Synthesis of Polymethine Styryl Cyanine Dyes and their Solvent Effects

Six polymethine styryl cyanine dyes have been synthesised. The solvent effects on the maximum absorption wavelength, Stokes shifts, and fluorescence efficiencies of these dyes have been studied. McRae equation and Nicol equation describing solvent effects on absorption wavelength have been compared, and it is found that McRae equation is more suitable here. The results show that Stokes shifts of these dyes in various solvents well fit Lippert equation, and the fluorescence quantum efficiencies are extremely affected by solvent properties.