Excited state electron transfer after visible light absorption by the Co(i) state of vitamin B12

Abstract

The first example of excited state electron transfer from cob(I)alamin is reported herein. Vitamin B₁₂ was anchored to a mesoporous TiO₂ thin film and electrochemically reduced to the cob(I)alamin form. Pulsed laser excitation resulted in rapid excited state electron transfer, k_et > 10⁸ s⁻¹, followed by microsecond interfacial charge recombination to re-form cob(I)alamin. The supernucleophilic cob(I)alamin was found to be a potent photoreductant. The yield of excited state electron transfer was found to be excitation wavelength dependent. The implications of this dependence are discussed.