CYCLIC VOLTAMMETRIC STUDIES OF HAFNIUM AND ZIRCONIUM PHTHALOCYANINES

Cyclic voltammograms of (OH)(2)HfPc(Cl) and (OH)(2)ZrPc(Cl) (Pc(-2) = phthalocyanine dianion) show one oxidation couple and two reduction co uples in the presence of a variety of solvent-electrolyte systems. All redox processes are centred on the phthalocyanine ring rather than th e metal. The first oxidation occurs at the phthalocyanine ligand to gi ve [HfPc(-1)](.+) and [ZrPc(-1)](.+) rr cation radical complexes. The two reduction couples correspond to the successive one-electron reduct ions 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 th e ring and the formation of the HfPc(-5)(.3-) species.