Electronic structure and surface properties of the mixed-valence doughnut shaped polyoxomolybdate nanocapsule Mo57V6

We report a detailed analysis of the electronic structure and results of molecular dynamics simulations for the large polyoxomolybdate [H₃Mo₅₇V₆(NO)₆O₁₈₃(H₂O)₁₈]^21- (Mo₅₇V₆) which is a highly symmetric anion with a complex electronic structure and exhibiting a unique variety of multifunctionality. The six vanadium centres are reduced with one electron each, the six Mo centres are bonded to non-innocent NO ligands and the additional six 4d electrons are mostly delocalised over the rest of molybdenum atoms. DFT calculations carried out with the solvent – modelled by a continuum approach – suggest that despite the large charge of the anion, the Mo₅₇V₆ framework can be easily reduced in polar solvents. Furthermore, the Mo₅₇V₆ cluster has 18 water molecules trapped in its internal cavity. Molecular dynamics simulations carried out with different solvent conditions suggest that the water molecules inside the cavity have a high ordered structure over a wide range of temperatures and give important information about the cluster anion interactions with the cations present in solution. The obtained results allow a better understanding of related properties of the giant ball-shaped polyoxometalates/Keplerates as the present cluster contains similar building blocks – like the (metal)₆O₆ type pores with crown ether-like structure.