NITROGEN NMR CHEMICAL-SHIFTS IN MESOIONIC COMPOUNDS - A COMPARISON OF THEORY AND EXPERIMENT

Ab initio results for the shielding constants in prototype mesoionic compounds are compared with experimental data. We find a linear relationship between the nitrogen chemical shifts computed in the coupled Hartree-Fock approximation with gauge-independent atomic orbitals and the observed values. An analysis of similar relationships for other molecules suggests that accurate theoretical results may be obtained directly in an ab initio approach incorporating correlation corrections.