Our research emphasizes the detailed application of a wide variety of spectroscopic methods combined with molecular orbital calculations to probe the electronic structure of a transition metal complex and its relation to physical properties and reactivity. Three areas of physical-inorganic and bioinorganic chemistry are of general interest.

The first is chemical and spectroscopic studies of metalloprotein active sites. The general philosophy of these studies is to treat the metalloprotein as a metal complex with an ultimate ligand and to extend the concepts of coordination chemistry, spectroscopy, and electronic structure to this system. Studies in Bioinorganic Chemistry thus far have focused on structure-function correlations over copper cluster containing proteins, detailed spectral and theoretical studies of the unusual electronic structures of the Blue Copper, CopperA and iron sulfur active sites and their contribution to electron transfer reactions, and active sites in mononuclear and binuclear non-heme iron enzymes involved in O 2 binding and activation.

The second research area is detailed spectroscopic and electronic structure studies of high symmetry transition metal complexes. This research involves the application of polarized single crystal electronic absorption, variable temperature-variable field magnetic circular dichroism, electron paramagnetic resonance, superconducting magnetic susceptibility, resonance Raman, photoelectron and x-ray absorption spectroscopies to important problems in transition metal chemistry. Topics of interest include excited state contributions to inorganic photochemistry, inorganic potential energy surfaces and the Jahn-Teller effect, excited state origin of ground state properties including antiferromagnetic exchange coupling and spin Hamiltonian parameters, electronic structures required for dioxygen binding, activation, multielectron reduction to water and O-O bond formation, and experimental evaluations of covalency. We are also very interested in the development of new spectroscopic methods in bioinorganic chemistry.

A third research emphasis is the development of synchroton spectroscopies (at SSRL) to solve important problems in inorganic chemistry. Projects include: 1) variable energy photoelectron spectroscopy (PES) to probe small molecule bonding interactions with metal oxide surfaces related to heterogeneous, homogeneous and biological catalysis; 2) PES studies of electronic structure and electronic relaxation contributions to electron transfer processes in transition metal complexes; 3) use of ligand K-edges in determining covalency of ligand-metal bonds; 4) development of metal L-edge X-ray absorption spectroscopy to probe metal sites in highly covalent ligand environments (e.g. heme vs. non-heme iron).

1) "Thermodynamic equilibrium between blue and green copper sites and the role of the protein in controlling function," S. Ghosh, X. Xie, A. Dey, Y. Sun, C.P. Scholes, and E.I. Solomon. Proc. Natl. Acad. Sci. USA 106, 4969 (2009).

2 "Geometric and Electronic Structure Differences Between the Type 3 Copper Sites of the Multicopper Oxidases and Hemocyanin/Tyrosinase," J. Yoon, S. Fujii, and E.I. Solomon. PNAS, 106, 6585 (2009).

3) "New Insights into the Mechanism of the Reaction of Activated Bleomycin with DNA," M.S. Chow, L.V. Liu and E.I. Solomon Proc Natl Acad Sci, 105, 13241 (2008).

4) "Mixed Valent Sites in Biological Electron Transfer," E.I. Solomon, X. Xie, A. Dey. Chemical Society Reviews, 37, 623 (2008).

5) "Reduction of O2 to H2O by the Multicopper Oxidases," E.I. Solomon, A.J. Augustine, J. Yoon, Dalt. Trans., 30, 3921 (2008).

6) "Substrate Activation for O2 Reactions by Oxidized Metal Centers in Biology," M.Y.M. Pau, J.D. Lipscomb and E.I. Solomon, PNAS (Invited Perspective), 104, 18355, (2007).

7) "Spectroscopic and Quantum Chemical Studies on Low-Spin Fe(IV)=O Complexes: Fe-O bonding and Its Contributions to Reactivity," A. Decker, J-U. Rohde, E.J. Klinker, S.D. Wong, L. Que, Jr. and E.I. Solomon, J. Am. Chem. Soc. , 129 15983, (2007).

8) "Electronic Structure of the Peroxy Intermediate and Its Correlation to the Native Intermediate in the Multicopper Oxidases: Insights into the Reductive Cleavage of the O-O Bond," J. Yoon and E.I. Solomon, J. Am. Chem. Soc. , 129 13127, (2007).

9) "Spectroscopic and Kinetic Studies of Perturbed Trinuclear Copper Clusters: The Role of Protons in Reductive Cleavage of the O-O Bond in the Multicopper Oxidase Fet3p," A.J. Augustine, L. Quintanar, C.S. Stoj, D.J. Kosman, and E.I. Solomon. J. Am. Chem. Soc , 129, 13118, (2007).

10) "Solvent Tuning of Electrochemical Potentials in the Active Sites of HiPIP vs Ferredoxin," A. Dey, F.E. Jenney Jr., M.W.W. Adams, E. Babini, Y. Takahashi, K. Fukuyama, K.O. Hodgson, B. Hedman, and E.I. Solomon, Science, 318,1464, (2007).