Mixed-valence (MV) compounds, containing an electron donor / acceptor bridged by covalent molecules, are important models for improving our understanding of electron transfer processes, which can lead to developments in areas such as solar energy conversion and molecular electronics. Recently, examples of MV compounds in which the electron donor / acceptor is bridged by self-complementary hydrogen bonds have appeared, although little is known about the possible mechanisms associated with stabilization of the MV state. In this talk we present our recent work, in which metal-metal quadruply bonded complexes with pendant 2-pyridone functional groups have been used to probe possible mechanisms for mixed-valency across hydrogen bonds. A series of compounds with different metals, ancillary ligands and bridging ligands have been prepared. Cyclic voltammetry has been used to probe stabilization of the MV state, and investigate the effects of ligand and metal substitution. EPR spectroscopy along with IR and UV/vis/NIR spectroelectrochemical studies have been used to probe the mechanism in more detail. These studies, combined with DFT calculations, indicate that in these compounds stabilization is a result of dipole-induced electron transfer that is related to the proton-coordinate of the bridging ligand, termed proton-coupled mixed valency. These results suggest that hydrogen bonded assemblies could have interesting charge-transport properties, leading to novel functional materials.

Charge transfer between hydrogen-bonded metal-metal quadruple bonds

253rd National Meeting (2017)

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