Inorganic and Solid State Chemistry — New approaches to the synthesis of inorganic clusters and solids are being developed, with emphasis on controlling structure as a means of tailoring physical properties
When a correlation between the chemical structure and a physical property of a material is postulated, measurements on compounds exhibiting a range of structural variations are required to establish its validity and, ultimately, to optimize performance for an application. Yet the controlled modification of inorganic structures remains, in many instances, an open challenge. Our research is directed toward developing general strategies for the synthesis of inorganic clusters and solids.
Recent mass spectrometric investigations have provided tantalizing glimpses of large new classes of metal-nonmetal clusters generated in the gas phase by laser ablation. Reactor systems intended to produce bulk quantities of ligand-stabilized analogues of these species are being tested. Characterization of the clusters resulting from this versatile synthetic technique should provide insight into the fundamental processes involved in the transport, nucleation and growth of binary solid materials.
A practical formalism for manipulating the degree of connectivity in simple solid frameworks is being elaborated. Termed dimensional reduction, the method relates how a binary parent solid can be dismantled by incorporating additional anions that serve to terminate intermetal bridges. A database of binary and ternary metal-halide and metal-chalcogenide structures is currently being analyzed to evaluate the scope and limitations of this formalism. Its utility will then be tested by applying dimensional reduction in the synthesis and characterization of new solid materials.
Magnetic bistability has now been observed in several high-spin clusters, raising the possibility of storing data at an extremely high density by localizing each bit of information in a single molecule. However, to improve the durability of data storage, clusters with a substantially higher demagnetization energy barrier (S2|D|) must be synthesized. The relative simplicity of the structures and exchange pathways in metal-cyanide cluster systems should make them much more amenable to the design of such single-molecule magnets than previously studied metal-oxo systems. Directed assembly routes to constructing high-spin metal-cyanide clusters are under investigation.
The demand for new porous materials that function as molecular sieves and catalysts has prompted interest in crystal engineering, a solution-based route to solid synthesis. The problems of interpenetrating frameworks and architectural frailty often encountered with this method can be avoided by using isotropically expanded structural components. For example, replacing the Fe2+ ions in Prussian blue with larger [Re6Q8]2+ (Q = Se, Te) cluster cores more than doubles the volume of the framework cavities. Characterization of these and related porous materials is ongoing.
Associate Professor, born 1969; B.A. Cornell University (1991); Ph.D. Harvard University (1995); Office of Naval Research Predoctoral Fellow (1991-1994); National Science Foundation Postdoctoral Fellow, University of California, Berkeley (1996-1997); Research Corporation Research Innovation Award (1998); Hellman Family Faculty Award (1999); Camille Dreyfus Teacher-Scholar Award (2000); Alfred P. Sloan Research Fellow (2001-2003); Wilson Prize (Harvard University, 2002). TR100 Award (2002); National Fresenius Award (2004).