NMR Studies on Interactions between Diperoxovanadate Complex and Pyridine-Like Ligands

To understand how the monodentate/bidentate pyridine-like ligands affect the reaction equilibrium, the interactions between diperoxovanadate complex [OV (O2)2(D2O)]-/[OV (O2)2(HOD)]-(abbr. bpV) and a series of pyridine-like ligands in solution were explored using multinuclear (1H, 13C, and 51V) magnetic resonance, COSY, HSQC, HMBC, and variable temperature NMR in 0.15 mol·L-1 NaCl ionic medium for mimicking the physiological condition. The reactivity among these organic ligands and bpV are 2,2′-bipyridine 4,4′-dicarboxylate-2,2′-bipyridine pyridine isonicotinate. The experimental results indicated that the coordinating ability of bidentate ligands is stronger than that of monodentate ligands, and the coordinating ability of unsubstituted ligands is stronger than that of corresponding carboxylate substituted ligands. The competitive coordination results in the formation of a series of new six-coordinated (pyridine or isonicotinate) or seven-coordinated (2,2′-bipyridine or 4,4′-dicarboxylate-2,2′-bipyridine) peroxovanadate species [OV(O2)2LL′]n-(LL′= pyridine-like ligands, n=1, 2, 3).