hexavanadate

Hexavanadate refers to a class of polyoxometalate clusters that contain six vanadium centers linked by oxide ligands. The most characteristic species are Lindqvist-type vanadates with the core often denoted as [V6O19]n−; the exact charge depends on protonation and the redox state of vanadium. In these clusters the six VO6 octahedra share edges to form a compact, highly symmetric oxide framework, often described as a capsule-like polyhedron with several terminal oxo groups.

Structure and relationship to other POMs: Hexavanadates are part of the Lindqvist family of polyoxometalates, which are built from six octahedral metal centers connected through shared oxide ligands. In the vanadium case, this yields a robust, three-dimensional oxide core that can host various lacunary or substituted forms upon chemical modification. The high connectivity and redox-active vanadium centers give these clusters distinctive electrochemical and catalytic properties.

Synthesis and chemistry: Hexavanadates are typically formed by controlled hydrolysis and condensation of vanadium(V) oxide or related vanadate solutions under alkaline conditions. In some cases templating cations or organic ligands stabilize lacunary or substituted derivatives. The clusters exhibit rich redox chemistry, able to undergo multiple electron transfers, which underpins catalytic and electrochemical applications. Functionalization is possible by substituting ligands at terminal oxygens or by attaching organic groups, yielding functionalized hexavanadates or lacunary derivatives that can coordinate to metal ions or organic moieties.

Applications and significance: Due to their redox activity and structural modularity, hexavanadates are studied for catalysis, including oxidation reactions, electrochemistry, and materials science as building blocks for molecular materials. They also contribute to fundamental investigations of polyoxometalate assembly, structure–property relationships, and potential applications in sensors and energy-related technologies.

See also: polyoxometalates; Lindqvist-type POMs; vanadium oxide chemistry.