Novel solvatochromic and halochromic sulfahydrazone molecular switch

Novel Sulfonamide-Tricyanofuran-Hydrazone (SULFATCFH) disperse dyes containing the sulfa drug nucleus and bearing a hydrazone recognition moiety were synthesized. The preparation involved azo-coupling between active methyl-containing tricyanofuran (TCF) heterocycle and the appropriately functionalized sulfonamide diazonium salt. The molecular structures of the produced sulfahydrazone compounds were confirmed using FTIR, H-1/C-13 NMR and (C, H, N) elemental analysis. Owing to the presence of an intramolecular charge transfer absorption in the visible region, these chromophores showed pronounced solvatochromic behavior in organic solvents of differing polarities. The pH molecular switch was accomplished by modulation of internal charge transfer via protonation and deprotonation of the sulfahydrazone in acetone solution. These systems exhibited reversible color changes in response to pH changes as a result of extensive charge delocalization in the hydrazono-form that led to a quinoid-type interaction. The UV-Vis absorption spectra demonstrated dramatic color change from yellow to blue due to solvatochromism and pH-responsiveness of the hydrazone recognition moiety. Mechanisms accounting for the solvatochromism and pH-responsiveness were proposed. The SULFATCFH compounds were applied to polyester fibers as disperse dyes and their fastness properties to wash, perspiration, rubbing and light were evaluated. (C) 2018 Elsevier B.V. All rights reserved.