New Synthesis Mehod And Properties Of Asymmetrial Water-solubility Squarylium Indocyanine Dyes

In acidic medium, water-soluble and water-insoluble indoles were synthesized from phenyl hydrazine sulfonic acid and phenylhydrazine as starting materials. Two series of N–alkyl–2,3,3–trimethyl–3H–indoleninium were synthesized involving nucleophilic reaction of two kinds of indoles and different N–alkyl reagents. Different N-substituted squaraine hemiindocyane dyes were synthesized by condensation of water-insoluble indoline quaternary ammonium and squaric diethyl ester. The new water-soluble asymmetric indole squaraine dyes which have not been reported previously were synthesized by condensation of water-insoluble N-substituted squaraine hemi-indocyane dyes and various N–alkyl–2,3,3–trimethyl–3H–indoleninium–5–sulfonates. These raw dyes were purified by C–18 reverse phase column chromatograph. Their structures were confirmed by 1H NMR. In the process of synthesizing of asymmetrical squarylium indocyanine, it is found that this two–step method in which the water-insoluble hemicyanine dyes were synthesized firstly is more suitable for synthesizing water-soluble asymmetric squarylium indocyanine dyes, because the yields of dyes synthesized with this two–step method are higher than those with traditional one–step method and the two–step method in which the water-soluble hemicyanine dyes were synthesized firstly.The spectra properties of eight kinds of dyes in five various solvents were checked. The results show that the dyes exhibited absorption maximum from 625 to 655 nm and fluorescence emission maximum from 632 to 668 nm. The Stokes Shifts are from 5 to 13 nm. All dyes synthesized in this paper display a high molar extinction coefficientsεgreater than 10⁵ mol^-1·cm^-1·L. The absorption spectra of these dyes exhibit negative solvatochromism in protonic solvents which is a blue shift of the absorption maximum with increasing solvent polarity and positive solvatochromism in aprotonic polar solvents that is a red shift of the absorption and emission maximum with increasing solvent polarity. The Fluorescence quantum yields of dyes in water are lower than those in other polar organic solvents. The absorption and emission spectra of the dyes at different pH values of aqueous solution were investigated. In the acidic (pH = 5.65) and alkaline (pH = 9.68) conditions, the absorbance of dyes in aqueous solution are increased significantly, however, when pH=1.85 the absorbance are decreased significantly. At the pH value of 5.65, aggrigation of dyes molecules are observed. The thermal stabilities of four kinds of dyes were tested. Decomposition temperatures of the dyes are all above 300℃, indicating that the four kinds of dyes have good thermal stability.The test results of photostability indicated that the photostability of SaFa (N-carboxy-benzyl-N'-carboxy benzyl) is the best,the photostability of SeFg(N-A benzyl-N'-NO2 benzyl) is the worst and the difference between others is negligible.The water-stabilities of the dyes are good from the test.