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标题：Symmetry breaking in self-assembled M4L6 cage complexes
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作者：Wenjing Meng ; Tanya K. Ronson ; Jonathan R. Nitschke 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2013
卷号：110
期号：26
页码：10531-10535
DOI：10.1073/pnas.1302683110
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Here we describe the phenomenon of symmetry breaking within a series of M4L6 container molecules. These containers were synthesized using planar rigid bis-bidentate ligands based on 2,6-substituted naphthalene, anthracene, or anthraquinone spacers and FeII ions. The planarity of the ligand spacer favors a stereochemical configuration in which each cage contains two metal centers of opposite handedness to the other two, which would ordinarily result in an S4-symmetric, achiral configuration. Reduction of symmetry from S4 to C1 is achieved by the spatial offset between each ligand's pair of binding sites, which breaks the S4 symmetry axis. Using larger CdII or CoII ions instead of FeII resulted, in some cases, in the observation of dynamic motion of the symmetry-breaking ligands in solution. NMR spectra of these dynamic complexes thus reflected apparent S4 symmetry owing to rapid interconversion between energetically degenerate, enantiomeric C1-symmetric conformations.
关键词：coordination chemistry ; metal–organic capsules ; self-assembly ; supramolecular chemistry ; stereochemistry