Invisible photochromism and on-off switch based on thiophene-imidazole fused derivatives: Synthesis, properties and applications

Abstract

Three novel diarylethene fluorescent molecules based on a thiophene-imidazole core have been successfully synthesized. Their photophysical properties, including photocyclization and ions response characteristics, as well as quantum chemical calculations were systematically investigated. All compounds exhibited significant invisible photochromism upon photocyclization, resulting in remarkable fluorescence “turn-off” properties. This phenomenon can be attributed to photoisomerization, specifically the transition from the open-ring isomer to the closed-ring isomer during this process, which was confirmed by 1H NMR data analysis. Moreover, AT-DPIo demonstrated high selectivity toward I− with pronounced changes in absorption from colorless to yellow and fluorescence from bright yellow to dark, enabling a limit of detection for I− at 9.75 × 10−7 mol L−1. These exceptional sensing properties make it suitable for rapid “naked-eye” detection of I− using test strips.