Synthesis of a Novel Fluorescent Reactive Dye Based on Coumarin-Benzimidazole for High Visibility Dyeing of Cotton

Two fluorescent reactive dyes based on coumarin-benzimidazole derivatives were synthesized, characterized, and dyed cotton fabric. First, (3-(1H-benzo[d]imidazol-2-yl)-7-(diethylamino)-2H-chromen-2-one) (CB) was reacted with cyanuric chloride to produce primary colorant. Two fluorescent reactive dyes were created by separately substituting sulfanilic acid and nicotinic acid into the original material. The synthesized dyes were characterized by FTIR, 1HNMR, 13CNMR, elemental analysis, and UV-Vis spectroscopy. Both water-soluble dyes exhibited a positive solvatochromism response with considerable fluorescent intensity and quantum yield in photophysical evaluations. The nicotinic acid substituted reactive dye, 3-carboxy-1-(4-chloro-6-(2-(7-(diethylamino)-2-oxo-2H-chromen-3-yl)-1H-benzo [d]imidazol-1-yl)-1,3,5-triazin-2-yl)pyridin-1-ium chloride (D3), showed the highest quantum yield (0.65 in aqueous form) and dyeing exhaustion (83 %) with a maximum emission wavelength of 512 nm when dyed on cotton fabric. High visibility and colorfastness assessments of the dyed fabrics confirmed, D3 could be successfully introduced as the first highly visible coumarin-benzimidazole fluorescent reactive dye for cotton, according to the international standard of high visibility clothing, ISO 20471:2013.