Molecular topology, Supramlecular chemistry, Chemical biology Supervisors: Jeremy K. M. Sanders, FRS (PhD advisor) and Elizabeth M. Nolan (postdoc advisor)
Cette these a ete faite dans le but de repondre a une problematique liee a la formation et l’etud... more Cette these a ete faite dans le but de repondre a une problematique liee a la formation et l’etude de nœuds et liens moleculaires. La majorite des nœuds et liens moleculaires synthetiques est base sur la coordination autour de metaux et leur utilisation entant que Template. Une strategie utilisant l’effet hydrophobe comme force motrice pour l’auto-assemblage de nœuds et liens moleculaires a ete developpee par notre groupe. Cette strategie se base sur la formation de motifs composes d’une unite amphiphile chargee entourant une unite hydrophobe dans un milieu aqueux. La multiplication de cette brique de base et leur association reversible (liaisons imine et hydrazone) via des elements de symetrie tels que des axes de symetrie Cn a permis l’obtention de differents nœuds et liens moleculaires : six [2]catenane ou hopf link, un nœud de trefle et deux nœuds de Salomon. L’etude poussee de ces edifices moleculaires a permis la decouverte d’une propriete de commutateur moleculaire de l’un de...
Conventional approaches to the synthesis of molecular knots and links mostly rely on metal templa... more Conventional approaches to the synthesis of molecular knots and links mostly rely on metal templation. We present here an alternative strategy that uses the hydrophobic effect to drive the formation of complex interlocked structures in water. We designed an aqueous dynamic combinatorial system that can generate knots and links. In this system, the self-assembly of a topologically complex macrocycle is thermodynamically favored only if an optimum packing of all its components minimizes the hydrophobic surface area in contact with water. Therefore, the size, geometry, and rigidity of the initial building blocks can be exploited to control the formation of a specific topology. We illustrate the validity of this concept with the syntheses of a Hopf link, a Solomon link, and a trefoil knot. This latter molecule, whose self-assembly is templated by halides, binds iodide with high affinity in water. Overall, this work brings a fresh perspective on the synthesis of topologically complex molecules: Solvophobic effects can be intentionally harnessed to direct the efficient and selective self-assembly of knots and links.
In this article, we use 1H NMR spectroscopy to study the spontaneous molecular motion of donor–ac... more In this article, we use 1H NMR spectroscopy to study the spontaneous molecular motion of donor–acceptor [2]catenanes in water.
... 3–5, R, Product, % a. 1, ZnEt 2, 3, i-Pr, 6a, 75. 2, BEt 3, 3, i-Pr, 6a, 21 b. 3, ZnEt 2, 3, ... more ... 3–5, R, Product, % a. 1, ZnEt 2, 3, i-Pr, 6a, 75. 2, BEt 3, 3, i-Pr, 6a, 21 b. 3, ZnEt 2, 3, sec-Bu, 6b, 75. ... a Isolated yield. b Starting material (77%) was recovered using 3 equiv of BEt 3 . c ZnMe 2 (5 equiv), 3 h. d ZnMe 2 (5 equiv), 18 h; pursuing the reaction for 3 days did not improve the ...
An Organic Knot When people tie knots, they grasp both ends of a strand and loop them around each... more An Organic Knot When people tie knots, they grasp both ends of a strand and loop them around each other. The task is rather more difficult at the molecular level, when there is no top-down organizing framework, and the strand needs to be coaxed into looping around itself. Recently, chemists have taken advantage of the tight geometrical restrictions of metal-ligand coordination to produce knot morphologies. Ponnuswamy et al. (p. 783 ; see the Perspective by Siegel ) now demonstrate the spontaneous assembly of a trefoil knot from organic fragments without assistance from metal centers. The topology appears to be driven by hydrophobic interactions among aromatic segments that minimize exposure to surrounding water through their overlap.
The discovery through dynamic combinatorial chemistry (DCC) of a new generation of donor-acceptor... more The discovery through dynamic combinatorial chemistry (DCC) of a new generation of donor-acceptor [2]catenanes highlights the power of DCC to access unprecedented structures. While conventional thinking has limited the scope of donor-acceptor catenanes to strictly alternating stacks of donor (D) and acceptor (A) aromatic units, DCC is demonstrated in this paper to give access to unusual DAAD, DADD, and ADAA stacks. Each of these catenanes has specific structural requirements, allowing control of their formation. On the basis of these results, and on the observation that the catenanes represent kinetic bottlenecks in the reaction pathway, we propose a mechanism that explains and predicts the structures formed. Furthermore, the spontaneous assembly of catenanes in aqueous dynamic systems gives a fundamental insight into the role played by hydrophobic effect and donor-acceptor interactions when building such complex architectures.
Previous studies on the mechanism of decatungstate photocatalyzed reactions of aliphatic alcohols... more Previous studies on the mechanism of decatungstate photocatalyzed reactions of aliphatic alcohols and of aromatic hydrocarbons in the presence of oxygen suggest that in the corresponding reactions of aryl alcohols, direct electron transfer can compete with hydrogen-atom transfer. A ...
Page 1. Catenanes DOI: 10.1002/anie.201106885 Templated Dynamic Synthesis of a [3]Catenane** Fabi... more Page 1. Catenanes DOI: 10.1002/anie.201106885 Templated Dynamic Synthesis of a [3]Catenane** Fabien BL Cougnon, Nicholas A. Jenkins, G. Dan Pantos,* and Jeremy KM Sanders* We present herein the unprece-dented ...
We report the efficient condensation of imine-basedmacrocycles from dialdehyde A and aliphatic di... more We report the efficient condensation of imine-basedmacrocycles from dialdehyde A and aliphatic diamines Bn in pure water. Within the libraries, we identified a family of homologous amphiphilic [2]catenanes, whose self-assembly is primarily driven by the hydrophobic effect. The length and odd-even character of the diamine alkyl linker dictate both the yield and the conformation of the [2]catenanes, whose particular thermodynamic stability further shifts the overall equilibrium in favour of imine condensation. These findings highlight the role played by solvophobic effects in the self-assembly of complex architectures.
Cette these a ete faite dans le but de repondre a une problematique liee a la formation et l’etud... more Cette these a ete faite dans le but de repondre a une problematique liee a la formation et l’etude de nœuds et liens moleculaires. La majorite des nœuds et liens moleculaires synthetiques est base sur la coordination autour de metaux et leur utilisation entant que Template. Une strategie utilisant l’effet hydrophobe comme force motrice pour l’auto-assemblage de nœuds et liens moleculaires a ete developpee par notre groupe. Cette strategie se base sur la formation de motifs composes d’une unite amphiphile chargee entourant une unite hydrophobe dans un milieu aqueux. La multiplication de cette brique de base et leur association reversible (liaisons imine et hydrazone) via des elements de symetrie tels que des axes de symetrie Cn a permis l’obtention de differents nœuds et liens moleculaires : six [2]catenane ou hopf link, un nœud de trefle et deux nœuds de Salomon. L’etude poussee de ces edifices moleculaires a permis la decouverte d’une propriete de commutateur moleculaire de l’un de...
Conventional approaches to the synthesis of molecular knots and links mostly rely on metal templa... more Conventional approaches to the synthesis of molecular knots and links mostly rely on metal templation. We present here an alternative strategy that uses the hydrophobic effect to drive the formation of complex interlocked structures in water. We designed an aqueous dynamic combinatorial system that can generate knots and links. In this system, the self-assembly of a topologically complex macrocycle is thermodynamically favored only if an optimum packing of all its components minimizes the hydrophobic surface area in contact with water. Therefore, the size, geometry, and rigidity of the initial building blocks can be exploited to control the formation of a specific topology. We illustrate the validity of this concept with the syntheses of a Hopf link, a Solomon link, and a trefoil knot. This latter molecule, whose self-assembly is templated by halides, binds iodide with high affinity in water. Overall, this work brings a fresh perspective on the synthesis of topologically complex molecules: Solvophobic effects can be intentionally harnessed to direct the efficient and selective self-assembly of knots and links.
In this article, we use 1H NMR spectroscopy to study the spontaneous molecular motion of donor–ac... more In this article, we use 1H NMR spectroscopy to study the spontaneous molecular motion of donor–acceptor [2]catenanes in water.
... 3–5, R, Product, % a. 1, ZnEt 2, 3, i-Pr, 6a, 75. 2, BEt 3, 3, i-Pr, 6a, 21 b. 3, ZnEt 2, 3, ... more ... 3–5, R, Product, % a. 1, ZnEt 2, 3, i-Pr, 6a, 75. 2, BEt 3, 3, i-Pr, 6a, 21 b. 3, ZnEt 2, 3, sec-Bu, 6b, 75. ... a Isolated yield. b Starting material (77%) was recovered using 3 equiv of BEt 3 . c ZnMe 2 (5 equiv), 3 h. d ZnMe 2 (5 equiv), 18 h; pursuing the reaction for 3 days did not improve the ...
An Organic Knot When people tie knots, they grasp both ends of a strand and loop them around each... more An Organic Knot When people tie knots, they grasp both ends of a strand and loop them around each other. The task is rather more difficult at the molecular level, when there is no top-down organizing framework, and the strand needs to be coaxed into looping around itself. Recently, chemists have taken advantage of the tight geometrical restrictions of metal-ligand coordination to produce knot morphologies. Ponnuswamy et al. (p. 783 ; see the Perspective by Siegel ) now demonstrate the spontaneous assembly of a trefoil knot from organic fragments without assistance from metal centers. The topology appears to be driven by hydrophobic interactions among aromatic segments that minimize exposure to surrounding water through their overlap.
The discovery through dynamic combinatorial chemistry (DCC) of a new generation of donor-acceptor... more The discovery through dynamic combinatorial chemistry (DCC) of a new generation of donor-acceptor [2]catenanes highlights the power of DCC to access unprecedented structures. While conventional thinking has limited the scope of donor-acceptor catenanes to strictly alternating stacks of donor (D) and acceptor (A) aromatic units, DCC is demonstrated in this paper to give access to unusual DAAD, DADD, and ADAA stacks. Each of these catenanes has specific structural requirements, allowing control of their formation. On the basis of these results, and on the observation that the catenanes represent kinetic bottlenecks in the reaction pathway, we propose a mechanism that explains and predicts the structures formed. Furthermore, the spontaneous assembly of catenanes in aqueous dynamic systems gives a fundamental insight into the role played by hydrophobic effect and donor-acceptor interactions when building such complex architectures.
Previous studies on the mechanism of decatungstate photocatalyzed reactions of aliphatic alcohols... more Previous studies on the mechanism of decatungstate photocatalyzed reactions of aliphatic alcohols and of aromatic hydrocarbons in the presence of oxygen suggest that in the corresponding reactions of aryl alcohols, direct electron transfer can compete with hydrogen-atom transfer. A ...
Page 1. Catenanes DOI: 10.1002/anie.201106885 Templated Dynamic Synthesis of a [3]Catenane** Fabi... more Page 1. Catenanes DOI: 10.1002/anie.201106885 Templated Dynamic Synthesis of a [3]Catenane** Fabien BL Cougnon, Nicholas A. Jenkins, G. Dan Pantos,* and Jeremy KM Sanders* We present herein the unprece-dented ...
We report the efficient condensation of imine-basedmacrocycles from dialdehyde A and aliphatic di... more We report the efficient condensation of imine-basedmacrocycles from dialdehyde A and aliphatic diamines Bn in pure water. Within the libraries, we identified a family of homologous amphiphilic [2]catenanes, whose self-assembly is primarily driven by the hydrophobic effect. The length and odd-even character of the diamine alkyl linker dictate both the yield and the conformation of the [2]catenanes, whose particular thermodynamic stability further shifts the overall equilibrium in favour of imine condensation. These findings highlight the role played by solvophobic effects in the self-assembly of complex architectures.
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Papers by Fabien Cougnon