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A simple, low-cost, and efficient device is proposed for the study of porous materials via NMR using small gas probes. Mainly built through additive manufacturing and being equipped with a radiofrequency solenoid microcoil, it only requires tiny quantities of sample and/or gas and is particularly suited for hyperpolarized xenon. The performances of this device have been accessed on a commercial sample of MCM-41 exhibiting multiporosity. Both the delivery mode of hyperpolarized xenon and the stopped-flow system are judged as efficient according to 2D 129Xe self-diffusion and EXSY experiments.

We report the synthesis of C3-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 synand antiwas assessed thanks to the determination of the X-ray structure of an intermediate compound. As previously observed with the tris-aza-cryptophanes analogs anti-1and syn-2(J. Org. Chem. 2021, 86, 11, 7648–7658), both compounds anti-5and syn-6show 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/syncryptophanes bearing suitable ligands in order to constitute potent 129Xe NMR-based sensors. An example is reported here with the synthesis of the tris-iodo derivatives anti-13and syn-14from compounds anti-5and syn-6.

We report the synthesis and optical resolution of C3-symmetrical tris-aza-cryptophanes anti-3and syn-4, as well as the study of their interaction with xenon viahyperpolarized 129Xe NMR. These molecular cages are close structural analogues of the two well-known cryptophane-A (1; chiral) and cryptophane-B (2; achiral) diastereomers since these new compounds differ only by the presence of three nitrogen atoms grafted onto the same cyclotribenzylene unit. The assignment of their relative (syn vs anti) and absolute configurations was made possible, thanks to the combined use of quantum calculations at the density functional theory level and vibrational circular dichroism spectroscopy. More importantly, our results show that despite the large structural similarities with cryptophane-A (1) and -B (2), these two new compounds show a very different behavior in the presence of xenon in organic solutions. These results demonstrate that prediction of the physical properties of the xenon@cryptophane complexes, only based on structural parameters, remains extremely difficult.

In this article, we present the synthesis of new cryptophane-type hosts capable of binding xenon in aqueous media and that may be useful for the development of xenon-based magnetic resonance imaging derivatives. The synthetic route proposed was chosen to facilitate both the introduction of water-solubilizing substituents and the functionalization of the host with a single arm showing recognition properties that constitute two crucial steps. This was made possible by preparing new cryptophane-223 derivatives bearing two different chemical functions that can be easily modified at a later stage. Thus, subsequent reactions allowed the design of a new cryptophane host able to bind zinc or nickel cations. The ability of this molecule to bind cationic species was assessed by calorimetric titration experiments and hyperpolarized 129Xe NMR. The advantages and disadvantages of this approach are discussed.

The known xenon-binding (±)-cryptophane-111 (1) has been functionalized with six [(η5-C5Me5)RuII]+([Cp*Ru]+) moieties to give, in 89% yield, the first water-soluble cryptophane-111 derivative, namely [(Cp*Ru)61]Cl6([2]Cl6). [2]Cl6exhibits a very high affinity for xenon in water, with a binding constant of 2.9(2) × 104M−1as measured by hyperpolarized 129Xe NMR spectroscopy. The 129Xe NMR chemical shift of the aqueous Xe@[2]6+species (308 ppm) resonates over 275 ppm downfield of the parent Xe@1species in (CDCl2)2and greatly broadens the practical 129Xe NMR chemical shift range made available by xenon-binding molecular hosts. Single crystal structures of [2][CF3SO3]6·xsolvent and 0.75H2O@1·2CHCl3reveal the ability of the cryptophane-111 core to adapt its conformation to guests.

Xenon‐Kapsel: Ein „intelligenter“ Zn2+‐Sensor für die Kernspintomographie (MRI) basiert auf 129Xe‐NMR‐Spektroskopie. Zn2+‐Ionen ändern die Resonanzfrequenz von Xenon, das in einem Cryptophan mit anhängendem Nitrilotriessigsäure‐Liganden eingeschlossen ist (siehe Bild). Mit hyperpolarisiertem Gas können mit diesem Konstrukt 100 nMZink mit einer Xenonbeladung detektiert werden; so wird eine 300‐mal niedrigere Nachweisgrenze erzielt als mit Gadoliniumchelaten.

Xenon capsule: A smart 129Xe NMR‐based sensor of Zn2+ions for magnetic resonance imaging (MRI) is proposed. The resonance frequency of xenon encapsulated in a cryptophane that bears a nitrilotriacetic ligand moiety varies when Zn2+ions are present in solution (see picture). With hyper‐polarized gas, such a construct enables detection of 100 nMzinc in one xenon batch, a threshold 300 times lower than achieved with gadolinium chelates.

AbstractArthropods were inventoried in crop fields and adjacent woody hedgerows of organic and conventional farms situated in south-central Ontario, Canada. The objective was to assess the total abundance, family richness, and composition of beneficial and phytophagous arthropods in the 2 farming systems and to examine the contributions of the vegetation present and landscape features on arthropod abundance and composition. Two hundred and forty sticky traps were installed (24 sites) and 170 sweep net collections were conducted (17 sites) in crop fields and adjacent woody hedgerows of organic and conventional sites. A total of 30 807 individual arthropods belonging to 131 families were recorded during the study. No spatial autocorrelation was detected among the arthropod samples. The study showed that beneficial and phytophagous arthropod abundance differed between organic and conventional sites (only with sweep net) but family richness did not. Beneficial arthropods were more abundant in woody hedgerows, while phytophagous arthropods were more abundant in crop fields. This study also demonstrated a strong relationship between plant and arthropod composition. Habitats (total old field cover, total hedgerow length, and Shannon diversity index, all within 250 m radius) in the surrounding landscape influenced arthropod composition but were not leading factors in explaining richness and abundance. It is therefore of prime importance to consider both local factors (management practices and local vegetation) and regional factors such as landscape features as explanatory variables when attempting to explain biodiversity.

Many farmland bird species are declining in North America and Europe, yet there are few data documenting bird use of agricultural landscapes, especially in Canada. This information is needed in order to identify candidate factors contributing to declines. We examined the influence of crop type and adjacent habitat on birds in fields of four crop types in three southern Ontario counties during the 1988 breeding (May-July) and 1987 and 1988 migration (August-September) seasons, using canonical correspondence analysis (CCA). Crops included apple Malusspp. orchards in Norfolk, soybeans Glycine maxin Essex, vineyards Vitaespp. in Niagara and corn Zea mays(maize) in all three counties. Bird assemblages differed between counties because corn in Norfolk had more adjacent wetlands and woodlands than those in Essex. During the breeding season (1988), significant habitat variables explaining variation in bird assemblages (in order of importance) were adjacent apple orchards, wetlands, and “other” wooded habitats and apple as the crop (as distinct from adjacent apple orchards). During migration, apple as the crop was most important, followed by crop type corn (distinct from adjacent corn), adjacent wetlands and adjacent other crops in 1988. Apple as the crop was most important, followed by grape as the crop (distinct from adjacent vineyards) and wetlands in 1987. Based on median vector distances in ordination space as a measure of the difference between breeding and migration periods, bird assemblages in soybean and corn in Essex changed most, while birds assemblages in apple orchards changed least, although differences were not significant among crops. Our results emphasize the importance of non-crop and crop habitats for birds during both breeding and migration seasons.

Two extensive databases were used to examine the pattern of species sensitivities to pesticides. The first database consisted of industry-sponsored data collated over several years by the Canadian regulatory authority (data on weed efficacy and crop margin of safety). The second dataset consisted of data submitted to the United States Environmental Protection Agency (U.S. EPA). On the whole we found that crop species were not consistently more, or less, sensitive to the herbicide tested than non-crop species. Within the Poaceae family (grasses), however, non-crop species exhibited higher sensitivity in 15 cases (out of 23), and only in five cases were crops more sensitive. The range of species sensitivity increases with an augmentation of numbers of species tested, suggesting that the number of species tested in current guidelines is insufficient. Principal Component Analyses showed that only two groups of species could be separated; in both databases, grass and broad-leaved species formed two distinct groups. Correlations between species demonstrated a relationship when comparing within genera or within families. The distribution-based method used with the Canadian database ascertained further the importance of testing more or other species than those recommended in the U.S. EPA guidelines. We concluded that, given the limitations of the current databases, further analyses could not be carried out. We suggest that an improved database on phytotoxicity is a prerequisite to refine the risk assessment of pesticide effects of non-target plants.

Abstract: The approach developed by Environment Canada to assess risk to aquatic and terrestrial plants in nontarget habitats potentially exposed to pesticides evaluated for registration is described. An anonymous sample of pesticide submissions is used to illustrate the approach and to examine its merits and limitations in relation to test species, response variability, testing protocols, ecological relevance, and comparability with other regulatory agencies. Future directions are identified, particularly in relation to impending nontarget-plant testing guidelines for pesticide registration in Canada. This approach incorporates some of the latest research and developments in the field of risk assessment for plants. The novelty of this approach also lies in the use of the plant screening data routinely generated by chemical pesticide companies, which is intended to provide a maximum amount of information to evaluators at minimal increment cost to registrants. The proposed approach can serve as a basis for guideline development and modernization for other jurisdictions.

Fluorescence correlation spectroscopy (FCS) has been used to analyze the plasma membrane fluidity and heterogeneity of multidrug resistant cells. At the single cell level, the effects of different membrane agents present in the extra-cellular medium have been explored. Firstly, we reveal a modification of plasma membrane heterogeneities according to the addition of a fluidity modulator, benzyl alcohol. On the other hand, revertants such as verapamil and cyclosporin-A appear to act more specifically on the slow diffusion sites, such as lipids microdomains.