John F. Endicott Title Professor Emeritus Division Inorganic Education BA Reed College (1957) Ph.D The Johns Hopkins University (1961) Postdoctoral Stanford Univ. (1961-63 with Henry Taube) Office Chem 321 Phone (313)577-2607 E-Mail

This is a research program examining the "whys" and "wherefores" of chemical reactivity. The reactions studied usually involve transition metal complexes in very simple condensed phase processes. A wide range of fundamental issues is examined and a wide variety of experimental techniques is employed. Electronic excited states of transition metal complexes have electronic structures that cannot be achieved in ground state species, and thus they can exhibit unique patterns of reactivity. This reactivity depends on both the electronic structures of reactants and the changes in the positions of atoms required as reactions proceed. During recent years most of the research in this group has been directed towards experimentally probing fundamental aspects of center-to-center, photoinduced electron and energy transfer processes in transition metal complexes. The ultimate goal of this work is to use the principles inferred in the design of new systems useful in energy conversion applications. In very recent years we have been exploring the use of a unique tool for probing the properties of transition metal charge transfer excited states: The effects of changes in excited state energies, of "innocent' ligands in the coordination sphere, etc., on variations in emission band shapes. The differences in molecular structure between a ground and an excited electronic state and the ground state can be represented by the sum of vibrational progressions in all of the ground state vibrational modes that involve atoms whose positions differ in the two states. The emission side bands correspond to the convolution of such sums. Thus, side band intensities are a measure of the differences in ground and excited state geometries, and their variations in series of related compounds provides information about the extent to which there is configurational mixing between electronic states, or alternatively the extent of charge delocalization between electron donors and acceptors. Thus, for the simple Ru(II)/bpy chromophore, the absorption of light transforms the ground state {Ru(II),bpy} electronic configuration into the excited state {Ru(III),bpy-} configuration, but variations of the L ligands in the [(L)Ru(bpy)] complexes can result in very large changes in side band intensity with or without changes in excited state energy. The techniques employed in this research can involve any or all of electrochemistry, X-ray crystallography, standard spectrophotometry, emission spectroscopy, computer controlled-laser flash photolysis, or the fast photoacoustic measurements.

J. F. Endicott, "The Photophysics and Photochemistry of Coordination Compounds", In Inorganic Electronic Structure and Spectroscopy Vol. II, E. I. Solomon and A. B. P. Lever (Eds.), Wiley: New York; 1999; Chapter 5; pp. 291-342.

J. F. Endicott, "Molecular Electron Transfer", In Volume 7 of Comprehensive Coordination Chemistry II (Eds., J. McCleverty and T. J. Meyer), Pergamon, 2003; Chapter 7.11; pages 657-730.

Y.-J. Chen, P. Xie and J. F. Endicott, “Electron- Transfer Emission Spectra of a Cyanide-Bridged, Cr(III)/Ru(II) Donor-Acceptor Complex: High Frequency (NH and CN) Vibronic Contributions from Empirical Reorganizational Energy Profiles,” J. Phys. Chem. A 2004, 108, 5041-5049.

P. Xie, Y.-J. Chen, Md. J. Uddin, and J. F. Endicott, "The Characterization of the High- Frequency Vibronic Contributions to the 77 K Emission Spectra of Ruthenium-Am(m)ine- Bipyridyl Complexes, Their Attenuation with Decreasing Energy Gaps and the Implications of Strong Electronic Coupling for Inverted-Region Electron Transfer", J. Phys. Chem. A 2005, 109, 4671-4689.

K. T. Szacilowski, P. Xie, A. Y. S. Malkhasian, M. J. Heeg, M. Y. Udugala-Ganehenege, L. E. Wenger and J. F, Endicott, "Solid-State Structures and Magnetic Properties of Halide-Bridged, Face-to- Face bis-Nickel(II)-Macrocyclic Ligand Complexes: Ligand Mediated Interchanges of Electronic Configuration", Inorg. Chem. 2005, 44, 6019-6033.