Study on structural variation of oxalate-oxodiperoxovanadate(V) from solid state to solution using NMR spectroscopy and theoretical calculation

In order to understand the geometric structure of oxalate-diperoxovanadate(V) K3[VO(O2)2(C2O4)]·H2O {abbr. bpV(ox)} in water, 51V and 13C NMR spectroscopy and density functional theory (DFT) calculations were employed to explore the difference with the solid structure of bpV(ox) from X-ray diffraction. It is suggested by the differences in the 51V and 13C isotropic chemical shifts between solid state and solution and verified by our DFT calculations that the geometry of bpV(ox) anion may undergo change upon dissolution. Besides, the 13C NMR spectra of the coordinated oxalate in bpV(ox) was first assigned with the help of DFT calculation. The combination of the NMR data and DFT calculations confirms that bpV(ox) is seven-coordinated pentagonal bipyramidal in solid, while it is six-coordinated pentagonal pyramidal when it dissolves in water. This study sheds some light on the coordination chemistry of peroxovanadium(V) complexes.