Design and synthesis of novel sulfa-azo dyes: a sustainable approach to textile dyeing combined with microwave energy

Abstract

As bacteria continue to resist antimicrobial medications, there is a need to develop new compounds. In this work, new sulfonamide-based azo dyes with antimicrobial qualities are synthesized and dyed on fabric using microwave irradiation, an energy-efficient substitute for traditional heating techniques. First, azo linkage was formed at the amine groups of sulfathiazole and sulfamethoxazole, then the diazonium salt coupled with different nucleophilic couplers like 1,3-indandione and 1-indanone. The produced dyes were structurally confirmed using mass, IR, ¹H NMR, and ¹³C NMR spectral data. Molecular docking studies revealed favorable binding affinity toward both pABA- and Pterin-binding amino acid residues, suggesting potential dual DHPS inhibitory behavior. Molecular docking studies of the synthesized sulfa-azo dyes showed encouraging antimicrobial activity. Potential dual inhibitors of DHPS were indicated by the fact that several dyes demonstrated binding with both pABA and Pterin amino acids. Additionally, certain dyes aligned with known co-crystallized inhibitors by interacting with fungal N-myristoyltransferase (NMT). The strongest antibacterial activity was shown by dyes made from indandione and indanone couplers. As a contemporary heating technique, microwave irradiation was used to increase reaction efficiency, lower chemical and water usage, and save energy. Through polarization processes such as electronic, atomic, and interfacial polarization, the improved interaction between microwave energy and polar molecules caused rapid internal heating. Significant improvements in conventional heating were shown by the localized hotspots produced by microwave exposure, which accelerated reaction kinetics and increased product yields. The microwave-assisted dyeing process reduced dyeing time by approximately 70% and enhanced dye uptake by 85% compared to conventional infrared heating.