Planar chiral zigzag-type [8] and [12]cyclophenylene belts were prepd. enantioselectively by rhodium-catalyzed enantioselective intramol. sequential cyclotrimerizations of a cyclic [oxypropynylbis(heptynyloxy)phenoxybis(heptynyl)phenylene] dimer and trimer. The obsd. enantioselectivity likely arose from the regioselective formation of a rhodacyclic intermediate from an unsym. triyne unit. The structure of the racemic zigzag [8]cyclophenylene belt was detd. by X-ray crystallog.; the homochiral belts mesh with one another to form columns in the solid state, with columns of alternating chiralities. The ring strain of the zigzag [8]cyclophenylene belt was smaller than that of the corresponding armchair-type cycloparaphenylene despite its smaller ring size because of the presence of strain-relieving m-terphenyl moieties. The effect of the no. of the benzene rings in the zigzag cyclophenylene belts on their UV/visible absorption and fluorescence was small because of the interruption of conjugation by the m-phenylene moieties, but the effect of bending on the absorption and emission peaks and on the abs. fluorescence quantum yield was significant. Modest anisotropy dissymmetry factors of the electronic CD and CPL spectra were obsd. for the zigzag [8]cyclophenylene belt. [on SciFinder(R)]
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