Multistimuli-Responsive Triphenylphosphine Anils: Development of a High-Contrast Wearable Ammonia Sensor

Stimuli-responsive organic materials with configurable luminescence are an important class of materials with potential use in sensing, data security, and display devices. Emergent vapofluorochromic materials, with the ability to sense and detect, are significant for real-time applications across the sectors. Specific market demand varies based on technological advancements, regulatory changes, and industry trends, making the discovery of such advanced materials essential. Aiming the design and engineering of solid-state emission, we report the synthesis and characterization of three simple Schiff bases 1–3, with nonplanar propeller triphenylphosphine functionality on the one end and functional group variation on the other end. Contrarily, the molecular solids 1 and 2 undergo emission quenching, while feeble emission in 3 (λmax 573 nm, ϕ 16%, and τ 3.118 ns) arises due to H-aggregate formation. Solid-state emission of 3 is further validated by aggregation-induced emission and thin-film studies. Existing as zwitterionic solids, due to intramolecular proton transfer of acidic proton, the solid forms respond to base exposures as observed during thin film studies, and further detailed vapochromic studies establish reversible emission switching in 2 and tuning in 3. Working of a simple demonstrative wearable sensor for the detection of ammonia fumes is reported. Electrochemical, crystallographic, computational, and mechanochromic studies have been carried out to understand the structure–function relationship.