Effect of Heterometal‐Functionalization and Template Exchange on the Redox Chemistry of Molecular Vanadium Oxides

Abstract

Polyoxometalates (POMs) have emerged as material of interest in many applications such as energy storage and conversion due to their redox activity and molecularly defined structure. However, especially for polyoxovanadates a lack of understanding between structural modifications and physicochemical properties remains. The present study leverages a lacunary dodecavanadate to systematically investigate the electronic effect of heterometal functionalization. While structural distortion affects the stability of the cluster, the redox potentials correlate with the overall cluster charge. Furthermore, we report the first bromide-templated analogue of this cluster family. While the halide anion is crucial for the formation of the cluster, no major effect on the electrochemical properties is observed. By improving the understanding of structure-property relationship in this work, we hope to enable a more predictable tuning of redox-properties of polyoxovandates.

Molecular Nanocomposites with Lanthanide- and Counter-Cation-Mediated Interfacial Electron Transfer between Phthalocyanine and Polyoxovanadate

“…The most interesting feature in all cyclic voltammograms is the appearance of the new redox process O1, which can be assigned to the oxidation of V IV in the {V12O32} cage matching earlier reports for one electron-reduced dodecavanadate bis-functionalised with Ce III . 37 (PcLn)2-{V12} compounds show comparable results with those obtained for PcLn-{V12}. For example, the (PcLu)2-{V12} is characterised by small cathodic shifts and low peak-current for all redox processes compared to the mono-substituted derivative (Fig.…”

“…It is noteworthy that the fully-oxidised, lacunary-type {V12O32}-cage 28 has been shown in numerous studies to be an excellent scaffold for functionalisation with 3d-, [29][30][31] 4f- [32][33][34] and alkaline-earth metal ions. [35][36][37] Cronin and co-workers were first to present a series of (nBu4N)2[LnV12O32Cl](H2O)2(CH3CN)2 compounds with late Ln ions (Gd III -Er III ) directly incorporated into the dodecavanadate cage. 33 Magnetic measurements revealed, however, the free Ln ion behaviour.…”

“…34 An elegant method for the synthesis of metal functionalised [V V 12O32Cl] 5using a "placeholder" strategy was introduced by Streb and co-workers. [29][30][31][32]36,37 For instance, stepwise functionalisation of (nBu4N)3(Me2NH2) 2[V12O32Cl], where the dimethylammonium cation assumes the placeholder function, with transition metal ions [29][30][31] or with an early Ln 32 representative Ce III resulted in mono-and bis-substituted vanadium-oxo clusters with enhanced redox activity. This ability of the [V V 12O32Cl] 5polyoxoanion to act as an electron reservoir, without undergoing substantial structural transformation, 38 was also used to stabilise lowvalent Fe I species.…”

A General Access Route to High‐Nuclearity, Metal‐Functionalized Molecular Vanadium Oxides

“…We propose that this might be linked to the high negative charge of {Ca 2 V 18 } (5−), so that stabilization, e.g. by cation association with protons or others might be a suitable route to enhance electron storage capacity [66] …”

“…by cation association with protons or others might be a suitable route to enhance electron storage capacity. [66]…”