EVALUATION OF ELECTRON-TRANSFER SITES IN RUTHENIUM(II) OCTAETHYLPORPHYRIN COMPLEXES OF THE TYPE (OEP)RU(CO)(L)

(OEP)Ru(CO) and (OEP)Ru(CO)(L) (where OEP = the dianion of octaethylporphyrin and L = an axial ligand) were electrochemically characterized in seven different nonaqueous solvents. The investigated complexes undergo two oxidations and either one or two reductions depending upon solvent. Both oxidations are ring centered, but this is not the case for reductions, which occur at either the porphyrin pi-ring system or the central metal ion depending upon the specific solution conditions and the sixth axial ligand. An overall Ru(II) --> Ru(I) reaction is suggested by thin-layer UV-visible spectroelectrochemical data in PhCN, CH3CN or PrCN, while pi-ring-centered reductions are suggested for the first reduction of (OEP)Ru(CO) in DMSO or py. Both reactions can be observed in THF with the initial reduction being ring centered followed by a conversion of the Ru(II) pi-anion radical to a Ru(I) form of the complex.