Complexes of Na-, Ca-, and Zn-montmorillonites with an aminated cyclodextrin

The uptake of mono-(6--aminoethylamino-6-deoxy)--cyclodextrin (CDen) by Na-, Ca- and Zn-montmorillonites has been examined at 25°C. Each of the first two minerals forms only one intercalated phase in which the CDen molecules are intercalated as a monolayer, while the third yields a mixture of two intercalated phases whose interlayer spaces are occupied by mono- and bilayers of the guest molecules. Intercalation proceeds by ion exchange with the interlayer cations for the Na-complex and by forming metalaminoethylamino chelate complexes for the others.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.     

Complexation of carboxylic acids and anions by alpha and beta cyclodextrins

A pH potentiometric method is used to measure complex formation constants of aqueous alpha- and/or beta-cyclodextrin with several carboxylic acids and carboxylate anions: butyric acid/butyrate; valeric acid/valerate; hexanoic acid/hexanoate; octanoic acid/octanoate; decanoic acid/decanoate; cyclohexanecarboxylic acid/cyclohexanecarboxylate and benzoic acid/benzoate. Standard enthalpies and entropies of complex formation are calculated from the temperature dependencies of the equilibrium constants. These thermodynamic parameters of the alpha-cyclodextrin complexes largely conform to a correlation based on complexes with other substrate species previously reported. Both standard enthalpies and entropies of formation of beta-cyclodextrin complexes are found to be more positive than the corresponding complexes of alpha-cyclodextrin with the same substrates. These observations lead to insights into the bonding mechanism of cyclodextrin complexation.     

环糊精包合作用对疏水缔合聚合物流变调节与应用

近年来,利用超分子作用力调节体系流变行为备受人们关注,已在多领域中展现出广泛的应用前景。而环糊精包合作用是一类重要的超分子作用力,向缔合聚合物水溶液中加入环糊精,将拆散缔合结构,引起粘度和粘弹性急剧下降;竞争客体或酶的加入又会诱导分子间发生新的组装行为,使体系流变性得到恢复。本文综述了基于环糊精包合作用的分子组装与流变调节在理论及应用方面的研究现状,重点介绍了环糊精对不同缔合聚合物溶液的流变影响规律和外加物质对体系流变恢复的调节。     

Syntheses of Polythioethers Tethered with Bulky Aryl Groups and Their Complexation with Late-Transition Metals

Abstract

New types of o-phenylene-bridged polythioethers tethered with extremely bulky aryl groups at their terminal sulfur atoms, such as TbtS(o-Phen)S(o-Phen)S(o-Phen)STbt (1) and TbtS(o-Phen)S(o-Phen)SS(o-Phen)S(o-Phen)STbt (2) (Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, o-Phen = o-phenylene), were synthesized and subjected to the complexation with several kinds of late-transition metals. In the case of polythioether 1, the reaction with RhCl₃·3H₂O in benzene/EtOH resulted in the formation of a unique bimetallic complex, in which a part of ligand 1 is lost and the resulting sulfur atom is directly bound to the other Rh metal center. Interestingly, similar treatment of 1 with IrCl₃·3H₂O afforded ethyl-coordinated mononuclear Ir complex. Furthermore, 1 underwent complexation with Na₂PdCl₄ in EtOH to give the corresponding square planar dichloropalladium complex coordinated with two inner sulfur atoms of 1, while the S₆-ligand 2 reacted with excess of Pd(PPh₃)₄ in benzene to afford a quite interesting trinuclear Pd complex multi-step metal insertion reactions.     

Synthesis and different molecular recognition of two dye-modified cyclodextrins with spacer of different length

Two β-cyclodextrin derivatives (1 and 2) bearing a hydroxyazobenzene unit, each having a butylene or a 4,7-dioxadecylene spacer between the cyclodextrin and the dye, were prepared, which showed guest-induced color changes with a marked difference in molecular recognition behavior in aqueous solution.     

Synthesis of novel modified p‐cyclodextrins and their fluorescence studies of inclusion complexation with Rhodamine B

Three novel β‐cyclodextrin derivatives have been synthesized and their inclusion complexation behavior with Rhodamine B (RhB) was investigated by the fluorescence spectroscopy.     

Circular dichroism spectra of the inclusion complexes of phlorizin in cyclodextrins

Two aromatic rings of a phlorizin molecule form inclusion complexes with -CD and -CD. Induced circular dichroism spectra of these complexes have been measured to estimate the orientation of the two aromatic rings in the hydrophobic space of CDs. Apparent complex formation constants have been also estimated for each complex. It is concluded that phlorizin forms a stronger inclusion complex with -CD than with -CD.     

Retention properties of cyclodextrins and modified cyclodextrins in reversed phase HPLC

Summary In the course of systematic studies on the solubility, hydrophobicity and complexation properties of cyclodextrins and modified cyclodextrins, the retention behavior of , , and of some glycosylated cyclodextrins has been examined by means of reverse phase HPLC. Mobile phase mixtures containing large amounts of water have been used because of the possible application of such systems to biological studies. Mobile phase mixtures with both methanol and acetonitrile show a linear relationship between the volume fraction of the organic part of the mobile phase and the logarithm of the capacity factor. The extrapolation of capacity factors to a total aquous system are used and compared to other techniques (including solubility) in order to evaluate the hydrophobic properties of the cyclodextrins. In particular, the solubility of cyclodextrins has been explored for a wide range of organic solvent/water mixtures. Whilst cyclodextrins are definitely the most hydrophobic, followed by glycosylated cyclodextrins, the others behave differently in the two mobile phase systems. The differences observed in the results are related to the chemical nature of the organic phase. Comparisons between chromatographic and solubility methods are given and interpretations are proposed. Some cyclodextrins have been modified to increase or modify not only the hydrophobicity but also the solubility, the complexation and the molecular recognition of drugs. The most important aim of this study was to define conditions and rules for further drug vectorization by cyclodextrin-drug complexation.     

The interactions of surfactant viologens with cyclodextrins

N-ethyl-N-hexadecyl-4,4-bipyridinium bromide (C₁₆VBr₂) andN-ethyl-N-octadecyl-4,4-bipyridinium bromide (C₁₈VBr₂) were used as electroactive probes to assess the interactions between surfactants and cyclodextrins. Cyclic voltammetry, visible spectroscopy, fluorescence spectroscopy and surface tension techniques were used to detect the formation of complexes between the surfactant viologen probes and- and-cyclodextrins. The voltammetric results suggest the formation of inclusion compounds in which the hydrophobic tail of the surfactant viologens penetrate the cyclodextrin cavity. The dimerization of the viologen cation radicals is essentially suppressed by the presence of-cyclodextrin (ACD) while no effects are observed in the presence of-cyclodextrin (BCD). The observed results are best explained by the relative solubility in aqueous media of each of the inclusion complexes in the several accessible viologen oxidation states.     

几种有机溶剂中15冠5及苯并15冠5与Mg~(2+)配合的NMR研究

本文用一维及二维NMR方法研究了溶剂对15冠5(15C5)和苯并15冠5(B15C5)与Mg~(2+)配合的影响。结果表明,在丙酮,乙腈,硝基甲烷,四氢呋喃以及氯仿中,冠醚与Mg~(2+)形成稳定的1:1配合物,且配合态与自由态冠醚间的化学交换在NMR标尺上为慢交换过程;而在二甲亚砜,二甲基甲酰胺,二甲基乙酰胺和吡啶中,由于溶剂对Mg~(2+)的竞争作用而使冠醚未能与Mg~(2+)有效配合。     

Comparative Study of the Inclusion Complexation of Pizotifen and Ketotifen with Native and Modified Cyclodextrins

The interaction of two benzocycloheptanes namely, pizotifen (Pizo) and ketotifen (Keto), with cyclodextrins (CDs: α-, β-, γ-, and HP-β-CDs) has been investigated by several techniques including phase solubility, X-ray powder diffractometry, ¹H-nuclear magnetic resonance and molecular mechanical modeling. The effects of CD type, pH, ionic strength and temperature on complex stability were also explored. The complex formation constant (K ₁₁) values for the Pizo/CD system follows the decreasing order β-CD > γ-CD > HP-β-CD > α-CD. However, for the Keto/CD system it follows the decreasing order γ-CD > β-CD > HP-β-CD > α-CD. The tendency of Pizo and Keto to complex with β-CD is driven to the extent of 70% by the hydrophobic effect. Complex formation of Keto and Pizo was substantially driven by entropy (>100 J⋅mol⁻¹⋅K⁻¹) but slightly retarded by enthalpy (3–8 kJ⋅mol⁻¹). ¹H-NMR and MM⁺ studies indicate multimodal inclusion of the methylpiperadine, thiophene and phenyl moieties into the β-CD cavity.     

Interactions of native and modified cyclodextrins with some B-vitamins

Interactions of native and modified α- and β-cyclodextrins with nicotinic acid, pyridoxine and pyridoxal were studied by isothermal titration calorimetry, solution calorimetry, and ¹H NMR spectroscopy at 298.15 K and pH 6.8. Weak 1:1 complex formation was found only between α-cyclodextrin and nicotinic acid. The stability constant and corresponding thermodynamic parameters of complex formation (Δ_c G, Δ_c H and Δ_c S) were calculated using the calorimetric data. The ¹H NMR data indicate the shallow insertion of the carboxylic group of the nicotinic acid molecule into α-CD cavity. For all other compounds the weak interactions, not accompanied by complex formation, were characterized by the enthalpic virial coefficients calculated on the basis of McMillan-Mayer approach. The obtained thermodynamic parameters were analyzed in the terms of influence of the solutes’ structure on the selectivity of intermolecular host-guest interactions.     

Determination of enantiomeric composition of samples by multivariate regression modeling of spectral data obtained with cyclodextrin guest-host complexes-Effect of an achiral surfactant and use of mixed cyclodextrins

The determination of the enantiomeric composition of samples by chemometric modeling of spectral data was investigated for samples of N,N′-bis-(-methylbenzyl) sulfamide and tryptophan methyl ester hydrochloride. Multivariate regression models (PLS-1) were developed from spectral data obtained on solutions containing N,N′-bis-(-methylbenzyl)sulfamide or tryptophan methyl ester hydrochloride in the presence of sodium dodecyl sulfate and mixed cyclodextrin host molecules. The regression models were subsequently used to predict the enantiomeric composition of laboratory-prepared test samples of N,N′-bis(-methylbenzyl)sulfamide or tryptophan methyl ester hydrochloride. The capability of the models to accurately predict the enantiomeric composition was evaluated in terms of the root-mean-square percent relative error (RMS %R.E.) as calculated from the results obtained with independently prepared validation sets of samples. It was found that the presence of SDS in most cases either had little effect on the predictive ability of the model or it actually reduced the predictive ability of the model. Moreover, it was found that the use of mixed CDs, either in the presence or absence of SDS, reduced the predictive ability of the regression model when compared with results obtained with individual CDs.     

Solvent‐dependent formation of inclusion complexes between methylated cyclodextrins and biodegradable polymers

The inclusion complexes (ICs) of unmodified natural and methylated α‐cyclodextrins (CDs) with biodegradable polymers, polyethylene glycol and poly(ε‐caprolactone), were prepared by two methods, that is, the one using water and the other using chloroform as the solvent for the respective CDs. The ICs obtained were characterized by IR, WAXD, DSC, and ¹³C CP/MAS NMR. It was found that the possibility and the phenomena of IC formation could be varied with the degree of methyl substitution of CD as well as the type of solvents used. Methylated α‐CDs showed the prominent characteristics of IC formation with polymers in the case where chloroform was used than in the case where water was used as the solvent for CDs, while vice versa in the case of native α‐CD. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 879–891, 2008     

气浮络合萃取分离富集L-苯丙氨酸的研究

结合溶剂浮选和络合萃取,提出了气浮络合萃取(floatation complexation extraction)的概念,应用该方法实现了对L-苯丙氨酸的分离富集。在试液的pH为11、NaCl浓度为0.20 mol/L、有机相为80%P204的正己烷溶液、通气流速为40 mL/min、通气时间为60 min的条件下对水相中L-苯丙氨酸进行气浮络合萃取。在分离富集的基础上,用pH<1的HCl水溶液对L-苯丙氨酸进行反萃取,通过紫外和红外光谱分析,确认了分离产物为L-苯丙氨酸。     

Complexation of N-alkyl(aryl)- and N,N-dialkylcarbamoylmethylphosphine oxides with the f-elements

Complexation of N-alkyl(aryl)carbamoylmethylphosphine oxides (CMPO) and their N, N-dialkyl analogs in neutral media was studied. N-Alkyl derivatives react with praseodymium and europium nitrates both in solution and in the individual state to give 1: 2 and 1: 3 complexes, depending on the ratio of the starting reagents; for N-aryl amides, 1: 3 complexes were obtained only. With the uranyl cation, both N-alkyl and N,N-dialkyl derivatives of CMPO form various 1: 1 complexes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1856–1862, September, 2008.     

Complexation of poly(ethylene glycol) with some salts of alkali-earth metals

The interaction of poly(ethylene glycol) with some salts of alkali-earth metals (Mg(ClO₄)₂, BaCl₂, SrCl₂, SrBr₂ and CaCl₂) in methanolic solutions was investigated by electroconductivity, viscometry, X-ray diffractometry and NMR. It was established that the conformation of macromolecules is strongly changed in the presence of Mg(ClO₄)₂. Chlorides and bromides of alkali-earth metals have a weak influence on macromolecule size. The formation of amorphous complexes in the PEG–Mg(ClO₄)₂ system and crystalline complexes in PEG–chloride systems of alkali-earth metals was shown.     

Complexation and Electronic Spectra of Neodymium(III)–Amino Acid–1,10-Phenanthroline Systems in Aqueous Solution

Complexation of neodymium(III)-glutamate(glu)-phenanthroline(phen), neodymium(III)-aspartate(asp)-phenanthroline(phen) ternary systems and the corresponding binary systems in aqueous solution are discussed at various values of pH. Based on change regularity of hypersensitive transition intensities, the neodymium(III)-aspartate-phenanthroline ternary complex has a general formula of Nd(asp)₃phen, but the composition of the complex of Nd(III) with glutamate and phenanthroline is complicated and has not been determined. The electronic spectra of these complexes were studied, Slater-Condon parametersF _k ^s and the Lande parameter ξ_4f were obtained. The rms deviation between calculated and observed energy levels is less than 43 cm⁻¹. Bonding in these complexes are also investigated and bonding parameters calculated. The results show that Nd(III) and amino acids form complexes by ionic linkage with carboxylic oxygens, but with some weak covalency. Besides, the degrees of covalency in ternary complexes are larger than those in binary complexes.     

复合发光材料[Eu（phen）2（NO3^-）]^2＋-MT的插层组装研究

合成了铕的邻菲罗啉配合物,并通过离子交换法将其配阳离子插层组装到了蒙脱土的片层间,制备出了一种超分子复合发光材料[Eu(phen)2(NO3-)]2 -MT。通过红外光谱、X射线衍射、热分析等手段对其进行了表征,并对其荧光性质进行了研究。结果表明,复合材料保持了蒙脱土良好的层柱结构特征,其单位质量稀土配合物的相对荧光强度较相应纯配合物有显著改善,复合材料片层间稀土配合物的热稳定性也较纯稀土配合物有所提高。     

含吡啶环大环多胺的合成及其与Cu(Ⅱ)的络合行为

本文以2,6-二溴甲基吡啶和对甲苯磺酰胺钠盐合成含吡啶环大环多胺,得到了尚未见文献报道的含四个吡啶环的三十二环胺. 2,6-二溴甲基-吡啶与甲苯磺酰胺钠盐在无水乙醇回流温度下得到1,9,17,25-四甲苯磺酰基大环多胺.用浓硫酸脱去N-甲苯磺酰基化合物的甲苯磺酰基, 生成标题大环多胺化合物. 配体与Cu(Ⅱ)的络合由紫外吸收光谱测定. 实验结果表明配体确与Cu^2^+以1:2络合成为双核络合物.