Effect of solvent on the quenching of fluorescence of safranine T(3,7-diamino-2,8-dimethyl-5-phenylphenazinium chloride) in binary solvent mixtures

Fluorescence quenching of 3,7-diamino-2, 8-dimethyl-5-phenylphenazinium chloride (safranine T (ST)) by halides and pseudo halides in binary solvent mixtures was investigated by steady-state fluorescence spectroscopy. Several parameters, such as dielectric constant, viscosity coefficient, image and fluorescence quantum yield have been investigated as a function of solvent compositions. In mixed solvents ST has been used as a probe for studying the microheterogenity of the mixture. The preferential solvations around ST in the excited state were determined. The Stern–Volmer quenching constants at different compositions of solvent mixtures were determined and the rational analysis of the results was attempted.