MOLECULAR LUMINESCENCE OF SOME ISOALLOXAZINES IN APOLAR SOLVENTS AT VARIOUS TEMPERATURES

Abstract

Abstract— –Spectral properties of isoalloxazines in organic solvents of low polarity are determined at 300 and 77 K. Vibrational structure in the spectra reveals a vibrational mode of 1250cm ‐ . The pure electronic transition energies are established to a greater accuracy than was done previously and comparison to theoretical data is made. Actual lifetimes up to 10 ns for fluorescence and 300 ms for phosphorescence are found. The ratio of the actual fluorescence lifetime and the radiative lifetime is found to agree well with the quantum yield. Solvent interactions hardly shift the energy of the first electronically excited singlet state but merely affect the Franck‐Condon envelope of the spectrum and the non radiative decay of the chromophore. In albne solutions at 77 K isoalloxazine clusters are formed exhibiting P‐type delayed fluorescence.