Multistimuli Response and Polymorphism of a Novel Tetraphenylethylene Derivative

Abstract Multi‐stimuli‐responsive fluorescent molecule tetraphenylethylene (TPE) derivative 1 is synthesized, which contains a TPE skeleton and peripheries of two methoxyl groups and one carboxyl group. It shows a typical aggregation‐induced emission behavior and also exhibits fluorescence responses to pH change and amine vapors, and multicolored mechanochromic properties. The emission of 1 can be reversibly switched among blue (1p‐f, 462 nm, Φ f = 7.4%), bright cyan (1p‐h, 482 nm, Φ f = 82.3%), and yellow (1p‐g, 496 nm, Φ f = 10.5%) with high contrast through solvent fuming, heating, or grinding. Molecule 1 occurs in four crystalline states (1c‐a, 1c‐b, 1c‐c, and 1c‐d) after crystallization from different solvents. The multicolored mechanochromic property is related to the different interactions and packing modes of molecules in the crystals. The crystals with weak fluorescent emission have characteristic porous structures and corresponding intensive XRD diffraction peaks, which are absent in the crystal with intensive fluorescent emission. The porous structures are critical for the fluorescence intensity of the molecules. Upon heating, the porous structures of crystals are damaged and fluorescence is significantly enhanced.