Synthesis and fluorescence properties of butadiyne-linked linear and cyclic carbazole oligomers

Butadiyne-linked linear and cyclic carbazole oligomers were successfully synthesized. The intensity of the emission band in the 0–0 band of the highly planar macrocyclics decreased compared to that of the 0–1 band. Contrary to this, for larger macrocycles having reduced planarity, the intensity of the emission of the 0–0 band increased as in the cases of the linear compounds. This suggests that the emission color of the π-conjugated molecule can be controlled not only by the difference between the cyclic and chain structures but also by the control of the planarity, and is expected to be a new principle for molecular design in the development of fluorescent materials.