Solid‐State TICT‐Emissive Cruciform: Aggregation‐Enhanced Emission, Deep‐Red to Near‐Infrared Piezochromism and Imaging In Vivo

Abstract Near‐infrared piezochromic materials presenting fluorescence responses with clear color differences and good penetrability have important potential applications, but a few such organic compounds are developed. Twisted intramolecular charge transfer (TICT) emission is versatile in solutions, especially for preparing bio/chem‐sensing materials due to the excellent sensitivity of the emission to alterations in the external environment. By analogy, the solid‐state TICT‐emissive chromophores are probably excellent candidates for the environmentally responsive material. Herein, X‐shaped π architectures that exhibit solid‐state TICT emission are developed, and their luminescent chromism and bioimaging properties are investigated. Initially, the cruciform fluorophore exhibits anomalous aggregation‐enhanced emission (AEE) and dual emission due to the existence of a TICT state. Interestingly, TICT emission is observed even in the aggregated state because the spacious environment around the bulky triphenylamine allows for rotation. During the compression process, the TICT‐based fluorophore demonstrates deep‐red to near‐infrared piezochromic behavior with a remarkable redshift (162 nm) and high sensitivity (15.1 nm GPa⁻¹). The bioimaging performance of the TICT‐emissive dye suggests its potential utility as a fluorescent probe for biological applications.