Solvent effect on the relative quantum yield and fluorescence quenching of 2DAM

The relative quantum yield of diethyl 2-acetamido-2-((3-oxo-3H-benzo[f]chromen-1 -yl)methyl) malonate [2DAM] is estimated using single point method with quinine sulfate as standard reference. The quantum yield varies between 0.1161 and 0.3181 depending on the nature of the solvent. The rates of radiative and non radiative decay constants are also calculated. The fluorescence quenching of [2DAM] by aniline is studied at room temperature, by steady state, in five different solvents namely acetonitrile (AN), 1,4 dioxane (DX), 1,2 dichloroethane (DCE), tetrahydrofuran (THF) and toluene (TOL), in order to explore various possible quenching mechanisms. The experimental results show a positive deviation in Stern Volmer plots for all solvents. Various parameters for the quenching process are determined by ground state complex, sphere of action static quenching model and finite sink approximation model. The magnitudes of these rate parameters indicate that positive deviation in the Stern-Volmer (SV) plot is due to both static and dynamic processes. Further, finite sink approximation model is used to check whether these bimolecular reactions were diffusion limited or not. The values of distance parameter R' and diffusion co efficient D are determined and then compared with the values of encounter distance R and diffusion coefficient D calculated using Stokes-Einstein equation. (C) 2014 Elsevier B.V. All rights reserved.