Fluorescent acid azo dyes from 3-(1,3-benzothiazol-2-yl)naphthalen-2-ol and comparison with 2-naphthol analogs

New four acid azo dyes were synthesized from aromatic amines containing acidic group and 3-(1,3-benzothiazol-2-yl) naphthalen-2-ol by diazotization and coupling reaction. These dyes were characterized by FTIR, 1H NMR and mass spectral analysis. Effect of solvent polarity and role of pH on photo physical properties such as absorption, emission were studied. All these acid azo dyes were applied on wool, silk and nylon whereupon fastness properties were evaluated. A parallel series of dyes using 2-naphthol in place of benzothiazolyl were made to investigate the effect of benzothiazolyl moiety on the fastness and photo physical properties.

► Synthesis and characterization of dyes from 3-(1,3-benzothiazol-2-yl)naphthalen-2-ol.
► Fastness properties were studied and compared with 2-naphthol based acid azo dyes.
► Enhanced photo stability was explained by ESIPT Phenomenon.
► Effects of pH and solvent polarity on photo physical properties were also studied.
► Due to presence of ESIPT, acid azo dyes fluoresce in solvents with lower intensity.