Green methodology to synthesis heterocyclic diazo dyes using superacid Aquivion® PFSA PW98 as an efficient catalyst

A heterocyclic diazo dye containing the coumarin structure, specifically 7-hydroxy-4-methyl-8-(4-nitrophenyl azo)-6-(4-nitrophenyl azo) coumarin, was prepared using Aquivion PFSA resin. This resin has been shown to be an interesting, effective, and selective acidic catalyst in the diazotization reaction. The dye was obtained by reacting a double molar amount of the aromatic amine, 4-nitro aniline, and then mixing the resulting diazonium salt with one mole of 7-hydroxy-4-methyl coumarin. The purity of this dye was confirmed by measuring the melting point and by thin-film chromatography (TLC). The molecular structure of the dye and the Azo-Hydrazone tautomeric was proven through spectroscopic methods such as 1H-NMR spectroscopy , UV-VIS and infrared spectroscopy IR. • A heterocyclic diazo dye containing coumarin structures was synthesized • Aquivion® PFSA PW98 resin has been shown to be an interesting, effective, and selective acidic catalyst in the diazotization reaction • The synthesized dye showed a color change with varying acidity of the medium • The Dye changes color from dark red to violet in alkaline medium due to the azo-hydrazone resonance • The azo form dominates in the solid state, as was proven in the IR • In the dye solution in dimethyl sulfoxide solvent, the hydrazone form dominates