Interfacial electron transfer (ET) processes are essential to all energy conversion reactions and can be broadly classified as inner- (ISET) or outer-sphere (OSET). For OSETs, the electrode serves as a chemically inert source or sink of electrons, whereas, for ISETs, electron transfer accompanies bond-rearrangement at the electrode surface. Although the free-energy landscape of an OSET reaction is well-described by Marcus-type models, there currently exist no analogous models for ISET reactions, despite the central role of ISETs in key energy conversion processes including the splitting of water and the reduction of carbon dioxide to fuel. The intrinsic heterogeneity of most catalytic surfaces makes it difficult, if not impossible, to unambiguously correlate the kinetics of ISET reactions to the local structure of the sites that undergo bond-rearrangement, impeding systematic investigations. We have developed a simple synthetic strategy for conjugating well-defined molecular active sites with the extended states of graphitic solids. As a result of the electronic coupling afforded by the conjugated surface linkage, these molecular surface sites activate substrates exclusively via the inner-sphere ET mechanisms typical of extended solid metal surfaces. These hybrid materials, thus, provide versatile model platforms for developing molecular-level descriptions of ISET reactions.

Molecular models of inner-sphere interfacial electron transfer

254th National Meeting (2017)

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