identify the prevailing intermolecular forces that determine for formation of dye inclusion crystals (DICs), simple crystalline substances that contain organic chromophores oriented and isolated in particular sectors during growth from solution. In this paper, we focus on orienting organic dyes within otherwise single crystals of inorganic salts such as potassium sulfate, potassium dihydrogen phosphate, and barium acetate. We emphasize the use of such crystals in chemical analysis, the determination of crystal growth mechanisms, and in the stabilization of reactive intermediates and electronically excited states.

9:00 AM *U1.3
SUPRAMOLECULAR CONTROL OF THE BULK MAGNETIC PROPERTIES OF MANGANOPORPHRYIN-BASED MAGNETS. Joel S. Miller , University of Utah, Dept. of Chemistry, Salt Lake City, UT; Arthur J. Epstein, The Ohio State University, Dept. of Physics and Dept. of Chemistry, Columbus, OH.

Coordination polymer-based magnets comprised of alternating [Mn(III)(porphryrin)]+ and [A]- (A = TCNE, TCNQ, C4(CN)6, chloranil) have been prepared and structurally and magnetically characterized. The [A]- is trans-$\mu$-bound to two adjacent Mn(III) sites in the chain. Adjacent sites exhibit antiferromagnetic coupling between the S = 1/2 [A]- quantum spin and the S = 2 Mn(III) classical spin and magnetic order occurs below 25 K. The intrachain coupling, as evidence by increasing Tmin, and fits to the Seiden expression for isolated chains comprised of alternating quantum {S = 1/2; [A].-} and classical {S = 2; [Mn(III)porphryrin)]+} spins is correlated with decreasing MnN4 - [TCNE]- dihedral angles. MO calculations identify the key overlap due to the sigma-dz2/pz on the [TCNE]- N bound to the Mn(III). Use of octaethylporphyrin leads to a antiferromagnet whereas use of tetraphenylporphryin and substituted tetraphenylporphryin leads to magnets with interchain ferromagnetic coupling and ferrimagnetic behavior. The differing magnetic behavior is attributed to enhanced ferromagnetic dipolar interactions for the latter class of magnets. The magneto-structure correlation as well as recent developments in this class of materials will be discussed.

9:30 AM U1.4
SOLID-STATE STRUCTURAL ORDERING IN STABLE ORGANIC RADICALS. Paul M. Lahti , Jacqueline Ferrer, Univ of Massachusetts, Dept of Chemistry, Amherst, MA; Clifford George, Naval Research Laboratory, Washington, DC.

Recent work in organic molecular magnetic materials has included efforts to design specific hydrogen-bonded and dipolar solid state interactions, which will act to assemble stable radicals into relative orientations that favor intermolecular ferromagnetic exchange interactions. We describe work aimed at design of such systems, with primary focus on one example, benzimidazole-2-tert-butyl-nitroxide (BIm-tBN). BIm-tBN forms stacks of molecules that are H-bonded together to produce a highly organized, centrosymmetric crystal structure. The relationship of isolated-molecule properties such as spin density distribution (investigated by ESR spectroscopy and DFT computations) to typical models for intermolecular exchange in the solid state will be outlined for this example, as well as prospects for extensions to related systems.

9:45 AM U1.5
SELF-ASSEMBLY OF LAYERED COORDINATION NETWORKS WITH CLAY-LIKE PROPERTIES. George K. H. Shimizu , Univ of Calgary, Dept of Chemistry, Calgary, Alberta, CANADA; Gary D. Enright, Chris I. Ratcliffe, Gabriela S. Rego, John A. Ripmeester, Dan D. M. Wayner, National Research Council of Canada, Steacie Institute for Molecular Sciences, Ottawa, Ontario, CANADA.

Clays and zeolites are rigid framework aluminosilicates with layered and channel motifs, respectively. From a metal coordination chemistry standpoint, these networks provide attractive model compounds owing to their robust nature, porousity and functionality. This presentation will discuss a family of lamellar metal coordination compounds, generated from fundamental design principles, and it's analogy to clay-like materials. A novel dithia ligand, designed to favor the formation of infinite frameworks, was synthesized and found to form a layered solid with silver(I). The observed structure is versatile as it can be tuned by changing the anion, ancillary ligands on the metals, or, significantly, by functionalizing the ligand itself. The prospect of organic derivatization offers a wide range of structural options and hence, variation in the physical properties of these complexes. Studies to date show interlayer swelling in the presence of solvent, selectivity in inclusion behavior and ion exchange ability.

10:15 AM U1.6
ETHYNYL-SUBSTITUTED TETRAHEDRAL MOLECULES: BUILDING BLOCKS FOR 3D-NETWORKS. Elena Galoppini , Wenzhuo Guo, Quiongying Fu, Rutgers University, Department of Chemistry, Newark, NJ; Richard Gilardi, Laboratory for the Structure of Matter, The Naval Research Laboratory, Washington, DC.

The ability to design organic crystals or polymers with large and dimensionally-fixed cavities may lead to materials exhibiting unprecedented and possibly useful properties. As part of this interest, we are studying molecules capable of selective and strongly directional intermolecular interactions (such as hydrogen bonds) and which may pack in a predictable manner. We present the synthesis and crystal structure of molecules with a tetrahedral core, such as methane and adamantane, substituted at the four vertices with phenylacetylenic units or phenylboronic esters. The tetrahedral core provides a rigid scaffold, which maintains fixed the orientation of the rod-like functional groups. Hydrogen bonding, metal-ligand coordination, polymerization reactions were used to connect the building blocks. Such molecules form diamondoid' crystals, three-dimensional networks obtained by connecting the four vertices of tetrahedra and which resemble the diamond structure.

10:30 AM *U1.7
MOLECULAR ENGINEERING OF NON-CENTROSYMMETRIC FILMS FOR NONLINEAR OPTICAL APPLICATIONS. Geoffrey J. Ashwell , Cranfield University, Molecular Electronics, Cranfield, UNITED KINGDOM.

Interest in Langmuir-Blodgett (LB) films for second-harmonic generation (SHG) stems from the requirement that the structure must be non-centrosymmetric and from the fact that the LB technique allows control of the packing at the molecular level. Amphiphilic materials, those with a hydrophilic head and a hydrophobic tail, may be aligned at the air-water interface but, when deposited, the layers tend to pack centrosymmetrically with the interfaces being alternately hydrophilic (head-to-head) and hydrophobic (tail-to-tail). This may be overcome by considering the molecular criteria for non-centrosymmetric deposition and, at Cranfield, Z-type structures have been routinely obtained by rendering the chromophore hydrophobic at both ends. This causes the LB film surface to be invariably hydrophobic and suppresses the natural tendency of the molecules to invert during deposition. There is a narrow range of alkyl chain lengths which allows the films to be non-centrosymmetric but long-term stability has been realised by considering the compatibility of the end groups within the multilayer. When carefully selected, non-centrosymmetric alignment arises and the second-harmonic intensity increases quadratically with the number of layers, i.e. as I(N)2w= I(1)2w N2, to thicknesses suitable for waveguiding. The lecture will focus on the optimisation of the nonlinear optical properties of LB films of a novel dye, E-4-[(N-octadecyl-6,7,8-trihydro-5-isoquinolylidene)methyl]-N,N-dibutylaniline octadecylsulfate. The films are transparent at the fundamental frequency and only slightly absorbing at the second-harmonic. Nonetheless, the susceptibility is high ($\chi$zzz(2) = 76 pm V-1 at 1.064 $\mu$m for I = 3.15 nm layer-1) and the second-harmonic intensity is the strongest to date from a weakly absorbing film.

11:00 AM *U1.8
GAS SORPTION ISOTHERMS FOR DESIGNED MICROPOROUS METAL-ORGANIC MATERIALS. O.M. Yaghi , Hailian Li, and Mohamed Eddaoudi, Arizona State University, Department of Chemistry and Biochemistry, Tempe, AZ.

Despite the exponential growth in the number of reports on crystalline metal-organic materials with open-framework structures, studies focusing on establishing their gas sorption isotherms and thus microporosity, remain largely unknown. This presentation will show that permanent micrOporosity, similar to that commonly observed in zeolites, can be achieved with metal-organic open frameworks. Gas sorption isotherm, surface area, and pore volume measurements for materials such as Zn(BDC)$\cdot$(DMF)(H20) having 5-15 $\AA$ diameter apertures will be presented. Key aspects to developing strategies for producing rigid and stable metal-organic frameworks with extended channels will be outlined.

11:30 AM *U1.9
TETRATHIAFULVALENES: VERSATILE BUILDING BLOCKS IN MACROCYCLIC AND SUPRAMOLECULAR CHEMISTRY. Jan Becher , Department of Chemistry, Odense University, Odense M, DENMARK.

The effective syntheses of a variety of tetrathiafulvalene building blocks, including pyrrolo- and 2,5-dihydropyrrolo-fused tetrathiafulvalenes have been developed, allowing easy construction and preparation of complex molecular assemblies. The facile deprotection of the 2-cyanoethyl group, a versatile protecting group for 1,3-dithiolium-2-thione-4,5-dithiolates and tetrathiafulvalene-thiolates (1), is an excellent method for the incorporation of tetrathiafulvalene units into macrocyclic and supramolecular compounds. The selective and stepwise protection-deprotection methodology have been used extensively by our group for the preparation of two and three dimensional macrocyclic (mono-, bis- and tricyclic) as well as tetrathiafulvalene-based supramolecular systems (2). Utilization of the thiolates generated by the new methodology are illustrated by recent examples of oligomeric and supramolecular tetrathiafulvalene-based systems, such as: Dendritic (3) and oligo-tetrathiafulvalenes, three dimensional tetrathiafulvalenophanes, tetrathiafulvalene-containing catenanes (4) or rotaxanes (5) as well as donor acceptor systems based on tetrathiafulvalene as the donating group.
References
1.    M. B. Nielsen, S. B. Nielsen and J. Becher, Self complexing Tetrathiafulvalene Macrocycles, a Tetrathiafulvalene Switch'', Chem. Commun., 1998, 475.
2.    M. B. Nielsen, N. Thorup and J. Becher, Synthesis of a criss-cross overlapped Tetrathiafulvalenophane and a topologically new [2]catenane'', J. Chem. Soc. Perkin 1, 1998, 1305.
3.    C. A. Christensen, L. M. Goldenberg, M. R. Bryce and J. Becher, Synthesis and electrochemistry of a tetrathiafulvalene (TTF)21-glycol dendrimer'', Chem. Commun., 1998, 509.
4.    K. B. Simonsen and J. Becher, Tetrathiafulvalene Thiolates'', Synlett, 1997, 1211. 5.    M. B. Nielsen and J. Becher, Two- and Three-Dimensional Tetrathiafulvalene Macrocycles'', Liebigs Ann/Recueil, 1997, 2177.

SESSION U2: MOLECULAR RECOGNITION IN SUPRAMOLECULAR SOLIDS (continued)
Chair: Omar M. Yaghi
Monday Afternoon, November 30, 1998
America South (W)
1:30 PM *U2.1
SYNTHESIS AND PROPERTIES OF HELICAL AROMATIC MOLECULES THAT SELF-ASSEMBLE INTO COLUMNS. Thomas J. Katz , Colin Nuckolls, Joseph M. Fox, Columbia Univ, Dept of Chemistry, New York, NY; Thierry Verbiest, Sven Van Elschocht, and André Persoons, K.U. Leuven, Laboratory of Chemical and Biological Dynamics, Leuven, BELGIUM; Andrew J. Lovinger, Bell Labs, Lucent Technologies, Murray Hill, NJ.

Molecules that resemble those forming chiral discotic mesophases, but whose core ring systems are twisted helically, have been synthesized in nonracemic form. Some self-assemble into columnar structures in solution, as do the pure materials in bulk and in Langmuir-Blodgett films. When they assemble, the circular dichroisms, specific rotations, and second harmonic generating ability all greatly increase. The circular dichroisms of one of the self-assembling materials is sufficiently large that it can be measured easily from a single monolayer. The long wavelength circular dichroisms of the synthesized helical metal-phthalocyanines split.
Unlike the nonracemic self-assembling molecules, the racemic ones do not organize into similarly large structures, and their second-harmonic generating ability is small. Among the materials prepared is the first columnar mesophase that has a nonracemic helical core.

2:00 PM *U2.2
FUNCTIONAL SUPRAMOLECULAR AND MACROMOLECULAR DENDRIMERS ON A LATTICE. V. Percec , The W.M. Keck Laboratories for Organic Synthesis, Department of Macromolecular Science, Case Western Reserve University, Cleveland, OH.

This presentation will discuss the elaboration of the first library of functional dendrons that self-assemble into cylindrical and spherical supramolecular dendrimers which subsequently self-organize into various cubic or columnar hexagonal lattices. Retrosynthetic analyses of these lattices by XRD allows the design of various classes of monomeric dendrons which after polymerization produce polymers with various architectures and shapes that self-organize in similar lattices with those of the parent supramolecular dendritic synthons. Applications in various areas of material science will be discussed.

2:30 PM U2.3
TEMPLATE DIRECTED ARCHITECTURAL ISOMERISM IN OPEN MOLECULAR FRAMEWORKS. Jennifer A. Swift , Adam M. Pivovar, Michael D. Ward, University of Minnesota, Department of Chemical Engineering and Materials Science, Minneapolis, MN.

Highly porous host lattices based on resilient 2-dimensional guanidinium-sulfonate hydrogen bonded networks that are connected continuously in the third dimension by 4,4'-biphenyldisulfonate pillars to generate a brick-like framework are described. The brick framework is a predictable architectural isomer of a previously observed guanidinium-sulfonate host lattice consisting of discrete bilayers. The amount of void space in the brick framework is nominally twice that of the bilayer form, with the framework occupying only 30% of the total volume. The host framework conforms to the different steric demands and occupancies of various aromatic guests by puckering of the flexible, yet resilient, hydrogen bonded network and by rotation (and/or twisting) of the pillars about their long axes, the latter also governing the width of the pores in the framework. The formation of the brick architecture can be attributed to steric templating by the included molecular guests and host-guest interactions that favor assembly of this framework over its bilayer counterpart. Inclusion of select guest molecules in brick frameworks yields polar crystals. Formation of such polar materials may be attributed to correlated guest-host-guest interactions, mediated through the corrugated guanidinium-sulfonate sheets. Development of these materials may yield a new class of NLO materials.

2:45 PM U2.4
NANOPARTICLE ENCAPSULATION USING RESORCINARENE-BASED SYSTEMS. Kevin B. Stavens, Stephen V. Pusztay, Ronald P. Andres, Alexander Wei , Purdue University, Depts. of Chemistry and Chemical Engineering, West Lafayette, IN.

Resorcinol-based calix[4]arenes (resorcinarenes) have demonstrated excellent potential for encapsulating and stabilizing nanosized particles. Gold clusters 2-5 nm in diameter were generated by vapor- and solution-phase techniques and were captured in millimolar hydrocarbon solutions of resorcinarenes and other surfactants. The capture efficiency of Au nanoparticles using resorcinarenes was several times greater relative to alkanethiols. Nanoparticles stabilized by several resorcinarene and binary resorcinarene-thiol systems were characterized by absorption spectroscopy and transmission electron microscopy. It was found that hydrogen bonding is an important factor in both capture efficiency and aggregate stability. The potential of resorcinarene-based encapsulation systems for creating ordered nanostructures will be discussed.

3:15 PM *U2.5
DESIGN, DISCOVERY AND SYNTHESIS OF REACTIVE SUPRAMOLECULAR ARRAYS. Bruce M. Foxman , Brandeis University, Dept. of Chemistry, Waltham, MA.

A supramolecular organic array, with an organized set of reactive groups, provides an opportunity to carry out either stereospecific or regiospecific chemical reactions, and/or reactions that cannot be performed in solution. Of course, not every array affords such an opportunity, and we must consider both the principles required for successful assembly, as well as experience-based procedures, to ensure success. While there is a considerable database of solid-state reactions, the number of new reaction classes has increased only slowly, with a consequent slow growth in design principles. As part of the concept of crystal engineering we can use our knowledge of molecular solid-state chemistry, crystal packing, and chemical reactivity to produce reactive materials. In recent years, we have designed several solid-state reactions by using structural analogies derived from the Cambridge Structural Database (three examples from organic and metal-organic chemistry will be discussed). Following the initial design work, we developed two new series of metal salts and complexes with unique reactivity properties. Solid metal alkynoates and alkenoates undergo oligomerization and polymerization reactions when exposed to Co-60 gamma-rays. For example, irradiation of solid sodium trans-2-butenoate leads to a linear trimer, one of eight possible diastereomers, in high yield. Studies of crystalline metal complexes containing such unsaturated ligands provide new insight into solid-state reactivity. In addition to the use of hydrogen bonding and bilayer interactions as agents for the production of reactive phases, changes in metal ion within an isomorphous set of structures may have profound effects on reactivity. The discussion will include a review of our expanding database of engineered reactive molecular crystals, and the implications of recent results on design criteria.

3:45 PM *U2.6
THE HYDROGEN BOND AND CRYSTAL ENGINEERING: CONSTRUCTING PREDICTABLE MOLECULAR ARCHITECTURES. Christer B. Aakeroy , Department of Chemistry, Kansas State University, Manhattan, KS.

Crystal engineering is governed by the nature and structural consequences of intermolecular forces, and the way in which such interactions are utilized for controlling the assembly of molecules into predictable structural motifs. A vital part of crystal engineering is therefore dedicated to the identification of robust intermolecular synthons that can be used as reliable connectors (microscopic ÎglueÌ) between molecules.
We have demonstrated that certain organic molecular building blocks have a propensity to form low-dimensional assemblies (chains, ribbons, layers) via complementary N-H...O, C-H...O and O-H...O hydrogen bonds. Through systematic structural studies of closely related compounds, we have been able to derive some guidelines for how we can design and build robust molecular scaffolding that can form the structural backbone in new functional solids. Furthermore, in an effort to design new transition-metal containing materials, we have combined the geometric features of well-known coordination chemistry (notably of silver(I)) with intermolecular connectors with a view to examining how the structural balance in such materials is determined by competition and/or collaboration between intermolecular synthons and the spatial requirements of transition-metal complexes.

4:15 PM U2.7
THE BINARY APPROACH TO SUPRAMOLECULAR STRUCTURE AND FUNCTION. Joseph W. Lauher , Frank W. Fowler, State University of New York, Department of Chemistry, Stony Brook, NY.

The function of a supramolecular entity depends upon the chemical composition and nature of the constituent molecules, as well as the symmetry and spatial properties of the assembly of molecules. Since one has little control over the actual supramolecular properties of a given molecule, one must approach a synthesis with a focus on the final supramolecular goal, as opposed to a focus on the identity of the individual molecules. A realization of the final goal may require the achievement of a specific structure, a specific function or both, since function often depends upon structure.
We have developed a binary approach to this problem, using one molecule to control the structure of a supramolecular assembly, while the second provides the function. Our approach is based upon a library of chemical functionalities that lead to predictable structural patterns based upon persistent patterns of hydrogen bonds. Molecules possessing these functionalities can be synthesized and used to control and determine supramolecular structure. A second functionality is added as a handle to control the second molecular entity, the one that provides the function or completes the structure of the final product. For this we have used a variety of interactions, including hydrogen bonds, metal-ligand coordination and halide-nitrogen interactions. Successful applications of the technique include the synthesis of a wide variety of layered structures, designed diacetylene polymerizations and the controlled spacing of metal atoms.

4:30 PM *U2.8
Wais Hosseini , Univ Louis Pasteur, Strasbourg, FRANCE.

Abstract Not Available

SESSION U3: THIN FILMS AND LAYERED STRUCTURES
Chair: Neal R. Armstrong
Tuesday Morning, December 1, 1998
America South (W)
8:30 AM *U3.1
SUPRAMOLECULAR LAMINATES WITH AFFINITY FOR AROMATIC GUESTS. Mike Zaworotko , Kumar S. Biradha, Department of Chemistry, The University of Winnipeg, Winnipeg, Manitoba, CANADA.

That solid state architecture profoundly influences bulk physical properties and therefore function of solids has provided impetus for recent activity in the field of crystal engineering. The nature of crystal engineering means that chemists can design new crystal structures without the need to develop new molecular structures. Rather, the chemist simply has to focus upon multifunctional exodentate moieties and the concept of supramolecular synthons . This presentation will focus upon the development of new classes of layered solid1 that might be of general interest for materials or separations applications. We shall present recent results involving organic solids based upon simple acids such as trimesic acid and trimellitic acid and discuss their significance in the following contexts: 1) what impact will crystal engineering have upon design and synthesis of covalent polymers?; 2) what opportunities might there be for applications of the new materials?
1. Sharma, C.V.K.; Zaworotko, M.J.; Rogers, R.D., 1997. Supramolecular Laminates'' Chem. Commun. , 1559-1560, 1997.

9:00 AM *U3.2
MOLECULAR SCAFFOLDS FROM DERIVATIVES OF 2,5-DIKETOPIPERAZINE. G. Tayhas R. Palmore , Tzy-Jiun Luo, Mary T. McBride, University of California, Department of Chemistry, Davis, CA; Terry A. Land, James J. DeYoreo, Lawrence Livermore National Laboratory, Livermore, CA.

Derivatives of 2,5-diketopiperazine (DKP) are known to assemble into hydrogen-bonded tapes in their crystalline solids. Hydrogen-bonded tapes can function as scaffolds for positioning guest molecules within the crystalline lattice, and depending on what substituents or guest molecules are chosen, there is the potential for creating solids with new bulk properties. We will describe our efforts at elucidating physical-organic trends between the molecular constituents and their assembly into crystalline solids using several methods of analysis: X-ray diffraction, NMR and IR spectroscopies, in situ atomic force microscopy, co-crystallization techniques and computer modeling.

9:30 AM *U3.3
FROM BENZENE TO 2D- AND 3D-NANOPARTICLES. Klaus Müllen, Max-Planck-Institute for Polymer Research, Mainz, GERMANY.

The benzene ring serves as versatile building block of carbon-rich 2D- and 3D-macromolecules. A novel cycloaddition-deprotection protocol provides dendritic polyphenylenes which are shape persistent 3D-nanoparticles. Suitably designed oligo- and polyphenylenes are transformed into giant polycyclic aromatic hydrocarbons (PAHs) by mild intramolecular cyclodehydrogenation. These PAHs constitute molecular (2D)-models of graphite. Their supramolecular ordering is a key prerequisite when elucidating their role as media for charge carrier transport in molecular electronics. Current-potential curves recorded by scanning tunneling microscopy for single PAH discs and the drastic increase of charge mobility as a result of their liquid-crystalline order in $\pi$-stacked columnar arrays are typical results of their physical characterization.

10:15 AM U3.4
THE EVOLUTION OF ORDERED POLYCRYSTALLINE FILMS DURING VAPOR DEPOSITION OF 4-AMINOBENZOPHENONE AND 4-(N,N-DIMETHYLAMINO)-3-ACETAMIDONITROBENZENE ON ALKALI HALIDE SUBSTRATES. John McAleese, David Sheen , John Sherwood and Qingwu Wang, University of Strathclyde, Department of Pure and Applied Chemistry, Glasgow, Scotland, UNITED KINGDOM.

The polycrystalline films which develop during the vapor deposition of the non-linear optical materials 4-aminobenzophenone (ABP) and 4-(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN) on prebaked KCL or KBr (001) faces show biaxial orientation along [110] and [$\bar{1}$10] directions, in common with many organic materials deposited on these substrates. During deposition, some interesting changes in film morphology have

SYMPOSIUM U Organics with Supramolecular Structure and Function November 30 - December 3, 1998 Chairs

Martin Bryce          Christopher Ober

Dept of Chemistry        Dept of MS&E

Univ of Durham          Cornell Univ

Durham,  DH1 3LE UNITED KINGDOM        327 Bard Hall

44-191-374-3118          Ithaca, NY 14853

607-255-8417

Michael Ward
Chemical Engineering and Materials Science
Univ of Minnesota
151 Amundson Hall
Minneapolis, MN 55455
612-625-3062

Symposium Support
*Army Research Office

* Invited paper

SESSION U1: MOLECULAR RECOGNITION IN SUPRAMOLECULAR SOLIDS
Chair: Bruce M. Foxman
Monday Morning, November 30, 1998
America South (W)
8:30 AM U1.1
CRYSTAL ENGINEERING OF DIAMONDOID NETWORKS FOR SECOND-ORDER NONLINEAR OPTICAL APPLICATIONS. Wenbin Lin , Zhiyong Wang, Ren-Gen Xiong, Department of Chemistry, Brandeis University, Waltham, MA.

The design of organic and metal-organic diamondoid frameworks has received considerable attention over the past decade, in part, because of the recognition that daimondoid networks have high propensity to pack in acentric space groups as a result of the lack of an inversion center. Acentric solids and thin films are of great interest owing to their potential applications as second-order nonlinear optical (NLO) materials. In fact, one of the best known inorganic second-order nonlinear optical materials, potassium dideuterophosphate (KDP), crystallizes as a diamondoid network. Despite the intense search over the past decade, acentric organic and metal-organic diamondoid frameworks have not been rationally synthesized to date. We have designed a novel approach to crystal engineering of acentric metal-organic diamondoid frameworks for second-order NLO applications. Our strategy relies on the use of four- or six- coordinate metal centers in combination with unsymmetrical, bifunctional linker groups. For example, both bis(isonicotinato)zinc and cadmium bis(4-pyridylacrylic acid) have been prepared hydrothermally. They both crystallize in acentric space groups, and possess a three-fold and five-fold interpenetrated diamondoid structure, respectively. Preliminary second harmonic generation measurements showed that these diamondoid networks exhibit second-order NLO efficiencies comparable to technologically important lithium niobate.

8:45 AM U1.2
ENGINEERING MIXED CRYSTALS. Bart Kahr , Loyd Bastin, Anand Subramony, Rich Gurney, Christine Mitchell.

While a great deal of effort recently has been directed at the design of molecular crystalline materials, especially by exploiting hydrogen bonds, little attention has been paid to the design of dilute solid solutions even though for some optical and spectroscopic applications molecules that are oriented and isolated from one another are requisite. We have been seeking to identify the prevailing intermolecular forces that determine for formation of dye inclusion crystals (DICs), simple crystalline substances that contain organic chromophores oriented and isolated in particular sectors during growth from solution. In this paper, we focus on orienting organic dyes within otherwise single crystals of inorganic salts such as potassium sulfate, potassium dihydrogen phosphate, and barium acetate. We emphasize the use of such crystals in chemical analysis, the determination of crystal growth mechanisms, and in the stabilization of reactive intermediates and electronically excited states.

9:00 AM *U1.3
SUPRAMOLECULAR CONTROL OF THE BULK MAGNETIC PROPERTIES OF MANGANOPORPHRYIN-BASED MAGNETS. Joel S. Miller , University of Utah, Dept. of Chemistry, Salt Lake City, UT; Arthur J. Epstein, The Ohio State University, Dept. of Physics and Dept. of Chemistry, Columbus, OH.

Coordination polymer-based magnets comprised of alternating [Mn(III)(porphryrin)]+ and [A]- (A = TCNE, TCNQ, C4(CN)6, chloranil) have been prepared and structurally and magnetically characterized. The [A]- is trans-$\mu$-bound to two adjacent Mn(III) sites in the chain. Adjacent sites exhibit antiferromagnetic coupling between the S = 1/2 [A]- quantum spin and the S = 2 Mn(III) classical spin and magnetic order occurs below 25 K. The intrachain coupling, as evidence by increasing Tmin, and fits to the Seiden expression for isolated chains comprised of alternating quantum {S = 1/2; [A].-} and classical {S = 2; [Mn(III)porphryrin)]+} spins is correlated with decreasing MnN4 - [TCNE]- dihedral angles. MO calculations identify the key overlap due to the sigma-dz2/pz on the [TCNE]- N bound to the Mn(III). Use of octaethylporphyrin leads to a antiferromagnet whereas use of tetraphenylporphryin and substituted tetraphenylporphryin leads to magnets with interchain ferromagnetic coupling and ferrimagnetic behavior. The differing magnetic behavior is attributed to enhanced ferromagnetic dipolar interactions for the latter class of magnets. The magneto-structure correlation as well as recent developments in this class of materials will be discussed.

9:30 AM U1.4
SOLID-STATE STRUCTURAL ORDERING IN STABLE ORGANIC RADICALS. Paul M. Lahti , Jacqueline Ferrer, Univ of Massachusetts, Dept of Chemistry, Amherst, MA; Clifford George, Naval Research Laboratory, Washington, DC.

Recent work in organic molecular magnetic materials has included efforts to design specific hydrogen-bonded and dipolar solid state interactions, which will act to assemble stable radicals into relative orientations that favor intermolecular ferromagnetic exchange interactions. We describe work aimed at design of such systems, with primary focus on one example, benzimidazole-2-tert-butyl-nitroxide (BIm-tBN). BIm-tBN forms stacks of molecules that are H-bonded together to produce a highly organized, centrosymmetric crystal structure. The relationship of isolated-molecule properties such as spin density distribution (investigated by ESR spectroscopy and DFT computations) to typical models for intermolecular exchange in the solid state will be outlined for this example, as well as prospects for extensions to related systems.

9:45 AM U1.5
SELF-ASSEMBLY OF LAYERED COORDINATION NETWORKS WITH CLAY-LIKE PROPERTIES. George K. H. Shimizu , Univ of Calgary, Dept of Chemistry, Calgary, Alberta, CANADA; Gary D. Enright, Chris I. Ratcliffe, Gabriela S. Rego, John A. Ripmeester, Dan D. M. Wayner, National Research Council of Canada, Steacie Institute for Molecular Sciences, Ottawa, Ontario, CANADA.

Clays and zeolites are rigid framework aluminosilicates with layered and channel motifs, respectively. From a metal coordination chemistry standpoint, these networks provide attractive model compounds owing to their robust nature, porousity and functionality. This presentation will discuss a family of lamellar metal coordination compounds, generated from fundamental design principles, and it's analogy to clay-like materials. A novel dithia ligand, designed to favor the formation of infinite frameworks, was synthesized and found to form a layered solid with silver(I). The observed structure is versatile as it can be tuned by changing the anion, ancillary ligands on the metals, or, significantly, by functionalizing the ligand itself. The prospect of organic derivatization offers a wide range of structural options and hence, variation in the physical properties of these complexes. Studies to date show interlayer swelling in the presence of solvent, selectivity in inclusion behavior and ion exchange ability.

10:15 AM U1.6
ETHYNYL-SUBSTITUTED TETRAHEDRAL MOLECULES: BUILDING BLOCKS FOR 3D-NETWORKS. Elena Galoppini , Wenzhuo Guo, Quiongying Fu, Rutgers University, Department of Chemistry, Newark, NJ; Richard Gilardi, Laboratory for the Structure of Matter, The Naval Research Laboratory, Washington, DC.

The ability to design organic crystals or polymers with large and dimensionally-fixed cavities may lead to materials exhibiting unprecedented and possibly useful properties. As part of this interest, we are studying molecules capable of selective and strongly directional intermolecular interactions (such as hydrogen bonds) and which may pack in a predictable manner. We present the synthesis and crystal structure of molecules with a tetrahedral core, such as methane and adamantane, substituted at the four vertices with phenylacetylenic units or phenylboronic esters. The tetrahedral core provides a rigid scaffold, which maintains fixed the orientation of the rod-like functional groups. Hydrogen bonding, metal-ligand coordination, polymerization reactions were used to connect the building blocks. Such molecules form diamondoid' crystals, three-dimensional networks obtained by connecting the four vertices of tetrahedra and which resemble the diamond structure.

10:30 AM *U1.7
MOLECULAR ENGINEERING OF NON-CENTROSYMMETRIC FILMS FOR NONLINEAR OPTICAL APPLICATIONS. Geoffrey J. Ashwell , Cranfield University, Molecular Electronics, Cranfield, UNITED KINGDOM.

Interest in Langmuir-Blodgett (LB) films for second-harmonic generation (SHG) stems from the requirement that the structure must be non-centrosymmetric and from the fact that the LB technique allows control of the packing at the molecular level. Amphiphilic materials, those with a hydrophilic head and a hydrophobic tail, may be aligned at the air-water interface but, when deposited, the layers tend to pack centrosymmetrically with the interfaces being alternately hydrophilic (head-to-head) and hydrophobic (tail-to-tail). This may be overcome by considering the molecular criteria for non-centrosymmetric deposition and, at Cranfield, Z-type structures have been routinely obtained by rendering the chromophore hydrophobic at both ends. This causes the LB film surface to be invariably hydrophobic and suppresses the natural tendency of the molecules to invert during deposition. There is a narrow range of alkyl chain lengths which allows the films to be non-centrosymmetric but long-term stability has been realised by considering the compatibility of the end groups within the multilayer. When carefully selected, non-centrosymmetric alignment arises and the second-harmonic intensity increases quadratically with the number of layers, i.e. as I(N)2w= I(1)2w N2, to thicknesses suitable for waveguiding. The lecture will focus on the optimisation of the nonlinear optical properties of LB films of a novel dye, E-4-[(N-octadecyl-6,7,8-trihydro-5-isoquinolylidene)methyl]-N,N-dibutylaniline octadecylsulfate. The films are transparent at the fundamental frequency and only slightly absorbing at the second-harmonic. Nonetheless, the susceptibility is high ($\chi$zzz(2) = 76 pm V-1 at 1.064 $\mu$m for I = 3.15 nm layer-1) and the second-harmonic intensity is the strongest to date from a weakly absorbing film.

11:00 AM *U1.8
GAS SORPTION ISOTHERMS FOR DESIGNED MICROPOROUS METAL-ORGANIC MATERIALS. O.M. Yaghi , Hailian Li, and Mohamed Eddaoudi, Arizona State University, Department of Chemistry and Biochemistry, Tempe, AZ.

Despite the exponential growth in the number of reports on crystalline metal-organic materials with open-framework structures, studies focusing on establishing their gas sorption isotherms and thus microporosity, remain largely unknown. This presentation will show that permanent micrOporosity, similar to that commonly observed in zeolites, can be achieved with metal-organic open frameworks. Gas sorption isotherm, surface area, and pore volume measurements for materials such as Zn(BDC)$\cdot$(DMF)(H20) having 5-15 $\AA$ diameter apertures will be presented. Key aspects to developing strategies for producing rigid and stable metal-organic frameworks with extended channels will be outlined.

11:30 AM *U1.9
TETRATHIAFULVALENES: VERSATILE BUILDING BLOCKS IN MACROCYCLIC AND SUPRAMOLECULAR CHEMISTRY. Jan Becher , Department of Chemistry, Odense University, Odense M, DENMARK.

The effective syntheses of a variety of tetrathiafulvalene building blocks, including pyrrolo- and 2,5-dihydropyrrolo-fused tetrathiafulvalenes have been developed, allowing easy construction and preparation of complex molecular assemblies. The facile deprotection of the 2-cyanoethyl group, a versatile protecting group for 1,3-dithiolium-2-thione-4,5-dithiolates and tetrathiafulvalene-thiolates (1), is an excellent method for the incorporation of tetrathiafulvalene units into macrocyclic and supramolecular compounds. The selective and stepwise protection-deprotection methodology have been used extensively by our group for the preparation of two and three dimensional macrocyclic (mono-, bis- and tricyclic) as well as tetrathiafulvalene-based supramolecular systems (2). Utilization of the thiolates generated by the new methodology are illustrated by recent examples of oligomeric and supramolecular tetrathiafulvalene-based systems, such as: Dendritic (3) and oligo-tetrathiafulvalenes, three dimensional tetrathiafulvalenophanes, tetrathiafulvalene-containing catenanes (4) or rotaxanes (5) as well as donor acceptor systems based on tetrathiafulvalene as the donating group.
References
1.    M. B. Nielsen, S. B. Nielsen and J. Becher, Self complexing Tetrathiafulvalene Macrocycles, a Tetrathiafulvalene Switch'', Chem. Commun., 1998, 475.
2.    M. B. Nielsen, N. Thorup and J. Becher, Synthesis of a criss-cross overlapped Tetrathiafulvalenophane and a topologically new [2]catenane'', J. Chem. Soc. Perkin 1, 1998, 1305.
3.    C. A. Christensen, L. M. Goldenberg, M. R. Bryce and J. Becher, Synthesis and electrochemistry of a tetrathiafulvalene (TTF)21-glycol dendrimer'', Chem. Commun., 1998, 509.
4.    K. B. Simonsen and J. Becher, Tetrathiafulvalene Thiolates'', Synlett, 1997, 1211. 5.    M. B. Nielsen and J. Becher, Two- and Three-Dimensional Tetrathiafulvalene Macrocycles'', Liebigs Ann/Recueil, 1997, 2177.

SESSION U2: MOLECULAR RECOGNITION IN SUPRAMOLECULAR SOLIDS (continued)
Chair: Omar M. Yaghi
Monday Afternoon, November 30, 1998
America South (W)
1:30 PM *U2.1
SYNTHESIS AND PROPERTIES OF HELICAL AROMATIC MOLECULES THAT SELF-ASSEMBLE INTO COLUMNS. Thomas J. Katz , Colin Nuckolls, Joseph M. Fox, Columbia Univ, Dept of Chemistry, New York, NY; Thierry Verbiest, Sven Van Elschocht, and André Persoons, K.U. Leuven, Laboratory of Chemical and Biological Dynamics, Leuven, BELGIUM; Andrew J. Lovinger, Bell Labs, Lucent Technologies, Murray Hill, NJ.

Molecules that resemble those forming chiral discotic mesophases, but whose core ring systems are twisted helically, have been synthesized in nonracemic form. Some self-assemble into columnar structures in solution, as do the pure materials in bulk and in Langmuir-Blodgett films. When they assemble, the circular dichroisms, specific rotations, and second harmonic generating ability all greatly increase. The circular dichroisms of one of the self-assembling materials is sufficiently large that it can be measured easily from a single monolayer. The long wavelength circular dichroisms of the synthesized helical metal-phthalocyanines split.
Unlike the nonracemic self-assembling molecules, the racemic ones do not organize into similarly large structures, and their second-harmonic generating ability is small. Among the materials prepared is the first columnar mesophase that has a nonracemic helical core.

2:00 PM *U2.2
FUNCTIONAL SUPRAMOLECULAR AND MACROMOLECULAR DENDRIMERS ON A LATTICE. V. Percec , The W.M. Keck Laboratories for Organic Synthesis, Department of Macromolecular Science, Case Western Reserve University, Cleveland, OH.

This presentation will discuss the elaboration of the first library of functional dendrons that self-assemble into cylindrical and spherical supramolecular dendrimers which subsequently self-organize into various cubic or columnar hexagonal lattices. Retrosynthetic analyses of these lattices by XRD allows the design of various classes of monomeric dendrons which after polymerization produce polymers with various architectures and shapes that self-organize in similar lattices with those of the parent supramolecular dendritic synthons. Applications in various areas of material science will be discussed.

2:30 PM U2.3
TEMPLATE DIRECTED ARCHITECTURAL ISOMERISM IN OPEN MOLECULAR FRAMEWORKS. Jennifer A. Swift , Adam M. Pivovar, Michael D. Ward, University of Minnesota, Department of Chemical Engineering and Materials Science, Minneapolis, MN.

Highly porous host lattices based on resilient 2-dimensional guanidinium-sulfonate hydrogen bonded networks that are connected continuously in the third dimension by 4,4'-biphenyldisulfonate pillars to generate a brick-like framework are described. The brick framework is a predictable architectural isomer of a previously observed guanidinium-sulfonate host lattice consisting of discrete bilayers. The amount of void space in the brick framework is nominally twice that of the bilayer form, with the framework occupying only 30% of the total volume. The host framework conforms to the different steric demands and occupancies of various aromatic guests by puckering of the flexible, yet resilient, hydrogen bonded network and by rotation (and/or twisting) of the pillars about their long axes, the latter also governing the width of the pores in the framework. The formation of the brick architecture can be attributed to steric templating by the included molecular guests and host-guest interactions that favor assembly of this framework over its bilayer counterpart. Inclusion of select guest molecules in brick frameworks yields polar crystals. Formation of such polar materials may be attributed to correlated guest-host-guest interactions, mediated through the corrugated guanidinium-sulfonate sheets. Development of these materials may yield a new class of NLO materials.

2:45 PM U2.4
NANOPARTICLE ENCAPSULATION USING RESORCINARENE-BASED SYSTEMS. Kevin B. Stavens, Stephen V. Pusztay, Ronald P. Andres, Alexander Wei , Purdue University, Depts. of Chemistry and Chemical Engineering, West Lafayette, IN.

Resorcinol-based calix[4]arenes (resorcinarenes) have demonstrated excellent potential for encapsulating and stabilizing nanosized particles. Gold clusters 2-5 nm in diameter were generated by vapor- and solution-phase techniques and were captured in millimolar hydrocarbon solutions of resorcinarenes and other surfactants. The capture efficiency of Au nanoparticles using resorcinarenes was several times greater relative to alkanethiols. Nanoparticles stabilized by several resorcinarene and binary resorcinarene-thiol systems were characterized by absorption spectroscopy and transmission electron microscopy. It was found that hydrogen bonding is an important factor in both capture efficiency and aggregate stability. The potential of resorcinarene-based encapsulation systems for creating ordered nanostructures will be discussed.

3:15 PM *U2.5
DESIGN, DISCOVERY AND SYNTHESIS OF REACTIVE SUPRAMOLECULAR ARRAYS. Bruce M. Foxman , Brandeis University, Dept. of Chemistry, Waltham, MA.

A supramolecular organic array, with an organized set of reactive groups, provides an opportunity to carry out either stereospecific or regiospecific chemical reactions, and/or reactions that cannot be performed in solution. Of course, not every array affords such an opportunity, and we must consider both the principles required for successful assembly, as well as experience-based procedures, to ensure success. While there is a considerable database of solid-state reactions, the number of new reaction classes has increased only slowly, with a consequent slow growth in design principles. As part of the concept of crystal engineering we can use our knowledge of molecular solid-state chemistry, crystal packing, and chemical reactivity to produce reactive materials. In recent years, we have designed several solid-state reactions by using structural analogies derived from the Cambridge Structural Database (three examples from organic and metal-organic chemistry will be discussed). Following the initial design work, we developed two new series of metal salts and complexes with unique reactivity properties. Solid metal alkynoates and alkenoates undergo oligomerization and polymerization reactions when exposed to Co-60 gamma-rays. For example, irradiation of solid sodium trans-2-butenoate leads to a linear trimer, one of eight possible diastereomers, in high yield. Studies of crystalline metal complexes containing such unsaturated ligands provide new insight into solid-state reactivity. In addition to the use of hydrogen bonding and bilayer interactions as agents for the production of reactive phases, changes in metal ion within an isomorphous set of structures may have profound effects on reactivity. The discussion will include a review of our expanding database of engineered reactive molecular crystals, and the implications of recent results on design criteria.

3:45 PM *U2.6
THE HYDROGEN BOND AND CRYSTAL ENGINEERING: CONSTRUCTING PREDICTABLE MOLECULAR ARCHITECTURES. Christer B. Aakeroy , Department of Chemistry, Kansas State University, Manhattan, KS.

Crystal engineering is governed by the nature and structural consequences of intermolecular forces, and the way in which such interactions are utilized for controlling the assembly of molecules into predictable structural motifs. A vital part of crystal engineering is therefore dedicated to the identification of robust intermolecular synthons that can be used as reliable connectors (microscopic ÎglueÌ) between molecules.
We have demonstrated that certain organic molecular building blocks have a propensity to form low-dimensional assemblies (chains, ribbons, layers) via complementary N-H...O, C-H...O and O-H...O hydrogen bonds. Through systematic structural studies of closely related compounds, we have been able to derive some guidelines for how we can design and build robust molecular scaffolding that can form the structural backbone in new functional solids. Furthermore, in an effort to design new transition-metal containing materials, we have combined the geometric features of well-known coordination chemistry (notably of silver(I)) with intermolecular connectors with a view to examining how the structural balance in such materials is determined by competition and/or collaboration between intermolecular synthons and the spatial requirements of transition-metal complexes.

4:15 PM U2.7
THE BINARY APPROACH TO SUPRAMOLECULAR STRUCTURE AND FUNCTION. Joseph W. Lauher , Frank W. Fowler, State University of New York, Department of Chemistry, Stony Brook, NY.

The function of a supramolecular entity depends upon the chemical composition and nature of the constituent molecules, as well as the symmetry and spatial properties of the assembly of molecules. Since one has little control over the actual supramolecular properties of a given molecule, one must approach a synthesis with a focus on the final supramolecular goal, as opposed to a focus on the identity of the individual molecules. A realization of the final goal may require the achievement of a specific structure, a specific function or both, since function often depends upon structure.
We have developed a binary approach to this problem, using one molecule to control the structure of a supramolecular assembly, while the second provides the function. Our approach is based upon a library of chemical functionalities that lead to predictable structural patterns based upon persistent patterns of hydrogen bonds. Molecules possessing these functionalities can be synthesized and used to control and determine supramolecular structure. A second functionality is added as a handle to control the second molecular entity, the one that provides the function or completes the structure of the final product. For this we have used a variety of interactions, including hydrogen bonds, metal-ligand coordination and halide-nitrogen interactions. Successful applications of the technique include the synthesis of a wide variety of layered structures, designed diacetylene polymerizations and the controlled spacing of metal atoms.

4:30 PM *U2.8
Wais Hosseini , Univ Louis Pasteur, Strasbourg, FRANCE.

Abstract Not Available

SESSION U3: THIN FILMS AND LAYERED STRUCTURES
Chair: Neal R. Armstrong
Tuesday Morning, December 1, 1998
America South (W)
8:30 AM *U3.1
SUPRAMOLECULAR LAMINATES WITH AFFINITY FOR AROMATIC GUESTS. Mike Zaworotko , Kumar S. Biradha, Department of Chemistry, The University of Winnipeg, Winnipeg, Manitoba, CANADA.

That solid state architecture profoundly influences bulk physical properties and therefore function of solids has provided impetus for recent activity in the field of crystal engineering. The nature of crystal engineering means that chemists can design new crystal structures without the need to develop new molecular structures. Rather, the chemist simply has to focus upon multifunctional exodentate moieties and the concept of supramolecular synthons . This presentation will focus upon the development of new classes of layered solid1 that might be of general interest for materials or separations applications. We shall present recent results involving organic solids based upon simple acids such as trimesic acid and trimellitic acid and discuss their significance in the following contexts: 1) what impact will crystal engineering have upon design and synthesis of covalent polymers?; 2) what opportunities might there be for applications of the new materials?
1. Sharma, C.V.K.; Zaworotko, M.J.; Rogers, R.D., 1997. Supramolecular Laminates'' Chem. Commun. , 1559-1560, 1997.

9:00 AM *U3.2
MOLECULAR SCAFFOLDS FROM DERIVATIVES OF 2,5-DIKETOPIPERAZINE. G. Tayhas R. Palmore , Tzy-Jiun Luo, Mary T. McBride, University of California, Department of Chemistry, Davis, CA; Terry A. Land, James J. DeYoreo, Lawrence Livermore National Laboratory, Livermore, CA.

Derivatives of 2,5-diketopiperazine (DKP) are known to assemble into hydrogen-bonded tapes in their crystalline solids. Hydrogen-bonded tapes can function as scaffolds for positioning guest molecules within the crystalline lattice, and depending on what substituents or guest molecules are chosen, there is the potential for creating solids with new bulk properties. We will describe our efforts at elucidating physical-organic trends between the molecular constituents and their assembly into crystalline solids using several methods of analysis: X-ray diffraction, NMR and IR spectroscopies, in situ atomic force microscopy, co-crystallization techniques and computer modeling.

9:30 AM *U3.3
FROM BENZENE TO 2D- AND 3D-NANOPARTICLES. Klaus Müllen, Max-Planck-Institute for Polymer Research, Mainz, GERMANY.

The benzene ring serves as versatile building block of carbon-rich 2D- and 3D-macromolecules. A novel cycloaddition-deprotection protocol provides dendritic polyphenylenes which are shape persistent 3D-nanoparticles. Suitably designed oligo- and polyphenylenes are transformed into giant polycyclic aromatic hydrocarbons (PAHs) by mild intramolecular cyclodehydrogenation. These PAHs constitute molecular (2D)-models of graphite. Their supramolecular ordering is a key prerequisite when elucidating their role as media for charge carrier transport in molecular electronics. Current-potential curves recorded by scanning tunneling microscopy for single PAH discs and the drastic increase of charge mobility as a result of their liquid-crystalline order in $\pi$-stacked columnar arrays are typical results of their physical characterization.

10:15 AM U3.4
THE EVOLUTION OF ORDERED POLYCRYSTALLINE FILMS DURING VAPOR DEPOSITION OF 4-AMINOBENZOPHENONE AND 4-(N,N-DIMETHYLAMINO)-3-ACETAMIDONITROBENZENE ON ALKALI HALIDE SUBSTRATES. John McAleese, David Sheen , John Sherwood and Qingwu Wang, University of Strathclyde, Department of Pure and Applied Chemistry, Glasgow, Scotland, UNITED KINGDOM.

The polycrystalline films which develop during the vapor deposition of the non-linear optical materials 4-aminobenzophenone (ABP) and 4-(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN) on prebaked KCL or KBr (001) faces show biaxial orientation along [110] and [$\bar{1}$10] directions, in common with many organic materials deposited on these substrates. During deposition, some interesting changes in film morphology have

SYMPOSIUM U Organics with Supramolecular Structure and Function November 30 - December 3, 1998 Chairs

Martin Bryce          Christopher Ober

Dept of Chemistry        Dept of MS&E

Univ of Durham          Cornell Univ

Durham,  DH1 3LE UNITED KINGDOM        327 Bard Hall

44-191-374-3118          Ithaca, NY 14853

607-255-8417

Michael Ward
Chemical Engineering and Materials Science
Univ of Minnesota
151 Amundson Hall
Minneapolis, MN 55455
612-625-3062

Symposium Support
*Army Research Office

* Invited paper

SESSION U1: MOLECULAR RECOGNITION IN SUPRAMOLECULAR SOLIDS
Chair: Bruce M. Foxman
Monday Morning, November 30, 1998
America South (W)
8:30 AM U1.1
CRYSTAL ENGINEERING OF DIAMONDOID NETWORKS FOR SECOND-ORDER NONLINEAR OPTICAL APPLICATIONS. Wenbin Lin , Zhiyong Wang, Ren-Gen Xiong, Department of Chemistry, Brandeis University, Waltham, MA.

The design of organic and metal-organic diamondoid frameworks has received considerable attention over the past decade, in part, because of the recognition that daimondoid networks have high propensity to pack in acentric space groups as a result of the lack of an inversion center. Acentric solids and thin films are of great interest owing to their potential applications as second-order nonlinear optical (NLO) materials. In fact, one of the best known inorganic second-order nonlinear optical materials, potassium dideuterophosphate (KDP), crystallizes as a diamondoid network. Despite the intense search over the past decade, acentric organic and metal-organic diamondoid frameworks have not been rationally synthesized to date. We have designed a novel approach to crystal engineering of acentric metal-organic diamondoid frameworks for second-order NLO applications. Our strategy relies on the use of four- or six- coordinate metal centers in combination with unsymmetrical, bifunctional linker groups. For example, both bis(isonicotinato)zinc and cadmium bis(4-pyridylacrylic acid) have been prepared hydrothermally. They both crystallize in acentric space groups, and possess a three-fold and five-fold interpenetrated diamondoid structure, respectively. Preliminary second harmonic generation measurements showed that these diamondoid networks exhibit second-order NLO efficiencies comparable to technologically important lithium niobate.

8:45 AM U1.2
ENGINEERING MIXED CRYSTALS. Bart Kahr , Loyd Bastin, Anand Subramony, Rich Gurney, Christine Mitchell.

While a great deal of effort recently has been directed at the design of molecular crystalline materials, especially by exploiting hydrogen bonds, little attention has been paid to the design of dilute solid solutions even though for some optical and spectroscopic applications molecules that are oriented and isolated from one another are requisite. We have been seeking to identify the prevailing intermolecular forces that determine for formation of dye inclusion crystals (DICs), simple crystalline substances that contain organic chromophores oriented and isolated in particular sectors during growth from solution. In this paper, we focus on orienting organic dyes within otherwise single crystals of inorganic salts such as potassium sulfate, potassium dihydrogen phosphate, and barium acetate. We emphasize the use of such crystals in chemical analysis, the determination of crystal growth mechanisms, and in the stabilization of reactive intermediates and electronically excited states.

9:00 AM *U1.3
SUPRAMOLECULAR CONTROL OF THE BULK MAGNETIC PROPERTIES OF MANGANOPORPHRYIN-BASED MAGNETS. Joel S. Miller , University of Utah, Dept. of Chemistry, Salt Lake City, UT; Arthur J. Epstein, The Ohio State University, Dept. of Physics and Dept. of Chemistry, Columbus, OH.

Coordination polymer-based magnets comprised of alternating [Mn(III)(porphryrin)]+ and [A]- (A = TCNE, TCNQ, C4(CN)6, chloranil) have been prepared and structurally and magnetically characterized. The [A]- is trans-$\mu$-bound to two adjacent Mn(III) sites in the chain. Adjacent sites exhibit antiferromagnetic coupling between the S = 1/2 [A]- quantum spin and the S = 2 Mn(III) classical spin and magnetic order occurs below 25 K. The intrachain coupling, as evidence by increasing Tmin, and fits to the Seiden expression for isolated chains comprised of alternating quantum {S = 1/2; [A].-} and classical {S = 2; [Mn(III)porphryrin)]+} spins is correlated with decreasing MnN4 - [TCNE]- dihedral angles. MO calculations identify the key overlap due to the sigma-dz2/pz on the [TCNE]- N bound to the Mn(III). Use of octaethylporphyrin leads to a antiferromagnet whereas use of tetraphenylporphryin and substituted tetraphenylporphryin leads to magnets with interchain ferromagnetic coupling and ferrimagnetic behavior. The differing magnetic behavior is attributed to enhanced ferromagnetic dipolar interactions for the latter class of magnets. The magneto-structure correlation as well as recent developments in this class of materials will be discussed.

9:30 AM U1.4
SOLID-STATE STRUCTURAL ORDERING IN STABLE ORGANIC RADICALS. Paul M. Lahti , Jacqueline Ferrer, Univ of Massachusetts, Dept of Chemistry, Amherst, MA; Clifford George, Naval Research Laboratory, Washington, DC.

Recent work in organic molecular magnetic materials has included efforts to design specific hydrogen-bonded and dipolar solid state interactions, which will act to assemble stable radicals into relative orientations that favor intermolecular ferromagnetic exchange interactions. We describe work aimed at design of such systems, with primary focus on one example, benzimidazole-2-tert-butyl-nitroxide (BIm-tBN). BIm-tBN forms stacks of molecules that are H-bonded together to produce a highly organized, centrosymmetric crystal structure. The relationship of isolated-molecule properties such as spin density distribution (investigated by ESR spectroscopy and DFT computations) to typical models for intermolecular exchange in the solid state will be outlined for this example, as well as prospects for extensions to related systems.

9:45 AM U1.5
SELF-ASSEMBLY OF LAYERED COORDINATION NETWORKS WITH CLAY-LIKE PROPERTIES. George K. H. Shimizu , Univ of Calgary, Dept of Chemistry, Calgary, Alberta, CANADA; Gary D. Enright, Chris I. Ratcliffe, Gabriela S. Rego, John A. Ripmeester, Dan D. M. Wayner, National Research Council of Canada, Steacie Institute for Molecular Sciences, Ottawa, Ontario, CANADA.

Clays and zeolites are rigid framework aluminosilicates with layered and channel motifs, respectively. From a metal coordination chemistry standpoint, these networks provide attractive model compounds owing to their robust nature, porousity and functionality. This presentation will discuss a family of lamellar metal coordination compounds, generated from fundamental design principles, and it's analogy to clay-like materials. A novel dithia ligand, designed to favor the formation of infinite frameworks, was synthesized and found to form a layered solid with silver(I). The observed structure is versatile as it can be tuned by changing the anion, ancillary ligands on the metals, or, significantly, by functionalizing the ligand itself. The prospect of organic derivatization offers a wide range of structural options and hence, variation in the physical properties of these complexes. Studies to date show interlayer swelling in the presence of solvent, selectivity in inclusion behavior and ion exchange ability.

10:15 AM U1.6
ETHYNYL-SUBSTITUTED TETRAHEDRAL MOLECULES: BUILDING BLOCKS FOR 3D-NETWORKS. Elena Galoppini , Wenzhuo Guo, Quiongying Fu, Rutgers University, Department of Chemistry, Newark, NJ; Richard Gilardi, Laboratory for the Structure of Matter, The Naval Research Laboratory, Washington, DC.

The ability to design organic crystals or polymers with large and dimensionally-fixed cavities may lead to materials exhibiting unprecedented and possibly useful properties. As part of this interest, we are studying molecules capable of selective and strongly directional intermolecular interactions (such as hydrogen bonds) and which may pack in a predictable manner. We present the synthesis and crystal structure of molecules with a tetrahedral core, such as methane and adamantane, substituted at the four vertices with phenylacetylenic units or phenylboronic esters. The tetrahedral core provides a rigid scaffold, which maintains fixed the orientation of the rod-like functional groups. Hydrogen bonding, metal-ligand coordination, polymerization reactions were used to connect the building blocks. Such molecules form diamondoid' crystals, three-dimensional networks obtained by connecting the four vertices of tetrahedra and which resemble the diamond structure.

10:30 AM *U1.7
MOLECULAR ENGINEERING OF NON-CENTROSYMMETRIC FILMS FOR NONLINEAR OPTICAL APPLICATIONS. Geoffrey J. Ashwell , Cranfield University, Molecular Electronics, Cranfield, UNITED KINGDOM.

Interest in Langmuir-Blodgett (LB) films for second-harmonic generation (SHG) stems from the requirement that the structure must be non-centrosymmetric and from the fact that the LB technique allows control of the packing at the molecular level. Amphiphilic materials, those with a hydrophilic head and a hydrophobic tail, may be aligned at the air-water interface but, when deposited, the layers tend to pack centrosymmetrically with the interfaces being alternately hydrophilic (head-to-head) and hydrophobic (tail-to-tail). This may be overcome by considering the molecular criteria for non-centrosymmetric deposition and, at Cranfield, Z-type structures have been routinely obtained by rendering the chromophore hydrophobic at both ends. This causes the LB film surface to be invariably hydrophobic and suppresses the natural tendency of the molecules to invert during deposition. There is a narrow range of alkyl chain lengths which allows the films to be non-centrosymmetric but long-term stability has been realised by considering the compatibility of the end groups within the multilayer. When carefully selected, non-centrosymmetric alignment arises and the second-harmonic intensity increases quadratically with the number of layers, i.e. as I(N)2w= I(1)2w N2, to thicknesses suitable for waveguiding. The lecture will focus on the optimisation of the nonlinear optical properties of LB films of a novel dye, E-4-[(N-octadecyl-6,7,8-trihydro-5-isoquinolylidene)methyl]-N,N-dibutylaniline octadecylsulfate. The films are transparent at the fundamental frequency and only slightly absorbing at the second-harmonic. Nonetheless, the susceptibility is high ($\chi$zzz(2) = 76 pm V-1 at 1.064 $\mu$m for I = 3.15 nm layer-1) and the second-harmonic intensity is the strongest to date from a weakly absorbing film.

11:00 AM *U1.8
GAS SORPTION ISOTHERMS FOR DESIGNED MICROPOROUS METAL-ORGANIC MATERIALS. O.M. Yaghi , Hailian Li, and Mohamed Eddaoudi, Arizona State University, Department of Chemistry and Biochemistry, Tempe, AZ.

Despite the exponential growth in the number of reports on crystalline metal-organic materials with open-framework structures, studies focusing on establishing their gas sorption isotherms and thus microporosity, remain largely unknown. This presentation will show that permanent micrOporosity, similar to that commonly observed in zeolites, can be achieved with metal-organic open frameworks. Gas sorption isotherm, surface area, and pore volume measurements for materials such as Zn(BDC)$\cdot$(DMF)(H20) having 5-15 $\AA$ diameter apertures will be presented. Key aspects to developing strategies for producing rigid and stable metal-organic frameworks with extended channels will be outlined.

11:30 AM *U1.9
TETRATHIAFULVALENES: VERSATILE BUILDING BLOCKS IN MACROCYCLIC AND SUPRAMOLECULAR CHEMISTRY. Jan Becher , Department of Chemistry, Odense University, Odense M, DENMARK.

The effective syntheses of a variety of tetrathiafulvalene building blocks, including pyrrolo- and 2,5-dihydropyrrolo-fused tetrathiafulvalenes have been developed, allowing easy construction and preparation of complex molecular assemblies. The facile deprotection of the 2-cyanoethyl group, a versatile protecting group for 1,3-dithiolium-2-thione-4,5-dithiolates and tetrathiafulvalene-thiolates (1), is an excellent method for the incorporation of tetrathiafulvalene units into macrocyclic and supramolecular compounds. The selective and stepwise protection-deprotection methodology have been used extensively by our group for the preparation of two and three dimensional macrocyclic (mono-, bis- and tricyclic) as well as tetrathiafulvalene-based supramolecular systems (2). Utilization of the thiolates generated by the new methodology are illustrated by recent examples of oligomeric and supramolecular tetrathiafulvalene-based systems, such as: Dendritic (3) and oligo-tetrathiafulvalenes, three dimensional tetrathiafulvalenophanes, tetrathiafulvalene-containing catenanes (4) or rotaxanes (5) as well as donor acceptor systems based on tetrathiafulvalene as the donating group.
References
1.    M. B. Nielsen, S. B. Nielsen and J. Becher, Self complexing Tetrathiafulvalene Macrocycles, a Tetrathiafulvalene Switch'', Chem. Commun., 1998, 475.
2.    M. B. Nielsen, N. Thorup and J. Becher, Synthesis of a criss-cross overlapped Tetrathiafulvalenophane and a topologically new [2]catenane'', J. Chem. Soc. Perkin 1, 1998, 1305.
3.    C. A. Christensen, L. M. Goldenberg, M. R. Bryce and J. Becher, Synthesis and electrochemistry of a tetrathiafulvalene (TTF)21-glycol dendrimer'', Chem. Commun., 1998, 509.
4.    K. B. Simonsen and J. Becher, Tetrathiafulvalene Thiolates'', Synlett, 1997, 1211. 5.    M. B. Nielsen and J. Becher, `Two- and Three-Dimensional Tetrathiafulvalene Macrocycles'', Liebigs Ann/Recueil, 1997, 2177.

SESSION U2: MOLECULAR RECOGNITION IN SUPRAMOLECULAR SOLIDS (continued)
Chair: Omar M. Yaghi
Monday Afternoon, November 30, 1998
America South (W)
1:30 PM *U2.1
SYNTHESIS AND PROPERTIES OF HELICAL AROMATIC MOLECULES THAT SELF-ASSEMBLE INTO COLUMNS. Thomas J. Katz , Colin Nuckolls, Joseph M. Fox, Columbia Univ, Dept of Chemistry, New York, NY; Thierry Verbiest, Sven Van Elschocht, and André Persoons, K.U. Leuven, Laboratory of Chemical and Biological Dynamics, Leuven, BELGIUM; Andrew J. Lovinger, Bell Labs, Lucent Technologies, Murray Hill, NJ.

Molecules that resemble those forming chiral discotic mesophases, but whose core ring systems are twisted helically, have been synthesized in nonracemic form. Some self-assemble into columnar structures in solution, as do the pure materials in bulk and in Langmuir-Blodgett films. When they assemble, the circular dichroisms, specific rotations, and sec