Preferential solvation and bimolecular quenching reactions of boronic acid dye at very low quencher concentrations studied by fluorescence spectrum in toluene and butanol binary mixtures

MELAVANKI, RAVEENDRA M; Bhavya, P ; Kusanur, Raviraj ; Thipperudrappa, J

Abstract

Inferable from the significance of solvent mixtures in practical chemistry, toluene (TL) and butanol (BL) mixtures are used to studyfluorescence behavior of boronic acid dye 2-methoxy-5-fluoro-phenyl boronic acid (2MEFPBA). At the inception, preferential solvation is examined in TL-BL, to understand specific and nonspecific interactions. Suppan’s dielectric enrichment model is further used to understand the nonideality and dielectric enrichment in TL-BL mixtures for preferential solvation. Bimolecular quenching reaction studies of 2MEFPBA with aniline as quencher are made in mixtures of TL–BLto know the effect of viscosity and dielectric constant variation at room temperature.
The quenching process is studied in all solvent mixtures by steady state and transient state method. Quenching is characterized by S-V plots having upward curvature. Analysis of modified S-V equations which accounts both static and dynamic quenching allows calculating bimolecular quenching rate constant. The bimolecular quenching reactions are found to be significantly larger. Further finite sink approximation model is invoked so as to check whether reactions are diffusion limited. The extents of these rate parameters demonstrate that positive deviations in the Stern-Volmer (S-V) plot are because of the presence of apparent static and dynamic quenching process.

Keyword(s)

2MEFPBA; Preferential solvation index; Suppan’s theory; high bimolecular quenching rate constant; sphere of action and Finite sink approximation model.

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