D-A-D structured triphenylamine fluorophore with bright dual-state emission for reversible mechanofluorochromism and trace water detection

The design and development of materials showing bright dual-state emission (DSE) in both dilute solutions and the solid state have attracted great interest due to their potential in a wide variety of applications. The present work reports the synthesis of a novel donor-acceptor-donor (D-A-D) structured fluorophore, 2TPACHO, with DSE characteristics using triphenylamine as an electron donor and benzaldehyde as an electron acceptor. 2TPACHO possesses typical intramolecular charge transfer (ICT) characteristics and presents a highly twisted molecular conformation in the crystal structure with multiple weak interactions. As a result, 2TPACHO exhibits strong emission in solution and the solid state (phi(THF) = 0.43, phi(solid) = 0.62). As a DSE material, 2TPACHO shows clear mechanofluorochromism in response to external mechanical stimuli in its solid state and capabilities of sensing trace water in organic solvents as a fluorescent probe in the dissolved state. This work provides new insight into the design of DSE fluorophores that function in both solutions and the solid state.