Design And Synthesis Of Indocyanine Dyes As Well As Their Spectral And Thermodynamic Properties

Indocyanine dyes,which are characterized by large molar extinction coefficient, high fluorescence quantum yeilds,relatively high stability,low melting point and large tunable range of maximum absorption wavelength,have become the most active varieties of dyes in biological fluorescence detection analysis,nonlinear optical materials,infrared laser dyes and optical disc recording media and so on.In this paper,the structure and the classification of indocyanine dyes are introduced.The synthetical progresses of the water-soluble indocyanine dyes and the application status of indocyanine dyes are reviewed.5-Methyl-6-oxoheptane-1-sulphonic acid is synthesised by alkylation,hydrolyzed and decarboxylated using ethyl 2-methylacetoacetate as a starting material. 1,2,3-Trimethyl-3-(4-sulphobutyl)-3H-indolium-5-sulphonate salt as a new intermediate is synthesised by the traditional Fisher synthetical method,and then two new kinds of water-soluble indocyanine dyes are prepared by the condensation of the intermediates with corresponding condensating agents respectively.These dyes are characterized by ~1H NMR,MS,IR and UV-vis.The UV-vis spectra of the two dyes in different solvents and temperatures are also investigated.The results indicate that with the increasing of refractive index of solvents,the maximum absorption wavelength of these dyes has a red-shift.Both of the dyes have good thermostability at 30-65℃. The non-covalent combination of the two dyes with DNA,BSA in the water is studied. The results of the fluorescence sprectra indicate that non-covalent combination of the dyes with DNA,BSA enhances their fluorescence intensity and especially the combination with BSA leads to substantial increase in fluorescence intensity.Aggregation behavior of three kinds of benzindocarbocyanine dyes in 50 volume %aqueous-methanol solution is studied by UV-Vis absorption spectral method.The results indicate that the three dyes all exist monomer-dimer equilibrium in 50 volume %aqueous methanol solutions,and the dimeric enthalpies△H_D of them are—42.5 kJ/mol,-15.1 kJ/mol,-18.9 kJ/mol at 25.0～49.0℃,respectively.The geometries of the three dyes are fully optimized using the theoretical arithmetic and the effect of dye molecule structure on their aggregation behavior is also discussed.