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)(H2O)](-) and a series of picoline-like ligands in solution were explored using ID multinuclear (H-1, C-13, and V-51) 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)(H2O)](-) is found to be picolinamide > N-methylpicolinamide > methyl picolinate > ethyl picolinate, 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. (c) 2005 Elsevier B.V. All rights reserved.