O reduction proton-coupled electron transfer by a V(III) aquo on a polyoxovanadate-alkoxide cluster.

We report the transfer of H-atoms from a reduced polyoxovanadate alkoxide [OctN][VO(OH)(OMe)] concerted proton-electron transfer. Oxygen reduction is compared between bridging and terminal O-H bonds revealing similar mechanisms, providing new insight to design criteria for metal-oxide electrocatalysts that faciliate oxygen reduction by concerted-proton electron transfer.

Heterometal Dopant Changes the Mechanism of Proton-Coupled Electron Transfer at the Polyoxovanadate-Alkoxide Surface.

The transfer of two H-atom equivalents to the titanium-doped polyoxovanadate-alkoxide, [TiVO(OCH)], results in the formation of a V(III)-OH site at the surface of the assembly. Incorporation of the group (IV) metal ion results in a weakening of the O-H bonds of [TiVO(OH)(OCH)] in comparison to its homometallic congener, [VO(OH)(OCH)], resembling more closely the thermodynamics reported for the one-electron reduced derivative, [VO(OH)(OCH)]. An analysis of early time points of the reaction of [TiVO(OCH)] and 5,10-dihydrophenazine reveals the formation of an oxidized substrate, suggesting that proton-coupled electron transfer proceeds via initial electron transfer from substrate to cluster prior to proton transfer.

Coordination-induced bond weakening of water at the surface of an oxygen-deficient polyoxovanadate cluster.

Hydrogen-atom (H-atom) transfer at the surface of heterogeneous metal oxides has received significant attention owing to its relevance in energy conversion and storage processes. Here, we present the synthesis and characterization of an organofunctionalized polyoxovanadate cluster, (calix)VO(OH)(OMe) (calix = 4--butylcalix[4]arene). Through a series of equilibrium studies, we establish the BDFE(O-H) of the aquo ligand as 62.

Mechanistic insight into rapid oxygen-atom transfer from a calix-functionalized polyoxovanadate.

We report accelerated rates of oxygen-atom transfer from a polyoxovanadate-alkoxide cluster following functionalization with a 4-butylcalix[4]arene ligand. Incorporation of this electron withdrawing ligand modifies the electronics of the metal oxide core, favoring a mechanism in which the rate of oxygen-atom transfer is limited by outer-sphere electron transfer.