Fluorescence quenching of a biologically active boronic acid derivative by aniline in different solvents

Abstract

Boronic acid derivatives are novel biologically active fluorescent molecules with numerous applications in various fields. A study of their fluorescent properties reveals some information that can be utilized in sensor design. One such study is fluorescence quenching. Here fluorescence quenching of 2-methoxypyridin-3-yl-3-boronic acid (2MPBA) in different solvents of a wide range of polarities has been carried out at room temperature by steady state fluorescence measurements. Aniline is used as the quencher. The positive deviation observed in Stern–Volmer (S-V) plots is analyzed using different quenching models. Various quenching parameters like S-V constant (KSV), quenching rate parameter (kq), volume constant (V), and kinetic distance (r) have been estimated using extended S-V equations. KSV is found to vary from 12.94 to 62.49 (mol/L)−1 with respect to solvents. From the calculated values of these parameters it is concluded that the static quenching mechanism is active in the studied system. However the reactions are diffusion-limited, which is confirmed by invoking the finite sink approximation model.