Electron Transfer in Mn-Tripod Complexes

Abstract

A heterogeneous electron-transfer rate constant k0 ≈ 7−8 × 10−7 cm s−1 for the reduction/oxidation of the bis-tripod complex [CpCoIII{P(OEt)2O}3]2MnIII/II redox couple was measured by cyclic voltammetry. The homogeneous self-exchange rate was calculated as k2 = 4.25·10−3M−1s−1 from the cross reaction of the MnII tripod complex with ferrocenium salt. X-ray structure determinations for both complexes showed a near regular octahedral oxygen coordination for the MnII complex and a sizeable Jahn−Teller distortion for the MnIII complex. Applying current ET theory for the comparison of heterogeneous and homogeneous rates and estimates of reorganization energies leads to the conclusion that the major part of the latter is due to inner reorganization of the Mn tripod.