ELECTROCHEMICAL AND SPECTROSCOPIC STUDIES OF A MOLYBDENUM COFACTOR MODEL IN AQUEOUS MICELLAR SOLUTION

A model of the molybdenum cofactor (Mo-co) of the molybdenum hydroxyla ses is examined in a variety of solvent environments that enhance the enzyme-mimetic properties of the complex. The complex MoO2(L-1), 1, wh ere L-1 = yl-(N,N'-bis(2-mercaptophenyl)-1,2-diaminoethane), has been studied by cyclic voltammetry and infrared spectroscopy in DMF and in aqueous micellar solution as a function solvent composition and of pH (see structure, Figure 1). As the DMF concentration is lowered and rep laced by aqueous micellar solution, E-1/2 values become more positive. In 95% aqueous micellar solution, the complex exhibits quasi-reversib le electrochemistry. As the pH is decreased form 9 to 4, the E-1/2 val ues for 1 become more negative. The IR asymmetric stretch of the Mo-ox o bond in 1 increases in frequency with decreasing pH. The relevance o f this work to the understanding of molybdenum hydroxylase enzymes is underscored, and the effectiveness of solubilization of complexes in m icellar solutions is discussed. (C) 1997 Elsevier Science Inc.