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Cryptophane-C is composed of two nonequivalent cyclotribenzylene caps, one of which contains methoxy group substituents on the phenyl rings. The two caps are connected by three OCH2CH2O linkers in an anti arrangement. Host-guest complexes of cryptophane-C with dichloromethane and chloroform in solution were investigated in detail by nuclear magnetic resonance techniques and density functional theory (DFT) calculations. Variable temperature proton and carbon-13 spectra show a variety of dynamic processes, such as guest exchange and host conformational transitions. The guest exchange was studied quantitatively by exchange spectroscopy measurements or by line-shape analysis. The conformational preferences of the guest-containing host were interpreted through cross-relaxation measurements, providing evidence of the gauche+2 and gauche−2 conformations of the linkers. In addition, the mobility of the chloroform guest inside the cavity was studied by carbon-13 relaxation experiments. Combining different types of evidence led to a detailed picture of molecular recognition, interpreted in terms of conformational selection. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Here the monocation complexes of seven anti -cryptophanes are examined with high-resolution ion-mobility mass spectrometry. The relative size of the [cation + cryptophane] + complexes were compared based on their measured mobilities and derived collisional cross sections. A paradoxical trend of structural contraction was observed for complexes of increasing cation size. Density functional theory confirmed encapsulation occurs for cation = Na + , K + , Rb + , Cs + and NH 4 + . However, cation = Li + preferred oxygen coordination at a linker over encapsulation within the cavity, leading to a slightly larger gas phase structure overall. Protonated cryptophanes yielded much larger collision cross sections via imploded cryptophane structures. Thus, competing physical effects led to the observed non-periodic size trend of the complexes. Trends in complexation from isothermal titration calorimetry and other condensed phase techniques were borne out by the gas phase studies. Further, predicted cavity sizes compared with the gas phase experimental findings reveal more about the encapsulation mechanisms themselves.

An anti -cryptophane decorated with three aromatic amine and three phenol groups shows a high affinity for the cesium and thallium cations in LiOH/H 2 O (0.1 M). The formation of the complexes was studied by 133 Cs NMR and by 205 Tl NMR spectroscopy at different temperatures. Characteristic signals for caged cesium and thallium were observed at a high field with respect to the signals of the free cations present in the bulk. Isothermal titration calorimetric experiments performed in LiOH/H 2 O (0.1 M) and NaOH/KCl buffer (pH = 13) allowed us to determine the parameter of complexation and to ascertain the high affinity of this cryptophane for cesium and thallium. A comparison with other cryptophanes that bind these two cations shows that the introduction of nitrogen atoms into the cryptophane backbone has an effect on the binding properties. The affinity for cesium and thallium(I) ions is in the following order of substitution: OH > NH 2 > OCH 2 COOH. This study paves the way to the design of new efficient host molecules for the extraction of these two cations in aqueous solution.

Cryptophane molecules are cage-like structures consisting in two hemispheres, each made of three benzene rings. These hemispheres are bound together with three O(CH 2 ) n Olinkers of various lengths giving rise to a plethora of cryptophane derivatives. Moreover, they are able to encapsulate neutral guests: CH 2 Cl 2 , CHCl 3 , …; and charged species: Cs + , Tl + , …. Finally, they exhibit chiroptical properties thanks to the anti arrangement of the linkers between the hemispheres. This work focuses on the Raman optical activity (ROA) signatures of Cryptophane-111 (n=1 for each linker). More specifically, we aim at simulating accurately its ROA spectra with and without a xenon atom inside its cavity. Experimental data (Buffeteau et al., 2017) have already demonstrated the effect of the encapsulation in the low-wavenumbers region. To generate the initial structures, we rely on the novel Conformer-Rotamer Ensemble Sampling Tool (CREST) program, developed by S. Grimme and co-workers. This is required due to the flexibility provided by the linkers. The CREST algorithm seems promising and has already been used to sample the potential energy surface (PES) of target systems before the simulation of their vibrational spectroscopies (Eikås et al., 2022). We observe large similarities between the two sets of conformers (one with and one without Xe encapsulated), demonstrating the robustness of the CREST algorithm. For corresponding structures, the presence of xenon pushed the two hemispheres slightly further apart. After optimization at the DFT level, only one unique conformer has a Boltzmann population ratio greater than 1%, pointing out the relative rigidity of the cage. Based on this unique conformer, our simulations are in good agreement with the experimental data. Regarding xenon encapsulation, the (experimental and theoretical) ROA signatures at low wavenumbers are impacted: slight shifts in wavenumbers are observed as well as a decrease in relative ROA intensity for bands around 150 cm -1 . The wavenumber shifts were very well reproduced by our simulations, but the experimental decrease in the ROA intensity was unfortunately not reproduced., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Self-assembly of a flexible tritopic aniline and 3-substituted 2-formylpyridine subcomponents around iron(II) templates gave rise to a low-spin Fe II 4 L 4 capsule, whereas a high-spin Fe II 3 L 2 sandwich species formed when a sterically hindered 6-methyl-2-formylpyridine was used. The Fe II 4 L 4 cage adopted a new structure type with S 4 to T or C II 4 L 4 framework with conformational plasticity, enabling it to adapt structurally from S 4 to T or C 3 symmetry upon guest binding. The cage also displayed negative allosteric cooperativity in simultaneously binding different guests within its cavity and at the apertures between its faces., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

We report the synthesis and absolute configuration (AC) of a chiral isotopologue of syn -cryptophane-B. Low chiral signatures were measured by polarimetry and electronic circular dichroism, whereas most significant chiroptical effects were observed by vibrational circular dichroism (VCD) and Raman optical activity (ROA). The comparison of experimental VCD and ROA spectra with those predicted by DFT calculations allows the determination of the AC of the two enantiomers as (-) 589 - MP - syn - 2 and (+) 589 - PM - syn - 2 .

A tetrahedral Fe II 4 L 4 cage assembled from the coordination of triangular chiral, face-capping ligands to iron(II). This cage exists as two diastereomers in solution, which differ in the stereochemistry of their metal vertices, but share the same point chirality of the ligand. The equilibrium between these cage diastereomers was subtly perturbed by guest binding. This perturbation from equilibrium correlated with the size and shape fit of the guest within the host; insight as to the interplay between stereochemistry and fit was provided by atomistic well-tempered metadynamics simulations. The understanding thus gained as to the stereochemical impact on guest binding enabled the design of a straightforward process for the resolution of the enantiomers of a racemic guest.

We report in this article the synthesis, the X-ray crystal structure of compound syn - 2 , and its binding properties with cesium and thallium in aqueous solution under basic conditions. Compound syn - 2 is the diastereomeric compound of anti - 1 that shows very high affinity for cesium and thallium in aqueous solution under the same conditions. Despite the close structural similarities that exist between the syn - 2 and anti - 1 compounds, they show large discrepancy in their ability to bind cesium and thallium cations in the same conditions. Indeed, the syn - 2 derivative has a lower affinity for these two cationic species and the binding constants are several orders of magnitude lower than those found for its congener. The large differences in affinity observed with these two compounds can be explained by the relative position of the six hydroxyl groups to each other., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Determination of stereochemistry and enantiomeric excess in chiral natural molecules is a research of great interest because enantiomers can exhibit different biological activities. Viniferin stilbene dimers are natural molecules present in grape berries and wine but also, in larger amount, in stalks of grapevine. Four stereoisomers of viniferin stilbene dimers (7aS,8aS)-E-ε-viniferin (1a), (7aR,8aR)-E-ε-viniferin (1b), (7aS,8aR)-E-ω-viniferin (2a), and (7aR,8aS)-E-ω-viniferin (2b) were isolated from grapevine stalks of Cabernet Sauvignon, Merlot and Sauvignon Blanc, using a combination of centrifugal partition chromatography (CPC), preparative and chiral HPLC. The structure elucidation of these molecules was achieved by NMR whereas the absolute configurations of the four stereoisomers were investigated by vibrational circular dichroism spectroscopy in combination with density functional theory (DFT) calculations. This study unambiguously established the (+)-(7aS,8aS) and (+)-(7aR,8aS) configurations for E-ε-viniferin and E-ω-viniferin, respectively. Finally, we show that Cabernet Sauvignon provided the quasi enantiopure (+)-(7aS,8aS)-E-ε-viniferin compound which presents the best anti-inflammatory and anti-oxidant activities., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

A new water-soluble xenon host system with great promise for the 129 Xe NMR-based biosensing approach is presented: the syn -cryptophane-222-hexacarboxylate. It compares favorably with its already known anti diastereomer, on the one hand, and with cucurbit[6]uril, on the other hand, in particular in terms of xenon binding constant and xenon in-out exchange, a key parameter for the efficiency of the most sensitive HyperCEST method.

Cryptophane cages can adopt either an anti or syn configuration that present different recognition properties. While the synthesis of anti -cryptophanes is well reported, the synthesis of syn -cryptophanes remains a challenge. Herein, we demonstrate that the use of HFIP as a co-solvent during the second ring closure reaction significantly affects the regioselectivity, providing easier access to the syn -cryptophane stereomers.

We report the synthesis of C 3 -symmetric cryptophanes decorated with three aromatic amine groups on the same CTB cap and their interaction with xenon. The relative stereochemistry of these two stereoisomers syn and anti was assessed thanks to the determination of the X-ray structure of an intermediate compound. As previously observed with the tris-aza-cryptophanes analogs anti - 1 and syn - 2 ( J. Org. Chem . 2021 , 86 , 11, 7648-7658), both compounds anti - 5 and syn show a slow in-out exchange dynamics of xenon at 11.7 T. Our work supports the idea that the presence of nitrogen atoms grafted directly onto the cryptophane backbone has a strong impact on the in-out exchange dynamics of xenon whatever their stereochemistry. This result contrasts with the case of other cryptophanes decorated solely with methoxy substituents. Finally, we demonstrate that these new derivatives can be used to design new 6 show a slow in-out exchange dynamics of xenon at 11.7 T. Our work supports the idea that the presence of nitrogen atoms grafted directly onto the cryptophane backbone has a strong impact on the in-out exchange dynamics of xenon whatever their stereochemistry. This result contrasts with the case of other cryptophanes decorated solely with methoxy substituents. Finally, we demonstrate that these new derivatives can be used to design new anti / syn cryptophanes bearing suitable ligands in order to constitute potent 129 Xe NMR-based sensors. An example is reported here with the synthesis of the tris-iodo derivatives anti - 13 and syn - 14 from compounds anti - 5 and syn - 6 .