Synthesis, spectroscopic properties and applications of novel N-heterocycle-containing benzotriazoles as UV absorbers

Two novel N-heterocycle-containing benzotriazole compounds, 5-(5-chloro-2-benzotriazolyl)-6-hydroxy-1,4-dimethyl-3-carbonitrile-2-pyridone (2) and 4-(5-chloro-2-benzotriazolyl)-5-methyl-2-phenyl-3-pyrazolone (4), were synthesized from reactant 4-chloro-2-nitroaniline via diazotization, azo coupling, reductive cyclization and acidification. Their structures were confirmed by FT-IR, 1H NMR, mass spectroscopy and elemental analysis. Their spectral properties were investigated and compared with that of a common commercial benzotriazole UV absorber Tinuvin 326. It is found that the novel N-heterocycle-containing benzotriazole compounds exhibit sharp single peak in the range of 280–400 nm and have much higher molar extinction coefficients than that of Tinuvin 326. Their anti-UV protection properties on polyester fabric were also evaluated and compound 4 was much superior to compound 2 due to its higher exhaustion.