ESIPT Core Containing Benzothiazole and Benzimidazole Based Fluorescent Acid Azo Dyes for Protein Fiber: Synthesis, Spectral Characteristics, and Fastness Evaluation

Abstract

Excited state intramolecular proton transfer (ESIPT) core containing, two series of benzothiazole and benzimidazole based fluorescent acid azo dyes were synthesized. These dyes analyzed and confirmed by ¹H NMR, ¹³C NMR, FT-IR and elemental analysis. Spectral characteristics of these dyes studied in different polarity solvents showed Stokes shift 2888–4678 cm^–1 and 2167–4837 cm^–1 for benzimidazole and benzothiazole series, respectively. Wool and silk fabric dyed with these dyes, shows 92.1–94.4% (benzimidazole) and 92.4–95.1% (benzothiazole) percentage exhaustion on wool. The dyed substrate evaluated for UV rays protective properties, antibacterial activity light, wash and rubbing fastness. Synthesized dyes show significant antibacterial activity when tested by Agar-well diffusion test against Staphylococcus aureus (Gram positive), Klebsiella pneumonia (Gram negative) bacteria.

Keywords:

• Acid dyes
• ESIPT
• benzothiazole
• benzimidazole
• 3-hydroxy-2-naphthoic acid

Acknowledgments

The authors recognise the financial funding received for R&D project from Ministry of Textiles, Govt. of India.