Nonlinear fluorescence quenching of newly synthesized coumarin derivative by aniline in binary mixtures.

The fluorescence quenching of newly synthesized coumarin (chromen-2-one) derivative, 4-(5-methyl-3-phenyl-benzofuran-2-yl)-6-chloro-chromen-2-one (MPBClC) by aniline in different binary solvent mixtures of benzene and acetonitrile have been reported by steady state fluorescence measurements. All the measurements were carried out at room temperature (296K). A positive curvature from linearity was observed in the Stern-Volmer (S-V) plot in all the solvent mixtures. Various rate parameters for the fluorescence quenching have been determined by sphere of action static quenching model and finite sink approximation model. The results show that the positive curvature in the S-V plot is due to both static and dynamic quenching processes. Further, with the use of finite sink approximation model, it is concluded that these bimolecular reactions are diffusion-limited.