Is the Spin-Orbit Coupling Important in the Prediction of the (51)V Hyperfine Coupling Constants of V(IV)O(2+) Species? ORCA Versus Gaussian Performance and Biological Applications

Density functional theory calculations of the V-51 hyperfine coupling (HFC) tensor A, have been completed for eighteen (VO2+)-O-IV complexes with different donor set, electric charge and coordination geometry. A tensor was calculated with ORCA software with several functionals and basis sets taking into account the spin-orbit coupling contribution. The results were compared with those obtained with Gaussian 03 software using the half-and-half functional BHandHLYP and 6-311g(d, p) basis set. The order of accuracy of the functionals in the prediction of A(iso), A(z) and dipolar term A(z,anis) is BHandHLYP > PBE0 >> B3PW > TPSSh >> B3LYP >> BP86 > VWN5 (for A(iso)), BHandHLYP > PBE0 >> B3PW > TPSSh > B3LYP >> BP86 > VWN5 (for A(z)), B3LYP > PBE0 similar to B3PW similar to BHandHLYP >> TPSSh > BP86 similar to VWN5 (for A(z,anis)). The good agreement in the prediction of A(z) with BHandHLYP is due to a compensation between the overestimation of A(iso) and underestimation of A(z,anis) (A(z) = A(iso) + A(z,anis)), whereas among the hybrid functionals PBE0 performs better than the other ones. BHandHLYP functional and Gaussian software are recommended when the (VO2+)-O-IV species contains only V-O and/ or V-N bonds, whereas PBE0 functional and ORCA software for (VO2+)-O-IV complexes with one or more V-S bonds. Finally, the application of these methods to the coordination environment of (VO2+)-O-IV ion in V-proteins, like vanadyl-substituted insulin, carbonic anhydrase, collagen and S-adenosylmethionine synthetase, was discussed.