EPR Studies of the Binding Properties, Guest Dynamics, and Inner‐Space Dimensions of a Water‐Soluble Resorcinarene Capsule

Ayhan, Mehmet Menaf; Casano, Gilles; Karoui, Hakim; Rockenbauer, Antal; Monnier, Valérie; Hardy, Micaël; Tordo, Paul; Bardelang, David; Ouari, Olivier

doi:10.1002/chem.201502212

Cited by 16 publications

(15 citation statements)

References 93 publications

(31 reference statements)

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“…For obtaining water-soluble and water-stable capsules, numerous covalent and noncovalent strategies have been tested, involving self-assembly by coordination bonds ( Yi et al, 2012 ; Yamashina et al, 2014 ; Cullen et al, 2015 ; Taylor et al, 2019 ; Percástegui et al, 2020 ), electrostatic interactions ( Corbellini et al, 2005 ; Martin et al, 2011 ; Zadmard et al, 2013 ), or hydrophobic clustering ( Gibb and Gibb, 2004 ; Hiraoka et al, 2010 ; Kondo et al, 2013 ; Suzuki et al, 2013 ; Jordan and Gibb, 2015 ; Suzuki et al, 2016 ; Kondo et al, 2017 ; Zhan et al, 2018 ; Hanafusa et al, 2020 ; Ashbaugh et al, 2021 ). Additional stabilization coming from interactions with guests (templation approach) is often beneficial or even crucial for stability ( Zhang et al, 2013 ; Ayhan et al, 2015 ; Tiefenbacher et al, 2015 ; Rahman et al, 2020 ), which, however, blocks the cavity for further applications. Although the self-assembly of container molecules in water is now quite well developed, the rational design of the cavity surface with properly spatially arranged binding sites ( Adriaenssens and Ballester, 2013 ), preferably in a chiral way, remains challenging.…”

Section: Introductionmentioning

confidence: 99%

Chiral Water-Soluble Molecular Capsules With Amphiphilic Interiors

Sakowicz

Szumna

2022

Front. Chem.

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We present the synthesis of new chiral water-soluble dimeric capsules by the multicomponent Mannich reaction between charged amino acids (glutamic acid or arginine), resorcinarene, and formaldehyde and by subsequent self-assembly. The zwitterionic character of the backbones enables electrostatic interactions between arms and induces self-assembly of dimeric capsules, namely, (L-ArgR)2 and (L-GluR)2, in water with a wide range of pH, as demonstrated by NMR, diffusion coefficient measurement, and circular dichroism. The assembly/disassembly processes are fast on the NMR timescale. This mode of dimerization leaves side chains available for additional interactions and creates chiral cavities of mixed hydrophobic/hydrophilic character. According to this characteristic, capsules do not bind fully nonpolar or fully polar guests but effectively encapsulate a variety of chiral molecules with mixed polar/apolar characters (aliphatic and aromatic aldehydes, epoxides, alcohols, carboxylic acids, amines, and amino acids) with moderate strength. We also demonstrate the formation of heterocapsules (GluR) (ArgR) (homo- and heterochiral) that utilize additional interactions between charged acidic and basic side chains and have better encapsulation properties than those of the homodimers.

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Section: Introductionmentioning

confidence: 99%

Chiral Water-Soluble Molecular Capsules With Amphiphilic Interiors

Sakowicz

Szumna

2022

Front. Chem.

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“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 Among the different families of molecular capsules, Rebek's type have shown features such as rigidity but can also display dynamic characters in some circumstances (elongated capsules, guest contraction and elongation upon capsular assembly). [11] In this study, a series of nitroxides was used with well-defined length and width to investigate the limit in terms of molecular size and volume for a guest to be correctly accommodated within the capsule. Recently, a well water soluble Rebek type capsule became available and was investigated with nitroxides (Figure 16).…”

Section: Nitroxides With Capsulesmentioning

confidence: 99%

“…[76] Small spin probes are observed to rotate faster inside the capsular assembly as Figure 16. DFT minimized structures of the pyridinium tailed water soluble Rebek's capsule with included nitroxides pointing to steric hindrance responsible for perturbation of the "ideal" self-assembling pattern and to possible tolerance regarding guest binding (adapted from reference, [11] 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 compared with the capsule while larger nitroxides tend to rotate at a regime closely related to the capsule one.…”

Section: Nitroxides With Capsulesmentioning

confidence: 99%

Nitroxide Radicals with Cucurbit[n]urils and Other Cavitands

Ouari

Bardelang

2018

Israel Journal of Chemistry

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The interface of nitroxide radicals with cucurbit[n]urils (CB[n]) is covered in this review. Either used as spin probes, spin labels, or stoppers for paramagnetic rotaxanes, nitroxides offer new opportunities to investigate CB[n] and their inclusion complexes, especially thanks to EPR spectroscopy. On the other hand, CB[n] also offer interesting opportunities to modulate nitroxide properties such as protection or structuring. The multiple back and forth between the two well‐established areas where nitroxides bring information about CB[n], and CB[n] modulate nitroxide properties, have enabled to shed some light at this new interesting interface.

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“…10,11 EPR spectroscopy has been successfully used to characterize a range of supramolecular complexes including cyclodextrins, 12−16 cucurbiturils, 17−22 and resorcinarenes. 23,24 In this work, several nitroxide radicals were used to probe the host−guest complexes for cage structures that had not previously been studied in this way. Analysis of EPR spectra allowed us to measure equilibrium constants for host−guest complex formation and characterize the polarity and rotational diffusion parameters of the encapsulated guests.…”

Section: ■ Introductionmentioning

confidence: 99%

“…For instance, Fujita et al. observed the encapsulation of two radicals in a coordination cage resulting in a radical pair in the triplet state. , EPR spectroscopy has been successfully used to characterize a range of supramolecular complexes including cyclodextrins, − cucurbiturils, − and resorcinarenes. , …”

Section: Introductionmentioning

confidence: 99%

Characterization of Host–Guest Complexes of Supramolecular Self-Assembled Cages Using EPR Spectroscopy

Nicholas

Chechik

2020

J. Phys. Chem. B

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Supramolecular self-assembled cages are interesting and useful structures that have a variety of different potential applications including catalysis, reaction control, and chemical transport and storage. It is therefore important to understand in detail how guest molecules interact with these cage structures and determine the characteristics of the host-guest complexes formed in order to develop these cages and their uses further. Previous studies into supramolecular assemblies such as cucurbiturils, cyclodextrins and resorcinarene capsules have demonstrated that EPR spectroscopy is particularly suitable for characterisation of the host-guest complexes of these structures with paramagnetic radical probes as guests, and this work aimed to extend these studies to cage structures.In this thesis, a number of different radical probes were investigated qualitatively with host cage structures of the form [M8L12][X]16, M = Cd or Co, L = C28H22N6 and X = ClO4 or Cl, comparing EPR spectra of radical in neat solvent to radical+cage solution to identify if binding had occurred. Competing guest molecules were used to confirm binding effects by displacing the radical probes and observing the effect on the EPR spectrum.Three nitroxide radical guests were identified for detailed binding studies: 4-oxo-TEMPO, 4-carboxy-TEMPO and 3-carboxy-PROXYL, and titrations of solutions of guest with cage solution were carried out. Simulations of the EPR spectra revealed the contributions of two components, bound and unbound radical, to the radical@cage complex spectra, allowing characteristics of the complex to be determined. The ratio between bound and unbound component allowed calculation of association constants for the complexes, whilst comparison between bound and unbound rotational diffusion rates showed that binding of radical led to restricted motion of the probe, and hence slower tumbling rates. Finally, changes in the hyperfine values were used to determine changes in the polarity of the environment of the radical.

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EPR Studies of the Binding Properties, Guest Dynamics, and Inner‐Space Dimensions of a Water‐Soluble Resorcinarene Capsule

Cited by 16 publications

References 93 publications

Chiral Water-Soluble Molecular Capsules With Amphiphilic Interiors

Chiral Water-Soluble Molecular Capsules With Amphiphilic Interiors

Nitroxide Radicals with Cucurbit[n]urils and Other Cavitands

Characterization of Host–Guest Complexes of Supramolecular Self-Assembled Cages Using EPR Spectroscopy

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