Multinuclear NMR spectroscopic and theoretical study on the interactions between diperoxovanadate complex and picoline-like ligands.

To understand the substituting effects of organic ligands on the reaction equilibrium, the interactions between diperoxovanadate complex OV(O(2))(2)(H(2)O) and a series of picoline-like ligands in solution were explored using 1D multinuclear ((1)H, (13)C, and (51)V) magnetic resonance, 2D diffusion ordered spectroscopy (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 picoline-like ligands with OV(O(2))(2)(H(2)O) is found to be picolinamide>N-methylpicolinamide>methyl picolinate>ethyl picolinate approximately propyl picoliniate>isopropyl picolinate. The substituting group influences the reactivity by either steric effect or electron-donating effect. Competitive coordination interactions result in a series of new seven-coordinated peroxovanadate species OV(O(2))(2)L (L=picoline-like ligands). Their coordination ways were confirmed by density functional calculations.