Electrochemical behavior of novel bis (aliphatic amine) ruthenium (II) and osmium (II) porphyrins

Abstract

Bis (aliphatic amine) ruthenium (II) and osmium (II) porphyrins, M (Por)-(H2NR)2 and M(Por)(HNR′2)2, [M=Ru and Os; Por=meso-tetrakis (p-tolyl) porphyrinato (TTP), meso-tetrakis (4-chlorophenyl) porphyrinato (4-Cl-TPP), meso-tetrakis (3, 5-dichlorophenyl) porphyrinato (3, 5-Cl-TPP) and meso—tetraphenyl porphyrinato(TPP); R=methyl, ethyl, iso-propyl and t-butyl; R′=methyl and ethyl] were synthesized by us. The electrochemical behavior of these complexes in 1, 2-dichloroethane with TBABF4 as supporting electrolyte, has been studied by cyclic voltammetry and controlled potential electrolysis. Bis (aliphatic amine) ruthenium (II) porphyrins under go reversible one-electron oxidation and one-electron reduction processes in 1,2-dichloroethane solution. The osmium (II) analogues is shown two oxidation couples III and V, an additional small wave IV. The redox potentials of these complexes are markedly dependent on the nature of the substituent bound to the phenyl group of the porphyrin ring. It is obvious that redox potentials increases the electron-withdrawing power of the substituents increases. The couple I was found at −0.34, −0.23 and −0.15 V vs Cp2 Fe+/0 (Cp2Fe=ferrocene) for Ru(TPP)(H2NBu-t)2, Ru(4-Cl-TPP) (H2NBu-t)2 and Ru(3,5-Cl-TPP)(H2NBu-t)2 respectively.