Isotopic Consequences of Host-Guest Interactions; Noncovalent Chlorine Isotope Effects.
Ontology highlight
ABSTRACT:
SUBMITTER: Paneth A
PROVIDER: S-EPMC8023698 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:A general method, focusing upon olefin metathesis, was developed for the recovery of homogeneous olefin metathesis catalysts from crude reaction solutions. This method utilizes the supramolecular host-guest interaction between an azobenzene-modified N-heterocyclic carbene ligand and a silica-grafted β-cyclodextrin to remove homogeneous catalyst in a heterogeneous manner, allowing for the recovery of more than 97% of ruthenium in solution. The robust and simple nature of the guest molecule allows for the application of this method to a wide range of homogeneous catalysts. This study reports the synthesis and characterization of the said precatalyst and host compound as well as proof-of-concept recovery trials for a number of common substrates, with the residual ruthenium content of reaction mixtures evaluated by inductively coupled plasma mass spectrometry.
| S-EPMC6641285 | biostudies-literature
Project description:There is ongoing interest in exploiting the antioxidant activity and other medicinal properties of natural monophenolic/polyphenolic compounds, but their generally low aqueous solubility limits their applications. Numerous studies have been undertaken to solubilize such compounds via supramolecular derivatization with co-crystal formation with biocompatible coformer molecules and cyclodextrin (CD) complexation being two successful approaches. In this study, eight new crystalline products obtained by complexation between methylated cyclodextrins and the bioactive phenolic acids (ferulic, hydroferulic, caffeic, and p-coumaric acids) were investigated using thermal analysis (hot stage microscopy, thermogravimetry, differential scanning calorimetry) and X-ray diffraction. All of the complexes crystallized as ternary systems containing the host CD, a phenolic acid guest, and water. On heating each complex, the primary thermal events were dehydration and liberation of the respective phenolic acid component, the mass loss for the latter step enabling determination of the host-guest stoichiometry. Systematic examination of the X-ray crystal structures of the eight complexes enabled their classification according to the extent of inclusion of each guest molecule within the cavity of its respective CD molecule. This revealed three CD inclusion compounds with full guest encapsulation, three with partial guest inclusion, and two that belong to the rare class of 'non-inclusion' compounds.
| S-EPMC7823409 | biostudies-literature
Project description:Deuteration of a hydrogen bond by replacing protium (H) with deuterium (D) can cause geometric changes in the hydrogen bond, known as the geometric H/D isotope effect (GIE). Understanding the GIEs on global structures and bulk properties is of great importance to study structure-property relationships of hydrogen-bonded systems. Here, we report a hydrogen-bonded host-guest crystal, imidazolium hydrogen terephthalate, that exemplifies striking GIEs on its hydrogen bonds, phases, and bulk dielectric transition property. Upon deuteration, the donor-acceptor distance in the O-H···O hydrogen bonds in the host structure is found to increase, which results in a change in the global hydrogen-bonded supramolecular structure and the emergence of a new phase (i.e., isotopic polymorphism). Consequently, the dynamics of the confined guest, which depend on the internal pressure exerted by the host framework, are substantially altered, showing a downward shift of the dielectric switching temperature.
| S-EPMC5797174 | biostudies-literature
Project description:In this study, the host-guest behavior of poly(amidoamine) (PAMAM) dendrimers bearing amine, hydroxyl, or carboxylate surface functionalities were investigated by paramagnetic NMR studies. 2,2,6,6-Tetramethylpiperidinyloxy (TEMPO) derivatives were used as paramagnetic guest molecules. The results showed that TEMPO-COOH significantly broaden the ¹H NMR peaks of amine- and hydroxyl-terminated PAMAM dendrimers. In comparison, no paramagnetic relaxation enhancement (PRE) was observed between TEMPO-NH?, TEMPO-OH and the three types of PAMAM dendrimers. The PRE phenomenon observed is correlated with the encapsulation of TEMPO-COOH within dendrimer pockets. Protonation of the tertiary amine groups within PAMAM dendrimers plays an important role during this process. Interestingly, the absence of TEMPO-COOH encapsulation within carboxylate-terminated PAMAM dendrimer is observed due to the repulsion of TEMPO-COO- anion and anionic dendrimer surface. The combination of paramagnetic probes and ¹H NMR linewidth analysis can be used as a powerful tool in the analysis of dendrimer-based host-guest systems.
| S-EPMC3677888 | biostudies-literature
Project description:As COVID-19 prevention efforts have become normalized, conflicts between guests and hotel staff, who must adhere to government protocols, can have a serious impact on host-guest interactions. Drawing on interaction ritual chain theory, this research explores the ritualized mechanism of host-guest interactions during the pandemic from the perspectives of staff and guests. By combining video ethnography and interviews, this study identifies the ritual ingredients, processes, outcomes, and collective symbols of COVID-19 prevention measures. Based on the attitudes and performance paths of staff and guests, the interaction chain may become longer or shorter, and result in guests becoming "insiders" or "outsiders" and leaving the interaction space. An integrated model of host-guest interactions based on interaction ritual theory is proposed.
| S-EPMC8853753 | biostudies-literature
Project description:A series of multiaddressable platinum(II) molecular rectangles with different rigidities and cavity sizes has been synthesized by endcapping the U-shaped diplatinum(II) terpyridine moiety with various bis-alkynyl ligands. The studies of the host-guest association with various square planar platinum(II), palladium(II), and gold(III) complexes and the related low-dimensional gold(I) complexes, most of which are potential anticancer therapeutics, have been performed. Excellent guest confinement and selectivity of the rectangular architecture have been shown. Introduction of pH-responsive functionalities to the ligand backbone generates multifunctional molecular rectangles that exhibit reversible guest release and capture on the addition of acids and bases, indicating their potential in controlled therapeutics delivery on pH modulation. The reversible host-guest interactions are found to be strongly perturbed by metal-metal and ?-? interactions and to a certain extent, electrostatic interactions, giving rise to various spectroscopic changes depending on the nature of the guest molecules. Their binding mode and thermodynamic parameters have been determined by 2D NMR and van't Hoff analysis and supported by computational study.
| S-EPMC4311808 | biostudies-other
Project description:The possible inclusion complexes of Cp(2)NbCl(2) into calixarenes hosts have been investigated. The existence of a true inclusion complex in the solid state was confirmed by a combination of NMR, ab-initio calculations, thermogravimetric analysis, FTIR, Raman and PXRD. Ab-initio calculations, (1)H NMR solution and solid state (13)C CP MAS NMR results demonstrated that p-sulfonic calix[6]arene does form an inclusion complex with Cp(2)NbCl(2). Raman spectroscopy showed, for the inclusion compound of p-sulfonic calix[6]arene-Cp(2)NbCl(2), a band between 500-850 cm(-1) characteristic of Nb-O vibration. This result suggests that Nb(V) may engage in coordination with the oxygen of the sulfonate group, as part of the host-guest interaction. However, it is important to mention that the niobocene dichloride (Cp(2)NbCl(2)) dissolves in water and undergoes oxidation and hydrolysis processes to yield Cp(2)NbCl(2)(OH) species. For that reason this band does not exclude that the Nb-O band belongs to Cp(2)NbCl(2)(OH). Solid State (13)C CP MAS NMR and solution (1)H NMR spectroscopies together with ab-initio results showed that Cp(2)NbCl(2) is included in the p-sulfonic calix[6]arene cavity, with both Cp rings inside the cavity. In contrast, the solution (1)H NMR results demonstrated that calix[6]arene does not form inclusion complex with Cp(2)NbCl(2) in CDCl(3) solution. Cp(2)NbCl(2) is not included in the calix[6]arene cavity, possibly due to the lack of sulfonate heads which promote Nb-O interactions and assist the inclusion of Cp(2)NbCl(2) into the cavity.
| S-EPMC3119540 | biostudies-literature
Project description:Synthetic host-guest chemistry is a versatile tool for biomedical applications. Characterization and detection of host-guest complexes in biological systems, however, is challenging due to the complexity of the biological milieu. Here, we describe and apply a mass spectrometric method to monitor the association and dissociation of nanoparticle (NP)-based host-guest interactions that integrates NP-assisted laser desorption/ionization (LDI) and matrix assisted laser desoption/ionization (MALDI) mass spectrometry. This LDI/MALDI approach reveals how NP surface functionality affects host-guest interactions in cells, information difficult to achieve using other techniques.
| S-EPMC4082387 | biostudies-literature
Project description:(1)H NMR and isothermal titration calorimetry (ITC) experiments were employed to obtain reliable thermodynamic data for the formation of the 1:1 inclusion complexes of fullerenes C(60) and C(70) with the buckycatcher (C(60)H(28)). NMR measurements were done in toluene-d8 and chlorobenzene-d5 at 288, 298, and 308 K, while the ITC titrations were performed in toluene, chlorobenzene, o-dichlorobenzene, anisole, and 1,1,2,2-tetrachloroethane at temperatures from 278 to 323 K. The association constants, K(a), obtained with both techniques are in very good agreement. The thermodynamic data obtained by ITC indicate that generally the host-guest association is enthalpy-driven. Interestingly, the entropy contributions are, with rare exceptions, slightly stabilizing or close to zero. Neither ?H nor ?S is constant over the temperature range studied, and these thermodynamic functions exhibit classical enthalpy/entropy compensation. The ?Cp values calculated from the temperature dependence of the calorimetric ?H values are negative for the association of both fullerenes with the buckycatcher in toluene. The negative ?Cp values are consistent with some desolvation of the host-cavity and the guest in the inclusion complexes, C(60)@C(60)H(28) and C(70)@C(60)H(28).
| S-EPMC4199543 | biostudies-literature
Project description:Chlorinated ethenes are prevalent groundwater contaminants. To better constrain (bio)chemical reaction mechanisms of reductive dechlorination, the position-specificity of reductive trichloroethene (TCE) dehalogenation was investigated. Selective biotransformation reactions (i) of tetrachloroethene (PCE) to TCE in cultures of Desulfitobacterium sp. strain Viet1; and (ii) of TCE to cis-1,2-dichloroethene (cis-DCE) in cultures of Geobacter lovleyi strain SZ were investigated. Compound-average carbon isotope effects were -19.0‰ ± 0.9‰ (PCE) and -12.2‰ ± 1.0‰ (TCE) (95% confidence intervals). Using instrumental advances in chlorine isotope analysis by continuous flow isotope ratio mass spectrometry, compound-average chorine isotope effects were measured for PCE (-5.0‰ ± 0.1‰) and TCE (-3.6‰ ± 0.2‰). In addition, position-specific kinetic chlorine isotope effects were determined from fits of reactant and product isotope ratios. In PCE biodegradation, primary chlorine isotope effects were substantially larger (by -16.3‰ ± 1.4‰ (standard error)) than secondary. In TCE biodegradation, in contrast, the product cis-DCE reflected an average isotope effect of -2.4‰ ± 0.3‰ and the product chloride an isotope effect of -6.5‰ ± 2.5‰, in the original positions of TCE from which the products were formed (95% confidence intervals). A greater difference would be expected for a position-specific reaction (chloride would exclusively reflect a primary isotope effect). These results therefore suggest that both vicinal chlorine substituents of TCE were reactive (intramolecular competition). This finding puts new constraints on mechanistic scenarios and favours either nucleophilic addition by Co(I) or single electron transfer as reductive dehalogenation mechanisms.
| S-EPMC6271514 | biostudies-literature