Interconvertible vanadium-seamed hexameric pyrogallol[4]arene nanocapsules

Research into stimuli-responsive controlled self-assembly and reversible transformation of molecular architectures has received much attention recently, because it is important to understand and reproduce this natural self-assembly behavior. Here, we report two coordination nanocapsules with variable cavities: a contracted octahedral V₂₄ capsule and an expanded ball-shaped V₂₄ capsule, both of which are constructed from the same number of subcomponents. The assemblies of these two V₂₄ capsules are solvent-controlled, and capable of reversible conversion between contracted and expanded forms via control of the geometries of the metal centers by association and dissociation with axial water molecules. Following such structural interconversions, the magnetic properties are significantly changed. This work not only provides a strategy for the design and preparation of coordination nanocapsules with adaptable cavities, but also a unique example with which to understand the transformation process and their structure-property relationships.

Adapting the cavity of a coordination capsule generally involves the addition or removal of subcomponents. Here, the authors report two vanadium-organic coordination nanocapsules with the same number of components but variable cavity sizes—an expanded ball and contracted octahedron—whose solvent-controlled interconversion is attributed to the versatile coordination geometry of the vanadium centers.

Small, beautiful and magnetically exotic: {V4W2}- and {V4W4}-type polyoxometalates

Minimal-nuclearity vanadato-tungstate clusters in [{V(IV)(dien)}4WO14]·4H2O () and [{V(IV)(dien)}4WO20]·6H2O () feature cores of edge-sharing WO6 octahedra, surrounded by a ring of four vanadyl groups. Surprisingly, the V(iv) centers in both and are ferromagnetically coupled, in contrast to all other known vanadato-polyoxotungstates featuring the ubiquituos V-O-W-O-V exchange pathways.