In iron-sulfur (Fe-S) proteins there is ample evidence for the existence of hydrogen bonds between the cysteine side chain, or inorganic sulfide as donor groups, and main chain amides as acceptor groups, (N-H . . . S interactions) yet the electronic consequences of these bonds remain open to debate. While several reports have discussed the influence of hydrogen bonding on the active sites of redox metalloproteins, structural models that include hydrogen bonds have been lacking. The proposed project focuses on the iron-sulfur (Fe-S) proteins where a relatively small number of studies have been reported on the effects of hydrogen bonding on redox potentials. Walters proposes to synthesize new metal thiolate complexes that incorporate N-H . . . S hydrogen bonds. He proposes to characterize these by X-ray crystallography, infrared, Raman spectroscopy and cyclic voltammetry. The data thus acquired will allow him to determine the effect of ligand N-H . . . S hydrogen bonding on metal-ligand bond enthalpies and anion complex redox potentials. By extrapolation these results will provide important insight into the control of redox potentials in iron-sulfur proteins and in electron- transfer proteins in general.