On the Base Strength of Some Nitrogen Heterocycles in the Excited State

Abstract

Abstract 1. The fluorescence and absorption spectra of aqueous solutions of quinoline, acridine and 2,8-diaminoacridine were observed at various pH values, and it became clear that the stabilization energy by proton addition is larger in the excited state than in the ground state. 2. The effects of hydrogen bonding and proton addition upon the spectra were confirmed to be the same in tendency. 3. On the basis of the fluorescence intensities in various organic solvents, some discussions were made about the contribution of non-bonding electron to the inner quenching of fluorescence. 4. The vapor spectrum of quinoline was-taken and line spectra were observed, which are most certainly attributable to n→π* transition.