A family of diastereomeric dodecanuclear coordination cages based on inversion of chirality of individual triangular cyclic helicate faces.
A family of diastereomeric dodecanuclear coordination cages based on inversion of chirality of individual triangular cyclic helicate faces.
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DOI：
10.1039/d0sc04347h
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发表时间：
2020-09-08
期刊：
影响因子：
8.4
通讯作者：
Ward MD
中科院分区：
文献类型：
--
作者：
Argent SP;Jackson FC;Chan HM;Meyrick S;Taylor CGP;Ronson TK;Rourke JP;Ward MD
十二核配位笼[Cd_（12）（Lnaph）_（12）（Lmes）_（4）]（BF_（4））_（24）由一组四个三角形的三核螺旋板{Cd_（3）（μ-Lnaph）_（3）}_（6+）（基于双配位桥联配体Lnaph）组成，它们通过四个三配位配体Lmes连接。结果是，四个三角形螺旋面板和立方八面体核心的四个Lmes帽三角形面形成立方八面体的八个三角形面的两个交替子集。晶体学研究表明，三角形螺旋面可以具有“顺时针”（C）或“逆时针”（A）螺旋度，并且每个面的螺旋度可以独立于其他面而变化，因为它们是机械分离的。这产生了一组三种非对映异构体，其中立方八面体中的所有四个环状螺旋面具有相同的手性（具有T对称性的AAAA/CCCC对映异构体;具有C3对称性的AAAC/CCCA对映异构体;和具有S4对称性的非手性AACC）。这反映了许多更简单的M4 L 6四面体笼的已知行为，根据每个单独金属中心周围的三螯合物手性的意义，这些四面体笼同样可以作为T，C3或S4异构体存在：但在这里，它被翻译成更大的规模，因为四个手性单元是整个三核螺旋面而不是单个金属中心。1H NMR光谱证实了三种非对映异构体的存在，它们具有不同的分子对称性，其比例与纯统计学上预期的略有不同;对非平衡样品（在制备溶液之前通过手动晶体拾取富集）的1H NMR测量表明，在溶液中的分布在几周内没有变化，表明笼组件的动力学惰性。所有三个非对映异构体的立方八面体的协调笼包含正方形和三角形的面，基于不同的手性的每个三角形面独立，已在结构上进行了表征。
The dodecanuclear coordination cage [Cd12(Lnaph)12(Lmes)4](BF4)24 consists of a set of four triangular, trinuclear helical panels {Cd3(μ-Lnaph)3}6+ (based on ditopic bridging ligands Lnaph), which are connected by four tritopic ligands Lmes. The result is that the four triangular helical panels and the four Lmes-capped triangular faces of the cuboctahedral core form two alternating subsets of the eight triangular faces of the cuboctahedron. Crystallographic investigations revealed that the triangular helicate faces can have ‘clockwise’ (C) or ‘anticlockwise’ (A) helicity, and that the helicity of each face can vary independently of the others as they are mechanically separated. This generates a set of three diastereoisomers in which all four cyclic helicate faces in the cuboctahedron have the same chirality (AAAA/CCCC enantiomers with T symmetry; AAAC/CCCA enantiomers with C3 symmetry; and achiral AACC with S4 symmetry). This mirrors the known behaviour of many simpler M4L6 tetrahedral cages which can likewise exist as T, C3 or S4 isomers according to the sense of tris-chelate chirality around each individual metal centre: but here it is translated onto a much larger scale by the four chiral units being entire trinuclear helicate faces rather than single metal centres. 1H NMR spectroscopy confirms the presence of the three diastereoisomers with their different molecular symmetries in a ratio slightly different from what is expected on purely statistical grounds; and 1H NMR measurements on a non-equilibrium sample (enriched by manual crystal-picking before preparing the solution) showed that the distribution does not change over several weeks in solution, indicating the kinetic inertness of the cage assemblies. All three diastereoisomers of a cuboctahedral coordination cage containing square and triangular faces, based on different chirality of each triangular face independently, have been structurally characterised.
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