The photoreactivity of the triplet excited state of thioxanthone (TX) was investigated employing the laser flash photolysis technique. The wavelength for the absorption maximum and the lifetime of the triplet excited state are solvent dependent. When hydrogen donor solvents were employed, a new band at 410 nm was observed in the triplet absorption spectrum, which was attributed to the ketyl radical derived from thioxantone. Quenching rate constants, k q, ranged from (1.7 ± 0.1) × 10(6) L mol-1 s-1 for toluene to ca. 10(9) L mol-1 s-1 for phenol and its derivatives containing polar substituents, as well as for indole, triethylamine and DABCO.
laser flash photolysis; tioxanthone; triplet excited state; solvent effect
