2009 Spring Symposium
New York University
Department of Chemistry
New York, NY
Abstract – Guest-free guanidinium organomonosulfonates (GMS) and their inclusion compounds display a variety of lamellar crystalline architectures distinguished by different “up-down” projections of the organomonosulfonate residues on either side of a two-dimensional (2D) hydrogen-bonding network of complementary guanidinium ions (G) and sulfonate moieties (S), the so-called GS sheet. The GS sheets in the inclusion compounds behave as “molecular jaws” in which organomonosulfonate groups projecting from opposing sheets clamp down on the guest molecules, forming ordered interdigitated arrays of the host organic groups and guests. Guest-free and inclusion compounds display a variety of architectures that reveal the structural integrity of two-dimensional GS sheet and the unique ability of these hosts to conform to the steric demands of the organic guests. Certain GMS host-guest combinations prompt formation of tubular inclusion compounds in which the GS sheet curls into cylinders with retention of the 2D GS network. The cylinders assemble into hexagonal arrays through interdigitation of the organosulfonate residues that project from their outer surfaces, crystallizing in high symmetry trigonal or hexagonal space groups. This unique example of network curvature and structural isomerism between lamellar and cylindrical structures, with retention of supramolecular connectivity, is reminiscent of the phase behavior observed in surfactant microstructures and block copolymers. The large number of host-guest combinations explored here permits grouping of the inclusion compound architectures according to the shape of the guests and the relative volumes of the organomonosulfonate groups, enabling more reliable structure prediction for this class of compounds than for molecular crystals in general. More recent results that demonstrate the inclusion of laser dyes with controlled states of aggregation, the introduction of molecular capsules, and unusual high symmetry structures will be described.
Speaker’s Biography – Michael Ward earned his B.A in Chemistry from William Paterson College of New Jersey in 1977, and PhD in Chemistry from Princeton University in 1981. He currently serves as the Silver Professor and Chair, Department of Chemistry, Director of Molecular Design Institute and Director of Materials Research Science and Engineering Center at New York University, New York City, NY. He is also Editor of Chemistry of Materials. His research interests include synthesis of molecular materials and crystal engineering, physical and electronic properties of molecular solids, nucleation and growth of organic and protein crystals, scanning probe microscopy and interfacial phenomena.