ABSORPTION AND FLUORESCENCE CHARACTERISTICS OF SOME 2-ARYL-BENZOTHIAZOLES AND 2-HETARYL-BENZOTHIAZOLES

The absorption and fluorescence characteristics of some 2-aryl- and 2- hetaryl-benzothiazoles were studied with respect to the nature of the substituents and the polarity of the solvents. The longest wavelength absorption maximum of these compounds is in the region 27 000-34 000 c m-1. The PPP-SCF-CI quantum chemical calculations show that they resul t from a singlet pi-pi transition. The fluorescence Franck-Condon tra nsition is between 19 000 and 28 000 cm-1. The fluorescence quantum yi eld of most of the investigated benzothizoles exceeds 0.5. The compoun ds do not phosphoresce in frozen ethanol solutions at 77 K.