Supramolecular interactions between ethylene-bridged oligoureas: nanorings and chains formed by cooperative positive allostery

Tilly, David; Žabka, Matej; Vitórica-Yrezábal, Iñigo J.; Sparkes, Hazel A.; Pridmore, Natalie E.; Clayden, Jonathan

doi:10.1039/d2sc04716k

Cited by 6 publications

(8 citation statements)

References 38 publications

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“…24−27 These molecules pack into cyclic supramolecular structures in the solid state that allow their terminal hydrogen-bonding capacity to be satisfied in an intermolecular manner. 26 We speculated that linking the termini of an ethylene-bridged scaffold into a ring (Figure 1f, dashed line) could lead to cyclic, fully intramolecularly hydrogen-bonded structures, in which the cyclic hydrogen-bonding network may result in a new class of cyclochiral structure.…”

Section: ■ Introductionmentioning

confidence: 99%

Dynamic and Persistent Cyclochirality in Hydrogen-Bonded Derivatives of Medium-Ring Triamines

Morris,

Wales,

Echavarren

et al. 2023

J. Am. Chem. Soc.

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Cyclic triureas derived from 1,4,7-triazacyclononane (TACN) were synthesized; X-ray crystallography showed a chiral bowl-like conformation with each urea hydrogen-bonded to its neighbor with uniform directionality, forming a "cyclochiral" closed loop of hydrogen bonds. Variable-temperature 1 H NMR, 1 H-1 H exchange spectroscopy, Eyring analysis, computational modeling, and studies in various solvents revealed that cyclochirality is dynamic (ΔG ‡ 25°C = 63−71 kJ mol −1 in noncoordinating solvents), exchanging between enantiomers by two mechanisms: bowl inversion and directionality reversal, with the former subject to a slightly smaller enantiomerization barrier. The enantiomerization rate substantially increased in the presence of hydrogen-bonding solvents. Population of only one of the two cyclochiral hydrogen-bond directionalities could be induced by annulating one ethylene bridge with a trans-cyclohexane. Alternatively, enantiomerization could be inhibited by annulating one ethylene bridge with a cis-cyclohexane (preventing bowl inversion) and replacing one urea function with a formamide (preventing directionality reversal). Combining these structural modifications resulted in an enantiomerization barrier of ΔG ‡ 25°C = 93 kJ mol −1 , furnishing a planar-chiral, atropisomeric bowlshaped structure whose stereochemical stability arises solely from its hydrogen-bonding network.

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Section: ■ Introductionmentioning

confidence: 99%

Dynamic and Persistent Cyclochirality in Hydrogen-Bonded Derivatives of Medium-Ring Triamines

Morris,

Wales,

Echavarren

et al. 2023

J. Am. Chem. Soc.

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“…In CDCl 3 , the major H-bonded urea 6a shows downfield shift of an NH proton, whereas the minor urea conformation 6b was observed in EXSY spectrum after NH irradiation. The higher population of 6b in acetone was the result of increased polarity and H-bond accepting ability of the solvent 4.…”

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confidence: 99%

“…The freely rotating CF 2 H group appears as a triplet in the 1 H and a doublet in the 19 F NMR spectra, with 2 J HF ∼ 54 Hz, which remains invariant between different conformers. However, certain benzylic or aliphatic 13 C{ 1 H} resonances appeared as triplets, due to an unusually large 4 J CF of around 4 Hz.…”

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confidence: 99%

“…Hydrogen-bonded foldamers, 1,2 and more recently polarity-coherent but conformationally flexible oligoureas based on ethylenediamine linkers 1 (Fig. 1A), 3 have found widespread use in structural chemistry 4 and catalysis, 5,6 and as switchable devices, 7 and have demonstrated potential biological applications. 8 Hydrogen-bonded foldamer structures incorporate a range of structural motifs, but the most common are oligoamides and oligoureas or thioureas.…”

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confidence: 99%

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Conformational preference in difluoroacetamide oligomers: probing the potential for foldamers with C–H⋯O hydrogen bonds

Žabka

Clayden

2023

Org. Biomol. Chem.

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“…Hydrogen-bond-driven self-assembly has played a central role in constructing supramolecular cages, − polymeric chains, − membranes, − and other elaborate three-dimensional architectures. − Various hydrogen-bond-donating and -accepting groups such as carboxyl, amide, guanidyl, and imidazolyl groups have been used as linkages to produce giant supramolecules; however, their final structures and properties are still largely governed by the structural flexibility and other secondary intermolecular interactions of their molecular components − and hence are not always predictable. Particularly in cases of flexible linear molecules, the chain length can be a crucial factor in dictating the structures of the final assembly. − In this sense, the investigation of self-assembling behaviors based on the precise chain length of novel linear molecular motifs is still important in this research area.…”

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confidence: 99%

Chain-Length-Dependent Hydrogen-Bonded Self-Assembly of Terminally Functionalized Discrete Polyketones

Shivakumar

Manabe

Yoneda

et al. 2023

Precision Chemistry

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Here, we report the synthesis and the chain-length-dependent self-assembling behaviors of discrete di-, tetra-, and hexaketones terminally functionalized with hydrogen-bonding carboxyl (C1, C2, and C3) and 3-acylaminopyridine groups (P1, P2, and P3). These polyketones were prepared by the coupling reactions of silylated analogues of 3,3-dimethylpentane-2,4-dione and t-butyl 2,2-dimethyl-3-oxobutanoate and the subsequent hydrolysis or amidation with 3-aminopyridine. Single-crystal X-ray diffraction analysis revealed that C1 and C2 form helical assemblies in which the components are connected by the dimerization of terminal carboxyl groups, whereas the longer C3 showed infinite hydrogen-bonded chains mediated by 1,4-dioxane used as a crystallization solvent. Pyridine-terminated P1 exhibited a three-dimensional hydrogen-bonded network owing to multiple NH···N(pyridine) hydrogen bonds in the solid state. P2 generated a double-helix-like fiber structure in the crystalline state. Among the pyridine-terminated polyketones P1–P3, only P2 showed gelation behavior in chloroform (100 mM concentration) at 25 °C. The scanning electron microscopy measurement of xerogel P2 revealed the formation of rod-like structures with a thickness of approximately 0.5–3.5 μm. These results demonstrate that the precise control of the polyketone chain length can significantly alter hydrogen-bonded self-assembly in the solid state and in solution even with the same terminal structures.

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Supramolecular interactions between ethylene-bridged oligoureas: nanorings and chains formed by cooperative positive allostery

Abstract: Ethylene-bridged oligoureas are dynamic foldamers in which the polarity of a coherent chain of intramolecular hydrogen bonds may be controlled by intra- or intermolecular interactions with hydrogen-bind donors or acceptors....

Cited by 6 publications

References 38 publications

Dynamic and Persistent Cyclochirality in Hydrogen-Bonded Derivatives of Medium-Ring Triamines

Dynamic and Persistent Cyclochirality in Hydrogen-Bonded Derivatives of Medium-Ring Triamines

Conformational preference in difluoroacetamide oligomers: probing the potential for foldamers with C–H⋯O hydrogen bonds

Chain-Length-Dependent Hydrogen-Bonded Self-Assembly of Terminally Functionalized Discrete Polyketones

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