Cyclic Oxothiomolybdates: Building Blocks for Cyclodextrin-Based Open Frameworks

Desolvation processes, though common in self-assembled biological structures, are rarely evidenced and utilized in the design of crystalline architectures. In this study, we introduce a novel approach using the [Mo₈S₈O₈(OH)₈(guest)]^2- complex, formed by the self-condensation of four [Mo^V ₂O₂S₂]^2- fragments around a guest unit (Mo^VIO₆H₄ or oxalate), as a chaotropic scaffold for crystallizing hybrid organic-inorganic systems with natural cyclodextrins. Our findings reveal that β-cyclodextrin (β-CD) facilitates the formation of host-guest complexes, while α-cyclodextrin (α-CD) induces the formation of a Kagome-type structure with significant voids. These new compounds were thoroughly characterized using X-ray diffraction (both powder and single-crystal), N₂ adsorption, elemental and thermogravimetric analysis. Additionally, solution studies using ¹H NMR titration and small-angle X-ray scattering (SAXS) demonstrated pre-association of the building units in solution. These results enhance our understanding of the design principles for supramolecular structures composed of inorganic polyanions and cyclodextrins.