ELECTROCHEMISTRY OF SOME 2ND-ROW TRANSITION-METAL PHTHALOCYANINE COMPLEXES

Redox properties of the phthalocyanine (pc) complexes of the second-ro w transition metals zirconium [Zr-IV(pc)], molybdenum [(MoO)-O-V(pc)], ruthenium [Ru-II(pc)], rhodium [Rh-III(pc)] and palladium [Pd-II(pc)] are correlated with the energy levels of the phthalocyanine ring and of the central metal. Oxidation and reduction occur exclusively at the phthalocyanine ring in Zr-IV(pc), Ru-II(pc) and Pd-II(pc) complexes, suggesting that the metal orbitals in these complexes are buried insid e the filled phthalocyanine levels. (MoO)-O-V(pc) shows metal redox ac tivity before any oxidation or reduction can be observed at the ring. Hence the Mo-V metal orbitals must lie between the highest occupied mo lecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the phthalocyanine ring. The site of redox activity in Rh-III(pc) d epends on the nature of the axial ligands.