51V solid-state NMR investigations and DFT studies of model compounds for vanadium haloperoxidases

Three cis-dioxovanadium(V) complexes with similar N-salicylidenehydrazide ligands modeling hydrogen bonding interactions of vanadate relevant for vanadium haloperoxidases are studied by 51V solid-state NMR spectroscopy. Their parameters describing the quadrupolar and chemical shift anisotropy interactions (quadrupolar coupling constant CQ, asymmetry of the quadrupolar tensor ηQ, isotropic chemical shift δiso, chemical shift anisotropy δσ, asymmetry of the chemical shift tensor ησ and the Euler angles α, β and γ) are determined both experimentally and theoretically using DFT methods. A comparative study of different methods to determine the NMR parameters by numerical simulation of the spectra is presented. Detailed theoretical investigations on the DFT level using various basis sets and structural models show that by useful choice of the methodology, the calculated parameters agree to the experimental ones in a very good manner.