To understand the effects of organic ligands of the diperoxovanadate complexes on the reaction equilibrium, the interactions between a series of diperoxovanadate complexes [OV(O₂)₂LL']ⁿ− [n＝1～3; 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 1-methylimidazole (abbr. N-Me-Im) in solution were explored using multinuclear (¹H, ¹³C, and ⁵¹V) 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 1-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(O₂)₂(N-Me-Im)]⁻ is formed due to the competitive coordination.

Key words: diperoxovanadate, 1-methylimidazole, interaction, NMR