Photochemical reaction of a dye precursor 4-chloro-1,2-phenylenediamine and its associated mutagenic effects

4-Chloro-1,2-phenylenediamine (4-Cl-o-PDA) is an aromatic diamine used as a precursor for manufacture of hair dyes and dyes of other purposes. 4-Cl-o-PDA has been found to be photomutagenic in bacteria when concurrently exposed to simulated sunlight irradiation. Irradiation of 4-Cl-o-PDA by either outdoor sunlight or indoor lamp, one main photoproduct appeared and it was found to be 2,3-diamino-7-chlorophenazine, a dimerized product through the excited state reaction of 4-Cl-o-PDA in the presence of oxygen. The isolated yield of 13% for 2,3-diamino-7-chlorophenazine is far better than the oxidation reaction of 4-Cl-o-PDA by H2O2 and may therefore be used as a synthetic method. The half live of transformation for 4-Cl-o-PDA in water (100 μM) is 39 min when exposed to outdoor sunlight. The photomutagenicity of 4-Cl-o-PDA and its photoproduct were tested in Salmonella typhimurium TA102. Under the same conditions, both compounds are photomutagenic. In addition, 2,3-diamino-7-chlorophenazine is both phototoxic and mutagenic.