Synthesis, Characterization and Solvatochromic Action of 4-Bromophenylazo-2-Naphtholazo-Benzene

Abstract

This study reveals the successful synthesis and comprehensive characterization of a novel disazo dye, 4-Bromophenylazo-2-Naphtholazo-Benzene, using accessible precursors through sequential diazotization and coupling reactions. The synthesis involved the diazotization of 4-bromoaniline and aniline, followed by stepwise coupling with 2-naphthol and benzene, yielding a maroon colored dye with high crystallinity and a melting point of 186 °C. Structural and functional analysis were conducted using UV-Visible spectrophotometry, Fourier Transform Infrared Spectroscopy (FTIR), Thin Layer Chromatography (TLC), Gas Chromatography-Mass Spectrometry (GC-MS), and elemental analysis. The UV-Vis spectrum revealed characteristic π–π* and n–π* transitions with absorption maxima up to 780 nm, attributed to the extended conjugation and presence of electron-withdrawing bromine substituents. FTIR spectra confirmed the presence of key functional groups such as azo (–N=N–) and aromatic C–Br, while GC-MS validated the compound’s molecular integrity through prominent base peaks. TLC analysis indicated moderate polarity (Rf = 0.76), and elemental composition corroborated the incorporation of bromine and nitrogen within the structure. The dye displayed excellent application potential, exhibiting high wash-, light-, and heat-fastness ratings (4–5) across a range of textile fibres including cotton, polyester, acrylic, and wool. These results highlight the compound’s chemical stability and suitability for commercial dyeing applications.