Transport of alkali-metal picrates through liquid membranes: Coupled action of w/o microemulsion droplets and lipophilic crown-ether carriers

The transport of potassium and sodium picrates is measured by a liquid membrane technique in the presence of two mobile carriers: water-in-oil microemulsion droplets and lipophilic crown-ethers. The fluxes are compared for two cases: (i) the crown-ether (dicyclohexano-18-crown-6 is assumed to be independent of the microemulsion droplet and (ii the crown-ether (dodecano- 18-crown-6) is assumed to be anchored in the droplet. A lower flux is observed when the microemulsion droplet and the crown-ether diffuse as a single entity. These results suggest that larger synergistic effects are obtained when the extractant can diffuse independently of the microemulsion droplet.     

Crown-containing spironaphthoxazines and spiropyrans. 3. Synthesis and investigation of the merocyanine form of crown-containing spirobenzothiazolinonaphthoxazine

A method for the synthesis of the spirobenzothiazolinonaphthoxazine, stable in the merocyanine form and containing a crown-ether fragment was developed. The complexing properties of the prepared merocyanine compound and the spectroscopic and photochromic characteristics of its complexes with alkaline earth metal cations were studied by NMR and UV spectroscopy. The results were analyzed using quantum-chemical calculations. The addition of alkaline earth metal perchlorates to a solution of a crown ether-containing merocyanine dye in MeCN results in the coordination of metal cations to two binding centers, namely, the crown-ether fragment and the merocyanine oxygen atom. This gives rise to two types of complexes, which differ substantially in their structurally. The complexation induces changes in the UV spectra and influences on the photochromic behavior of the prepared compound.     

Coordination and structural studies of crowned-porphyrins

Simple chelating agents have been synthesized using a porphyrin and a covalently linked crown-ether. Depending on the relative spatial arrangement of both motifs, the resulting ligands, either a macrotricycle or bis-macrocycles, differ one from another by their flexibility or their aptitude to chelate bivalent or trivalent cations. The coordination chemistry as well as the structural study of these ligands and complexes are reported. In the particular case of the macrotricycle, the crown-ether motif, perpendicular to the porphyrin induces a side selectivity for the coordination of lead(II) outside the cavity. Furthermore, the coordination of zinc(II) implies a change of conformation of the ligand in which the crown-ether is parallel to the porphyrin.     

单冠醚取代酞菁形成的络合物中的荧光猝灭

在溶液中,单冠醚取代酞菁依靠冠醚的络合作用可以和含碱金属离子的受体分子形成络合物．这种络合物的形成有利于酞菁和受体分子间的光致电子转移反应,使得酞菁的荧光被强烈地猝灭．根据体系的化学平衡和酞菁荧光被受体分子猝灭的机制建立了数学模型,运用实验数据和最小二乘法曲线拟合得到了酞菁和受体分子形成的络合物的稳定常数．     

Synthesis of crown-containing 2-styrylbenzothiazoles. Effect of alkali metal cations on the condensation of crown-ether benzaldehydes with 2-methylbenzothiazole

Methods for the synthesis of unknown 2-styrylbenzothiazoles containing crown ether moieties with different combinations of O, S, and N-heteroatoms based on the Wittig reaction or condensation of 2-methylbenzothiazole with crown-ether benzaldehydes in the presence of strong bases or acids are proposed. The condensation in the presence of bases is accompanied by complex formation with participation of the crown ether moiety of the benzaldehyde. The complex formation has a pronounced influence on the yield of the target product and the pattern of condensation of 2-methylbenzothiazole with crown-ether benzaldehydes.     

模式识别用于压电晶体传感器阵列定量检测有机蒸汽混合物

本文应用9个压电晶体组成传感器阵列, 每片晶体上分别涂有不同种类的冠醚衍生物, 用它来定量检测二元及三元有机蒸汽混合物, 在数据处理中比较了两种模式识别方法---偏最小二乘法(PLS)和人工神经网络法(ANN), 实验证明, ANN法在预测准确度上明显优于PLS法, 本文还讨论了解决神经网络训练过拟合现象的方法。     

Crown-ether annelated dithiadiazafulvalenes

The synthetic approaches towards crown-ether annelated dithiadiazafulvalenes (DTDAF) are described. As evidenced by electrochemistry, the reaction of N,N′-bridged-bisthiazolium salts in basic medium favors the formation of the DTDAF via an intramolecular coupling while the reaction of N,N′-bridged-bisthiazoline selone with trivalent phosphorus derivative leads to the donor core via an intermolecular coupling. The complexation of various metal cations on these crown-ether annelated DTDAF is investigated by electrochemistry.     

新型四硫富瓦烯硫杂冠醚衍生物的合成

在高度稀释条件下, 经4,5-二溴甲基-1,3-二硫杂环戊烯-2-硫酮(7)和多缩乙二醇的1,ω-二巯基衍生物的缩合反应, 方便地合成了4,5-位带二硫杂冠醚残基的2-硫代-1,3-二硫杂环戊烯的衍生物8a～8d, 中间体硫杂冠醚8c～8d的合成中有明显的“模板效应”. 在亚磷酸三乙酯存在下, 8a～8d经自偶联生成新型的对称双臂四硫富瓦烯(TTF)硫杂冠醚衍生物10a～10d, 而与4,5-二甲硫基-1,3-二硫杂环戊烯-2-酮(9)经交叉偶联生成新型的非对称单臂四硫富瓦烯硫杂冠醚衍生物11a～11d. 用循环伏安法研究了上述目标化合物的电化学性质和离子传感性质.     

Photochemical ion receptor based on a structurally distorted ruthenium(II) complex having a crown-ether moiety at the 3,3'-positions on the 2,2'-bipyridine ligand.

Ru(bpy)2(CE-bpy)2+ was prepared where bpy and CE-bpy were 2,2'-bipyridine and bpy having a crown-ether moiety at the 3,3'-positions, respectively. Although Ru(bpy)2(CE-bpy)2+ showed only very weak emission in acetonitrile, recognition of Na+, Li+, or K+ by the crown-ether moiety in CE-bpy resulted in increases in both the emission intensity and the lifetime of the complex, demonstrating that it acted as a photoreceptor. The results were discussed in terms of a steric hindrance between the 3,3'-substituents on CE-bpy and structural changes in both CE-bpy and the complex upon ion recognition, as studied by variable-temperature 1H-NMR and steady-state/dynamic emission spectroscopy of the complex.     

A (H2O)4/crown ether network spanned between organometallic complex metal fragments

[Mo(eta3)-C3H5)(CO)2(bipy*)Cl] undergoes trigonal twist rearrangements in solution, so that three isomers are coexisting. It was used as a starting material leading to a dinuclear complex containing a hydrogen-bonded network of H(2)O and crown-ether molecules between two Mo(eta3-C3H5)(CO)2(bipy*) moieties.     

Controlled synthesis and alkaline earth ion binding of switchable formamidoxime-based crown ether analogs

The partial positive charge of amide protons is used to promote macrocyclization and form crown-ether analogs. Their deprotonation generates very selective pH-switchable alkaline earth ion receptors only in the presence of an appropriate substrate.     

Extraction chromatographic separation of radionuclides of strontium,cesium and barium with the use of TVEX-DCH18C6

Extraction chromatographic behaviour of cesium, barium and strontium on TVEX impregnated by crown-ether dicyclohexyl-18-crown-6 was studied. Data obtained were used as the base of the technique of radiostrontium isolated from environmental objects.     

Crown-ether functionalised second coordination sphere palladium catalysts by molecular imprinting

Functionalisation of the second coordination sphere of a molecularly imprinted Pd complex was achieved by localising within the polymeric cavity a crown-ether receptor capable of altering the catalytic activity of the reactive site.     

Exemple de reaction a l'interface solide-liquide: oxydation de naphtalenediols par le superoxyde de potassium

The oxidation of 1,2 and 1,3-dihydroxynaphtalenes with potassium superoxide in aprotic media is a heterogeneous to reaction at the solid-liquid interface, leading to the 2-hydroxy-1,4-naphtoquinone with good yields even if the addition of crown-ether is omitted.     

Organic chemosensors with crown-ether groups (review)

Recent advances in the chemistry of organic chemosensors containing crown-ether groups are reviewed. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1123–1151, August, 2008.     

Synthesis of crown-containing xanthine derivatives

A number of new derivatives of xanthine, hypoxanthine, theophylline, and theobromine containing crown-ether substituents at the nitrogen atoms of the imidazole or pyrimidine nucleus was synthesized. Translated from Khimiya Geterot-siklicheskikhTranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1266–1269, September, 1992.     

Photosensitive supramolecular systems based on amphiphilic crown ethers

An amphiphilic crown-ether styryl dye was synthesized and its properties at the interfaces were investigated. This dye, which in monolayers interacts with some cations and shows reversible changes of the light reflection after photoactivation near the absorption maximum, is an excellent component of functional organized systems.     

Finkelstein Reaction in Functionalized Crown-ether Ionic Liquids

Recent years, crown ethers have been used in many fields, including phase transfer catalysis, chromatography stationary phase, ionselective electrode, and concentration of metal ions, etc1.. However, the toxicity of free crown ethers makes them unsuitable for industrial use2. Introduction of a crown ether as a functional group to functionalized ionic liquids has been reported3. These functionalized ionic liquids will combine the excellent properties of crown ether and ionic liquids without los…     

Crown-containing spirooxazines and spiropyrans

Methods for the synthesis of new spironaphthooxazines containing an aza-15-crown-5 fragment in two different positions (5′ and 9′) were developed. The spectral and photochemical properties of these compounds suggest that two competitive complexation processes occur with alkaline-earth or rare-earth metal cations differing in efficiency and selectivity. A metal cation occupies the optimum position in the crown-ether cavity with respect to the donor oxygen atom of the merocyanine form of the dye and thus can affect more strongly its spectral and photochemical properties than in the case of intermolecular interaction. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1974–1983, October, 1999.     

Polymerization and molecular recognition in the monolayers of the surface-active derivatives of crown-ethers

The four surface-active derivatives of crown-ethers with a variety of fatty alkyl chains were synthesized and studied in monolayers at various conditions. The areas per crown-ether molecule in monolayers are increasing significantly in the presence of various alkali metal cations in the aqueous subphase. These effects can be explained as complex formation between crown-ethers in the monolayers and cations from aqueous subphase, causing a change in the conformation of the polyether ring of the molecule at the interface. This is accompanied with the change in the cation selectivity (Na⁺ > Li⁺ > K⁺ > Cs⁺) as compared with the series in volume (K⁺ > Cs⁺ > Na⁺ > Li⁺). Polymerization of the crown-ether monolayer allows to stabilize the conformation of the molecule at the interface as if tuned to the definite cation.