MULTIREFERENCE CONFIGURATION-INTERACTION AND DENSITY-FUNCTIONAL STUDYOF THE AZETIDINE RADICAL-CATION AND THE NEUTRAL AZETIDIN-1-YL RADICAL

The geometry and the hyperfine structure of the four-membered rings az etidin-1-yl radical (C3H6N) and azetidine radical cation (C3H6NH+) hav e been studied. The geometries of both molecules were optimized using Moller-Plesset perturbation theory as well as density functional appro aches, while the hyperfine structure was calculated using the multiref erence configuration interaction with perturbational correction (MRD-C I/B-K) and density functional methods. The geometry of the radical cat ion was found to be planar, while the neutral radical is puckered with an optimized puckering angle of 22-23 degrees. Employing a [6s3p/4s] AO basis the N-14 isotropic hyperfine coupling constants (hfcc's) are 15.1 G in the neutral radical and 22.5 G in the radical cation, compar ed to the experimental values of 14.1 and 19.5 G. For the isotropic hf cc's of the beta protons qualitative agreement between experiment and the present study was found. The influence of the molecular geometry a nd the theoretical treatment upon the values of the hfcc's has been st udied, and some trends in the hfcc's of both molecules are discussed.