NMR studies on interactions between diperoxovanadate and N-substituted picolinamide

Abstract

To understand the substituting effects of organic ligands on the reaction equilibrium, the interactions between diperoxovanadate complex [OV(O-2)(2)(D2O)(-)/[OV(O-2)(2)(HOD)](-) and a series of N-substituted picolinamide ligands in solution were explored using multinuclear (H-1, C-13, and V-51) magnetic resonance, COSY, DOSY, and variable temperature NMR in 0.15 mol/L NaCl ionic medium for mimicking the physiological conditions. The order of reactive capability of the picolinamide-like ligands with [OV(O-2)(2)(D2O)](-)/[OV(O-2)(2)(HOD)](-) is as follows: N-methylpicolinamide approximate to N-(2-hydroxyethyl)picolinamide > N-ethylpicolinamide>N-propylpicolinamide. The substituting group influences the reactivity by an electron effect. Competitive coordination interactions result in a series of new seven-coordinated peroxovanadate species [OV(O-2)(2)L](-) (L=N-substituted picolinamide).