Interactions of Environmental Pollutant Aromatic Amines With Photo Excited States of Thiophene Substituted 1,3,4-Oxadiazole Derivative: Fluorescence Quenching Studies

Abstract

In the present work, the fluorescence quenching of novel thiophene substituted1,3,4-oxadiazole derivative 2-(4-(4-vinylphenyl) phenyl)-5-(5-(4-vinylphenyl)thiophen-2-yl)-1,3,4-oxadiazole (TSO) by five different environmental pollutant aromatic amine derivatives like 2,4-dimethylaniline, 3-chloroaniline, 4-chloroaniline, o-anisidine, and m-toluidine has been studied at room temperature through steady-state and time-resolved methods. It is observed that, the quenching efficiency is highest in the case of o-anisidine and least in the case of 3-chloroaniline. The fluorescence quenching mechanism between TSO and aromatic amines is analysed through different quenching models. The results suggest that, the fluorescence quenching is due to diffusion assisted dynamic or collisional quenching according to the sphere of action static quenching model and according to the finite sink approximation model, the bimolecular quenching reactions are due to the collective effect of dynamic and static quenching. Further, cyclic voltammetry and DFT studies suggest that the fluorescence quenching is due to electron transfer. Binding equilibria analysis confirms the 1:1 stoichiometric ratio between fluorophore and the quencher.

Keywords: 1,3,4-oxadizole; 2,4-dimethylaniline; Aromatic amines; Fluorescence quenching; Stern–Volmer; m-toluidine; o-anisidine.