Synthesis and evaluation of changes induced by solvent and substituent in electronic absorption spectra of some azo disperse dyes

Five azo disperse dyes were prepared by diazotizing 4′-aminoacetophenone and p-anisidine and coupling with varies N-alkylated aromatic amines. Characterization of the dyes was carried out by using UV–vis, FTIR and 1H NMR spectroscopic techniques. The electronic absorption spectra of dyes are determined at room temperature in fifteen solvents with different polarities. The solvent dependent maximum absorption band shifts, were investigated using dielectric constant (ɛ), refractive index (n) and Kamlet–Taft polarity parameters (hydrogen bond donating ability (α), hydrogen bond accepting ability (β) and dipolarity/polarizability polarity scale (π*)). Acceptable agreement was found between the maximum absorption band of dyes and solvent polarity parameters especially with π*. The effect of substituents of coupler and/or diazo component on the color of dyes was investigated. The effects of acid and base on the visible absorption maxima of the dyes are also reported.

The variation of λmax (nm) of dye 4 as a function of π*.Figure optionsDownload as PowerPoint slideHighlights
► In this study five azo disperse dyes synthesized and characterized.
► The solvatochromic behavior of synthesized dyes evaluated in selected solvents.
► The influence of the substituent and pH changes on the dyes considered by comparison of the absorption maxima of these dyes in solutions.