Knot tied around an octahedral metal centre

Adams, Harry; Ashworth, Eleanor; Breault, Gloria A.; Guo, Jun; Hunter, Christopher A.; Mayers, Paul C.

doi:10.1038/35081143

Cited by 102 publications

(50 citation statements)

References 11 publications

(3 reference statements)

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“…Alas, however, mixing of the dumbbell DB-H 14 ⅐14PF 6 with 2b and 3 in MeNO 2 failed to give a clear solution; even under highly dilute conditions and after prolonged stirring time, no convincing experimental data were obtained that pointed to the formation of the desired [15]rotaxane. The very low solubility of the dumbbell template finally put a limit on the template-directed, thermodynamic synthesis of the linear polyrotaxanes in one-pot reactions, at least with hexafluorophosphate anions as the counterions.…”

Section: Resultsmentioning

confidence: 99%

“…Changing the solvent to CD 3 CN did not enhance the formation of the desired [11]rotaxane. The situation surrounding the formation of the [15]rotaxane was even more discouraging insofar as the suspension in the reaction did not become clear even under highly dilute conditions and with stirring at room temperature for several days. Heating of the reaction mixture led to decomposition of the starting materials.…”

Section: Resultsmentioning

confidence: 99%

“…The formation of the [11]rotaxane (a 21-component selfassembly) and the [15]rotaxane (a 29-component self-assembly) using similar clipping protocols, however, encountered practical problems associated, most likely, with the extremely poor solubilities of the dumbbell templates in MeNO 2 , conferring low solubilities on the rotaxanes as well. Specifically, the clipping reaction for the formation of the [11]rotaxane was performed under moderately dilute conditions, for example, 2.5 mg of the dumbbell in 10 ml of CD 3 NO 2 , wherein the mixture became nearly clear within 2 h. 1 H NMR spectra and HR-ESI-MS (not shown) revealed partial formation of the desired [11]rotaxane with other products dominating the reaction mixture.…”

Section: Resultsmentioning

confidence: 99%

“…M echanically interlocked and knotted compounds, such as rotaxanes (1)(2)(3)(4)(5), catenanes (6-10), suitanes (11,12), trefoil knots (13)(14)(15)(16)(17), Borromean rings (18)(19)(20), and Solomon knots (21), represent challenging synthetic goals that have nevertheless been realized. These molecular compounds are usually synthesized by a template-directed approach (22) that depends on molecular recognition and self-assembly processes.…”

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confidence: 99%

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Efficient production of [ n ]rotaxanes by using template-directed clipping reactions

Leung

Stoddart

2007

Proc. Natl. Acad. Sci. U.S.A.

116

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In this article, we report on the efficient synthesis of well defined, homogeneous [n]rotaxanes (n up to 11) by a template-directed thermodynamic clipping approach. By employing dynamic covalent chemistry in the form of reversible imine bond formation, [ dynamic covalent chemistry ͉ molecular recognition ͉ polyrotaxanes ͉ self-assembly ͉ template-directed synthesis M echanically interlocked and knotted compounds, such as rotaxanes (1-5), catenanes (6-10), suitanes (11, 12), trefoil knots (13-17), , and Solomon knots (21), represent challenging synthetic goals that have nevertheless been realized. These molecular compounds are usually synthesized by a template-directed approach (22) that depends on molecular recognition and self-assembly processes. Recently, their potential applications as molecular switches for nanoelectronics (23, 24) and molecular actuators for constructing artificial muscles (25), for fabricating smart surface materials (26), and for controlling the nanoscale release of molecules trapped in mesoporous silica (27)(28)(29) were demonstrated. Polyrotaxanes and well defined, homogeneous oligorotaxanes, in which the recognition sites on a dumbbell (an axle terminated by bulky stoppers) are encircled by large rings or macrocycles (wheels) by dint of molecular recognition, have become (30-36) one of the most intensively investigated subjects in mechanical chemistry. A general synthetic method for making rotaxanes, namely, the ''threading-followed-by-stoppering'' approach (Fig. 1, method A), involves (30-32) several macrocycles. First, the macrocycles are threaded onto oligomeric or polymeric axles carrying recognition sites at prescribed intervals along the axles to form pseudorotaxanes, then both ends of the axles are stoppered with bulky groups. Although this approach is relatively simple, it does not provide complete control over the number of threaded macrocycles, that is, the rings or beads are often not threaded onto all of the available recognition sites on the axles. Alternatively, a template-directed ''clipping'' approach (Fig. 1, method B), in which the macrocycles are formed from acyclic precursors in the presence of templating recognition sites on the dumbbells, has provided (33-36) a versatile means for the construction of some lower-order rotaxanes. Nonetheless, the efficient synthesis of well defined, homogeneous, higher-order polyrotaxanes continues to be a challenge to synthetic chemists.Recently, dynamic covalent chemistry (37-40), exemplified by reversible imine formation (41, 42), metal-ligand exchange (43), and olefin metathesis (44, 45), has been demonstrated to be an effective tool for the preparation of various exotic mechanically interlocked molecular compounds. It has been found that, in the presence of an appropriate template, one of the possible compounds in the dynamic library, after mixing the different components, can be amplified to give the thermodynamically most stable product. We have reported (see refs. 46-49) an example of such a template-directed synthesis of ...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Efficient production of [ n ]rotaxanes by using template-directed clipping reactions

Leung

Stoddart

2007

Proc. Natl. Acad. Sci. U.S.A.

116

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“…Zwischen den Bipyridineinheiten induzierten Bisphenol-Z-Derivate die bençtigten Biegungen (Schema 3). [70] Der Über-handknoten Zn9 konnte anschließend mittels RCM zu Kleeblattknoten 12 oder 13 geschlossen werden, je nachdem wie lang die verwendete Kette war. [71] Eine besonders kurze und effiziente Synthese von Kleeblattknoten kann mit Lanthanoidionen als Te mplat erreicht werden (Schema 4).…”

Section: Angewandte Chemieunclassified

Molekulare Knoten

Fielden¹,

Leigh²,

Woltering³

2017

Angewandte Chemie

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Der erste synthetische Kleeblattknoten wurde in den späten 1980er Jahren hergestellt. Kompliziertere Knotentopologien wurden jedoch erst in den letzten Jahren in molekularer Form erhalten. Die Verknotung molekularer Stränge erzeugt sterische Einschränkungen und kann so wichtige physikalische und chemische Eigenschaften verleihen, unter anderem Chiralität, starkes und selektives Binden von Ionen und katalytische Aktivität. Da die Anzahl und Komplexität molekularer Knoten steigt, wird es für Chemiker immer wichtiger, die Knotennomenklatur anderer Disziplinen zu verwenden. Hier geben wir einen Überblick über die Synthesestrategien für molekulare Knoten und beschreiben die Grundlagen der Knoten‐, Zopf‐ und Tangle‐Theorie in einem für Chemiker und molekulare Strukturen angemessenen Umfang.

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A Ring-in-Ring Complex

et al. 2002

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Over the past two decades a vast array of interlocked and intertwined molecular compounds-specifically, catenanes, rotaxanes, and knots [1] -have been assembled using supramolecular assistance (templation [2] ) as the key element in their synthesis [3] under either kinetic [4] or thermodynamic [5] control. Although these synthetic protocols have been implemented more recently for the construction of more intricate variants, such as oligocatenanes, [6] molecular necklaces, [7] and cyclic daisy chains [8] to name but a few, the topological challenge of the de novo synthesis of Borromean ring compounds [9] still presents a considerable hurdle to be overcome. Our way of addressing this challenge is to employ recognition motifs to create initially stable ring-in-ring superstructures [10] which could serve as templates for subsequent catenation. Here, we report 1) the design and noncovalent synthesis of a prototype, mutually orthogonal, partially preorganized, ring-in-ring complex, together with 2) the solid-state characterization of the 1:1 complex in the context of the X-ray crystal structures of its two separate ring components, and 3) the solution-state behavior of the 1:1 complex.Previously, we have shown [11] that bisparaphenylene[34]crown-10 (BPP34C10) can encircle two dibenzylammonium (DBA ) ions simultaneously by locating the two NH 2 centers 6.9 ä apart in the polyether loops of BPP34C10 and relying upon N ÀH ¥¥¥ O hydrogen bonds to form a stable 1:2 (DBA & BPP34C10 ' DBA ) complex. Thus, it seemed not unreasonable to us that BPP34C10 might also be able to complex (Figure 1) with a suitably proportioned dicationic Figure 1. Employing precedent in the design and synthesis of a proposed 1:1 complex formed between BPP34C10 and 1-2 H 2 , together with an overlaid set of 70 co-conformations of BPP34C10 ¥ 1-2 H 2 sampled from the last 70 ps of a 100-ps MD experiment. macrocycle containing two NH 2 centers. After inspection of the solid-state superstructure [11] of the 1:2 complex formed between BPP34C10 and DBA , and construction of CPK space-filling molecular models, we concluded that the macrocycle 1-2 H 2 was a suitable candidate for further investigation. Our intuition was given a considerable boost by the results of the molecular dynamics (MD) calculations. [12] They predicted the existence of a stable co-conformation [13] in which the BPP34C10 ring encircles the dicationic macrocycle, such that the polyether loops surround the NH 2 centers, namely, the 1:1 (BPP34C10 ' 1-2 H 2 ) complex (illustrated in Figure 1) might constitute a discrete supermolecule.The synthesis (Scheme 1) of the dicationic macrocycle 1-2 H ¥ 2 PF 6 was achieved by employing a bis-Wittig reaction in the key cyclization step. The bisphosphonium salt [14] 2-H ¥ 3 PF 6 was protected (Boc 2 O/Et 3 N/MeOH) to give 3 ¥ 2 PF 6[15] M.Abstracts of Papers, Part 1, 222nd National Meeting of the American Chemical Society (Chicago, IL) 2001, MEDI 307.[16] Female Rhesus monkeys (body weight 4.0 ± 7.0 kg) were sedated with 10 mg kg À1 of ketamine ...

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Knot tied around an octahedral metal centre

Cited by 102 publications

References 11 publications

Efficient production of [ n ]rotaxanes by using template-directed clipping reactions

Efficient production of [ n ]rotaxanes by using template-directed clipping reactions

Molekulare Knoten

A Ring-in-Ring Complex

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