环糊精包结物的形成及光谱表征

环糊精包结物的制备、结构、性质和应用研究一直是环糊精化学的重要内容。本文对近年来关于环糊精的形成条件、制备方法、包结类型、检测手段和表征方法进行了较详细的综述 ,希望对环糊精应用研究工作的进行起到积极的、科学的指导作用。     

Tunable Synthesis of Sub-20 nm Gold Nanoparticles Capping with Cyclodextrin for Host–Guest Molecular Recognition on Nano-Surface

Gold nanoparticles capping with three types of natural cyclodextrins are synthesized, allowing for precise control over their sizes ranging from 9 to 20 nm. These nanoparticles exhibit remarkable colloidal stability during long-term storage, as well as excellent tolerance to saline, acidic, and alkaline conditions. Importantly, the assembly of nanoparticles is performed by using the silica nanospheres functionalized with cinnamyl group and the gold nanoparticle capping with three types of cyclodextrin, highlighting the selective formation of core-satellite superstructure based on the host–guest molecular recognition on nano-surface between different nanoparticles.     

Supramolecular encapsulation of 1,3‐bis(1‐adamantyl)imidazolium chloride by β‐cyclodextrins: towards inhibition of C(2)‐H/D exchange

The study of the hydrogen/deuterium exchange reactions of the C(2)‐proton for different carbene precursors has been carried out in the absence and presence of β‐cyclodextrin in D₂O at 25°C. Formation of the inclusion complexes of imidazolium salts with the native β‐cyclodextrin and the β‐dimethylcyclodextrin is demonstrated by 1D and 2D ¹H NMR, ESI/HRMS and a molecular modelling study. Formation of the inclusion complexes of imidazolium salts with the native β‐cyclodextrin and the β‐dimethylcyclodextrin is a simple and efficient method to modify the acidity of the imidazolium H(2) and to modify its environment. Encapsulation of 1,3‐disubstituted imidazolium chloride by β‐cyclodextrins results in the inhibition of the H(2)/D exchange in the complex. Copyright © 2008 John Wiley & Sons, Ltd.     

Hydrogen bonding dynamics of cyclodextrin–water solutions by depolarized light scattering

Depolarized light scattering measurements performed on aqueous solutions of α‐cyclodextrin are used for investigating the hydration properties of this natural cyclic oligosaccharide, which is well known for its ability to form inclusion complexes with a large variety of guest hydrophobic molecules. The spectral analysis allows the characterization of the solvent relaxation process assigned to hydration water, which is found to be seven to eight times slower than the bulk. As a structural information, the number of water molecules involved in the hydration process is also estimated at about 46. These results are a key step for understanding the role played by water in determining the properties of different forms of cyclodextrins and their derivatives, in turn related to complexation ability of these macrocycles. Copyright © 2011 John Wiley & Sons, Ltd.     

Fluorescence enhancement of the aflatoxin B1 by forming inclusion complexes with some cyclodextrins and molecular modeling study

The interaction between the aflatoxin B₁ (AFB₁) and three cyclodextrins, α-cyclodextrin (α-CD), β-cyclodextrin (β-CD) and heptakis-2,6-dimethyl-o-β-cyclodextrin (ome-CD), was studied by spectrofluorescence technique. It was found that the inclusion association behavior occurs for the complexes of cyclodextrins with AFB₁. The fluorescence of AFB₁ is generally enhanced in the complexes with cyclodextrins in aqueous solutions. The inclusion complex constants of the three types of cyclodextrins at different temperatures were evaluated from Benesi-Hildebrand plot and also by non-linear regression analysis. These cyclodextrins can only form the 1:1 (host:guest) inclusion complex in the studied temperature range of 20-50 °C. The enthalpy (ΔH°) and entropy (ΔS°) changes of complexation were extracted from the temperature dependency of complex formation constants (K). Temperature-dependent measurements showed that the association step is controlled by enthalpy-entropy compensation effect. The use of ome-CD generally resulted in the greatest fluorescence intensity. On the other hand, the discrepancy between the exhibited enhanced fluorescence and thermodynamic parameters (ΔG°) is proposed to be different only by the orientation of the AFB₁ within the cyclodextrin cavity. To find the most favorable structure, the geometry of complex was investigated by molecular modeling approach employing the semiemperical HF-SCF calculations.     

Complexation of niflumic acid with native and hydroxypropylated α‐ and β‐cyclodextrins in aqueous solution

Interactions between niflumic acid and native and hydroxypropylated α‐ and β‐cyclodextrins (CDs) were investigated by ¹H NMR, UV‐vis spectroscopy, densimetry, and calorimetry at pH = 7.4 (phosphate buffer) and T = 298.15 K. Thermodynamic parameters of 1:1 complex formation were calculated and discussed in terms of influence of cavity size and availability of hydroxypropyl substituents on the complex stability. The ¹H NMR data indicated the inclusion of niflumic acid into macrocyclic cavity of all CDs under study. It was found that both phenyl and pyridine rings of niflumic acid molecule can be included in the cyclodextrin cavity. The co‐existence of two different kinds of 1:1 inclusion complexes in the solution was suggested. In spite of the fact that binding of niflumic acid with α‐cyclodextrin is more enthalpically favorable, stability of the inclusion complexes is very low due to the enthalpy–entropy compensation effect. Complex formation of β‐CDs with niflumic acid is characterized by the higher enthalpy and entropy changes caused by more intense dehydration. Introduction of hydroxypropyl groups in the cyclodextrin molecule was found to promote the binding with niflumic acid. Copyright © 2008 John Wiley & Sons, Ltd.     

A facile and flexible process of β-cyclodextrin grafted on Fe3O4 magnetic nanoparticles and host-guest inclusion studies

In this study, a kind of novel surface-functionalized magnetic nanoparticles was fabricated by the Fe₃O₄ nanoparticles surface modification with mono-6-deoxy-6-(p-tolylsulfonyl)-cyclodextrin (6-TsO-β-CD), which were employed to interact with uric acid and their behavior was investigated by electrochemical methods. The architecture has been characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA), which confirmed that cyclodextrins have been effectively functionalized on the surface of Fe₃O₄ nanoparticles. The analyses of vibration sample magnetometer (VSM) verified that the nanoparticles owned good magnetic property. The grafted β-cyclodextrin on the Fe3O4 nanoparticles contributed to as a modified electrode for detecting uric acid with cyclic voltammograms. Electrochemical results revealed that the new materials could exhibit excellent molecules recognition ability and show high electrochemical response. The new nanoparticles simultaneously had unique properties of magnetic nanoparticles and cyclodextrins through combining their individual distinct advantages.     

SEM-mapped micro-photoluminescence studies of highly luminescent micro-clusters in erbium-doped silicon-rich silicon oxide

This paper reports on the formation of unique micrometer-scale clusters in erbium-doped silicon-rich silicon oxide (ErSRSO) thin films produced by thermal evaporation. Through scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), we identify these micro-clusters as structures where the film curves away from the substrate to encase erbium-rich aggregates. Even though erbium aggregation has been reported to cause quenching, we demonstrate that the micro-clusters as a whole can exhibit significantly enhanced erbium photoluminescence (PL), with emissions over 24 times brighter than the surrounding non-cluster region. Mapping micro-photoluminescence measurements onto SEM images reveals that the erbium aggregates alone do not generate the enhanced PL, but rather the thin film encasing the aggregates is the origin of the emissions. Analysis of the PL Stark splitting shows a correlation between the micro-clusters’ fine structure and the strength of their PL. Taken together, the above evidence indicates that the micro-clusters’ strong PL is produced by changes in the local environment of the Er³⁺ inside the thin film surrounding the erbium-rich aggregates.     

Supramolecular assemblies of azobenzene‐β‐cyclodextrin dimers and azobenzene modified polycaprolactones

Click chemistry is employed to couple two β‐cyclodextrins at both ends of azobenzene moiety yielding dumbbell‐shaped amphiphiles (AZO‐β‐CD dimer) constructed by rigid aromatic building blocks as “body”, and hydrophilic cyclodextrins as “head” with almost quantitative yield and purity. Bulk aggregates formed by the self‐assembly of the supraamphiphiles through π–π stacking and hydrophobic effect are observed. Meanwhile, the rationally designed polyesters, named as AZO‐PCL with controllable molecular weights and low polydispersities, are successfully synthesized by ring‐opening polymerization of ε‐caprolactone in the presence of p‐aminoazobenzene as initiator. In the aqueous phase, very stable spherical particles are formed by host–guest interactions between AZO‐β‐CD and AZO‐PCLs; the spherical aggregates inherit the photo‐responsiveness of azobenzene. The detailed aggregation and disaggregation behaviors are fully investigated by TEM, SEM, NMR, 2D NOESY, IR, UV and XRD measurements. Compared to the previous works, our newly developed system can be fabricated with more readily manners, avoiding tedious synthetic process; the reversible and dynamic nature of the non‐covalent interactions also can be modulated alternatively by UV or visible light. Thus, such dumbbell‐shaped supra‐amphiphiles are of great potential applications in the controlled delivery systems. Copyright © 2014 John Wiley & Sons, Ltd.     

Metal-iodide cyclodextrins as model quasi-one-dimensional compounds

The synthesis and electrical and magnetic properties of two metal-iodide cyclodextrin compounds are described. Both Ba and Fe ions were added to the α-cyclodextrins to form needle-shaped single crystals. The compounds have electrical conductivities of about 10^?9 (ω cm)^?1 at room temperature. The Ba compound is diamagnetic but the Fe compound shows Curie-Weiss behavior in its susceptibility between 1.5 and 108 K, with an effective moment of 4.5 μ_B and a Weiss temperature of ?5.6 K. The results indicate antiferromagnetic interactions between Fe(II) ions. A discussion is given of some problems associated with synthesizing quasi-one-dimensional conductors or magnetic compounds, using the cyclodextrins as a basis.