An investigation on the vertical electronic spectra of trans-difluorodiimide (N 2F 2), diazirine (N 2CH 2) and difluorodiazirine (N 2CF 2)

Abstract

The effect of replacing H by F on the electronic spectra is investigated for the molecules trans -N 2 H 2 , trans -N 2 F 2 and N 2 CH 2 , N 2 CF 2 using a combined self-consistent field configuration-interaction (SCF—Cl) method. The relative stabilization of the molecular orbitals follows the inequality N + (σ) ⋍ π ≫ n − (σ) in the case of N 2 F 2 and π ≫ n + (σ) ≫ n − (σ) in the case of N 2 CF 2 . Contrary to the general belief that the fluorine substitution causes a blue-shift in the electronic spectra of molecules, the calculations suggest a red-shift for the π→π* transition in trans -N 2 F 2 . The necessity of configuration interaction calculation for certain singlet states examined is stressed.