Reconciling the valence state with magnetism in mixed-valent polyoxometalates: the case of a {VOF@VO} cluster.

The electronic structure and magnetism of the recently synthesised mixed-valent {VOF@VO} (1) host-guest polyoxovanadate envisaged as a potential building block of a molecule-based quantum computer are analysed using density functional theory (DFT) and effective Hamiltonian calculations. The form of the t-J like effective Hamiltonian has been inspired by the acquired DFT data, and the valence state used in DFT calculations has been suggested by the fits to the experimental magnetic data with the effective Hamiltonian. This self-consistent approach breaks through the magnetochemical limitations of vanadium-oxo cluster 1, giving results fully concordant with the experiment and allowing us to determine the valence state of 1, which contrary to other members of this host-guest family appears to feature 9 valence electrons.