Nonempirical calculations of NQR spectrum parameters of azetidine

Abstract

The components of the 14N electric field gradient (EFG) tensor, the corresponding nuclear quadrupole coupling constant (NQCC) X, and the asymmetry parameter q of azetidine were calculated using the restricted Hartree--Fock--Roothaan method. The geometry of azetidine was optimized with the 4-31G basis set, and the values of the ring puckering angle (0) and the angle between the N--H bond and the CNC plane ([3) were refined with the 6-31G* basis set. The effect of choice of geometry on calculated NQR parameters was studied. To clarify the origin of EFG at the nitrogen atom nucleus, the contributions from individual bond orbitals and lone electron pairs to the EFG tensor components eqi i were calculated in the framework of the LMO approach. It was demonstrated that the 4-31G + 6-31G*//6-31G* level calculations give NQCC and q values of azetidine that are in good agreement with the results of MW spectroscopy.