Anion-Driven Reversible Switching of Metal-Centered Stereoisomers in Metallopeptides
Anion-Driven Reversible Switching of Metal-Centered Stereoisomers in Metallopeptides
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金属肽中金属中心立体异构体的阴离子驱动可逆转换
DOI：
10.1002/chem.201300361
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Eiji Yashima
中科院分区：
文献类型：
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作者：
Naoki Ousaka;Yuki Takeyama;Eiji Yashima
阴离子识别是生物系统中最重要的事件之一因此，在过去的二十年里，化学家们已经合成了各种各样的人工阴离子受体，不仅是为了理解这些复杂的生物过程，而且也是为了开发新的传感器和目标阴离子的转运体，以及阴离子诱导的超分子催化除了阴离子识别，目前超分子化学中一个有趣的话题已经发展成为阴离子模板超分子[4]的组装和阴离子诱导的构象变化，如螺旋-螺旋反转，[5]螺旋-线圈转变，[6]和分子开关[7]，这些主要依赖于特定的阴离子结合到精心设计的由氢键供体基团组成的构建块，如酰胺和尿素基团和/或金属。众所周知，金属组装的阴离子受体，[9]由八面体金属离子和2,2 ‘ -联吡啶（bpy）衍生物组成，在5,5 ’位置具有二级酰胺基团，如三（5,5 ' -二取代-bpy）金属配合物，能够通过三点氢键与阴离子强配位这种金属配合物在金属中心（D或L）周围具有类似螺旋桨的手性。如果使用单取代的bpy配体，而不是双取代的bpy，与不稳定的金属离子（如FeII）一起使用，则所得到的金属配合物除了对映体外还具有两个额外的立体异构体（fac和mer），从而产生四个处于动态平衡的立体异构体；face - d, face - l, mer-D, mer-L（方案1）。
Anion recognition is one of the most important events in biological systems.[1] Therefore, chemists have synthesized a large variety of artificial anion receptors over the last two decades, not only to understand such sophisticated biological processes, but also for developing novel sensors and transporters for target anions [2] as well as for anion-induced supramolecular catalysis.[3] Besides anion recognition, one of the current interesting topics in supramolecular chemistry has evolved into the anion-templated assembly of supramolecules [4] and anion-induced conformational changes, such as helix–helix inversion,[5] helix–coil transition,[6] and molecular switches [7] that mostly rely on a specific anion binding to well-designed building blocks consisting of hydrogen-bonding donor groups, such as amide and urea moieties and/or metals.[8]It is known that metal-assembled anion receptors,[9] composed of an octahedral metal ion and 2, 2’-bipyridine (bpy) derivatives functionalized with secondary amide groups at the 5, 5’-positions, such as tris (5, 5’-disubstituted-bpy) metal complexes, are capable of strongly coordinating to an anion through three-point hydrogen bonding.[10] Such a metal complex has a propeller-like chirality around the metal center (D or L). If a mono-substituted bpy ligand is used, instead of the disubstituted bpy, together with a labile metal ion, such as FeII, the resulting metal complex possesses two additional stereoisomers (fac and mer) in addition to the enantiomers, leading to four stereoisomers that are under dynamic equilibrium; fac-D, fac-L, mer-D, and mer-L (Scheme 1).