Spectral electrochemical study of extracomplexes of Ru(II) octaphenyltetraazaporphine with pyridine and pyrazine

Extracomplexes of Ru(II) octaphenyltetraazaporphine with pyridine and pyraz ine (L(2)Ru(II)TAPPh(8); L = py, pyz) are studied by cyclic and differentia l pulse voltammetry and spectral electrochemistry. In dichloromethane, the central metal atom undergoes quasi-reversible oxidation with the formation of [L(2)Ru(III)TAPPh(8)](+), and the reduction occurs of the macrocyclic li gand with the formation of pi-anion radical [L(2)Ru(II)TAPPh(8)](.-) (E-1/2 (Ru-II/III) = 0.69 and 0.91 V; E-1/2(TAPPh(8)(2-/3-)) = -1.15 and -0.97 V, for L = py and pyz, respectively). Strong pi-acceptor features of the tetra azaporphine macrocyclic ligand promote its reduction to pi-anion radical an d, by hindering its oxidation to pi-cation radical, simultaneously stabiliz e the lowest oxidation states of the complexing metal.