An investigation of the chromium oxidation state of a monoanionic chromiumtris(catecholate) complex by X-ray absorption and EPR spectroscopies

Recent crystal structures of DMSO reductases show that the active site is d eeply buried inside the protein matrix. We have evaluated the effect of enc apsulation on the reduction potential of the oxo-Mo(V) center by designing new thiol-containing ligands. The molybdenum complexes exhibit little varia tion in the g --> Mo charge transfer transition and in the EPR g values; ho wever, they exhibit a variation in the Mo(V/IV) reduction potential. Taken together, the results strongly indicate that, in these molecules, solvent m odulates the reduction potential. The results led us to suggest that the di fference in the Mo(V/IV) reduction potential for different DMSO reductases may be modulated by solvent.