Effect of fluorescence quenching on 6BAAC in different solvents

Abstract

The fluorescence quenching studies of 6-bromo-3-azidoacetyl coumarin (6BAAC) by aniline in four different solvents, namely acetonitrile, benzene, dioxane, and toluene, were carried out at room temperature to understand quenching mechanisms. The Stern–Volmer plots have been found to be nonlinear with a positive deviation for all the solvents studied. To interpret these results we have invoked the ground state complex formation and sphere of action static quenching models. Using these models various quenching rate parameters have been determined. The magnitudes of these parameters suggest that the sphere of action static quenching model agrees well with the experimental results. Hence the positive deviation is attributed to the static and dynamic quenching. Further, with the use of the finite sink approximation model, it was possible to check these bimolecular reactions as diffusion-limited and to estimate independently distance parameter R′ and mutual diffusion coefficient D. Finally an effort has been made to correlate the values of R′ and D with the values of the encounter distance R and the mutual coefficient D determined using Edward’s empirical relation and the Stokes–Einstein relation.