Solvent-binding and solvation effects on the electrode reactions of tetraphenylporphyrin carbonyl complexes of ruthenium(II)

Article abstract of DOI:10.1021/ic00140a007

The electron-transfer reactions of (5,10,15,20-tetraphenylporphyrin)ruthenium(II) carbonyl, (TPP)Ru(CO), was investigated in 12 nonaqueous solvents. In 10 of these solvents the complex existed in solution as (TPP)Ru(CO)(S), where S is a solvent molecule. This complex could be reversibly oxidized to yield [(TPP)Ru(CO)(S)]⁺ or reduced to yield [(TPP)Ru(CO)(S)]^-. Potentials for the former reactions were related to the Kamlet and Taft β parameter while those for the latter reactions were linearly related to the solvent acceptor number. Stability constants were calculated for addition of each solvent molecule as a sixth axial ligand to (TPP)Ru(CO) in CH₂Cl₂-0.1 M TBAP. Stability constants for formation of (TPP)Ru(CO)(S) ranged from log β₁ = 1.46 for addition of nitromethane to log β₁ = 4.63 for pyridine addition. Finally, correlations were made between the stability constants and the spectral properties of each complex.