Ultraviolet Absorption and Fluorescence Studies of 1-Methyl-2(1H)-Pyridinimine and Derivative in Polar and Non-Polar Solvents

Abstract

The ultraviolet (u.v.) and fluorescence spectra and relative fluorescence intensities of 1-methyl-2(1H)-pyridinimine (1-MIP) and 1,2-dimethylpyridinimine (2-MIP) were measured in several solvents at room temperature. The solvents’ effect on the absorption and fluorescence spectra of MIP indicates that the ππ* transition shifts to higher energies (shorter wavelengths) are due to solvents’ interactions and the formation of the pyridinium cation. One major difference in the u.v. and fluorescence spectra is the small relative intensity in non-polar solvents. This was attributed to the proximity effect of ππ* and nπ* states which can lead to vibronic interactions, and to distortions of the excited-state potential surfaces. In polar solvents, however, these two states are shifted in energy due to solvent–solute interactions, which decrease the energy of the potential surface.