Syntheses And Properties Of Water-soluble Symmetrical Squarylium Bis-indocyanine Dyes

and2,3,3-trimethyl-3H-indole-5-sulfonic acid were synthesized by reaction of phenyl hydrazine and phenyl hydrazine sulfonic acid with3-methyl-2-butanone respectively. The products reacted with different saturated dihalides and different N-alkyl reagents to obtain different bis-quaternary ammonium salts and a series of mono-indoline-quaternary ammonium salts respectively. Five squarylium bis-indocyanine dyes whose structures have not been reported were prepared by reaction of bis-semiindocyanine dyes with ethyl squaric acidate. The raw dyes were purified by C-18reverse phase column chromatograph and their structures were confirmed by1HNMR.The spectral properties of the target products were checked. The spectral properties included the UV-Vis spectra, fluorescence emission spectra and photo-stability in various solvents. The results show that the bis-cyanine dyes exhibit absorption maximum in range of630-658nm, emission maximum from640to658nm, molar extinction coefficients about105mol-1cm-1L. Compared with that in organic solvents such as methanol and ethanol, the bis-cyanine dyes have lowest values of quantum yields in water. The Stokes shifts of bis-cyanine dyes ranged from6to17nm. Compared with symmetrical squarylium mono-indocyanine dyes with the same subtituent, the photo-stability of the bis-cyanine dyes were much better obviously.The UV-Vis spectra of the water-soluble symmetrical squarylium indolecyanine dyes in the different solvents show two variations generally such as positive solvatochromism and negative solvatochromism. It is found that the variation in different solvents and spectral shape of the bis-cyanine dyes were similar to the mono-cyanine dyes.The stability order of different dyes in the water:the stability of two kinds of cyanine dyes with ethyl linker is Esqd (N-benzyl)> Esqc (N-ethyl) and the stability of three kinds of cyanine dyes with butyl linker is Bsqa (N-carbenicillin)> Bsqd (N-benzyl)> Bsqc (N-ethyl). The order of the stability in different solvents:Methanol> Ethanol>Water.