Journal of Inclusion Phenomena and Macrocyclic Chemistry最新文献

The temperature sensitivity of paramagnetic chemical shifts in ¹H NMR spectra for the [Co(DTPA)]³⁻ complex in 10% gelatin gel (as a model substrate of human or animal tissues) was studied in detail. The maximum temperature sensitivity of the chemical shifts d(δ_exp)/dT studied in the gelatin gel of the complex was found to be 0.73 ppm/K (which is about 7% higher than in the previously studied D₂O solution of the compound). It turned out that the studied complex is characterized by the highest temperature sensitivity of chemical shifts in the NMR spectra among the complexes of paramagnetic d-elements. Moreover, this complex also shows the highest temperature sensitivity of chemical shifts taking into consideration the half-width of the signal itself (|CT|/W = 0.8 K⁻¹). The [Co(DTPA)]³⁻ complex can be considered as a promising compound for the design of temperature-sensitive NMR probes aimed at determining the local temperature in aqueous media and prospective MRI-assisted disease diagnosis.

Biological systems display a range of sophisticated functions that cannot be performed by artificial systems, through intricate cooperative structural changes involving multiple functional units. The designability and structural flexibility of peptides are demonstrated by biological systems that display cooperative structural changes; these properties also make them well-suited for the formation of artificial systems that display such changes. The problem with the use of peptide frameworks is that long peptide residues, which are not suitable for gram-scale use, are required for the formation of stable ordered structures. However, if ordered structures containing peptides could be constructed by coordinating them to metal ions, peptides could be widely used to develop sophisticated functional materials. Crystal packing can be used for the design of functional materials made from simple molecules because it provides a way to place the components relative to each other. Although crystalline systems have been reported in which the small size of the cavities has been attributed to the flexibility of the peptide, recently, large systems with giant cavities have been developed with flexible peptides. In this review, we summarize the formation of cooperative multicomponent systems in the crystalline state using metal complexes of simple peptides, along with recent advances in the construction of giant artificial systems using short peptides.

The dissymmetrical and dipolar Y(III) complex 2 and its cationic precursor 1, containing the proligands 5,10,15,20-tetrakis(4-bromophenyl)porphyrin L1 and 1-anisyl-1,3-butanedione L2, were synthesized at fairly high yields, ranging from 40 to 78%, by conventional and microwave-assisted techniques, and were isolated as a microcrystalline compound. The products obtained in each case were characterized by ¹H-NMR, mass spectrometry, elemental analysis, Med-IR and Far-IR. The IR information collected shows good agreement with respect to the density functional theory (DFT) calculations carried out, validating the molecular geometry in each case. This innovative one-pot microwave-based method contributes an efficient pathway for obtaining challenging molecular architectures based on monoporphyrinate complexes without Diglyme.

The designing of efficient macrocyclic complexes for the alteration in nucleic acids and understanding is still in debate. Herein, to study the deoxyribonucleic acid (DNA) interaction with MN₅-complexes, two macrocyclic complexes, A (Mn^II) and B (Fe^II), have been synthesized and characterized using multiple analytical techniques. The electronic absorption, fluorescence, and electrochemical methods were utilized to examine the binding ability of both complexes with calf thymus-DNA (ct-DNA). The spectral results were found to be in good agreement with the interaction of both complexes with ct-DNA, as also supported by the remarkable decrease in both anodic peak current (i_pa) and cathodic peak current (i_pc) during cyclic voltammetric analysis in the presence of ct-DNA. The spectral investigations clearly indicated the higher binding affinity of complex A as compared to complex B towards ct-DNA. Additionally, both complexes were also found to be potential antibacterial agents.

Purpose

The anti-migraine drugs show first-pass metabolism, short half-life, and low bioavailability resulting in repeated dose or overdose effect. Polymeric, biodegradable and highly porous nanosponges emerge as a promising carrier for migraine treatment to improve aqueous solubility, stability and bioavailability.

Method

Ergotamine nanosponges prepared by interfacial polymerization method wherein hydroxypropyl beta-cyclodextrin inclusion complex was crosslinked using toluene diisocyanate. Caffeine used as a permeation enhancer for ergotamine by forming soluble molecular complex with cyclodextrin moiety of nanosponges. Further, nanosponges were characterized for particle size, zeta potential, entrapment efficiency, percentage drug release profile, antioxidant activity, photostability and instrumental analytical studies.

Results

Caffeine significantly improved the permeation of ergotamine nanosponges. The particle size for optimized nanosponges was 693.5 ± 11.7 nm, zeta potential of − 19.4 ± 5.69 mV with high colloidal stability and maximum entrapment efficiency of 98.88 ± 2.8%. In-vitro and ex-vivo studies exhibited controlled release profiles of ergotamine 81.6% ± 3.4% and 79% ± 4.2% for 24 h, respectively. Nanosponges demonstrated higher antioxidant activity 85.68% ± 1.23% whereas photostability data showed no significant decrease in drug content indicating good stability. Fourier transform infrared spectroscopy confirmed significant interaction of ergotamine with cyclodextrin-based nanosponges.

Conclusion

Nanosponges showed improvement in bioavailability of ergotamine and long-term stability offering inexpensive, productive and safe alternative for migraine.

Graphical abstract

Porphyrins are photoactive molecules with an 18 electron π-conjugated system, and exposure to light promotes electrons to higher energy levels. They are currently gaining popularity because of their special applications’ unique optoelectronic properties. They also serve as fluorescent chemosensors for detecting different types of various chemicals. In this review, we will focus on the representative cases of porphyrinoid fluorophores according to the kinetic and mechanism of the electron/energy transfer process, including popular mechanisms like ICT, PET, FRET, PCET, 2PE, etc. This paper was divided into the following sections: the first is mainly about electron transfer (ET) mechanisms in porphyrinoid fluorophores for probing biological systems. The second section discusses the ET processes of hybridized material and quantum dots. Section three is regarding ET to characterize the interaction of porphyrinoids with model proteins. The combination of porphyrin components like dyad/triad and their characterizations was subjected in the fourth section.

This paper presents the results of studying the structural features of inclusion compounds based on the cucurbit[8]uril macrocycle and the cobalt(III) and ruthenium(III) complexes (trans-[Co(en)₂Cl₂]⁺ and trans-[Ru(en)₂Cl₂]⁺) within the framework of the density functional theory taking into account the course of the reaction in the aqueous solution. Formation thermodynamics of the complexes in the cavitands was evaluated by taking into account the most probable number of water molecules inside cucurbit[8]uril. In this methodology, the complexation was considered as a substitution reaction in which the guest complex displaces partially or completely the water molecules that are located inside the cavity. The water molecules present in the cavitand were shown to play an important role in the fixation of the guest complex inside the cavity due to the hydrogen bonds with the oxygen portals. The role of water molecules in the fixation of the complex in the cavity of the macrocycle with the formation of a particular structure is shown. The symmetrical arrangement of the fixing water molecules in the portals leads to a more symmetric arrangement of the metal complex in the cucurbit[8]uril cavity, while their asymmetric localization leads to a significant turn of the complex. Comparison of the main geometric characteristics according to the calculation and X-ray structural analysis showed good agreement. The thermodynamic parameters of the formation of the inclusion compound are estimated. It is shown that the energy contribution of macrocycle deformation to the energetics of formation of the inclusion compound is insignificant.

The complexation behavior of diprotonated phenylenediamine isomers with decamethylene cucurbit[6]uril (Me₁₂Q[6]) in 1:1 and 1:2 stoichiometry was investigated in vacuum and solution using density functional theory (DFT). Among the isomers, o-phenylenediamine (oPDA) forms an exclusion complex in 1:1 stoichiometry, while others form an inclusion complex. In the 1:2 stoichiometry, at least one of the guest molecule lie on the surface of the Me₁₂Q[6] cavity. The structural reorganization was found to depend on the mode of interaction of the guest molecule. In the gas phase, the enthalpy and Gibbs free energy are negative for all the complexes demonstrating the encapsulation process is spontaneous and thermodynamically favorable. In the solution phase, the enthalpy and entropy are negative for complexes with guest molecules meta- and para-isomers of phenylenediamine. For oPDA as a guest, the enthalpy and entropy are positive indicating the complex formation to be nonspontaneous. The MESP isosurface of complexes shows a higher accumulation of charge in the 1:2 stoichiometry, which reduces their stability. AIM analysis shows the interaction between oPDA and Me₁₂Q[6] is due to hydrogen bonding with moderate strength, while for the other isomers, interactions between the benzene group and the Me₁₂Q[6] cavity were noticed. EDA analysis shows the larger contribution is the electrostatic attraction and it decreases with the increase in the guest ratio. The formation of inclusion complexes by mPDA and pPDA and the surface adsorption of oPDA on Me₁₂Q[6] and the higher accumulation of positive charge during solvation in oPDA@Me₁₂Q[6] complexes make them labile in the solution phase.

Graphical abstract

In recent years, a number of interlocked molecules such as rotaxanes, catenanes, polyrotaxanes, and polycatenanes have been actively synthesized. Cyclodextrins (CDs) are representative building blocks of these interlocked molecules; however, very few reports are available on CD-based catenanes and polycatenanes. In this review article, we provide an overview of CD-based interlocked molecules and introduce examples of CD-based catenanes and polycatenanes. Finally, the perspectives of research on CD-based catenanes and polycatenanes are discussed.

Calix[4]arene-based materials have been investigated to develop selective, sensitive, and low cost chemical sensors due to their simple, low cost synthesis, and wide range of chemical and physical properties. In this study, bisbenzothiazole-p-tert-butylcalix[4]arene-thiourea (BBTC[4]T) molecules were employed to produce thin films via Langmuir–Blodgett (LB) thin film fabrication technique. The optical properties and gas sensing abilities of these BBTC[4]T LB films were examined by Surface Plasmon Resonance (SPR) method. In order to illuminate the optical properties of calix[4]arene-based LB films the Winspall software was utilized by fitting the experimental data obtained from SPR device. The values of 1.23 ± 0.07 nm and 1.53 ± 0.05 were determined for the thickness per monolayer and the refractive index of BBTC[4]T-based LB films, respectively. The fabricated optical sensor was employed for its sensing abilities against to organic vapours (acetone, ethyl alcohol, methyl alcohol and isopropyl alcohol) via the mechanism of host–guest interaction. The current study also describes the diffusion coefficients of these organic vapours to illuminate the swelling dynamics’ BBTC[4]T-based LB thin films by performing the early-time Fick’s diffusion equation. The responses of calix[4]arene-based optical sensor in terms of the shift in reflective intensity and the values of diffusion coefficients showed that BBTC[4]T molecules can be developed as potential chemical sensor element for acetone vapour compared to alcohol vapours.