Peripheral Substituent Effect on 'Turn-On' Fluorescence of BODIPY Derivatives for Sensing Benzene Moieties

Abstract

In this work, a series of dipyrrometheneboron difluoride (BODIPY) derivatives, BT-F, BT-H, and BT-OMe, was prepared to study the peripheral substituent effect on 'turn-on' fluorescent for benzene moieties including benzene, toluene, and xylene (BTX). The photophysical- and electrochemical properties of the three compounds were systematically studied by steady-state UV-visible and PL spectroscopies, and cyclic voltammetry along with DFT calculations. Among various organic solvents, all compounds selectively showed strong 'turn-on' fluorescence in BTX solvents, proving that these compounds can be used as BTX probes. As the portion of BTX increases, the emission band shows a hypsochromic shift, indicating that the enhanced emission originated from exciplex formation in the excited state. Among them, BT-OMe, which has methoxy groups at peripheral positions, showed the highest sensing capability to BTX. The electron-donating nature of the methoxy group enhances the electron population on the BODIPY core and the triphenylamine groups, which results in strong interaction with BTX in the excited state.