Triphenanthro‐Anellated [18]Annulenes with Alkoxy Side Chains ‐ A Novel Class of Discotic Liquid Crystals Two different types 6 and 16 of [18]annulenes condensed with phenanthrene systems were prepared by cyclocondensation reactions (Schemes 2 and 3). The central 18‐membered rings do not show a macrocyclic diamagnetic ring current. Conformational analyses and X‐ray analyses in the solid state reveal non‐planar structures in which aromatic “islands” are connected by (E)‐configurated olefinic bridges. The introduction of long alkoxy side chains yields a new class of discotic liquid crystals; either ND or hexagonal columnar phases are generated, which were characterized by DSC, microscopy with polarized light, and small‐angle scanning X‐ray.

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2,5‐Dialkoxy Substituted Oligo‐ and Poly(1,4‐phenyleneethenylene)s O‐Alkylation and regioselective Rieche formylation of 2‐methylhydroquinone (1) yields the 2,5‐dialkoxy‐4‐methylbenzaldehydes 4a–j. The corresponding azomethines 5a–j enter in a strongly alkaline medium a selfcondensation reaction leading to the title compounds 6/7a–j. These conjugated oligomers and polymers possess highly regular structures with exclusively (E)‐configurated double bonds. GPC, IR, 1H‐, 13C‐NMR and MS‐FD measurements were used for their characterization. Somewhat different results were obtained for the similarly prepared Schiff base 5l which contains chlorine substituents in the side chains. Cleavage of hydrogen chloride leads not only to unsaturated alkoxy groups; additionally, cyclization reactions (5l → 8l) are observed.

Investigations on the Photoconductivity of Alkoxy Substituted Oligo‐ and Poly(1,4‐phenyleneethenylene)s The photoreactivity and the photoconductivity of the mono‐ and dialkoxy substituted oligo‐ and poly(1,4‐phenyleneethenylene)s 1/1′a‐n were investigated in order to optimize the photoconducting properties of these materials. Increasing the length of the side chains enhances the average length of the main chain during the polycondensation and decreases the band gap till the limit of convergence is reached. The highest photoconductivity was observed for the 2,5‐dipropyloxy system 1/1′j. Longer side chains render the charge transfer from chain to chain more difficult. The measurements were performed in dispersion layers and related to the industrial standard 3. Compound 1m was also measured in a pure state as transparent film and compared to a poly(N‐vinylcarbazole) film which shows a dye‐sensitized photoconductivity. In both cases the optimized systems 1/1′ were markedly superior to the standards. The highest sensitivity could be observed for wavelengths λ lying close to the absorption maxima λmax. The compounds 1/1′ have a high photostability on irradiation with visible light; however, they are rapidly destroyed by UV light (254 nm).