Emission Shift Regulation and Amorphous Mechanofluorochromic Behavior of Donor–Acceptor Aggregation‐Induced Emission Luminogens through N‐Alkyl‐Substitution of Imidazole

Subtle modification on chemical structures plays a key role in determining aggregate morphology and mechanofluorochromic (MFC) behaviors. Herein, aggregation‐induced emission (AIE)‐active tetraphenylethene‐functionalized vinylogous‐dicyano aryl derivatives with different of N‐substituent groups ( T‐1 : R=‐H and T‐M : R=‐CH 3 ) have been designed and synthesized, and systematically investigated the effect of substituents on their aggregate morphology and MFC behavior. The single crystal X‐ray analysis and density functional theory calculations illustrate that T‐1 and T‐M exhibit clear twisted spatial conformations and intramolecular charge transfer (ICT) characteristics. Meanwhile, T‐1 and T‐M show completely opposite directions of emission shifts after grinding. The T‐1 exhibits obvious blue‐shift (32 nm) trend without N‐alkyl modification, while T‐M shows red‐shifted (26 nm) upon grinding. Moreover, the T‐1 achieves blue‐shifted MFC behaviors by amorphous states transition, and overcomes the limitations of conventionally ordered crystalline MFC materials. The phenomenons may be ascribable to mechano‐induced short‐range molecular order within the amorphous state. The powder X‐ray diffraction, scanning electron microscopy, and differential scanning calorimetry analysis confirm amorphous states transition process. The T‐1 and T‐M reveal that partial reversible opposite MFC properties, AIE characteristic, and N‐alkyl modification play a functional role in tuning their MFC behaviors and morphology structural changes.