Synthesis and Spectral Properties of Fluorescent Phthalimidylhydrazone Disperse Dyes and their Application to Poly(ethylene terephthalate) Dyeing

A series of fluorescent phthalimidylhydrazone disperse dyes based on pyrrolinone esters were synthesized and characterized using Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance (H-1-NMR) spectroscopy, and elemental analysis. The synthesized dyes were confirmed to be keto-hydrazone tautomers and were found to be mixtures of Z/E isomers, with the Z form being predominant, via H-1-NMR spectroscopy. Although the effect of N-alkylation in phthalimide on the absorption spectra and color properties of the dyed poly(ethylene terephthalate) (PET) was negligible, dyes that contained a longer N-alkyl substituent achieved higher color yields on the PET fabrics, owing to their increased hydrophobicity. The synthesized dyes exhibited a reasonably intense fluorescence in the solution state, with a quantum yield of 0.109-0.122, as well as in the dyed fabric. The phthalimidylhydrazone disperse dyes exhibited excellent color fastness after a mild alkaline treatment instead of the conventional reduction clearing, which causes environmental problems due to the high biochemical oxygen demand and alkalinity in dyehouse effluents.