Aggregation-induced enhanced emission of a carbazole derivative with asymmetric group

Abstract A novel carbazole-based compound (L) has been synthesized with an asymmetric group, which possesses obviously intramolecular charge transfer (ICT) process that was confirmed from the positive solvatochromic photophysical properties in different polar solvents. The introduction of nitro unit into L structure led the weak fluorescence emission, caused from the strong electron accepting character of nitro unit. L also demonstrated to exhibit superior aggregation-induced enhanced emission (AIEE) properties. The torsion degree between C1-C18 bond and N19-C23 bond was 94.098°, the introduction of benzoimidazolylcarbazole attached to the carbazole core generated the torsion degree of the whole molecule, which prevented π-π stacking between adjacent molecules and brought about AIEE property. The results were verified by time dependent density functional theory (TD-DFT) calculations. The tortuosity of L molecule also brought about inferior planarity in whole molecule, then the molecules of L can organize through intermolecular interactions to form tiny crystals at nanosacle in water-medium solutions. The AIEE character of L was effectively applied in bioimaging of HepG2 cancer cells.