First reversible electrogeneration of triply oxidized nickel porphyrins and porphycenes: formation of nickel(III) pi dications

A nonaqueous medium is used to reveal three reversible one-electron oxidations which influence a Ni(II) porphyrin or porphyrene to form (P)Ni and (OEPc) Ni. A Pi cation radical and dication are produced in a systematic method to coordinate with the primary two oxidations. A Ni(II/III) interaction is observed at half-wave potentials during the third oxidation. The Fe(II) and CO(II) complexes show metal-centered oxidations with TPP, OEPc or ORTPP macrocycles, with half-wave potentials that are compared to the Ni(II) porphyrins.