Synthesis and Comprehensive Examination of New Non-Toxic Heterocyclic Mono-Azo Acid Dyes: Investigating Biological Activity, Application on Fabric, Solvatochromism, and DFT Insights

A series of acid dyes (BT1-BT5) capable of imparting antimicrobial properties to the polyamide fabric was synthesized. This approach aims to reduce energy-intensive processes in the textile production by eliminating the need for additional antimicrobial finishing step. Various analytical methods were applied to characterize the resulting dyes, and their solvatochromic properties were examined in solvents with varying levels of polarity and pH. The geometries of these synthetic colorants were optimized using the B3LYP/6-31G (d, p) method, and their electronic excitation properties were determined through TD-DFT. These dyes were then used for the coloration of wool and nylon-6 fabrics at a shade depth of 4% owf (On Weight of Fabric). Subsequently, evaluation of their fastness attributes was conducted. Encouraging results were observed for wash, perspiration, and rubbing fastness. The lightfastness was found to be comparatively better on wool than on nylon-6. Experiments were conducted to evaluate the efficacy of these chromophores against a range of bacterial and fungal strains. The dye BT3 exhibited significant antibacterial activity, while the dye BT2 demonstrated potency against all of the tested fungal strains. These chromophores were also tested on BJ Human Fibroblast Cells, which showed that these are non-cytotoxic.