The locations of triphenylamine and tetraphenylethene on a cyclohexyl ring define a luminogen as an AIEgen or a DSEgen

Abstract

There is growing interest in achieving dual-state emission (DSE) in the luminescent materials community due to their strong application potential in both dilute solutions and the solid state. The design of DSE luminogens (DSEgens) mainly relies on traditional luminophores with extended π frameworks. The modification of an unconjugated stator with aryl pendants promises to obtain DSEgens with high quantum yields (Φ_PL) but has not yet been demonstrated. This study presents the first example of DSEgen engineering by attaching tetraphenylethene (TPE) and triphenylamine (TPA) to a saturated cyclohexyl ring in an isolated fashion. The TPE and TPA units and their anchoring sites on the cyclohexyl ring exert significant impacts on the photophysical properties of these luminogens. Among the synthesized compounds, a cyclohexyl ring modified with two TPE units (TPEcTPE) or a TPE carbonyl and a TPA (TPEcTPA) exhibited aggregation-induced emission (AIE), while a cyclohexyl ring modified with a TPA carbonyl and a TPE (TPAcTPE), a positional isomer of TPEcTPA, exhibited DSE. TPAcTPE possesses a much higher solid-state Φ_PL (66.12%) than TPEcTPE (13.11%) and TPEcTPA (12.18%). With TPAcTPE, specific recognition of PA over various nitroaromatic compounds in both solutions and the solid state and ultrasensitive detection of trace water in organic solvents were demonstrated.