Three-dimensional conjugated macrocycle with large polyaromatic blocks constructed by post-π-extension

Generally, the conjugated homo-macrocycles (CHMs) are synthesized by covalently linking the repeating subunits. However, large subunits are often difficult to conjugate together due to severe stereo-hindrance. Meanwhile, large polyaromatic blocks can not only incorporate its appealing electronic and optical properties into CHMs but also distort the CHMs from planar to three-dimensional (3D) molecular structure. Here we synthesized the 3D CHM composed of large polyaromatic units by post-π-extension. Specifically, cyclo-m-phenylenes, as the cyclic precursor, were π-extended by C-C coupling and then subjected to dehydrocyclization, affording cyclo-1,3-dibenzo[e,1]pyrenylenes (CMDP). The structures of CMDPs were unambiguously characterized by single crystal X-ray diffraction, showing a congested and strained 3D conformation, which was also confirmed by theoretical calculations. Compared with the monomer, CMDPs showed redshifted absorption and emission, as well as a tenfold enhancement in photoluminescence quantum yield, which could be attributed to their 3D conformation.