James McCusker
Professor Office: 437 Chemistry
Phone: 517-355-9715 106 /
Websites: Research Group - Area
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Synthesis and Spectroscopy of Transition Metal Complexes
(Research Description PDF - 1026 kb)The McCusker Group is interested in the physical and photophysical properties of transition metal complexes. Our approach relies on a confluence of synthetic chemistry, a host of physical techniques ranging from magnetism to femtosecond time-resolved spectroscopy, and high-level theory. The simultaneous examination of chemical problems on all three of these fronts places us in a unique position to explore the physical chemistry of inorganic compounds.
Ultrafast Spectroscopy of Transition Metal Complexes. Our research efforts in this area concern the short time scale photo-induced dynamics of transition metal complexes. By "short time scale", we refer to processes occurring between the time a photon is absorbed by a molecule and the point at which that molecule is fully relaxed in its lowest-lying excited state. Some of the questions we are addressing with this research include the following: 1) what is the general time scale for excited-state evolution in transition metal complexes? 2) what is the mechanism of this process? 3) how do the geometric and electronic structures of the compounds, the surrounding medium, and other factors couple to and/or influence this process? and 4) to what extent can we use this information to control excited-state dynamics? Certain of these questions are very fundamental in nature, whereas others are geared toward work on solar energy conversion. What distinguishes the group, we believe, is our ability to carry out both the synthesis and spectroscopic characterization of a wide range of inorganic molecules. This enables us to systematically examine chemical perturbations to excited-state electronic and geometric structure, and in so doing develop a comprehensive picture of how transition metal chromophores absorb and dissipate energy.
Electron Exchange and Chemical Dynamics. Electron exchange is a term which describes the electrostatic interactions that can exist among unpaired electrons in molecules. Our group is interested in understanding the influence electron exchange has on the chemistry of inorganic compounds. Metal-quinone complexes are providing the framework for studying the photophysics of exchange-coupled molecules. The redox activity of the quinone ligand provides a facile mechanism for turning "on" or "off" electron exchange, allowing us to probe the effects of spin coupling on excited-state dynamics in closely related sets of chemical systems. A second area concerns reaction dynamics, where the emphasis is on electron and energy transfer processes in polynuclear metal clusters. Through detailed studies of synthetically tailored molecules, we are examining whether or not the electron exchange interactions present in such clusters plays a functional role in their reactivity. Coupled to this experimental work are theoretical studies that exploit recent advances in density functional theory. We believe that these combined efforts will allow us to forge an important link between magnetism and the electron/energy transfer chemistry of molecules, as well as provide insights into the possible role of electron exchange in the biochemistry of metalloproteins.
Selected Publications
Ultrafast Dynamics of 2E State Formation in Cr(acac)3, E. A. Juban and J. K. McCusker, J. Am. Chem. Soc. 2005, 127, 6857.Intramolecular Excimer Formation in a Naphthalene-Appended Dinuclear Iron-oxo Complex, L. B. Picraux, B. T. Weldon, and J. K. McCusker, Inorg. Chem. 2003, 42, 273.
Femtosecond Absorption Spectroscopy of Transition Metal Charge-Transfer Complexes, J. K. McCusker, Acc. Chem. Res. 2003, 36, 876.
Electron Injection Dynamics of Ruthenium and Osmium Polypyridyl Complexes Adsorbed Onto Nanocrystalline TiO2 Photoelectrodes, D. Kuciauskas, J. E. Monat, R. Villahermosa, H. B. Gray, N. S. Lewis, and J. K. McCusker, J. Phys. Chem. B 2002, 106, 9347.
Bimolecular Electron and Energy Transfer Reactivity of Exchange-Coupled Dinuclear Fe(III) Complexes, B. T. Weldon, D. E. Wheeler, J. P. Kirby, and J. K. McCusker, Inorg. Chem. 2001, 40, 6802.
Ultrafast Electron Localization Dynamics Following Photo-Induced Charge Transfer, A. T. Yeh, C. V. Shank, and J. K. McCusker, Science, 2000, 289, 93.
