Synthesis of Pyridine Clubbed Tetrahydrobenzo[b]thiophene Azo Dye Analogues Using the Gewald Reaction: Catalytic Optimization, Antibacterial, and Dye Investigation.

A series of novel pyridine-bearing tetrahydrobenzo[b]thiophene-3-carbohydrazide mono azo dyes was synthesized by combining the Gewald and azo dye approaches with basic catalytic optimization of the intermediate product. We investigated the in vitro activity of the synthesized compounds against selected gram-positive and gram-negative bacterial strains and the dyeing potential was investigated by dyeing cotton, linen, cotton and silk fabrics using a fastness test. Benzo-fused phenol-substituted compound showed very good antibacterial activity against P. aeruginosa (ZOI, 18 μg/mL) and B. subtilis (ZOI, 18.5 μg/mL), while showing good antibacterial potency on S. aureus (ZOI, 12.5 μg/mL). The SAR study also revealed that the presence of the nitro group in meta and para positions uplifted the antibacterial activity to the moderate stage in gram-negative bacterial strains. Additionally, assessing the dyeing performance by dry and wet rubbing fastness properties, compounds with α-naphthol, p-nitrophenol, and o-cresol fragments were observed as the most promising fabric dye candidates with excellent results referencing the grayscale and may lead to exploit in the textiles industry for dyeing clothes in future. [ABSTRACT FROM AUTHOR]