Photodimerization of chlorpromazine radical CPZS.+ under the irradiation of UV light

CPZS.+ radical excited at S atom in the phenothiazine ring was obtained by illumination of aqueous solution of chlorpromazine (CPZ..) for 15 min with UV light (303 nm). The radicals in oxygenated solution formed green, dimeric photoproduct CPZSOOSCPZ (m. wt. 628 +/- 1) lambda max. 741.9 nm, IR spectrum 760, 1470, 3400 cm1, fluorescence emission at 485 nm (max. excitation 365 nm). The dimer decomposed in alkaline methanol (pH 10.0) with intensive luminescence (max. at 500 nm).