One-step synthesis of a multi-functional imidazole luminescent sensor with AIE, acid-responsive, and sulfate-sensing properties

Abstract

A novel TBM-based chemosensor exhibiting multi-stimuli-responsive photophysical behaviour has been designed and systematically investigated through combined experimental and computational studies. In solution, the sensor displays distinct intramolecular charge-transfer (ICT) absorption and emission, with aggregation-induced emission (AIE) observed in mixed solvents due to restriction of intramolecular motion. Pronounced acidochromic behaviour upon protonation and selective recognition of HSO₄⁻ result in enhanced and red-shifted absorption. In the solid state, TBM exhibits bright yellow emission and mechanochromic luminescence arising from mechanically induced changes in molecular packing. Density functional theory and time-dependent density functional theory calculations provide insight into the electronic structure, charge-transfer characteristics, and stimulus-induced modulation of the photophysical properties. These findings demonstrate that the TBM scaffold effectively integrates ICT, aggregation effects, and external-stimuli sensitivity, highlighting its potential for chemical sensing and stimuli-responsive luminescent applications.