To understand the effects of organic ligands of the diperoxovanadate complexes on the reaction equilibrium, the interactions between a series of diperoxovanadate complexes [OV(O-2)(2)LL '](n-) [n=1 similar to 3; LL '=oxalate, abbr. oxa; picolinate, abbr. pic; 2,2 '-bipyridine, abbr. bipy; and 1,10-phenanthroline, abbr. phen. The corresponding peroxovanadate species abbreviate bpV(oxa), bpV(pic), bpV(bipy), and bpV(phen)] and I-methylimidazole (abbr. N-Me-Im) in solution were explored using multinuclear (H-1, C-13, and V-51) magnetic resonance, COSY, and variable temperature NMR in 0.15 mol/L NaCl ionic medium for mimicking the physiological conditions. The experimental results indicated the activity order of these four complexes with I-methylimidazole as follows: bpV(oxa)> bpV(pic)> bpV(bipy)> bpV(phen). Both the coordinating capability and the steric effect of the organic ligands affect the reaction equilibrium. At the same time, a new six-coordinated peroxovanadate species [OV(O-2)(2)(N-Me-Im)](-) is formed due to the competitive coordination
