Novel amino acid‐stilbene quaternary ammonium salt fluorescent whitening agents: synthesis, optical properties, acid resistance and anti‐bacterial activity

Abstract With 4,4'‐diaminostilbene‐2,2'‐disulfphonic acid, 2,4,6‐trichloro‐1,3,5‐triazine and N,N‐dimethyldodecylamine as main raw materials, a stilbene quaternary ammonium salt intermediate was synthesised by condensation and quaternisation reaction under the catalysis of sodium hydroxide, and then reacted with two different amino acids to prepare novel amino acid‐stilbene quaternary ammonium salt fluorescent whitening agents. The structures of target compounds were characterized by Fourier Transform–infrared and proton nuclear magnetic resonance spectroscopy. Their photophysical properties, whitening performance and firmness in aqueous solution were assessed by means of ultraviolet absorption spectra, fluorescence emission spectra and a cotton fibre application test. The results showed that the two amino acid‐stilbene quaternary ammonium salt fluorescent whitening agents had a good whitening effect on cotton fibres and displayed strong acid resistance. Compared with the traditional fluorescent whitening agent C186, their firmness was greatly improved. The anti‐bacterial activities against three strains were evaluated in vitro. The results showed that they exhibited significant anti‐bacterial activity against the selected strains, and the respective minimum inhibitory concentration values against Candida albicans and Escherichia coli were 16.8 and 8.16 μg/ml.