Journal of Inclusion Phenomena and Macrocyclic Chemistry最新文献

Here we report on the host behaviour of compounds N, N’-bis(9-phenyl-9-xanthenyl)propane-1,3-diamine (H1) and N, N’-bis(9-phenyl-9-xanthenyl)butane-1,4-diamine (H2) in the presence of potential guest species cyclohexanone (CYC) and 2-, 3- and 4-methylcyclohexanone (2MeCYC, 3MeCYC and 4MeCYC). H1 only formed a complex with CYC, whilst all four guest solvents were enclathrated by H2. Thermal analyses in conjunction with SCXRD experiments revealed that more energy was required to remove guest species from the crystals of their complexes when they were housed in discrete cavities compared with guest molecules retained in channels. Only in H1·CYC was identified an intramolecular (host)N‒H···N(host) hydrogen bond, while complexes H2·2(CYC), H2·2(3MeCYC) and H2·4MeCYC all experienced strong (host)N‒H···O(guest) hydrogen bonds which assisted in retention of the guests in the complexes; this interaction type was absent in both H1·CYC and H2·2(2MeCYC). Hirshfeld surface analyses demonstrated that the amounts of (guest)O···H(host) interatomic interactions were comparable and ranged between 11.1 and 13.9%. Guest competition experiments showed that H2 possessed an affinity for, more usually, 3MeCYC, despite the complex H2·2(3MeCYC) being the least thermally stable one. Finally, it was established that H1 and H2 would not be appropriate host compounds for separations of mixed cyclohexanones through supramolecular chemistry strategies.

As a booming research theme, heterogeneous catalysts have demonstrated significant advantages over homogeneous catalysts in terms of stability, recyclability, and separability from the reactant mixture. In this study, a supramolecular coordinated polymer (P[5]-SCP) was synthesized by complexing thiazole-derived pillar[5]arene (P[5]) with Pd(II), which was obtained by nucleophilic substitution between 1,4-bis(2-Bromoethoxy) pillar[5]arene and 4-methyl-5-(β-hydroxyethyl) thiazole. The chemical component and structure of the P[5]-SCP were confirmed by NMR, EA, FI-IR, XPS, XRD, SEM, TEM, HR MS. In the Suzuki–Miyaura coupling reaction, the catalytic activity, stability, and recyclability were thoroughly evaluated. The P[5]-SCP had excellent catalytic activity in mild reaction conditions (up to 81% yield) and exhibited little loss of activity after at least five recycles. Furthermore, catalyst P[5]-SCP was easily synthesized from simple raw materials and low-cost, thereby a novel pillar[5]arene based-NHC catalyst was developed in green heterogeneous catalysis.

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Steroid hormones play a crucial role in the body by acting as chemical messengers. They are, however, poorly soluble in water, and cyclodextrins can increase their solubility thus leading to increased bioavailability when used in drug formulations. Accuracy in the prediction of the free energy of binding of cyclodextrin/steroid inclusion complexes with simulation is important because of the potential value it brings by providing low-cost predictions of the real-life behavior of the cyclodextrin/steroid inclusion complex and the potential for high-through-put screening. Many computational methods exist, and it is therefore important to understand the ability of current theoretical models to accurately predict the free energy of binding for these inclusion complexes. We focused specifically on the estimation of the free energy of binding of inclusion complexes of four steroids: Hydrocortisone, dexamethasone, prednisolone, and 6α-methylprednisolone with native α-CD, β-CD, γ-CD, (2-hydroxy)propyl-β-CD, and sulfobutylether-β-CD by phase solubility as well as with α, β, and γ-CD by simulations. The simulations were assessed with both docking and the molecular mechanics combined with the generalized Born and surface area (MM/GBSA) continuum solvation approach. Considering the phase solubility diagram, (2-hydroxy)propyl-β-CD and sulfobutylether-β-CD dissolved more steroids in the higher concentration range as expected. The assessment of the free energy of binding obtained from the phase solubility and theory showed that the MM/GBSA method has shown promise in reliably generating accurate predictions in the field of calculating the free energy of binding of steroids/cyclodextrins with a correlation coefficient (R²) = 0.94.

The aim of this review is to compile important results of single-crystal X-ray diffraction method, vibrational and NMR studies conducted on alkali metal ion complexes of some small ring benzo-crown ethers namely benzo-15-crown-5, dibenzo-15-crown-5 and benzo-12-crown-4 to determine their structure, stoichiometry and conformation in the solid-state. This review focuses on solid-state architectural diversity of alkali metal ion complexes studied by single-crystal X-ray diffraction method. Investigations of these complexes are significant as the interactions of alkali metal ions with these crown ethers mimic those present in nature between univalent ions and several bioligands. The benzo group in the macrocycle allows to monitor the complexation event by fluorescence studies and extends the applications of these crown ethers to fluorescent ion sensors. The selected small ring benzo oxa-crown ethers have cavities that match the size of the alkali metal ions and give stable complexes with them. The review presents results related to variation in infrared and Raman spectra of the ligands with changes in their crystal structure and conformation on complexation with alkali salts. Single-crystal X-ray diffraction studies of these complexes help to confirm the chemical structure, stoichiometry, stable conformation and presence of associated solvent molecules in the solid state. As noncovalent interactions are involved in the formation of these complexes, they are capable of forming supramolecular assemblies for building smart functional materials.

Graphical Abstract

The inclusion compounds of auranofin (AF) and its iodide derivative (AF-I) with HP-β-CD were recently identified and characterized experimentally. In the present work, classical molecular dynamics and the quantum computational GFN2-xTB method were applied to investigate the inclusion processes. As a result, both approaches identified AF-I@HP-β-CD as the most favourable system, as observed experimentally. The higher stability of AF-I@HP-β-CD was explained by entropy and solvation factors, with the GFN2-xTB method providing a stability constant (logK_1:1) in good agreement with the experimental results: 0.21–1.21 for AF@HP-β-CD and 1.31–2.33 for AF-I@HP-β-CD (the experimental values are 1.48 and 2.52, respectively). The preferred inclusion mode for AF-I@HP-β-CD has a triethylphosphine (-PEt₃) group pointed towards the head portion of the HP-β-CD where the HP groups are attached (labelled P2). The P2 mode showed short contacts between -CH₂CH₃ groups (-PEt₃) and -H-3 only (inside the CD cavity), which is also supported by ROESY experiments.

Hosts, a key component of inclusion complexes, are cyclic oligomeric compounds containing a cavity in which another component of the complex is bound by non-covalent forces. Chiral hosts are particularly important and interesting because they allow the study of specific intermolecular interactions and molecular recognition. The most important classes of chiral hosts and their physicochemical properties are briefly reviewed. An important part of this Review is the description of selected concepts necessary to understand the properties and behavior of inclusion complexes studied by the most suitable analytical method for studying inclusion complexes—nuclear magnetic resonance.

The geometrical structures of cucurbit[n]uril (CB[n], n = 5–8 and their complexes with molnupiravir (MLP) drug have been investigated using the DFT computations. The complexation energies and electronic properties of CB[n]/MLP complexes were also computed. The host–guest interactions in the complexation are occurred through the of dipole–dipole interactions which are the hydrogen bonds between the O−H or N−H of molnupiravir and oxygen atoms of CB[n]s. The CB[n]/MLP host–guest complexation in both gas and water are found to be an exothermic reaction with negative complexation energy values. By means of the NBO analysis and MEP contours, the partial charge transfers from CB[n]s to molnupiravir are displayed. After drug complexation, the electronics properties of CB[n]s are significantly changed. This means that CB[n]s can act as a host for appropriately molnupiravir guest, even in aqueous solution.

Thymol and carvacrol belong to the class of terpenoids that usually contribute to the flavor, color, and development of plants, and their complexation with CD has been recently reported. Due to their structural similarities, including such guests in CD poses a challenging task to theoretical methodologies. With the present contribution, we applied the recently developed GFN2-xTB multi-equilibrium approach to study the inclusion of those guests into β-CD. The inclusion of 1-adamantane carboxylic acid in β-CD was also investigated for comparison. The study was conducted with a progressive increase in the number of systems in steps, comprising 792, 1,188, and 1,584 systems. Therefore, for the three guest/host pairs studied, complete optimization in vacuum and water with the ALPB continuum method was applied to 10,692 systems at the GFN2-xTB level of theory. Furthermore, single-point calculations at the B97-3c/def2-TZVPP level of theory were carried out using the SMD solvation model. As a result, beyond determining the experimental trend, we addressed that the additional degree of freedom represented by the gamma Euler parameter decreased the errors related to the estimated adjusted binding constants. On the other hand, the use of the B97-3c/def2-TZVPP in conjunction with the set of systems selected by GFN2-xTB (ALPB) must be further investigated since the experimental trend was obtained only with a basis in the difference in electronic energies.

Graphical Abstract

1,4-Phenylene-bis(di-p-tolylmethanol) (H), a host compound with the wheel-and-axle design, formed complexes with organic guest solvents pyridine (PYR) and 2-, 3- and 4-methylpyridine (2MP, 3MP and 4MP). The host: guest (H: G) ratios were 1:3, 1:2, 1:2 and 1:1, respectively. Host crystallization experiments from mixed guests demonstrated H to prefer both PYR and 4MP; however, it was established that these difficult-to-separate (by fractional distillations) guest mixtures cannot be purified/separated by means of H through supramolecular chemistry strategies owing to these selectivities for PYR and 4MP being less than optimal. Single crystal X-ray diffraction experiments showed that each guest compound was held in its complex by means of a classical hydrogen bond with H, and that one of the preferred guests, PYR, experienced a significantly shorter contact of this type than the other guests. Hirshfeld surface analyses demonstrated that PYR was also involved in a greater percentage of (guest)N···H(host) interactions compared with the other guest molecules. Thermal analyses, on the other hand, revealed that 4MP (also a favoured guest species) formed the most stable complex of the four in this investigation. These results with H were compared to those obtained when employing a closely related host compound from a previous report, 1,4-bis(diphenylhydroxymethyl)benzene: while both host species preferred the same guests (PYR and 4MP), the extent of the selectivity of that host compound compared with H in the present work was significantly more enhanced. Thus, minor modifications may deleteriously affect the selectivity behaviour of closely related host compounds.

β-Cyclodextrin plays a crucial role in augmenting the activity of metal complexes by ameliorating their solubility, stability, and reactivity, therefore the thio-functionalized β-cyclodextrin based amino ligand mono-6-deoxy-(o-aminobenzylthio)-β-cyclodextrin (4) was synthesized and analyzed by elemental analyses, AAS, UV–visible, FTIR, and ¹H NMR spectroscopy. The newly synthesized Fe III) complex was soluble in water. The Fe(III) complex's spectral analysis using FTIR confirmed that the ligand aided the metal ion coordinate by way of the sulfur atom of the β-cyclodextrin moiety and the nitrogen atoms of the two ligand molecules, with two H₂O occupying the fifth and sixth coordination sites. Additionally, the mass spectrometry verifies that the intended Fe(III) complex has synthesized. Density functional theory (DFT) was used to calculate different electronic parameters of the optimized structure of Fe(III) complex to reveal its stability. Antimicrobial metal complexes that are suitable for therapeutic application are known to be more stable and bioavailable when β-cyclodextrin is introduced, therefore studies have been done to inquire into the possible comparative in vitro antibacterial activity of the Fe(III) complex and free ligand against two gram positive (Bacillus subtilis, and Staphylococcus aureus) and two gram negative bacteria (Escherichia coli, Klebsiella pneumoniae) strains. Molecular docking was used to further corroborate these capabilities.