Ab Initio Calculation of Nuclear Magnetic Resonance Chemical Shift Anisotropy Tensors I. Influence of Basis Set on the Calculation of P Chemical Shifts

The influence of changes in the contracted Gaussian basis set used for ab initio calculations of nuclear magnetic resonance (NMR) phosphorous chemical shift anisotropy (CSA) tensors was investigated. The isotropic chemical shift and chemical shift anisotropy were found to converge with increasing complexity of the basis set at the Hartree-Fock (HF) level. The addition of d polarization function on the phosphorous nuclei was found to have a major impact of the calculated chemical shift, but diminished with increasing number of polarization functions. At least 2 d polarization functions are required for accurate calculations of the isotropic phosphorous chemical shift. The introduction of density functional theory (DFT) techniques through the use of hybrid B3LYP methods for the calculation of the phosphorous chemical shift tensor resulted in a poorer estimation of the NMR values, even though DFT techniques result in improved energy and force constant calculations. The convergence of the NMR parameters with increasing basis set complexity was also observed for the DFT calculations, but produced results with consistent large deviations from experiment. The use of a HF 6-311++G(2d,2p) basis set represents a good compromise between accuracy of the simulation and the complexity of the calculation for future ab initio calculations of P NMR parameters in larger complexes. * Author to whom correspondance should be addressed: [email protected]