METAL COMPLEXES WITH TETRAPYRROLE LIGANDS. 50. REDOX POTENTIALS OF SANDWICHLIKE METAL BIS(OCTAETHYLPORPHYRINATES) AND THEIR CORRELATION WITH RING-RING DISTANCES

Article abstract of DOI:10.1021/ja00221a028

On the basis of prior work describing the synthesis and structure of sandwichlike metal bis(porphyrinates) M(OEP)2 (I:M=Y, La, ..., Lu, except Pm), the electron-transfer reactions of these double-deckers are presented.Apart from the Ce^IV complex Ce(OEP)2 (1c), all the other species contain M^III ions that are not affected in the redox reactions.The neutral M^III complexes 1 are porphyrin ?-radicals yielding the porphyrin ?-diradical cations ⁺ (2) upon reversible one-electron oxidation and the monoanions ^- (3) or the porphyrin ?-radical dianions ^2- (4) upon reversible one- or two-electron reduction.Ce(OEP)2 (1c) is reversibly oxidized to the porphyrin ?-radical cation ⁺ (2c).The quasi-reversible reduction of (1c) gives the anion ^- (3c) with Ce^III.For the neutral M^III complexes 1, the energies of the near-infrared absorption bands and the redox potentials for the processes 1<->2 are correlated with the ionic radii r_I. of the tervalent central ions M^III.A decrease of the ring oxidation potentials parallels a decrease of the ionic radii and, hence, the ring-ring distances in the double-deckers.