Assignment of helical sense for poly(phenylacetylene) bearing achiral galvinoxyl chromophore synthesized by helix-sense-selective polymerization
Assignment of helical sense for poly(phenylacetylene) bearing achiral galvinoxyl chromophore synthesized by helix-sense-selective polymerization
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DOI：
10.1021/ma050864a
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发表时间：
2005-11-15
期刊：
影响因子：
5.5
通讯作者：
Aoki, T
中科院分区：
文献类型：
--
作者：
Kaneko, T;Umeda, Y;Aoki, T
以[Rh（norbornadiene）Cl]（2）为催化剂，在（R）-1-苯乙胺或（S）-1-苯乙胺存在下，使{4-[（3，5-二叔丁基-4-羟基苯基）（3，5-二叔丁基-4-氧代环己-2，5-二烯亚基）甲基]苯基}乙炔（简称（4-乙炔基苯基）羟基galvinoxyl）聚合，得到红色聚合物。聚合物的圆二色性（CD）光谱表明，在不对称条件下，尽管存在非手性单体，但螺旋-有义选择性聚合诱导了过量的单手螺旋聚乙炔主链。结果表明，CD信号强度依赖于温度，并随着温度的升高而可逆地降低，尽管彼此的右手和左手构象之间的能量差几乎为零。由聚合物几何形状计算的氢galvinoxyl发色团的吸收区（420 nm）中的CD信号的符号表明，在（R）-1-苯乙胺存在下通过聚合诱导过量的右手螺旋。
{4-[(3,5-Di-tert-butyl-4-hydroxyphenyl)(3,5-di-tert-butyl-4-oxocyclohexa-2,5-dienylidene)methyl] phenyl}acetylene (abbreviated as (4-ethynylphenyl)hydrogalvinoxyl) was polymerized using [Rh(norbornadiene)Cl](2) catalyst in the presence of (R)-1-phenylethylamine or (S)-1-phenylethylamine to give red polymers. The circular dichroism (CD) spectra of polymers indicated that an excess of one-handed helical polyacetylene backbone was induced by helix-sense-selective polymerization under the asymmetric condition despite the achiral monomer. Results show that the CD signal intensity depends on temperature and decreases reversibly with increasing temperature, although the energy difference between the right-handed and left-handed conformations of each other is almost zero. The sign of the CD signal in the absorption region (420 nm) of the hydrogalvinoxyl chromophore, which was calculated from the polymer geometry, suggests that the excess of right-handed helix was induced by polymerization in the presence of (R)-1-phenylethylamine.