Multinuclear nuclear magnetic resonance and density functional theoretical studies on the structure of bisperoxovanadium complexes with bidentate donors

Solid state and solution 51V and 13C NMR studies on four fundamental bisperoxovanadium complexes containing bidendate donor ligands were reported, together with DFT calculations of structural and NMR parameters. The 51V solid-state NMR characterization of the four complexes with [VO(O2)2L]n− anion {abbr. bpVL, where L = oxalic acid dianion (ox), pyridine-2-carboxylic acid (pic), bipyridine (bipy), and 1,10-phenanthroline (phen)} show that the ligands have a significant effect on the electric-field gradient tensor, with the quadrupolar coupling constant ranging from 4.0 to 5.8 MHz. The experimental and theoretical results suggest that the vanadium center of bpVpic, bpVphen and bpVbipy in solid state and aqueous solution are all seven-coordinated except that bpVox is six-coordinated in aqueous solution. The steric space hindrance of the organic ligands and the bonding between vanadium with the coordination influences the activity of bpVL complexes.