Study of the electronic spectra of 2-fluoro-5-chloropyridine and determination of the excited state dipole moment

Abstract

Abstract The ultraviolet absorption spectrum in the region 300-190 nm in the vapour phase and in solution in different solvents, and the luminescence emission spectra in ethanol and cyclohexane at 77 K have been measured for 2-fluoro-5-chloropyridine and analysed. The molecule shows two systems of absorption bands corresponding to the π→π* transition II and π→π* transition III. The oscillator strength of the two systems of absorption bands in solutions and the excited state dipole moment in the 1 π, π* state have been determined. The half-life of phosphorescence in cyclohexane is measured and found to be 3·6 s.