Journal of Inclusion Phenomena and Macrocyclic Chemistry最新文献

Hydroxypyridinones (HOPOs) are excellent class of chelators that have been gaining attention in the field of pharmaceutical drugs by their high chelating efficacy and specificity with different metal ions. Among all the metal ions, they exhibit a high binding affinity towards iron (III) and are clinically used as iron chelators nowadays. The HOPO family has different isomers, out of which 3,4-HOPO possesses applicability for designing drugs. The effect of methyl substitution on different positions of pyridinone ring also plays an essential role in deciding the pM values, thus describing the metal affinity. Several metal ions like Fe, Al, Cu, Zn, and some actinides are found to exhibit good chelation efficacy with HOPOs. In terms of denticity, there are various forms of HOPO. Among these, discussion on bidentate, tetradentate, hexadentate, octadentate, and dendrimers will be done here. This review systematically summarizes the various literature reports on the design and pharmacological activities of the newly developed HOPOs and their derivatives, including antibiotics, anticancer, and antineurodegeneratives.

The paramagnetic lanthanide complexes with polyaminopolycarboxylate (PAPC) ligands attract considerable attention from the standpoint of potential applications thereof as relaxation agents used in medical magnetic resonance imaging (MRI) and in luminescent materials, as well as owing to promising use thereof as paramagnetic labels for studying the properties of biopolymers since they exhibit thermodynamic stability, good solubility in aqueous media and moderate toxicity. For the last decades, the NMR methods have been used to determine the physical and chemical properties of paramagnetic Ln compounds. The studies concerning paramagnetic NMR lanthanide-induced shifts (LISs) in dissolved Ln complexes, as well as the analysis of band shape as a function of temperature make it possible to obtain valuable information on the structure, intra- and intermolecular dynamics and paramagnetic properties thereof. This review is devoted solely to the following features: firstly, the processes of intramolecular dynamics of lanthanide complexes with polyamino-polycarboxylate ligands such as DOTA, EDTA and DTPA and their derivatives studied by NMR; secondly, the LISs of lanthanide complexes with EDTA, DOTA, DTPA and some of their derivatives depending on temperature and pH. Moreover, in this review, for the first time, the dependence of the activation energy of molecular dynamics in complexes with polydentate ligands on the atomic number of the lanthanide cation is analyzed and a monotonic change in energy is detected, which is due to the effect of lanthanide contraction. It should be noted that this phenomenon is quite general and may also appear in the future in many other series of lanthanide complexes with both other multidentate ligands and with bidentate and monodentate ligands. In the future, it is possible to predict the dependence of the properties of certain lanthanide complexes on the ionic radius of the lanthanide cation based on the approaches presented in the review. In this review, we have also presented the dynamic NMR as the main research method widely used to analyze the processes of molecular dynamics, and the structural studies based on the NMR relaxation spectroscopy and LIS analysis.

A 14-membered hexamethyl-tetraazamacrocycle, viz. Me₆[14]diene.2HClO₄ (L.2HClO₄), afforded a mixture of isomeric ligands, Me₆[14]anes, upon reduction with NaBH₄ and extraction by CHCl₃ at pH > 12. These ligands were separated by fractional crystallization from xylene and were designated as ‘tet-a’ and ‘tet-b.’ The interaction of ‘tet-b’ with excess acrylonitrile was fairly stereoselective and formed an N-pendent derivative, ‘tet-bx’, in which two cyano-ethyl groups were attached to trans N-atoms that are sterically less crowded. Aeration of ‘tet-bx’ and cobalt(II) acetate salt in methanol, followed by its treatment with HCl, yielded a bluish-green product, viz. trans-[Co(‘tet-bx’)Cl₂]Cl. trans-[Co(‘tet-bx’)Cl₂]Cl underwent axial substitution reactions with KSCN and KNO₃ and subsequent axial substitution and anion exchange reactions with NaNO₂, KBr, and KI to produce six-coordinated octahedral complexes, viz. bluish-green trans-[Co(‘tet-bx’)(NCS)₂]Cl, light-blue trans-[Co(‘tet-bx’)(NO₃)₂]Cl, yellow trans-[Co(‘tet-bx’)(NO₂)₂]NO₂, green trans-[Co(‘tet-bx’)Br₂]Br, and red trans-[Co(‘tet-bx’)I₂]I. These complexes were characterized using different modern analytical and spectroscopic techniques. The antibacterial activities of the N-pendent ligand and its cobalt(III) complexes on four types of selected bacteria were investigated.

Roof-shaped host compounds trans-α,α,α′,α′-tetraphenyl-9,10-dihydro-9,10-ethanoanthracene-11,12-dimethanol H3 and trans-α,α,α′,α′-tetra(p-chlorophenyl)-9,10-dihydro-9,10-ethanoanthracene-11,12-dimethanol H6 were assessed for their host potential and selectivity behaviour when presented with single or mixed guest solvents comprising o-xylene, m-xylene, p-xylene and ethylbenzene (o-Xy, m-Xy, p-Xy and EB). H3 included each solvent with 3:1 host:guest ratios, while the ratios preferred by H6 were more varied (4:3, 1:1 and 3:2). More importantly, the selectivity behaviour of these two host compounds was observed to be entirely different: H3 possessed only a very modest preference for o-Xy (37.9–68.2%) when recrystallized from various equimolar binary, ternary and quaternary guest mixtures, while H6 was considerably more selective, preferring m-Xy (the least favoured guest of H3) with selectivities ranging from 57.7 to 91.4% in analogous conditions. The latter result was obtained in o-Xy/m-Xy mixtures and demonstrates that H6 may be employed as a purification tool for mixtures of these two xylenes via host–guest chemistry protocols. A single crystal diffraction experiment on 3(H3)·o-Xy (containing the preferred guest of H3) revealed that the guest was retained in the host crystal by means of a singular (host)m-Ar–H···π(guest) interaction that measured 2.73 Å (148°) as well as numerous other host···guest interactions involving only the aromatic protons of the free host phenyl groups and the guest methyl protons or aromatic carbons and protons (2.20–2.54 Å, 121–125°). Thermal analyses explained the preference of H3 for o-Xy, while these were less informative for the complexes of H6.

Beta-carotene (BC) is a vitamin A precursor and has potential anticancer benefits, but the delivery of BC is hindered by its low solubility and storage instability. To overcome these challenges, this study investigated the use of fabricated cyclodextrin-based nanosponges (CDNS) using different ratios of two cross-linkers, epiclon (EPI) and hexamethylene diisocyanate (HMDI) to form inclusion complex with BC. The ratios of crosslinkers to βCD for two most optimaly encapsulated CDNSs-BC were determined to be 2:1 for EPI and 4:1 for HMDI with loading efficiency of 61.46% and 59.61%, respectively. The charachterization tests were carefully done for two optimal CDNSs. Encapsulation significantly improved the solubility by ~ 10 folds, 30-day storage stability by 40% compared to BCs. The in vitro release of the two encapsulated products showed no burst release. The MTT assay revealed a variable increase in cytotoxic effect in both normal and cancer cells compared to free BC. Overall, the CDNSs appear to be promising carriers for the delivery of BCs.

This study presents the development of a new and sensitive polyvinyl chloride electrode based on cadmium oxide (CdO) nanoparticles and N-phenylaza-15-crown-5 for the selective determination of cadmium cations. To this end, synthesized cadmium oxide nanoparticles were characterized through XRD, FT-IR and FESEM analysis. Then, CdO nanoparticles were applied as a modifier for the fabrication of the proposed electrode. The optimum membrane composition to construct the electrode comprised poly(vinyl chloride) (30%), nitrobenzene (61%), cadmium oxide nanoparticle (3%) and N-phenylaza-15-crown-5 (6%). The Nernstian slope of the electrode was obtained 27.3 ± 0.3 mV/decade in the 1.0 × 10^–8 to 1.0 × 10^–1 M concentration range, and the detection limit was obtained as 9.8 × 10^–9 M. The response time of the electrode was short (5 s), while its reversibility and lifetime were high. It was revealed that the operation pH range of the electrode ranged between 2 and 9, and the electrode had a very good selectivity to cadmium cations among the other interfering ions. Further, the electrode was successfully used as a potentiometric sensor in complexometric titrations and the measurement of cadmium cations in the environmental waters.

Graphic abstract

Cyclodextrins (CDs) are biocompatible, cyclic oligosaccharides that are widely used in various industrial applications and have intriguing interfacial science properties. While CD molecules typically have low surface activity, they are capable of stabilizing emulsions by inclusion complexation of oil-phase components at the oil/water interface, which results in Pickering emulsion formation. Such surfactant-free formulations have gained considerable attention in recent years, owing to their enhanced physical stability, improved tolerability, and superior environmental compatibility compared to conventional, surfactant-based emulsions. In this review, we critically describe the latest insights into the molecular mechanisms involved in CD stabilization of Pickering emulsions, including covering practical aspects such as methods to prepare CD-based Pickering emulsions, lipid encapsulation, and relevant stability issues. In addition, the rheological and textural features of CD-based Pickering emulsions are discussed and particular attention is focused on promising examples for drug delivery, cosmetic, and nutraceutical applications. The functionality of currently developed CD-based Pickering emulsions is also summarised, including examples such as antifungal uses, and we close by discussing emerging possibilities to utilize the molecular encapsulation of CD-based emulsions for translational medicine applications in the antiviral and antibacterial spaces.

The comparative encapsulation of the Alzheimer’s drug memantine (3,5-dimethyladamantan-1-amine), used as its hydrochloride salt, within the cavity of two different sized para-sulfonatocalix[n]arenes (sCX[n]; n = 4 or 8) was analysed by ¹H NMR spectroscopy. Addition of either macrocycle to memantine results in selective upfield shifts of all drug proton resonances of between 0.50 and 1.72 ppm for sCX[4] and between 0.80 and 1.53 ppm for sCX[8]. Memantine binding results in the observation of an extra sCX[4] resonance for the macrocycle’s methylene protons, which is not observed for the larger sCX[8], indicating a potential change in shape of the sCX[4] upon host–guest formation. Difference in changes to the chemical shift of the memantine doublet-of-doublets resonance for both macrocycles indicates a potential change in shape of memantine upon host–guest formation. From Job Plots, memantine binds to sCX[4] in a 1:1 ratio with a binding constant of 6.6 × 10⁶ M⁻¹, whereas binding to sCX[8] is in a 1:2 host–guest ratio. Overall, the results indicate that memantine forms subtly different host–guest complexes with different sized sCX[n] homologues, which could be used to tune the drug delivery potential of the macrocycle for different pharmaceutical applications.