Facile synthesis of novel monodisperse linear 3,9-linked oligocarbazoles

Novel monodisperse linear 3,9-linked oligocarbazoles (OCAs) were prepared stepwise using Ullmann coupling reaction in seal-tubes. The resulting OCAs were soluble in common organic solvents. The UV-vis spectra of OCAs exhibited small red shift and their intensities increased linearly with the increase of the carbazole moieties, suggesting that no intramolecular π-interactions appeared at ⩽8-mer. All the OCAs gave strong fluorescence and it was found that the conjugated degree of linear OCAs would be saturated when the number of carbazole units reaches four.