INFLUENCE OF ELECTRON-DONOR SUBSTITUENTS ON THE LUMINESCENCE BEHAVIOR OF A 2-AMINOAZINE

A comparative luminescence study of 5 related 2-aminoazines indicates that there is a dependence of emission polarization and other photophysical parameters upon the extent of charge transfer in the lowest excited singlet and triplet states, The phosphorescence emission polarization is shown to increase from - 0.1 to + 0.28 for substituents with an increasing tendency toward electron donation, while only minor changes occur in the triplet state energy. An electron donor substituent increases intersystem crossing and the phosphorescence yield, which is accompanied by a decreasing fluorescence yield, and a decreasing phosphorescence lifetime.