Single-molecule nanosized polycyclic aromatics with alternant five- and six-membered rings: Synthesis and optical properties

A synthetic protocol for a novel family of symmetric polycyclic aromatics with a benzene or cyclooctatetraene (COT) ring as the core and alternant fused benzene and cyclopentadiene rings as branches has been developed. The TiCl4-promoted cyclizations construct both planar trimers and tubelike tetramers via the in situ generation of the benzene or COT skeleton. The structures of 6b, 7a, 7b, and 10 have been characterized by H-1 and C-13 NMR spectra and MALDI-TOF mass spectroscopy. These polycyclic aromatics also exhibit interesting optical properties.