Spectroscopic and theoretical study on the interaction between diperoxovanadate complexes and glycyl-histidine

The interaction between diperoxovanadate complexes (K3[VO(O2)2(C2O4)]·H2O and [VO(O2)2(D2O)]−/[VO(O2)2(HOD)]−) and glycyl-histidine (abbr. GlyHis) in solution was studied by 1D NMR including variable-temperature NMR, 2D diffusion ordered spectroscopy (DOSY), HMQC and density functional theory (DFT) calculations. The results indicate that a pair of [VO(O2)2(GlyHis)]− isomers is formed. The vanadium in the new species is coordinated by either the ɛ-N or δ-N in the imidazole ring. The relative ratio of the isomers was affected by temperature. Theoretical calculation results provide a reasonable explanation on the relative coordination capability of different nitrogen sites. Solvation effect is shown to be important for the reactivity of the interaction system.