Red/NIR‐Emissive Benzo[d]imidazole‐Cored AIEgens: Facile Molecular Design for Wavelength Extending and In Vivo Tumor Metabolic Imaging

Abstract Aggregation‐induced emission (AIE) luminogens (AIEgens) with red/near‐infrared (NIR) emissions are appealing for applications in optoelectronics and biomedical engineering owing to their intrinsic advantages of efficient solid‐state emission, low background, and deep tissue penetration. In this context, an AIEgen with long‐wavelength emission is synthesized by introducing tetraphenylethene (TPE) to the periphery of electron‐deficient spiro ‐benzo[ d ]imidazole‐2,1′‐cyclohexane (BI). The resulting AIEgen, abbreviated as 2TPE‐BI, adopts a donor–acceptor structure and shows bathochromic absorption and emission with a larger Stokes shift of 157 nm in acetonitrile than that based on benzo[ c ][1,2,5]thiadiazole. It also exhibits a high solid‐state fluorescence quantum yield of 56.6%. By further insertion of thiophene to its molecular structure generates 2TPE‐2T‐BI with higher conjugation and NIR emission. 2TPE‐2T‐BI can be fabricated into AIE dots for in vivo metabolic labeling through bio‐orthogonal click chemistry. These results open a new approach for facile construction of long‐wavelength emissive AIEgens based on the BI core.