Effect of Solvent Polarity on Fluorescence Quenching of New Indole Derivatives by CCl₄

Abstract

ABSTRACT The fluorescence quenching of solutes 3-[5′-methyl-3′-phenylindol-2′-yl]-s-triazolo [3,4-b] [1,3,4] thiadiazol-6(5H)-thione (MPITTT) and 3-phenyl-2,5-bis-[thiosemicarbazido] indole (PbisTI) by carbon tetrachloride (CCl4) in dioxane and acetonitrile mixtures has been studied at room temperature by steady-state fluorescence measurements. The positive deviation from linearity has been observed in the Stern–Volmer (S-V) plots for both fluorophores in different composition of mixed solvents even at moderate CCl4 concentration (0.10 mol dm−3). Various quenching parameters of the quenching processes have been determined using the extended S-V equation and have been found to be dependent on the solvent polarity. Further, with the use of the finite sink approximation model, it is concluded that the bimolecular quenching reactions are diffusion limited, and the distance parameter R′ and mutual diffusion coefficient D are estimated independently.