Strained and Unstrained Macrocycles Composed of Carbazole and Butadiyne Units: Electronic State and Optical Properties

Cu­(OAc)2 catalyzes dehydrogenative condensation of 3,6-bis­(2-ethynylphenyl)­carbazole in the presence of O2 to afford the cyclization product 1 and cyclodimer 2. Compound 1 contains bent carbazole and butadiyne groups, while 2 has a less strained structure with Z shape around the two parallel butadiyne groups. Optical properties of the compounds are discussed based on the electronic states estimated from electrochemical measurement and density functional theory calculation.