Chun Yuan Liu
Jinan University, China
Title: Electron coupling and electron transfer between two bridged dimolybdenum units
Biography
Biography: Chun Yuan Liu
Abstract
Bridged dimolybdenum dimers, denoted as [Mo2]-bridge-[Mo2], are favorable model compounds for study of electronic coupling and electron transfer because of the unique electronic structure of the [Mo2] unit. The formation of the metal-metal multiple bond removes the d orbtal degeneracy, rendering the Mo2 unit a s2π4d2 electronic configuration. Therefore, as an electronic donor-bridge-acceptor system, the transferring electron is specified to be the d electrons and donor-acceptor electron transfer can be probed by the metal (d) to bridging ligand (π*) and bridging ligand (π) to metal (d) and vibronic (d) metal to metal (d) charge transfer absorptions in accordance with suppexchange theory. By varying the ancillary ligands and the bridging ligands, a diverse of complexes of this type have been synthesized and studied. The electronic coupling matrix elements (H) are evaluated according to the Mulliken-Hush and CNS theories, which give consistent results. The mixed-valence properties are discussed in terms of Robin-Day's scheme. System transition from Class II to Class III via Class II-III is examined in a series of four complexes with subtle structural differences. The d®d electron transfer kinetics in symmetrical as well as asymmetrical systems has been investigated, conforming well to the semi-classical two-state model and the Marcus-Hush theory. In study of the photoinduced electron transfer, we found the d*®d back electron transfer is faster than the process from the bridge to the Mo2 center by one order of magnitude, while in the latter case, the electron transfer distance is shorter but the electronic coupling is much stronger. This controversial electron transfer phenomenon is tentatively attributed to a quantum incoherent pathway.
