A quadruply stranded metallohelicate and its spontaneous dimerization into an interlocked metallohelicate
A quadruply stranded metallohelicate and its spontaneous dimerization into an interlocked metallohelicate
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DOI：
10.1002/anie.200703162
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发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Kuroda, Reiko
中科院分区：
文献类型：
--
作者：
Fukuda, Morihiko;Sekiya, Ryo;Kuroda, Reiko
离散超分子系统（[MxLy]系统；M=过渡金属离子，L=配体）的配位驱动自组装已成为当前超分子化学研究的热点之一。这是因为其优异的特性，如易于制备和高产率的目标[MxLy]超分子，以及其在材料科学中的潜在应用在过去的二十年里，人们对各种形态的精细[MxLy]系统的制造进行了广泛的研究其中，金属螺旋酸盐[3]由于其固有的手性以及作为功能材料的结构组分的潜在用途而受到特别的关注虽然单链、双链和三重链金属螺旋酸盐已经被广泛报道，但四链金属螺旋酸盐却很少被报道[4,5]本文报道了四股螺旋金属酸盐的设计和合成及其自发二聚化成联锁结构（方案1）。之前，Fujita etal。使用刚性配体，并报道了一个有趣的由十个组分组成的互锁超分子结构的自组装，以及通过部分分解将两个不同的预制笼重组为互锁结构本文所述的研究表明，具有柔性配体的金属酸酯在形成联锁结构的同时最终保持单体单元的完整性。我们设计的配体的新颖之处在于使用二苯甲酮作为扭曲的起源：二苯甲酮通常采用非平面的C2对称，这是由于邻近苯基环的氢原子之间的空间排斥，在溶液中，苯基环在CcarbonylÀCphenyl键处的快速旋转使对映体处于平衡状态。我们将二苯甲酮框架与两个柔性的3-吡啶甲氧基偶联，形成了桥接配体4,4 ' -双（3-吡啶甲氧基）二苯甲酮（L1; Scheme2）。通过PM6计算[8]证实了其扭曲结构（见支持信息中的图1），二苯甲酮部分的两个苯环之间的二面角为59.68。我们预计，倾向于采用方形平面几何结构的L1和PdII离子的自组装，
Coordination-driven selfassembly of discrete supramolecular systems ([MxLy] systems; M= transitionmetal ion, L= ligand) has become one of the most intensely researched fields of current supramolecular chemistry. This is because of its excellent features such as the ease of preparation and high yield of target [MxLy] supramolecules as well as its potential applications in material sciences.[1] Over the past two decades, extensive studies have been made on the fabrication of elaborate [MxLy] systems with various morphologies.[2] Among them, metallohelicates [3] have received particular attention because of their potential use as structural components of functional materials as well as their inherent chirality.[4] Although single-, double-, and triple metallohelicates have been well-documented,[4, 5] quadruply stranded metallohelicates have been rarely reported.[6] Herein we report the design and synthesis of a quadruply stranded metallohelicate and its spontaneous dimerization into an interlocked structure (Scheme 1). Previously, Fujita etal. used rigid ligands and reported an interesting selfassembly of an interlocked supramolecular structure from ten components, as well as the reorganization of two different preformed cages into an interlocked structure by partial decomposition.[7] The study described herein shows that a metallohelicate with flexible ligands dimerizes to form an interlocked structure while ultimately keeping the integrity of the monomer unit.The novelty of our design for the ligand which would give rise to the quadruply stranded metallohelicate lies in the use of benzophenone as the origin of twist: Benzophenone usually adopts a nonplanar C2 symmetry as a result of steric repulsion between the hydrogen atoms of neighboring phenyl rings and, in solution, the enantiomers are in equilibrium by rapid rotation of the phenyl rings at the CcarbonylÀCphenyl bonds. We coupled the benzophenone framework with two flexible 3-pyridylmethoxy groups to create the bridging ligand 4, 4’-bis (3-pyridinemethoxy) benzophenone (L1; Scheme2). Its twisted structure was confirmed by PM6 calculations [8](see FigureS1 in the Supporting Information), which show a dihedral angle of 59.68 between the two phenyl rings of the benzophenone moiety. We expected that self-assembly of L1 and PdII ions, which prefer to adopt a square-planar geometry,