PERTURBATION OF THE ELECTRONIC-ENERGY LEVELS AND FLUORESCENCE BEHAVIOR OF 2-AMINOPYRIDINE BY METHYL SUBSTITUTION

The fluorescence of methyl-substituted derivatives of 2-aminopyridine has been studied and compared with CNDO-CI calculations. The similarity of the variation of the lowest 1π,π* oscillator strength and the variation of fluorescence yields provide a basis for understanding the fluorescence of these molecules. The results support vibronic coupling between close lying 1n,π* and 1π,π* states, whose inversion may be achieved by proper positioning of the methyl group. Comparison of the measured fluorescence yields of these molecules with those reported for methyl-substituted benzenes supports the view that coupling of 1π,π* and 1n,π* states is a source of enhanced radiationless deactivation. © 1979 American Chemical Society.