Factors that influence the spectroscopic properties of 1,3-bis[p-substituted-(phenylamino)]squaraines

• Type of substituent in phenyl ring vary the spectroscopic properties of squaraines.
• Fluorescence lifetime for 1,3-bis(phenylamino)squaraines is about 3.0 ns.
• Fluorescence quantum yield correlates very good with fluorescence lifetime.
• Rate constant of radiative process depends on viscosity of solvent.
• Viscosity of solvent does not effect on the rate of non-radiative deactivation.

The spectroscopic characteristics of a series of ten aminosquaraine dyes that differ in the type of chemical substituent at the p-position of the phenyl ring were investigated. The effect of solvent on the properties of the dyes in their ground and excited state is described. The absorption and emission properties, fluorescence lifetime and rate constants for radiative and non-radiative deactivation processes are also presented. The dyes displayed very short fluorescence lifetimes (about 3 ns) and dependence of the radiative deactivation process on the solvent viscosity.

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