Synthesis, X-Ray Structure Analysis and Topochemical Photopolymerization of 2,5-Dimethoxyphenyl- and Quinone-substituted Octa-3,5-diynes

The octa-3,5-diynes 3a–g have been synthesized. Subsequent oxidation of 3a–g gave the 1,8-quinone-substituted octa-3,5-diynes 4a–g. The molecular structures of the diynes α-3b, β-3b, 3c, 3e, 3f and 4f have been determined by X-ray diffraction. UV-irradiation of diyne 3c afforded in a single crystal-to-single crystal transformation the highly-ordered polymer 5 under topochemical control. The transformation of 3c into polymer 5 was observed by X-ray diffraction analysis. Irradiation of 4d yielded the first quinone-substituted intensive-blue poly(but-1-en-3-ynylene) 5, which turned red after work up.