Hole delocalization in oxidized cerium(IV) porphyrin sandwich complexes

Optical absorption, electron paramagnetic resonance, and resonance Raman spectra are reported for the one-electron oxidation products of the Ce(IV) sandwich porphyrins, Ce(OEP)/sub 2/ and Ce(TPP)/sub 2/ (OEP = octaethylporphyrin; TPP = tetraphenylporphyrin). These data, in conjunction with electrochemical measurements, indicate that the holes of both oxidized species are delocalized on the vibrational and probably the electronic time scales. In Ce(OEP)/sub 2//sup +/, the hole is delocalized through purely porphyrin-porphyrin interactions. In Ce(TPP)/sub 2//sup +/, delocalization is further facilitated by participation of the f orbitals of the Ce(IV) ion. The different characteristics of the redox orbitals of Ce(OEP)/sub 2//sup +/ and Ce(TPP)/sub 2//sup +/ are accounted for by the fact that oxidation occurs from an a/sub lu/-like orbital in the former complex and from an a/sub 2u/-like orbital in the latter.