Theoretical Study of Fluorinated Pyridine Cations

Cations of fluorinated pyridines（pentafluoropyridine，2，6-difluoropyridine，and 2-fluoropyridine）have been studied by using density functional B3LYP method in conjunction with 6-31G（d，p），6-311G（d，p），6-31+G（d，p），and 6-311+G（d，p）basis sets. B3LYP geometry optimization and frequency analysis calculations indicate that the pentafluoropyridine cation，2，6-difluoropyridine cation，and 2-fluoropyridine cation have C2v，C2v，and Cs structures in the 2A2，2A2，and 2A" ground states，respectively. The calculated geometries of the cations and the parent molecules were compared. The natural population analysis calculations at the B3LYP level with different basis sets were performed on the three cations and the three parent molecules. The isotropic hyperfine coupling constants in the three cations（radicals）were calculated. The vertical and adiabatic ionization potential（VIP and AIP）values of the pentafluoropyridine，2，6-difluoropyridine，and 2-fluoropyridine molecules were calculated by using the B3LYP method，and the calculated VIP values are in excellent agreement with experiment.