Molecular mechanism of polyacrylate helix sense switching across its free energy landscape.
Molecular mechanism of polyacrylate helix sense switching across its free energy landscape.
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DOI：
10.1021/ja4002508
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发表时间：
2013-04
影响因子：
15
通讯作者：
A. Pietropaolo;T. Nakano
中科院分区：
文献类型：
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作者：
A. Pietropaolo;T. Nakano
具有可切换螺旋方向的螺旋聚合物是手性功能材料的通用框架。在这项工作中，我们重建了螺旋聚（2，7-双（4-叔丁基苯基）芴-9-基丙烯酸酯）[聚（BBPFA）]的自由能景观，因为它的外消旋化是选择性地由光驱动，没有任何化学键的重排。手性反转是通过原子自由能模拟手性指数作为反应坐标来实现的。自由能景观再现实验的电子圆二色光谱。我们建议，手性反转的聚（BBPFA）收益从左手31螺旋通过多态自由能途径，以达到右手31螺旋。反转由联苯单元的旋转触发，活化势垒为38 kcal/mol。据我们所知，这是第一份报告的手性反转机制的螺旋聚合物确定在一个定量的方式在原子自由能模拟的框架。
Helical polymers with switchable screw sense are versatile frameworks for chiral functional materials. In this work, we reconstructed the free energy landscape of helical poly(2,7-bis(4-tert-butylphenyl)fluoren-9-yl acrylate) [poly(BBPFA)], as its racemization is selectively driven by light without any rearrangement of chemical bonds. The chirality inversion was enforced by atomistic free energy simulations using chirality indices as reaction coordinates. The free energy landscape reproduced the experimental electronic circular dichroism spectra. We propose that the chirality inversion of poly(BBPFA) proceeds from a left-handed 31 helix via multistate free energy pathways to reach the right-handed 31 helix. The inversion is triggered by the rotation of biphenyl units with an activation barrier of 38 kcal/mol. To the best of our knowledge, this is the first report on the chiral inversion mechanism of a helical polymer determined in a quantitative way in the framework of atomistic free energy simulations.