A Molecular Ce2@Ih-C80 Switch-Unprecedented Oxidative Pathway in Photoinduced Charge Transfer Reactivity

We report for the first time the versatile Ce-2@I-h-C-80 building block toward synthesizing a novel electron donor-acceptor conjugate, Ce-2@I-h-C-80-ZnP (1) A systematic investigation of the charge transfer chemistry documents a reductive charge transfer (i e, formation of (Ce-2@I-h-C-80)(center dot-)-(ZnP)(center dot+)) in nonpolar media (i e, toluene/THF), while an oxidative charge transfer (i.e., formation of (Ce-2@I-h-C-80)(center dot+)(ZnP)(center dot-)) dominates in polar media (i.e, benzonitnle/DMF). Reduction of the [Ce-2](6+) cluster, which is highly localized and collinearly arranged with respect to the quaternary bridge carbon, is sufficiently exothermic in all solvents. Notably weak is the electronic coupling between the [Ce-2](6+) cluster and the electron-donating ZnP The oxidation of C-80(6-) and the simultaneous reduction of ZnP, on the other hand, necessitate solvent stabilization In such a case, the strongly exothermic (Ce-2@I-h-C-80)(center dot-)(ZnP)(center dot 4) radical ion pair state formation is compensated within the framework of a nonadiabatic charge transfer by a C-80(6-)/ZnP electronic matrix element, as the sum of good overlap and short distance, that exceeds that for [Ce-2](6+)/ZnP.