RESEARCH INTERESTS:

We are interested in inorganic and organometallic complexes and materials that possess interesting electronic, optical, magnetic, and photophysical properties. Central to our research is the use of high-resolution and time-resolved spectroscopic methods to probe the structures, bonding, and dynamics of the ground states and electronic excited states of molecules. This knowledge enables us to rationally design new complexes and materials with specific and enhanced properties.

One of our goals is to prepare and understand transition-metal analogues of conjugated organic polymers. These hybrid materials are interesting because the metal centers enhance the optical and redox properties of the polymers and provide sites for locally controlling them. We have prepared many examples of conjugated organometallic compounds and polymers from multiply M—M and M—L bonded building blocks and systematically explored the electronic and structural relationships between them and their organic counterparts. Of particular current interest are poly(metallophenylene-ethynylene)s and their applications in molecular electronics. Through judicious choice of the equatorial ligands, these polymers can be addressed optically and electrochemically at the monomer level, yet maintain the π conjugation of their organic analogues.

A second subject of study is the development of self-assembling periodic overlayers for patterning surfaces. We have discovered a broad class of supramolecular materials based on high-valent metal-alkylidyne building blocks that form weak dative bonds with a variety of neutral bridging ligands. The resulting 1-D and 2-D materials assemble further via noncovalent (CH/π) interactions, resulting in materials with controlled interpolymer geometries. The materials are strongly luminescent, providing a signaling mechanism for reporting on interactions between the molecular grid and its environment.

A third area of research centers on understanding the nature of metal–ligand multiple bonds. Complexes containing these linkages are important catalysts in synthetic, biological, and industrial chemistry, but the electronic differences among, for example, MO, MN, and MC bonds are understood largely at a qualitative level. Spectroscopic and theoretical studies on sets of related complexes such as those below are directed at quantifying the relationships among these multiple bonds.

Selected References

Effects of Cation-Anion Interactionsof the Photophysical Properties ofAnionic d⁰ Tungsten-BenzylidyneComplexes. Inorg. Chim. Acta, 345, 309 (2003).

Electronic Spectra and Structures of d² Molybdenum–Oxo Complexes. Effects of Structural Distortions on Orbital Energies, Two-Electron Terms, and the Mixing of Singlet and Triplet States. Inorg. Chem., 41, 6973 (2002).

Vibrational Spectroscopy and Normal-Mode Analysis of Tungsten–Methylidyne Complexes. Insight into the Nature of M=C–H Bonding. J. Phys. Chem. B, (2000).

Metal-Metal Multiple Bonds, in Inorganic Electronic Structure and Spectroscopy, Vol. II, Wiley: New York p. 343 (1999).

Synthesis and Reactions of Metallo-diethynylbenzenes: Building Blocks for Redox-Active Poly(phenyleneethynylene)s. Chem. Comm., 589 (1999).