Temperature‐Induced Chiroptical Changes in a Helical Poly(phenylacetylene) Bearing N,N‐Diisopropylaminomethyl Groups with Chiral Acids in Water |
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Authors: | Kanji Nagai Katsuhiro Maeda Dr Yoshihisa Takeyama Takahiro Sato Prof Dr Eiji Yashima Prof Dr |
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Institution: | 1. Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University, Chikusa‐ku, Nagoya 464‐8603, Japan, Fax: (+81)?52‐789‐3185;2. Yashima Super‐Structured Helix Project, Exploratory Research for Advanced Technology (ERATO), Japan Science and Technology Agency (JST), Creation Core Nagoya 101, 2266‐22 Shimoshidami, Moriyama‐ku, Nagoya 463‐0003, Japan;3. Department of Macromolecular Science, Osaka University, Machikaneyama‐cho, Toyonaka, Osaka 560‐0043, Japan |
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Abstract: | A stereoregular poly(phenylacetylene) bearing an N,N‐diisopropylaminomethyl group as the pendant (poly‐ 1 ) changed its structure into the prevailing one‐handed helical conformation upon complexation with optically active acids in water. The complexes exhibited induced circular dichroism (ICD) in the UV/Vis region of the polymer backbone. Poly‐ 1 is highly sensitive to the chirality of chiral acids and can detect a small enantiomeric imbalance in these acids, in particular, phenyl lactic acid in water. For example, a 0.005 % enantiomeric excess of phenyl lactic acid can be detected by CD spectroscopy. The observed ICD intensity and pattern of poly‐ 1 were dependent on the temperature and concentration of poly‐ 1 , probably due to aggregations of the polymer at high temperature as revealed by dynamic light scattering and AFM. On the basis of the temperature‐dependent ICD changes, the preferred chiral helical sense of poly‐ 1 was found to be controlled by noncovalent bonding interactions by using structurally different enantiomeric acids. |
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Keywords: | chirality circular dichroism helical structures induced helices poly(phenylacetylene)s |
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