Maeda Katsuhiro, Tamaki Shinji, Tamura Kazumi, Yashima Eiji
Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan, Fax: (+81) 52-789-3185.
Present Address: Institute for Advanced Research, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan.
Chem Asian J. 2008 Mar 7;3(3):614-624. doi: 10.1002/asia.200700279.
A novel, cis-transoidal poly-(phenylacetylene) bearing a carboxybiphenyl group as the pendant (poly-1) was prepared by polymerization of (4'-ethoxycarbonyl-4-biphenylyl)acetylene with a rhodium catalyst followed by hydrolysis of the ester groups. Upon complexation with various chiral amines and amino alcohols in dimethyl sulfoxide (DMSO), the polymer exhibited characteristic induced circular dichroism (ICD) in the UV/Vis region due to the predominantly one-handed helix formation of the polymer backbone as well as an excess of a single-handed, axially twisted conformation of the pendant biphenyl group. Poly-1 complexed with (R)-2-amino-1-propanol showed unique time-dependent inversion of the macromolecular helicity. Furthermore, the preferred-handed helical conformation of poly-1 induced by a chiral amine was further "memorized" after the chiral amine was replaced with achiral 2-aminoethanol or n-butylamine in DMSO. In sharp contrast to the previously reported memory in poly((4-carboxyphenyl)acetylene), the present helicity memory of poly-1 was accompanied by memory of the twisted biphenyl chirality in the pendants. Unprecedentedly, the helicity memory of poly-1 with achiral 2-aminoethanol was found to occur simultaneously with inversion of the axial chirality of the biphenyl groups followed by memory of the inverted biphenyl chirality, thus showing a significant change in the CD spectral pattern.
通过用铑催化剂使（4'-乙氧羰基-4-联苯基）乙炔聚合，随后酯基水解，制备了一种新型的、带有羧基联苯基作为侧基的顺反式聚（苯乙炔）（聚-1）。在二甲基亚砜（DMSO）中与各种手性胺和氨基醇络合时，由于聚合物主链主要形成单手螺旋以及侧基联苯基存在过量的单手轴向扭曲构象，该聚合物在紫外/可见区域表现出特征性的诱导圆二色性（ICD）。与（R）-2-氨基-1-丙醇络合的聚-1显示出独特的大分子螺旋度随时间的反转。此外，在手性胺被DMSO中的非手性2-氨基乙醇或正丁胺取代后，由手性胺诱导的聚-1的优先手性螺旋构象进一步被“记忆”。与先前报道的聚（（4-羧基苯基）乙炔）中的记忆形成鲜明对比的是，聚-1的当前螺旋度记忆伴随着侧基中扭曲联苯手性的记忆。前所未有的是，发现聚-1与非手性2-氨基乙醇的螺旋度记忆与联苯基团轴向手性的反转同时发生，随后是反转的联苯手性的记忆，从而显示出CD光谱模式的显著变化。
