Theoretical study on the tetranuclear endohedral vanadyl carboxylates with guest-switchable redox properties and large polarizability

Abstract

The polarizability and redox properties for the tetranuclear vanadium–oxide–carboxylates have been investigated using density functional theory (DFT). These so-called inorganic crown ethers possess large polarizabilities, which are equivalent to fullerene and generate large polarization on the guest anions into the host. The dipole-induced dipole interaction between the host and the guest anions induces charge transfer from the guest to the host, which is enhanced with the increasing polarization. Moreover, the redox potentials are sensitive to different guests inside the host bowl, and they shift negatively as compared to the isolated host bowl. In contrast, the modification of the methyl group by CH₂tBu on the rim of the bowl has evoked higher polarizability (over 560 a.u.) with larger polarization on the guest anions and more negative redox potentials. The weak interaction energies in accord with the organic crown ether incorporating alkali metal ions indicate that the guest anions can move freely inside and outside the host bowl, so this kind of inorganic crown ether may exhibit potential guest-switchable redox properties based on reversible complexation–decomplexation and will be expected to find applications in ion recognition and selectivity studies based on the sensitivity to different guests.