Cyclic voltammetric studies of hafnium and zirconium phthalocyanines

Abstract Cyclic voltammograms of (OH) 2 HfPc(Cl) and (OH) 2 ZrPc(Cl) (Pc(-2) = phthalocyanine dianion) show one oxidation couple and two reduction couples in the presence of a variety of solvent-electrolyte systems. All redox processes are centred on the phthalocyanine ring rather than the metal. The first oxidation occurs at the phthalocyanine ligand to give [HfPc(-1)] ·+ and [ZrPc(-1)] ·+ π cation radical complexes. The two reduction couples correspond to the successive one-electron reductions of the phthalocyanine ligand to give MPc(-3) ·− and MPc(-4) 2− species. A third reduction couple, observed only for solutions (OH) 2 HfPc(Cl) in dimethyl sulfoxide, is assigned to further reduction of the ring and the formation of the HfPc(-5) ·3− species.