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| Content Provider | World Health Organization (WHO)-Global Index Medicus |
|---|---|
| Author | Cave, Gareth W. V. Forgan, Ross S. Peters, Andrea J. Stoddart, J. Fraser Tangchaivang, Nicholas Khan, Saeed I. Meyer, Cari D. Chichak, Kelly S. Cantrill, Stuart J. |
| Description | Author Affiliation: Meyer CD ( The California NanoSystems Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095-1569, USA.) |
| Abstract | The dynamic solution equilibria between molecular Borromean rings (BRs) and Solomon knots (SKs), assembled from transition metal-templated macrocycles, consisting of exo-bidentate bipyridyl and endo-tridentate diiminopyridyl ligands, have been examined with respect to the choice of the metal template and reaction conditions employed in the synthesis of the metalated BRs, otherwise known as Borromeates. Three new Borromeates, their syntheses templated by $Cu^{II},$ $Co^{II},$ and $Mn^{II},$ have been characterized extensively (two by X-ray crystallography) to the extent that the metal centers in the assemblies have been shown to be distanced sufficiently from each other not to communicate. The solid-state structure of the $Co^{II}–Borromeate$ reveals that six MeOH molecules, arranged in a [OH⋅⋅⋅O] hydrogen bonded, chair-like conformation, are located within its oxophilic central cavity. When a mixture of $Cu^{II}$ and $Zn^{II}$ is used as the source of templation, there exists a dynamic equilibrium, in MeOH at room temperature, between a mixed-metal BR and a SK, from which the latter has been fractionally crystallized. By employing appropriate synthetic protocols with $Zn^{II}$ or $Cd^{II}$ as the template, significant amounts of SKs are formed alongside BRs. Modified crystallization conditions resulted in the isolation of both an all-zinc BR and an all-zinc SK, crystals of which can be separated manually, leading to the full characterization of the all-zinc SK by $^{1}H NMR$ spectroscopy and X-ray crystallography. This doubly interlocked [2]catenate has been identified retrospectively in recorded spectra, where it was attributed previously to a Borromeate with a $Zn^{II}$ cation coordinated to the oxophilic interior walls of the ensemble. Interestingly, these $Zn^{II}-templated$ assemblies do not interconvert in MeOH at room temperature, indicating the significant influence of both the metal template and solvent on the solution equilibria. It would also appear that $d^{10}$ metal ions favor SK formation—no evidence of $Cu^{II}-,$ $Co^{II}-,$ or $Mn^{II}-templated$ SKs has been found, yet a 1:0.9 ratio of BR:SK has been identified by $^{1}H NMR$ spectroscopy when $Cd^{II}$ is used as the template. |
| ISSN | 09476539 |
| e-ISSN | 15213765 |
| Journal | Chemistry - A European Journal |
| Issue Number | 42 |
| Volume Number | 16 |
| Language | English |
| Publisher | Wiley-VCH;ChemPubSoc Europe |
| Publisher Date | 2010-11-08 |
| Publisher Place | Germany |
| Access Restriction | Open |
| Subject Keyword | Chemistry |
| Content Type | Text |
| Resource Type | Article |
| Subject | Organic Chemistry Catalysis |
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