NMR and theoretical study on the coordination and solution structures of the interaction between diperoxovanadate complexes and histidine-like ligands

Abstract

To simulate the types of coordination and solution structures of the active site of haloperoxiclases, the interaction systems between diperoxovanadate complexes [OV(O-2)(2)L](n-) (n = 1 or 3, L = oxalate or H2O) and a series of histidine-like ligands in solution have been studied by using 1 D multinuclear (H-1, C-13, and V-51) NMR, 2D diffusion ordered spectroscopy, and variable-temperature NMR in 0.15 mol/L NaCl ionic medium, representing the physiological conditions of human blood. Some direct NMR data are given for the first time. The reactivity among the histidine-like ligands is imidazole > 2-methylimidazole > camosine approximate to 4-methylimidazole > histidine. Competitive coordination interactions result in a series of new peroxovanadate species [OV(O-2)(2)L '](-) (L ' = histidine-like ligands). When the ligands are 4-methylimidazole, histidine, and camosine, a pair of isomers have been observed, which are attributed to different types of coordination between vanadium atom and ligands. The results of density functional theory calculations provided a reasonable explanation on the relative reactivity of the histicline-like ligands and the molar ratios of isomers. Theoretical results signify the importance of the solvation effect for the reactivity and stability of the interaction systems.