Molecular and electron-spin structures of a ring-shaped mixed-valence polyoxovanadate (IV, V) studied by 11B and 23Na solid-state NMR spectroscopy and DFT calculations

Abstract

11B and 23Na solid-state nuclear magnetic resonance (NMR) spectra of ring-shaped paramagnetic crystals of H15[V7IVV5VB32O84Na4]·13H2O containing seven d1 electrons from VIV were studied. Magic-angle-spinning (MAS) and multiple-quantum MAS NMR experiments were performed at moderate (9.4T) and ultrahigh magnetic fields (21.6T). The NMR parameters for quadrupole and isotropic chemical shift interactions were estimated by simulation of the NMR spectra and from relativistic density functional theory (DFT) calculations. Four Na ions incorporated into the framework were found to occupy four distinct sites with different populations. The DFT calculation showed that d1 electrons with effectively one up-spin caused by strong antiferromagnetic interactions were delocalized over the 12V ions.