Site-selective halogenation of mixed-valent vanadium oxide clusters

Abstract

Here, we expand on the synthesis and characterization of chloride-functionalized polyoxovanadate-alkoxide (POV-alkoxide) clusters, to include the halogenation of mixed-valent vanadium oxide assemblies.

Modelling local structural and electronic consequences of proton and hydrogen-atom uptake in VO2 with polyoxovanadate clusters

“…transition metals, halides) within the hexavanadate core. 24,25,61,62,64,[73][74][75] In these examples, the heteroatom-functionalised POV-alkoxide clusters adopt electronic structures where the site-differentiated ion is decoupled from the electronic structure of the remaining vanadyl ions of the Lindqvist core. These findings serve to deepen our understanding of the electronic architecture of molecular metal oxides, as well as indicate that doping motif is relevant to the physicochemical effects observed for a doped material.…”

“…Previous reports reveal that the formation of trivalent vanadium centres in cluster assemblies is possible upon formation of an oxygen defect; however, these ions typically remain electronically decoupled from other vanadyl sites in the core. 24,25,31,[37][38][39] Evidence for this phenomenon is observed upon chemical oxidation of the cluster; in all reported examples, oxidised forms of oxygen-deficient POV-alkoxide clusters retain a site-differentiated V III centre at the defect site (i.e. the oxidation event occurs across vanadyl ions composing the remainder of the cluster core).…”

“…the oxidation event occurs across vanadyl ions composing the remainder of the cluster core). 24,25,37,38 Inspection of the CV of 2-V IV 6O6(OSiMe3) 1reveals its instability under electroanalytical conditions. Anodic scans of the cluster produce a mixture of species, as indicated by the appearance of new electrochemical features located at E1/2 = -0.704, -0.155, and +0.519 V vs. Fc +/0 .…”

“…[17][18][19][20] Unlike the majority of POVs reported that are isolated with high-valent vanadium(V) centres, [21][22][23] Lindqvist-type polyoxovanadate-alkoxide (POValkoxide) clusters can be isolated in a reduced state, where all six vanadium ions adopt tetravalent oxidation states, allowing our group to study these compounds as models for VO2. [24][25][26] Additionally, the vanadium centres within these clusters adopt edge-sharing pseudo-octahedral coordination geometries that are analogous to the immediate chemical environment of vanadium(IV) ions in all known phases of VO2. [27][28][29][30] While these clusters possess delocalised electronic structures that can mimic local electronic communication between adjacent vanadium centres, they lack the extended band structure and Mott physics of the bulk material, limiting the effectiveness of our model to understanding the local consequences of surface reactivity and atomistic changes within VO2.…”

Physicochemical Factors That Influence the Deoxygenation of Oxyanions in Atomically Precise, Oxygen-Deficient Vanadium Oxide Assemblies

“…Like bulk metal oxides, these three-dimensional polynuclear assemblies are composed of redox-active transition metal ions (e.g., vanadium, molybdenum, tungsten, tantalum, niobium, etc. ), linked together by bridging oxygen atoms. , Generally, these systems exhibit rich electronic structures that present the ability to mediate multielectron redox processes. − ,,− With relevance to gaining molecular-level insight into the reactivity of heterogeneous metal oxide systems, the mechanism of OAT reactivity with POMs has been indirectly investigated and is speculated to undergo a mechanism similar to that of OAT chemistry with extended solids (e.g., the Mars–van Krevelen mechanism) …”