The chaotropic character of Keggin-type polyoxotungstate anions was evaluated with respect to their ability to bind to γ-cyclodextrin (γ-CD) by varying the global charge density of the nanometer-sized polyanion. The...

The complexation of Keggin-type polyoxometalates (POMs) with g-cyclodextrin (g-CD) leads to supramolecular inclusion assemblies in aqueous solution driven by chaotropic effect. The strength of the interaction between g-CD and oxidized or one-electron reduced POMs in a series of molybdenum and vanadium monosubstituted phospho-and silico-tungstates,[XW11MO40] n-Keggin-type anions where X = P or Si and M = Mo V/VI or V IV/V , has been evaluated by isothermal titration calorimetry (ITC), NMR spectroscopy and cyclic voltammetry. Such a study reveals the host-guest binding constant K1:1 increases strongly with the decrease of the global ionic charge of the POM unit. There is almost one magnitude order of variation in K1:1 per charge unit, where K1:1 falls down from about 10 5 to values close to zero as ionic charge varies from 3-to 6-. Such POMs with molybdenum and vanadium addenda offer the possibility of tuning the hostguest association strength by simple addition/removal of one electron to POMs, opening new avenue for the design of smart materials through redox stimuli.