A facile and highly efficient green synthesis of carbazole derivatives containing a six-membered ring

A facile and efficient green protocol for the synthesis of carbazole derivatives containing a six-membered ring, via an aldol condensation and solvent-free Michael addition reaction, has been developed. The compounds were characterized by 1H NMR, 13C NMR, IR, ESI-MS and HR-MS spectroscopic techniques and also, for one example, by X-ray crystallography. The cyclohexyl unit was introduced into the carbazole derivatives and utilized as a sterically demanding group for the purpose of increasing the non-planarity of the carbazole derivatives and reducing self-quenching, leading to improved optical and electronic properties. The influence of solvent polarity on the ultraviolet absorption and fluorescence characteristics was observed and investigated. The majority of the carbazole derivatives have high fluorescence quantum yields in dichloromethane, ethanol, acetonitrile and DMF.

► A facile protocol for the synthesis of carbazole derivatives has been developed.
► The cyclohexyl group was introduced into carbazole derivatives.
► The solvent effect on the UV absorption and fluorescence was studied.