Density functional theory calculations of nuclear quadrupole coupling constants with calibrated N-14 quadrupole moments

Density functional calculations of the electric field gradient tensor at th e nitrogen nucleus in 13 test molecules, containing 14 nitrogen sites, have been performed using the linear combination of Gaussian-type orbital Kohn- Sham density functional theory (LCGTO-KSDFT) approach. Local and gradient c orrected functionals were used for all-electron calculations. All the molec ular structures were optimized at their respective levels of theory with ex tended basis sets. Calibrated N-14 nuclear quadrupole moments were obtained through a fitting procedure between calculated electric field gradients an d experimental nuclear quadrupole coupling constants of the test set of mol ecules for each basis set and functional considered. With these calibrated N-14 nuclear quadrupole moments, the nuclear quadrupole coupling constants of the following selected systems were determined: fluoromethylisonitrile, pyridine, pyrrole, imadazole, pyrazole, 1,8-bis(dimethyl-amino)naphthalene, cyclotetramethylenetetranitramine, cocaine and heroin.