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Werner M Nau - One of the best experts on this subject based on the ideXlab platform.
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encapsulation of ionic liquids inside Cucurbiturils
Organic and Biomolecular Chemistry, 2020Co-Authors: Khaleel I Assaf, Husam Abed Alfattah, Alaa F Eftaiha, Sanaa K Bardaweel, Mohammad A Alnajjar, Fatima Alsoubani, Abdussalam K Qaroush, Musa I Elbarghouthi, Werner M NauAbstract:Cucurbit[n]urils (CBn, n = 6–8) serve as molecular receptors for imidazolium-based ionic liquids (ILs) in aqueous solution. The amphiphilic nature of 1-alkyl-3-methylimidazolium guests (Cnmim), with a cationic imidazolium residue and a hydrophobic alkyl chain, enabled their complexation with CBn through a combination of the hydrophobic effect and ion–dipole interactions. 1H NMR experiments revealed that the cavity of CBn can host the hydrophobic chain of the ILs, while one of the carbonyl rims served as a docking site for the imidazolium ring. The structure of the complexes was further analyzed by molecular dynamics (MD) simulations, which indicated that the cavity of CB6 can accommodate up to 5 carbon atoms, while the larger cavity of CB7 and CB8 can encapsulate longer alkyl chains in folded conformations. Isothermal titration calorimetry (ITC) experiments provided up to micromolar affinity of ILs to CBn in aqueous solution, which was independently quantified by indicator displacement titrations.
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Cucurbiturils as supramolecular inhibitors of DNA restriction by type II endonucleases
Organic & biomolecular chemistry, 2015Co-Authors: Cátia Parente Carvalho, Werner M Nau, Amir Norouzy, Vera Ribeiro, Uwe PischelAbstract:Cucurbiturils (CB6 and CB7) were shown to inhibit the enzymatically catalyzed restriction of plasmids and linear DNA. This effect can be inverted by supramolecular masking of the macrocycles through competitive complexation with polyamines. These experiments provide supramolecular control of biocatalytic processes.
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the hydrophobic effect revisited studies with supramolecular complexes imply high energy water as a noncovalent driving force
Angewandte Chemie, 2014Co-Authors: Frank Biedermann, Werner M Nau, Hansjorg SchneiderAbstract:Traditional descriptions of the hydrophobic effect on the basis of entropic arguments or the calculation of solvent-occupied surfaces must be questioned in view of new results obtained with supramolecular complexes. In these studies, it was possible to separate hydrophobic from dispersive interactions, which are strongest in aqueous systems. Even very hydrophobic alkanes associate significantly only in cavities containing water molecules with an insufficient number of possible hydrogen bonds. The replacement of high-energy water in cavities by guest molecules is the essential enthalpic driving force for complexation, as borne out by data for complexes of cyclodextrins, cyclophanes, and Cucurbiturils, for which complexation enthalpies of up to -100 kJ mol(-1) were reached for encapsulated alkyl residues. Water-box simulations were used to characterize the different contributions from high-energy water and enabled the calculation of the association free enthalpies for selected cucurbituril complexes to within a 10% deviation from experimental values. Cavities in artificial receptors are more apt to show the enthalpic effect of high-energy water than those in proteins or nucleic acids, because they bear fewer or no functional groups in the inner cavity to stabilize interior water molecules.
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Cucurbiturils as fluorophilic receptors
Supramolecular Chemistry, 2014Co-Authors: Khaleel I Assaf, Werner M NauAbstract:We report the formation of strong inclusion complexes between the macrocyclic host cucurbit[7]uril (CB7) and more than 20 perfluorinated compounds (PFCs) in aqueous solution. The binding constants and structures of the complexes were determined through a combination of dye displacement titrations, 19F as well as 1H NMR spectroscopy, and quantum chemical calculations. The high affinities, for example 1.2 × 107 M− 1 for perfluorohexane and 1.1 × 108 M− 1 for perfluoro(methylcylohexane), are driven, among others, by the low polarisability of the cucurbituril cavity, which favours the binding of non-polarisable guests such as PFCs. The complexation-induced chemical shifts of the 19F resonances are downfield in cases where a conformational flexibility allows the (partial) interconversion of gauche conformations (favoured in water) to anti conformations (favoured inside the cavity of CB7). Only for conformationally rigid substrates, for example SF6 and (CF3)3COH, upfield shifts prevail. These are attributed to ...
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A simple assay for quality binders to Cucurbiturils.
Chemistry (Weinheim an der Bergstrasse Germany), 2014Co-Authors: Julián Vázquez, Werner M Nau, Patricia Remón, Roy N. Dsouza, Alexandra I. Lazar, Jesús F. Arteaga, Uwe PischelAbstract:A new approach towards the rapid identification of quality binders to Cucurbiturils--those that combine high affinity with high selectivity for a particular homologue--was developed. The assay exploits macrocycle-specific optical fingerprints (colorimetric or fluorimetric) of carefully selected indicators dyes. The screening of a guest library revealed known (e.g., adamantane derivatives) and new (e.g., terpenes) quality binders. The predictive power of the assay was underpinned by the modeling of the involved thermodynamic equilibria.
Vladimir P. Fedin - One of the best experts on this subject based on the ideXlab platform.
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a previously unrecognised hydronium di cation in the crystal structure of a cucurbituril derivative
Chemical Communications, 2005Co-Authors: Ivan Bernal, Uday Mukhopadhyay, Vladimir P. Fedin, Alexander V. Virovets, William CleggAbstract:Examination of the crystal structure of the adduct of hydronium tetrachloroferrate dichloride with cucurbituril resulted in the discovery that the hydronium cation present therein is not the well known H7O3+ species; rather, it is an unprecedented cyclic species of composition (H14O6)2+, templated by the formation of five hydrogen bonds to cucurbituril.
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Supramolecular compounds of cucurbituril with molybdenum and tungsten chalcogenide cluster aqua complexes
Russian Chemical Bulletin, 2003Co-Authors: M. N. Sokolov, Danil N. Dybtsev, Vladimir P. FedinAbstract:The review surveys the synthesis and structures of a new class of supramolecular compounds composed of the macrocyclic cavitand cucurbituril and molybdenum or tungsten chalcogenide clusters. The structural motifs of supramolecular compounds and factors influencing their formation are considered.
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Supramolecular chemistry of Cucurbiturils
Russian Chemical Reviews, 2002Co-Authors: O A Gerasko, Denis G. Samsonenko, Vladimir P. FedinAbstract:The main principles of the design of supramolecular compounds starting from organic macrocyclic cavitands,viz., cucurbit[n]urils [C 6 H 6 N 4 O 2 ] n (n=5–10), are considered. The presence of the hydrophobic inner cavity along with polar carbonyl groups forming the cucurbituril portals are responsible for high specificity of the formation of host–guest complexes. The unique ability of Cucurbiturils to act as synthetic molecular containers is discussed. In these containers, bimolecular reactions between specially selected guests proceed with high regio- and stereoselectivity. The review surveys new data on the directed construction of supramolecular organic–inorganic compounds through the formation of an extensive network of hydrogen bonds between the portal oxygen atoms of Cucurbiturils and water molecules of metal aqua complexes. The bibliography includes 108 references.
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cucurbituril as a new macrocyclic ligand for complexation of lanthanide cations in aqueous solutions
European Journal of Inorganic Chemistry, 2002Co-Authors: Denis G. Samsonenko, Vladimir P. Fedin, Alexander V. Virovets, Maxim N. Sokolov, Janusz Lipkowski, O A Gerasko, Javier G Platas, Rita Hernandezmolina, Alfredo MederosAbstract:(Aqua)lanthanide complexes with cucurbituril {[Gd(NO3)(H2O)4](C36H36N24O12)}(NO3)2·7H2O (1), {[Gd(NO3)(C2H5OH)(H2O)3](C36H36N24O12)}(NO3)2·5.5H2O (2), {[Ho(NO3)(H2O)4](C36H36N24O12)}(NO3)2·7H2O (3), {[Yb(NO3)(H2O)4](C36H36N24O12)}(NO3)2·6H2O (4), {[La(H2O)6(SO4)](C36H36N24O12)}(NO3)·12H2O (5), {[Gd(H2O)4]2(C36H36N24O12)3}Br6·45H2O (6), and {[Ce(H2O)5]2(C36H36N24O12)2}Br6·26H2O (7) were obtained in high yield by reaction of cucurbituril with aqueous solutions of lanthanide(III) species. The crystal structures of the compounds show a packing of 1:1, 2:2, and 2:3 in the (cucurbituril)lanthanide complexes in which cucurbituril plays a bidentate ligand role, and water molecules of the (aqua)lanthanide complexes form hydrogen bonds with carbonyl groups of the cucurbituril molecule. The guest water molecule is situated in the cucurbituril molecule cavity of 2 and 5. The crystal structure of 6 is a packing of three-deck sandwiches, built from alternating cucurbituril molecules and Gd(H2O)43+ ions. The largest distance between outermost oxygen atoms in the sandwiches is 30.04 A. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)
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supramolecular assemblies based on cucurbituril adducts of hydrogen bonded molybdenum and tungsten incomplete cuboidal aqua complexes
Inorganic Chemistry, 2000Co-Authors: Vladimir P. Fedin, Alexander V. Virovets, Maxim N. Sokolov, Danil N. Dybtsev, O A Gerasko, William CleggAbstract:Six cis coordinated H2O molecules of the triangular cluster complexes M3(μ3-S)((μ2-S)3(H2O)9]4+ (M = Mo, W) (hydrogen bond donors) complementary to six portal oxygen atoms of cucurbituril (acceptors). The shape and symmetry of the building blocks induce specific crystal structures.
Shiyan Chen - One of the best experts on this subject based on the ideXlab platform.
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white light emission from cucurbituril based host guest interaction in the solid state new function of the macrocyclic host
ACS Applied Materials & Interfaces, 2018Co-Authors: Yu Xia, Shiyan ChenAbstract:Energy transfer and interchange are central for fabricating white light-emitting organic materials. However, increasing the efficiency of light energy transfer remains a considerable challenge because of the occurrence of “cross talk”. In this work, by exploiting the unique photophysical properties of cucurbituril-triggered host–guest interactions, the two complementary luminescent colors blue and yellow for white light emission were independently obtained from a single fluorophore dye rather than energy transfer. Further study suggested that the rigid cavity of Cucurbiturils efficiently prevented the aggregation of the dye and improved its thermal stability in the solid state by providing a regular nanosized fence for each encapsulated dye molecule. As a result, a novel macrocycle-assisted supramolecular approach for obtaining solid, white light-emitting organic materials with low cost, high efficiency, and easy scale-up was successfully demonstrated.
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White Light Emission from Cucurbituril-Based Host–Guest Interaction in the Solid State: New Function of the Macrocyclic Host
2018Co-Authors: Yu Xia, Shiyan ChenAbstract:Energy transfer and interchange are central for fabricating white light-emitting organic materials. However, increasing the efficiency of light energy transfer remains a considerable challenge because of the occurrence of “cross talk”. In this work, by exploiting the unique photophysical properties of cucurbituril-triggered host–guest interactions, the two complementary luminescent colors blue and yellow for white light emission were independently obtained from a single fluorophore dye rather than energy transfer. Further study suggested that the rigid cavity of Cucurbiturils efficiently prevented the aggregation of the dye and improved its thermal stability in the solid state by providing a regular nanosized fence for each encapsulated dye molecule. As a result, a novel macrocycle-assisted supramolecular approach for obtaining solid, white light-emitting organic materials with low cost, high efficiency, and easy scale-up was successfully demonstrated
Stefan Kubik - One of the best experts on this subject based on the ideXlab platform.
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Influence of cyclic and acyclic Cucurbiturils on the degradation pathways of the chemical warfare agent VX.
Organic & biomolecular chemistry, 2020Co-Authors: Beatrice Andrae, Daniel Bauer, Patrick Gaß, Marianne Koller, Franz Worek, Stefan KubikAbstract:The highly toxic nerve agent VX is a methylphosphonothioate that degrades via three pathways in aqueous solution, namely through the hydrolysis of the P–O or P–S bonds, or the cleavage of the C–S bond at the 2-aminoethyl residue. In the latter case, an aziridinium ion and a phosphonothioate is formed. Here it is shown that acyclic or cyclic Cucurbiturils inhibit these reactions in phosphate buffer at physiological pH and thus stabilise the nerve agent. When using unbuffered basic solutions as the reaction medium, however, in which the P–S or P–O bonds are normally hydrolysed preferentially, Cucurbiturils turned out to strongly shift VX degradation towards the cleavage of the C–S bond. Cucurbit[7]uril, in particular, has a so pronounced effect under suitable conditions that it almost completely suppresses the formation of products resulting from the other degradation pathways. Investigations involving VX analogues in combination with computational methods suggest that one reason for the reaction control exerted by the Cucurbiturils is the preorganisation of VX for aziridinium ion formation. In addition, cucurbit[7]uril also lowers the transition state of the reaction by stabilising the positive charge developing on the way to the product. Cucurbiturils thus have a marked effect on the reactivity of a highly toxic nerve agent, which potentially allows using them for decontamination purposes.
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Functionalisable acyclic Cucurbiturils
Organic Chemistry Frontiers, 2019Co-Authors: Daniel Bauer, Beatrice Andrae, Patrick Gaß, Danjano Trenz, Sabine Becker, Stefan KubikAbstract:Synthetic strategies are described to prepare acyclic cucurbituril derivatives with two different types of appended functional groups, one that mediates water solubility and another one that allows further functionalisation. The syntheses started with the coupling of a 1,4-disubstituted naphthalene derivative containing one 2-chloroethoxy and one 3-sulfonatopropoxy group to a suitable tetrameric glycoluril-derived precursor. This reaction afforded two regioisomers, differing in the relative orientation of the peripheral substituents, which could be separated in a straightforward fashion and structurally characterised. Both isomers were then converted into the corresponding diazides and diamines that served to append further residues by, respectively, copper(I)-catalysed azide–alkyne cycloaddition or amide formation. Binding studies showed that the functionalised dianionic acyclic Cucurbiturils thus obtained possess a notable cation affinity in water, albeit a lower one than an analogue with four peripheral negatively charged substituents. This work constitutes the basis for the development of water-soluble acyclic Cucurbiturils whose applications could potentially go beyond the use as receptors.
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Correction: Functionalisable acyclic Cucurbiturils
Organic Chemistry Frontiers, 2019Co-Authors: Daniel Bauer, Beatrice Andrae, Patrick Gaß, Danjano Trenz, Sabine Becker, Stefan KubikAbstract:Correction for ‘Functionalisable acyclic Cucurbiturils’ by Daniel Bauer et al., Org. Chem. Front., 2019, DOI: 10.1039/C9QO00156E.
O A Gerasko - One of the best experts on this subject based on the ideXlab platform.
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Supramolecular chemistry of Cucurbiturils
Russian Chemical Reviews, 2002Co-Authors: O A Gerasko, Denis G. Samsonenko, Vladimir P. FedinAbstract:The main principles of the design of supramolecular compounds starting from organic macrocyclic cavitands,viz., cucurbit[n]urils [C 6 H 6 N 4 O 2 ] n (n=5–10), are considered. The presence of the hydrophobic inner cavity along with polar carbonyl groups forming the cucurbituril portals are responsible for high specificity of the formation of host–guest complexes. The unique ability of Cucurbiturils to act as synthetic molecular containers is discussed. In these containers, bimolecular reactions between specially selected guests proceed with high regio- and stereoselectivity. The review surveys new data on the directed construction of supramolecular organic–inorganic compounds through the formation of an extensive network of hydrogen bonds between the portal oxygen atoms of Cucurbiturils and water molecules of metal aqua complexes. The bibliography includes 108 references.
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cucurbituril as a new macrocyclic ligand for complexation of lanthanide cations in aqueous solutions
European Journal of Inorganic Chemistry, 2002Co-Authors: Denis G. Samsonenko, Vladimir P. Fedin, Alexander V. Virovets, Maxim N. Sokolov, Janusz Lipkowski, O A Gerasko, Javier G Platas, Rita Hernandezmolina, Alfredo MederosAbstract:(Aqua)lanthanide complexes with cucurbituril {[Gd(NO3)(H2O)4](C36H36N24O12)}(NO3)2·7H2O (1), {[Gd(NO3)(C2H5OH)(H2O)3](C36H36N24O12)}(NO3)2·5.5H2O (2), {[Ho(NO3)(H2O)4](C36H36N24O12)}(NO3)2·7H2O (3), {[Yb(NO3)(H2O)4](C36H36N24O12)}(NO3)2·6H2O (4), {[La(H2O)6(SO4)](C36H36N24O12)}(NO3)·12H2O (5), {[Gd(H2O)4]2(C36H36N24O12)3}Br6·45H2O (6), and {[Ce(H2O)5]2(C36H36N24O12)2}Br6·26H2O (7) were obtained in high yield by reaction of cucurbituril with aqueous solutions of lanthanide(III) species. The crystal structures of the compounds show a packing of 1:1, 2:2, and 2:3 in the (cucurbituril)lanthanide complexes in which cucurbituril plays a bidentate ligand role, and water molecules of the (aqua)lanthanide complexes form hydrogen bonds with carbonyl groups of the cucurbituril molecule. The guest water molecule is situated in the cucurbituril molecule cavity of 2 and 5. The crystal structure of 6 is a packing of three-deck sandwiches, built from alternating cucurbituril molecules and Gd(H2O)43+ ions. The largest distance between outermost oxygen atoms in the sandwiches is 30.04 A. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)
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supramolecular assemblies based on cucurbituril adducts of hydrogen bonded molybdenum and tungsten incomplete cuboidal aqua complexes
Inorganic Chemistry, 2000Co-Authors: Vladimir P. Fedin, Alexander V. Virovets, Maxim N. Sokolov, Danil N. Dybtsev, O A Gerasko, William CleggAbstract:Six cis coordinated H2O molecules of the triangular cluster complexes M3(μ3-S)((μ2-S)3(H2O)9]4+ (M = Mo, W) (hydrogen bond donors) complementary to six portal oxygen atoms of cucurbituril (acceptors). The shape and symmetry of the building blocks induce specific crystal structures.