This project, funded by the Inorganic, Bioinorganic and Organo- metallic Chemistry Program, will involve studies of con- formational gating, and electronic coupling between redox centers through hydrogen bonds, in electron transfer reactions. The effects of second coordination sphere interactions between ruthenium(II) ammine complexes and complexation agents on electron transfer reactions with Ru(III) oxidants will be used as the model for conformational effects that may be involve in electron transfers in biopolymers. In the second case, electron transfer between Ru(II) and Co(III) through hydrogen bonds will be examined. Stopped flow spectroscopic and rotating disk voltammetric measurements will be used in the study of these reactions. Detection of hydrogen bonded Ru(II)/Ru(III) mixed valence dimers will be attempted using electronic, NMR and FTIR spectroscopies. %%% Electron transfer is one of the most important processes in biological systems but many questions remain concerning the mechanisms of these electron transfers. In addition to in vitro studies of the actual biological molecules, which are frequently very difficult to interpret, studies of model systems that are designed to simulate one aspect of the biological process can be especially helpful in determining what structural and electronic features of the biological system have significant effects on reaction rates. This project, to be pursued by undergraduate scholars, will examine two of the factors that are believed to affect the rates of electron transfer in certain biological molecules. The first is the ability of hydrogen bonds to serve as conduits for electron transfer between donor and acceptor, in this case between two transition metal centers. There is accumulating evidence that suggests that electron transfer may be coincident with, or preceeded by, a change in the structure of a protein that surrounds the electron donor or acceptor. A model has also been designed to probe this concept, again based on reactions between two transition metal complex ions. Studies such as these may ultimately result in better treatment of certain physiological disorders and new methods solar energy conversion based on models of biological systems.
