A COMPARATIVE-STUDY - THE PHOTOPHYSICS OF 2-PHENYLBENZOXAZOLES AND 2-PHENYLBENZOTHIAZOLES

The photophysical properties of 2-phenylbenzothiazole and 2-phenylbenzoxazole were compared. At room temperature 2-phenylbenzothiazole in n-heptane exhibits a broad, structureless absorption and a low fluorescence yield of approximate to 0.005 (tau(f)< 200 ps). In contrast, 2-phenylbenzoxazole shows a structured absorption and a high fluorescence yield, Phi(f) approximate to 0.78+/-0.05 (tau(f) approximate to 1.5 ns) .These spectral differences arise from a drastic change in the dynamics of C-1-C-1, torsional motion, as evidenced in the temperature-dependent studies, spectral properties of their derivatives and AM1 calculations.