The Experts below are selected from a list of 4305 Experts worldwide ranked by ideXlab platform
David A Leigh - One of the best experts on this subject based on the ideXlab platform.
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a Molecular endless 74 Knot
Nature Chemistry, 2021Co-Authors: Jonathan J Danon, David A Leigh, Jeanfrancois Lemonnier, Stephen D P Fielden, George F S Whitehead, Steffen L WolteringAbstract:Current strategies for the synthesis of Molecular Knots focus on twisting, folding and/or threading Molecular building blocks. Here we report that Zn(ii) or Fe(ii) ions can be used to weave ligand strands to form a woven 3 × 3 Molecular grid. We found that the process requires tetrafluoroborate anions to template the assembly of the interwoven grid by binding within the square cavities formed between the metal-coordinated criss-crossed ligands. The strand ends of the grid can subsequently be joined through within-grid alkene metathesis reactions to form a topologically trivial macrocycle (unKnot), a doubly interlocked [2]catenane (Solomon link) and a Knot with seven crossings in a 258-atom-long closed loop. This 74 Knot topology corresponds to that of an endless Knot, which is a basic motif of Celtic interlace, the smallest Chinese Knot and one of the eight auspicious symbols of Buddhism and Hinduism. The weaving of Molecular strands within a discrete layer by anion-template metal–ion coordination opens the way for the synthesis of other Molecular Knot topologies and to woven polymer materials. A combination of metal- and anion-template synthesis directs the weaving of Molecular weft and warp strands in the assembly of a 3 × 3 interwoven grid. Connection of the ligand strands by alkene metathesis produces the topology of a seven-crossing endless Knot, an important cultural and religious symbol.
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Knotting a Molecular strand can invert macroscopic effects of chirality
Nature Chemistry, 2020Co-Authors: Nathalie Katsonis, David A Leigh, Federico Lancia, Lucian Pirvu, Alexander Ryabchun, Fredrik SchaufelbergerAbstract:Transferring structural information from the nanoscale to the macroscale is a promising strategy for developing adaptive and dynamic materials. Here we demonstrate that the Knotting and unKnotting of a Molecular strand can be used to control, and even invert, the handedness of a helical organization within a liquid crystal. An oligodentate tris(2,6-pyridinedicarboxamide) strand with six point-chiral centres folds into an overhand Knot of single handedness upon coordination to lanthanide ions, both in isotropic solutions and in liquid crystals. In achiral liquid crystals, dopant Knotted and unKnotted strands induce supraMolecular helical organizations of opposite handedness, with dynamic switching achievable through in situ Knotting and unKnotting events. Tying the Molecular Knot transmits information regarding asymmetry across length scales, from Euclidean point chirality (constitutional chirality) via Molecular entanglement (conformation) to liquid-crystal (centimetre-scale) chirality. The magnitude of the effect induced by the tying of the Molecular Knots is similar to that famously used to rotate a glass rod on the surface of a liquid crystal by synthetic Molecular motors.
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comment on coordination driven self assembly of a Molecular Knot comprising sixteen crossings
Angewandte Chemie, 2018Co-Authors: David A Leigh, Jeanfrancois Lemonnier, Steffen L WolteringAbstract:The remarkable metalla-Knot obtained by Kim, Jung, Chi and colleagues is an 818 Knot, a metalla-Knot that comprises eight crossings, not sixteen. It is the first Knot to be synthesized having the 818 topology. Like several previous Molecular Knots, it adopts a conformation that does not correspond to the reduced form of the Knot and has additional persistent nugatory crossings.
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braiding a Molecular Knot with eight crossings
Science, 2017Co-Authors: Jonathan J Danon, Anneke Kruger, David A Leigh, Jeanfrancois Lemonnier, Alexander J Stephens, Inigo J Vitoricayrezabal, Steffen L WolteringAbstract:Knots may ultimately prove just as versatile and useful at the nanoscale as at the macroscale. However, the lack of synthetic routes to all but the simplest Molecular Knots currently prevents systematic investigation of the influence of Knotting at the Molecular level. We found that it is possible to assemble four building blocks into three braided ligand strands. Octahedral iron(II) ions control the relative positions of the three strands at each crossing point in a circular triple helicate, while structural constraints on the ligands determine the braiding connections. This approach enables two-step assembly of a Molecular 819 Knot featuring eight nonalternating crossings in a 192-atom closed loop ~20 nanometers in length. The resolved metal-free 819 Knot enantiomers have pronounced features in their circular dichroism spectra resulting solely from topological chirality.
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allosteric initiation and regulation of catalysis with a Molecular Knot
Science, 2016Co-Authors: Vanesa Marcos, Jeanfrancois Lemonnier, Alexander J Stephens, Inigo J Vitoricayrezabal, Steffen L Woltering, Javier Jaramillogarcia, Alina L Nussbaumer, Alberto Valero, David A LeighAbstract:Molecular Knots occur in DNA, proteins, and other macromolecules. However, the benefits that can potentially arise from tying molecules in Knots are, for the most part, unclear. Here, we report on a synthetic Molecular pentafoil Knot that allosterically initiates or regulates catalyzed chemical reactions by controlling the in situ generation of a carbocation formed through the Knot-promoted cleavage of a carbon-halogen bond. The Knot architecture is crucial to this function because it restricts the conformations that the Molecular chain can adopt and prevents the formation of catalytically inactive species upon metal ion binding. UnKnotted analogs are not catalytically active. Our results suggest that Knotting molecules may be a useful strategy for reducing the degrees of freedom of flexible chains, enabling them to adopt what are otherwise thermodynamically inaccessible functional conformations.
Kiwhan Chi - One of the best experts on this subject based on the ideXlab platform.
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the first quantitative synthesis of a closed three link chain 613 using coordination and noncovalent interactions driven self assembly
Journal of the American Chemical Society, 2020Co-Authors: Jatinder Singh, Dong Hwan Kim, Eunhee Kim, Jaehoon Jung, Hyunuk Kim, Rizky Hadiputra, Kiwhan ChiAbstract:Engineering of supraMolecular topologies offers potential opportunities for tailoring their properties to various function and applications. However, the synthesis of interlocked or intertwined compounds, catenanes, links or Knots, is a challenge. Previously, we used coordination-driven self-assembly and noncovalent interactions (NCIs) between metal-based acceptors and multipyridyl donors to create supraMolecular topologies with increasing complexity. Self-assembling components of fixed length and geometry have been utilized for the production of topologies such as Borromean rings, Solomon links, Hopf's link, "rectangle in rectangle", and an 818 Molecular Knot. However, recent synthesis of a linear [3]catenane by us witnessed the importance of flexible ligands along with coordination-driven self-assembly and NCIs in self-assembling units. This flexibility provides distinctive angularity for the recognition of various NCIs and thus offers tremendous possibilities for realizing complex supraMolecular topologies. This study proposed a selective and quantitative synthesis, and also the first X-ray characterization of a closed three-link chain (a prime link of [3]catenane with 6 crossings) via two component coordination-driven self-assembly. The experiments based upon concentration, guest template, and solvent effects were systematically presented. Furthermore, the experimental finding was supported by density functional theory calculations, which highlighted the necessity of the multiple NCIs along with appropriate geometry of the [2 + 2] rings.
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coordination driven self assembly of a Molecular Knot comprising sixteen crossings
Angewandte Chemie, 2018Co-Authors: Dong Hwan Kim, Nem Singh, Eunhee Kim, Jaehoon Jung, Hyunuk Kim, Kiwhan ChiAbstract:Molecular Knots have become highly attractive to chemists because of their prospective properties in mimicking biomolecules and machines. Only a few examples of Molecular Knots from the billions tabulated by mathematicians have been realized and Molecular Knots with more than eight crossings have not been reported to date. We report here the coordination-driven [8+8] self-assembly of a higher-generation Molecular Knot comprising as many as sixteen crossings. Its solid-state X-ray crystal structure and multinuclear 2D NMR findings confirmed its architecture and topology. The formation of this Molecular Knot appears to depend on the functionalities and geometries of donor and acceptor in terms of generating appropriate angles and strong π-π interactions supported by hydrophobic effects. This study shows coordination-driven self-assembly offers a powerful potential means of synthesizing more and more complicated Molecular Knots and of understanding differences between the properties of Knotted and unKnotted structures.
Steffen L Woltering - One of the best experts on this subject based on the ideXlab platform.
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a Molecular endless 74 Knot
Nature Chemistry, 2021Co-Authors: Jonathan J Danon, David A Leigh, Jeanfrancois Lemonnier, Stephen D P Fielden, George F S Whitehead, Steffen L WolteringAbstract:Current strategies for the synthesis of Molecular Knots focus on twisting, folding and/or threading Molecular building blocks. Here we report that Zn(ii) or Fe(ii) ions can be used to weave ligand strands to form a woven 3 × 3 Molecular grid. We found that the process requires tetrafluoroborate anions to template the assembly of the interwoven grid by binding within the square cavities formed between the metal-coordinated criss-crossed ligands. The strand ends of the grid can subsequently be joined through within-grid alkene metathesis reactions to form a topologically trivial macrocycle (unKnot), a doubly interlocked [2]catenane (Solomon link) and a Knot with seven crossings in a 258-atom-long closed loop. This 74 Knot topology corresponds to that of an endless Knot, which is a basic motif of Celtic interlace, the smallest Chinese Knot and one of the eight auspicious symbols of Buddhism and Hinduism. The weaving of Molecular strands within a discrete layer by anion-template metal–ion coordination opens the way for the synthesis of other Molecular Knot topologies and to woven polymer materials. A combination of metal- and anion-template synthesis directs the weaving of Molecular weft and warp strands in the assembly of a 3 × 3 interwoven grid. Connection of the ligand strands by alkene metathesis produces the topology of a seven-crossing endless Knot, an important cultural and religious symbol.
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comment on coordination driven self assembly of a Molecular Knot comprising sixteen crossings
Angewandte Chemie, 2018Co-Authors: David A Leigh, Jeanfrancois Lemonnier, Steffen L WolteringAbstract:The remarkable metalla-Knot obtained by Kim, Jung, Chi and colleagues is an 818 Knot, a metalla-Knot that comprises eight crossings, not sixteen. It is the first Knot to be synthesized having the 818 topology. Like several previous Molecular Knots, it adopts a conformation that does not correspond to the reduced form of the Knot and has additional persistent nugatory crossings.
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braiding a Molecular Knot with eight crossings
Science, 2017Co-Authors: Jonathan J Danon, Anneke Kruger, David A Leigh, Jeanfrancois Lemonnier, Alexander J Stephens, Inigo J Vitoricayrezabal, Steffen L WolteringAbstract:Knots may ultimately prove just as versatile and useful at the nanoscale as at the macroscale. However, the lack of synthetic routes to all but the simplest Molecular Knots currently prevents systematic investigation of the influence of Knotting at the Molecular level. We found that it is possible to assemble four building blocks into three braided ligand strands. Octahedral iron(II) ions control the relative positions of the three strands at each crossing point in a circular triple helicate, while structural constraints on the ligands determine the braiding connections. This approach enables two-step assembly of a Molecular 819 Knot featuring eight nonalternating crossings in a 192-atom closed loop ~20 nanometers in length. The resolved metal-free 819 Knot enantiomers have pronounced features in their circular dichroism spectra resulting solely from topological chirality.
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allosteric initiation and regulation of catalysis with a Molecular Knot
Science, 2016Co-Authors: Vanesa Marcos, Jeanfrancois Lemonnier, Alexander J Stephens, Inigo J Vitoricayrezabal, Steffen L Woltering, Javier Jaramillogarcia, Alina L Nussbaumer, Alberto Valero, David A LeighAbstract:Molecular Knots occur in DNA, proteins, and other macromolecules. However, the benefits that can potentially arise from tying molecules in Knots are, for the most part, unclear. Here, we report on a synthetic Molecular pentafoil Knot that allosterically initiates or regulates catalyzed chemical reactions by controlling the in situ generation of a carbocation formed through the Knot-promoted cleavage of a carbon-halogen bond. The Knot architecture is crucial to this function because it restricts the conformations that the Molecular chain can adopt and prevents the formation of catalytically inactive species upon metal ion binding. UnKnotted analogs are not catalytically active. Our results suggest that Knotting molecules may be a useful strategy for reducing the degrees of freedom of flexible chains, enabling them to adopt what are otherwise thermodynamically inaccessible functional conformations.
Dong Hwan Kim - One of the best experts on this subject based on the ideXlab platform.
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the first quantitative synthesis of a closed three link chain 613 using coordination and noncovalent interactions driven self assembly
Journal of the American Chemical Society, 2020Co-Authors: Jatinder Singh, Dong Hwan Kim, Eunhee Kim, Jaehoon Jung, Hyunuk Kim, Rizky Hadiputra, Kiwhan ChiAbstract:Engineering of supraMolecular topologies offers potential opportunities for tailoring their properties to various function and applications. However, the synthesis of interlocked or intertwined compounds, catenanes, links or Knots, is a challenge. Previously, we used coordination-driven self-assembly and noncovalent interactions (NCIs) between metal-based acceptors and multipyridyl donors to create supraMolecular topologies with increasing complexity. Self-assembling components of fixed length and geometry have been utilized for the production of topologies such as Borromean rings, Solomon links, Hopf's link, "rectangle in rectangle", and an 818 Molecular Knot. However, recent synthesis of a linear [3]catenane by us witnessed the importance of flexible ligands along with coordination-driven self-assembly and NCIs in self-assembling units. This flexibility provides distinctive angularity for the recognition of various NCIs and thus offers tremendous possibilities for realizing complex supraMolecular topologies. This study proposed a selective and quantitative synthesis, and also the first X-ray characterization of a closed three-link chain (a prime link of [3]catenane with 6 crossings) via two component coordination-driven self-assembly. The experiments based upon concentration, guest template, and solvent effects were systematically presented. Furthermore, the experimental finding was supported by density functional theory calculations, which highlighted the necessity of the multiple NCIs along with appropriate geometry of the [2 + 2] rings.
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coordination driven self assembly of a Molecular Knot comprising sixteen crossings
Angewandte Chemie, 2018Co-Authors: Dong Hwan Kim, Nem Singh, Eunhee Kim, Jaehoon Jung, Hyunuk Kim, Kiwhan ChiAbstract:Molecular Knots have become highly attractive to chemists because of their prospective properties in mimicking biomolecules and machines. Only a few examples of Molecular Knots from the billions tabulated by mathematicians have been realized and Molecular Knots with more than eight crossings have not been reported to date. We report here the coordination-driven [8+8] self-assembly of a higher-generation Molecular Knot comprising as many as sixteen crossings. Its solid-state X-ray crystal structure and multinuclear 2D NMR findings confirmed its architecture and topology. The formation of this Molecular Knot appears to depend on the functionalities and geometries of donor and acceptor in terms of generating appropriate angles and strong π-π interactions supported by hydrophobic effects. This study shows coordination-driven self-assembly offers a powerful potential means of synthesizing more and more complicated Molecular Knots and of understanding differences between the properties of Knotted and unKnotted structures.
Hyunuk Kim - One of the best experts on this subject based on the ideXlab platform.
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the first quantitative synthesis of a closed three link chain 613 using coordination and noncovalent interactions driven self assembly
Journal of the American Chemical Society, 2020Co-Authors: Jatinder Singh, Dong Hwan Kim, Eunhee Kim, Jaehoon Jung, Hyunuk Kim, Rizky Hadiputra, Kiwhan ChiAbstract:Engineering of supraMolecular topologies offers potential opportunities for tailoring their properties to various function and applications. However, the synthesis of interlocked or intertwined compounds, catenanes, links or Knots, is a challenge. Previously, we used coordination-driven self-assembly and noncovalent interactions (NCIs) between metal-based acceptors and multipyridyl donors to create supraMolecular topologies with increasing complexity. Self-assembling components of fixed length and geometry have been utilized for the production of topologies such as Borromean rings, Solomon links, Hopf's link, "rectangle in rectangle", and an 818 Molecular Knot. However, recent synthesis of a linear [3]catenane by us witnessed the importance of flexible ligands along with coordination-driven self-assembly and NCIs in self-assembling units. This flexibility provides distinctive angularity for the recognition of various NCIs and thus offers tremendous possibilities for realizing complex supraMolecular topologies. This study proposed a selective and quantitative synthesis, and also the first X-ray characterization of a closed three-link chain (a prime link of [3]catenane with 6 crossings) via two component coordination-driven self-assembly. The experiments based upon concentration, guest template, and solvent effects were systematically presented. Furthermore, the experimental finding was supported by density functional theory calculations, which highlighted the necessity of the multiple NCIs along with appropriate geometry of the [2 + 2] rings.
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coordination driven self assembly of a Molecular Knot comprising sixteen crossings
Angewandte Chemie, 2018Co-Authors: Dong Hwan Kim, Nem Singh, Eunhee Kim, Jaehoon Jung, Hyunuk Kim, Kiwhan ChiAbstract:Molecular Knots have become highly attractive to chemists because of their prospective properties in mimicking biomolecules and machines. Only a few examples of Molecular Knots from the billions tabulated by mathematicians have been realized and Molecular Knots with more than eight crossings have not been reported to date. We report here the coordination-driven [8+8] self-assembly of a higher-generation Molecular Knot comprising as many as sixteen crossings. Its solid-state X-ray crystal structure and multinuclear 2D NMR findings confirmed its architecture and topology. The formation of this Molecular Knot appears to depend on the functionalities and geometries of donor and acceptor in terms of generating appropriate angles and strong π-π interactions supported by hydrophobic effects. This study shows coordination-driven self-assembly offers a powerful potential means of synthesizing more and more complicated Molecular Knots and of understanding differences between the properties of Knotted and unKnotted structures.