FTIR Spectroelectrochemical Investigation of the trans-[Ru(NO)(dimethylglyoximate)2Cl] Complex: Vibrational Characterization of the NO+/0 and RuIII/II Redox Couples

Abstract

This paper deals with the spectroelectrochemical characterization of the Ru^III/II and N0^+/0 oxidation states of the trans-Ru(NO)(dmgH)₂Cl] complex (dmgH = dimethylglyoximate ion). The cyclic voltammograms of the complex in acetonitrile solution exhibited a reversible wave at -0.09 V versus SHE, and two less intense waves at 1.19 and 1.41 V. Visible-UV spectra were recorded at -0.4 and 1.5 V, however, the absorption bands collapsed into a single tail, providing little information on the redox states involved. In contrast, in the FTIR measurements at -0.4 V, the v(NO) peak shifted from 1878 to 1855cm^?1, without changing the vibrational peaks of the dmgH ligand, indicating an electrochemical process involving the NO^+/0 redox couple. At 1.5 V, the changes in the vibrational peaks of the NO and dig lagans indicated a redox process associated with the Ru^III/II redox'couple. The existence of an open and a cyclic hydrogen bridged configuration was proposed, in order to explain the occurrence of two electrochemical waves at positive potentials.