Theoretical study of the structure, IR and NMR of the bis-peroxo-oxovanadate species containing-histidine peptides

The molecular structures, IR spectroscopy, 1H, 13C and 51V NMR spectroscopy of three bis-peroxo-oxovanadate species containing histidine peptides were studies on theoretical grounds. The geometry optimizations and IR spectra in gas phase were carried out with the DFT (B3LYP functional) method and the spectra of the peptides under study were obtained with the gauche-including atomic orbital (GIAO) method as implemented in the GAUSSIAN 09 package. The standard 6-31+G∗ basis set and core-valence effective core potential Lanl2dz were employed. New coordination modes were found in the potential curves for the rotation through the V−N coordination bond. They bent up and down (Bu, Bd) with the imidazole ring aligned with the V–O(peroxo) bond and also bent with respect to the VO group. In addition, the parameters describing quadrupolar and chemical shift anisotropy interactions are determined theoretically. In particular, this results help to solve apparent inconsistencies found in the 51V NMR solution spectroscopy of the three bis-peroxo-oxovanadate complexes. The gathered evidence furthers the understanding of the electronic implications and structure–activity relationships in the case of histidine peptide-containing bis-peroxo-oxovanadate structures.