冠醚与碱金属苦味酸盐在氯仿中形成络合物的电导

测定了氯仿中碱金属苦味酸盐——冠醚络合物的电导率及络合比。确定了体系中电导率、冠醚浓度和络合比之间的关系。讨论了这些结果的某些应用。     

冠醚与轻稀土苦味酸盐配合物的合成和性质

冠醚对稀土苦味酸盐的萃取研究已有较多报道,但与萃取过程密切相关的冠醚与稀土苦味酸盐配合物的研究却报道不多,本工作合成了文献中尚未见报道的轻稀土苦味酸盐RE(Pic)_3(RE=La、Pr、Nd、Sm、Eu和Gd)与18-冠-6(18C6)的固体配合物并研究其组成和性质。     

4'-取代苯并-15-冠-5-苦味酸分子络合物的核磁共振研究

研究了15种4'-取代苯并-15-冠-5-及其与苦味酸所形成的电荷转移络合物的~1HNMR,测定了其中12种络合物的络合常数.络合常数,参考线RFL-[D]的斜率以及络合物前后4'-取代苯并-15-冠-5-各类质子与苯并-15-冠-5-相应的质子化学位移之差△δ均与Hammett取代基常数[σ~p+σ~m]呈线性关系.根据取代基对各类质子化学位移变化的影响.讨论了有关化合物的结构与性能的关系.     

质子化4，4＇-联吡啶盐与二苯并-24-冠-8的包合行为

通过^1HNMR,ESI—MS,紫外-可见光谱等分析手段研究了两个新的质子化联吡啶盐客体与冠醚二苯并-24-冠-8在溶液中和气态下的包合行为．研究结果表明,质了化的联吡啶盐与冠醚主要形成1：1的超分子包合物,且存在夹心式的几何结构,双质子化的联吡啶盐比单质子化的联吡啶盐具有更强的结合冠醚的能力,其缔合常数分别为200,116L·mol^-1．     

质子化4,4’-联吡啶盐与二苯并-24-冠-8的包合行为

通过1H NMR, ESI-MS, 紫外-可见光谱等分析手段研究了两个新的质子化联吡啶盐客体与冠醚二苯并-24-冠-8在溶液中和气态下的包合行为. 研究结果表明, 质子化的联吡啶盐与冠醚主要形成1∶1的超分子包合物, 且存在夹心式的几何结构, 双质子化的联吡啶盐比单质子化的联吡啶盐具有更强的结合冠醚的能力, 其缔合常数分别为200, 116 L•mol－1.     

4′-取代苯并-15-冠-5-苦味酸分子络合物的核磁共振研究

研究了15种4＇-取代苯并-15-冠-5及其与苦味酸所形成的电荷转移络合物的~1H NMR,测定了其中12种络合物的络合常数。络合常数、参考线REL～[D]的斜率以及络合前后4＇-取代苯并-15-冠-5各类质子与笨并-15-冠-5相应的质子化学位移之差△σ均与Hammett取代基常数[σ_p σ_m]呈线性关系。根据取代基对各类质子化学位移变化的影响,讨论了有关化合物的结构与性能的关系。     

稀土冠醚配合物的研究 Ⅸ.苯并-15-冠-5及4′-硝基苯并-15-冠-5对稀土离子的配合作用

冠醚稀土固体配合物的研究已有些报道,我们亦曾合成了苯并-15-冠-5的衍生物的稀土盐固体配合物,而关于冠醚对于稀土离子在溶液中的配合反应的研究尚较少.本工作采用离子选择性电极测定冠醚配合物稳定常数的方法,研究了苯并-15-冠_5(L_1)及4’-硝基苯并-15-冠-5(L_2)在甲醇溶液中对十种稀土离子的配合反应,按形成1∶1配合物计算了它们的稳定常数,并就与稀土离子半径相近的钙离子、钠离子在相同的实验条件下的竞争配合能力进行了讨论.     

双冠醚研究(Ⅳ)——Schiff碱型和仲胺型双-(苯并15冠-5)对碱金属苦味酸盐的萃取行为

仲胺型双冠醚与四苯硼酸碱金属盐在丙酮溶液中。25℃下的电导说明它们与Na~+可能形成1∶1络合物(冠醚单元∶金属离子),而与K~+、Rb~+、Cs~+离子则形成2∶1络合物。用Schlff碱型和仲胺型双-(苯并15-冠-5)在水-氯仿体系中进行萃取,测量了分配比D和萃取平衡常数K,发现后者的K值均大于前者。双冠醚F_2对K~+的萃取能力最强,选择性最佳。     

18-冠-6·硝酸稀土络合物的热分析

大环聚醚(冠醚)化合物是一类很有发展前途的络合剂,可以和很多种金属盐形成较稳定的络合物,它们与稀土盐类的络合作用可望在稀土元素的分离中得到应用。我们采用了热差(DTA)、热重(TG)等分析方法,并辅以红外光谱分析,较系统地研究了大环聚醚18-冠-6与除 Ce、Pm(没有样品)以外的镧系稀土硝酸盐所形成络合物的热分解行为,观察了这些络合物热分解的特点以及络合物稳定性的差别,和与中心原子     

质谱法研究气相中18-冠醚-6与氨基酸的非共价相互作用

利用电喷雾电离质谱研究了在气相条件下18-冠醚-6与20余种天然氨基酸及其异构体间的非共价相互作用。定性结果表明,在气相中18-冠-6可以与氨基酸形成化学计量比为1∶1的非共价复合物。配制一系列不同浓度的18-冠-6分别与固定浓度的氨基酸反应,利用质谱测得反应物和产物的质谱峰,计算冠醚分别与L-苯丙氨酸、L-酪氨酸、L-赖氨酸和L-天冬氨酸反应的复合物结合常数lg Ka分别为3.90、3.75、4.06和3.64,基于此建立了校准曲线。通过竞争反应实验,以上述4种氨基酸与冠醚复合物的结合常数为参考值,可推算得到其余氨基酸与冠醚的结合常数。实验结果表明,冠醚-氨基酸复合物的稳定性与氨基酸的种类相关,节碱性氨基酸以及侧链是烷基(或氢原子)的氨基酸对冠醚的亲和性更好,而酸性氨基酸(如L-丝氨酸)以及侧链上有酰胺键的氨基酸,对冠醚的亲和性较低。研究了18-冠-6对L型氨基酸及其D型异构体的手性选择性,结果表明,18-冠-6只能识别部分中性氨基酸。     

Alkali cation binding of polymers with different sized crown ethers and photodimerizable units

The polymers which have different sized crown ethers as alkali cation binding sites and photodimerizable cinnamoyl units were prepared by the cationic copolymerization of corresponding monomers. The crown–cation complexation ratio (1:1 or 2:1) was investigated by measuring quantum yields ? of the photodimerization of the crown-connected cinnamoyl units in the presence of alkali metal chlorides and also by measuring the shift of λ_max of alkali metal picrates in THF on addition of the crown polymers. A significant 1:2 complex formation of alkali cations with two different sized crown ether units in the side chain of the polymers was confirmed. The alkali metal cation binding ability and selectivity of the polymers, which were studied by a method of picrate salts extraction, were markedly different from those expected from the combination of polymers of same ring-size crown ether units. When irradiated with ultraviolet (UV) light, the cinnamic acid ester groups of the polymers caused dimerization even in dilute solutions. The cation binding ability of the polymers was largely enhanced by the photodimerization of the cinnamoyl moieties with suitable template cations.     

Ion binding properties of poly(ethylene oxide)-based networks in dioxane and toluene

Binding constants of alkali picrates to poly(ethylene oxide)-based networks were measured spectrophotometrically in dioxane at 25 and 40°C. The networks were synthesized from aliphatic tri- or tetrafunctional isocyanates and α,ω-diamino-poly-(ethylene glycol)s. The slopes of the Klotz binding plots appear to decrease in the lower picrate concentration range, suggesting that binding of the salt becomes more difficult at high picrate content. It was shown that under saturation conditions six to seven ethylene oxide units are required to bind a sodium picrate ion pair. The affinity of the PEO-resins for the alkali picrate can be enhanced by immobilizing a poly(crown ether) in the network. A number of competition experiments for sodium picrate in toluene was also carried out to obtain the affinity of soluble ligands for alkali salts. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1819–1824, 1997     

Mono-, bis-, and tris(crown ether)s assembled around 1,3,5-triaroylbenzene scaffolds

A concise and experimentally straightforward method for assembling multiple benzo(crown ether) units around 1,3,5-triaroylbenzene scaffolds has been developed. Symmetrical tris(crown ether)s possessing three benzo(15-crown-5) or three benzo(18-crown-6) peripheral substituents have been prepared in good yield via cyclotrimerization of monomeric enaminones. Efficient cross-cyclotrimerizations have also been demonstrated through construction of unsymmetrical triaroylbenzenes functionalized with only one or two benzo(15-crown-5) moieties. The alkali cation-binding abilities of these mono- and polytopic crown ethers have been probed through picrate extraction experiments and isothermal titration calorimetry. Thermodynamic binding parameters uncovered using the latter technique reveal increasing K+/Na+ selectivity in the benzo(15-crown-5) series of compounds as a function of increasing numbers of benzo(crown) units. The data also indicate that the triaroylbenzene-derived bis- and tris-crown ethers do not engage in intramolecular chelation of cations too large to be accommodated by individual crown macrorings. Instead, cation/triaroylbenzene stoichiometries and binding profiles indicate formation of alkali metal-bridged dimers.     

Polysalt complexes of poly(vinylbenzo-18-crown-6) and of poly(crown acrylate)s with polyanions

Macrocyclic polyether or crown ether ester derivatives of acrylic and methacrylic acid were synthesized and polymerized. The cation binding properties of the polymers determined by extraction of picrate salts were similar to those obtained for poly(crown ether)s derived from styrene. In the presence of a crown-complexable cation both polymers form insoluble polysalt complexes with sodium carboxymethylcellulose, potassium poly(styrene sulfonate), and potassium polyacrylate. The extent of precipitation depends on the type and concentration of cation as well as on the ratio polyanion to poly(crown ether). The precipitate appears to have an equal number of positive and negative charges. An insoluble hydrogen-bonded complex is formed in the absence of salt when poly(vinylbenzo-18-crown-6) and poly(acrylic acid) are mixed in 0.01M HCl. Organic solutes bound to the poly(crown ether)s, which occur in an aqueous mixture of poly(vinylbenzo-18-crown-6) and picrate anions, are precipitated with the poly(crown ether) when the polysalt complex is formed.     

A new fluorescent calix crown ether: synthesis and complex formation with alkali metal ions

We synthesised a new N-benzylaza-21-crown-7 ether 5 with a dihydroxy coumarin as a fluorescence sensor and investigated the binding behaviour towards alkali metal cations in methanol by fluorescence titrations. The association constants are within one order of magnitude, with the exception of sodium. Potassium is the preferred binding partner (K(Na)=330 M(-1); K(K)=8600 M(-1); K(Rb)=8200 M(-1); K(Cs)=4400 M(-1)). The corresponding aza-21-crown-7 ether (6) was attached by a methylene unit to a resorcarene to give fluorescent calix crown ether 12. The binding abilities of the calix crown ether towards alkali metal ions in methanol have also been investigated, and an increasing complex stability, distinct for potassium and rubidium in comparison with 5, was found: K(Na)=440 M(-1); K(K)=110,000 M(-1); K(Rb)=63,000 M(-1); K(Cs)=20,000 M(-1). Like bis(crown ether)s, a cooperative complexation of the crown ether and the cavitand scaffold can be assumed. The proposed complex geometry is supported by Kohn-Sham DFT calculations for the potassium and caesium complexes.     

Dendritic effects of crown ether-functionalized dendrimers on the solvent extraction of metal ions

The ability of a series of crown ether-functionalized dendrimers to function as alkali metal picrate extraction agents is assessed by liquid-liquid extraction and ¹H NMR titration experiments. Crown ether-functionalized dendrimers that contain Fréchet-type poly(benzyl ether) dendrons of different generation as building blocks display different extraction characteristics toward alkali metal cations. Positive and negative dendritic effects depending on the generation of the dendrimer are assigned in the complexation behaviour of the dendritic host compounds.     

Synthesis,alkali metal picrate extraction,and alkali metal cation binding selectivities of some new cage‐annulated polyoxamacrocyclic crown ethers

Five new cage‐annulated crown ethers, i.e., 4a, 4b, 6b, 11a, and 11b, have been synthesized and their respective alkali metal picrate extraction profiles along with that of a previously synthesized host molecule, 6a, have been obtained. These results are compared with the corresponding results obtained for electrospray ionization mass spectrometric (ESI‐MS) measurements of relative binding selectivities displayed by the same hosts toward a series of alkali metal chlorides. Among the crown‐5 hosts studied, 6a displays enhanced avidity toward complexation with K⁺ picrate in liquid‐liquid extraction experiments. Among the three crown‐6 hosts, 4b proved to be the best alkali metal picrate extractant and displayed significant levels of avidity toward complexation with the larger alkali metal cations (i.e., K⁺, Rb⁺, and Cs⁺). The trends in the picrate extraction and the ESI‐MS results obtained herein show several notable similarities and some differences. The similarities generally stem from size‐selective binding properties that are intrinsic to the different cavity sizes of the cage‐annulated macrocycles, whereas the differences reflect the important influence of solvation effects on the binding properties of the macrocycles.     

Cyclitol based metal complexing agents. Preference for the extraction of lithium by myo-inositol based crown-4-ethers depends on the relative orientation of crown ether oxygen atoms

myo-Inositol derived crown-4-ethers in which two of the oxygen atoms in the crown ether moiety have different relative orientations were prepared. Metal picrate binding studies revealed that the crown ether having 1,3-diaxial orientation shows the highest selectivity for binding to lithium although the crown ether having 1,2-diequatorial orientation exhibited the highest binding constant for lithium picrate. These results suggest that relative binding affinity of metal ions to crown ethers can be tuned by varying the relative orientation of crown ether oxygen atoms. The relevance of these results to the previously observed regioselectivity during the O-substitution of myo-inositol orthoesters is discussed.     

Synthetic, structural, and theoretical investigations of alkali metal germanium hydrides--contact molecules and separated ions

The preparation of a series of crown ether ligated alkali metal (M=K, Rb, Cs) germyl derivatives M(crown ether)_nGeH₃ through the hydrolysis of the respective tris(trimethylsilyl)germanides is reported. Depending on the alkali metal and the crown ether diameter, the hydrides display either contact molecules or separated ions in the solid state, providing a unique structural insight into the geometry of the obscure GeH₃^? ion. Germyl derivatives displaying M? Ge bonds in the solid state are of the general formula [M([18]crown‐6)(thf)GeH₃] with M=K ( 1 ) and M=Rb ( 4 ). The compounds display an unexpected geometry with two of the GeH₃ hydrogen atoms closely approaching the metal center, resulting in a partially inverted structure. Interestingly, the lone pair at germanium is not pointed towards the alkali metal, rather two of the three hydrides are approaching the alkali metal center to display M? H interactions. Separated ions display alkali metal cations bound to two crown ethers in a sandwich‐type arrangement and non‐coordinated GeH₃^? ions to afford complexes of the type [M(crown ether)₂][GeH₃] with M=K, crown ether=[15]crown‐5 ( 2 ); M=K, crown ether=[12]crown‐4 ( 3 ); and M=Cs, crown ether=[18]crown‐6 ( 5 ). The highly reactive germyl derivatives were characterized by using X‐ray crystallography, ¹H and ¹³C NMR, and IR spectroscopy. Density functional theory (DFT) and second‐order Møller–Plesset perturbation theory (MP2) calculations were performed to analyze the geometry of the GeH₃^? ion in the contact molecules 1 and 4 .     

Azidocryptands-synthesis, structure, and complexation properties

Cryptands bearing an intraannular azido substituent have been synthesized and characterized spectroscopically. Their complexation properties were investigated by picrate extraction analysis. The oxygen-containing cryptands were found to be good ligands for alkali cations, with a preference for Li(+) and Na(+). The molecular structure of the complex with KBr was determined by X-ray crystallography. In this, the first structurally characterized complex of an aryl azide bound to a metal cation, the potassium cation was found to show ninefold coordination to four oxygen atoms and two nitrogen atoms of the crown ether moiety, to the bromide anion and to N1 of the azido group, as well as C1 of the benzene ring.