Accordion-like oscillation of contracted and stretched helices of polyacetylenes synchronized with the restricted rotation of side chains

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机构：

[1] Yoshida, Yoshiaki

[2] 1,Mawatari, Yasuteru

[3] Motoshige, Asahi

[4] Motoshige, Ranko

[5] Hiraoki, Toshifumi

[6] Wagner, Manfred

[7] Müllen, Klaus

[8] 1,Tabata, Masayoshi

来源：

Tabata, M. (tabata@mmm.muroran-it.ac.jp) | 1600年 / American Chemical Society卷 / 135期

关键词：

A chiral substituted acetylene; (s)-2-octyl propiolate; was stereoregularly polymerized using a catalyst; Rh(nbd)Cl]2; at 40 C in methanol to give the corresponding helical polymer; Ps2OcP. The changes of 1H and 13C NMR spectra in line shapes and splitting patterns were consistently interpreted in terms of restricted rotation around the ester O-*C bond; ∼O-*CΕHΕ(R)∼; R = a branched CHΕ3 in the ester side chains rather than the helix inversion with the aid of a 3-site jump model. Three peaks due to the branched methyl HΕ proton and its Cη carbon observed at 0 C suggested the formation of three rotamers called A; B; and C; based on the presence of the contracted helix and stretched helix forms that have an intrinsic helical pitch. Furthermore; an accordion-like helix oscillation (HELIOS) along the main chain axis was proposed to explain the temperature dependence spectral changes observed in 1H and 13C NMR; UV-vis; and circular dicromism (CD) spectra. The temperature dependence UV-vis and CD spectra of Ps2OcP corroborate the presence of contracted and stretched one-handed helix sense polymers in solution in which the helical pitches and their persistence lengths depend on the temperature. © 2013 American Chemical Society;

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Journal article (JA)

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