ABINITIO CALCULATIONS OF CHEMICAL-SHIFT AND QUADRUPOLE COUPLING TENSORS IN PHO32-

Structural characteristics (bond lengths and angles) have been calculated by using GAUSSIAN 86 and the 6-31G* basis at the Hartree-Fock level of theory for PHO32- and its acidic forms. The results of these calculations compare favorably to solution-state data from NMR and solid-state data from both electron and neutron diffraction. Isotropic chemical shifts and shift anisotropies for phosphorus and hydrogen in the PHO32- anion and its protonated analogues have also been calculated. The 6-311G** basis correctly predicts a linear correlation between both the proton and phosphorus isotropic chemical shift and the PH bond distance in PHO32-, and it correctly predicts a linear correlation between both proton and phosphorus chemical shift anisotropies and the PH bond distance. However, the 4-31G* basis erroneously predicts a rapidly changing quadratic relation between the phosphorus and proton chemical shift tensors and the PH bond distance in PHO32-. The 4-31G* basis incorrectly predicts the trend between the solution pH (protonation) and the phosphorus isotropic chemical shift that is seen in solution-state NMR. The deuterium quadrupole coupling constant in PDO32- is calculated by using the 6-31G* basis and is shown to vary as a function of solution pH. © 1990 American Chemical Society.