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用电导法研究了甲醇溶液中Na~ ,K~ ,Rb~ ,Cs~ 与新合成的冠醚2,3-苯并-8,15-二甲基-18C6,2,3-苯并-8,11,15-三甲基-18C6以及苯并-15C5,18C6的配位作用,计算了1∶1配合物的稳定常数.18C6对碱金属离子具有显著的选择性,而其二甲基及三甲基取代物的选择性则较差.冠醚环上引入苯环及甲基使配合物的稳定常数降低,在甲醇中碱金属离子与18C6配合物稳定性次序为K~ >Rb~ >Cs~ >Na~ ,2,3-苯并-8,15-二甲基-18C6配合物稳定性次序为K~ >Rb~ >Na~ >Cs~ ,2,3-苯并-18,11,15-三甲基-18C6配合物稳定性次序为K~ >>Na~ >Rb~ >Cs~ .引入甲基对Na~ 配合物稳定性的影响小于K~ ,Rb~ ,Cs~ ,即阳离子半径对配合物稳定性有较大的影响.在所研究的浓度范围内,碱金属离子-冠醚体系当量电导的降低程度与按配合物结构的预测一致.本文结果为设计具有特定选择性的冠醚结构提供了线索. 相似文献
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氮杂冠醚研究(Ⅵ)——含中心功能基氮杂冠醚的合成 总被引:1,自引:0,他引:1
含中心功能基的冠醚化合物及其对金属离子的络合行为,已有较多的报导。Cram等报导,在含芳环的冠醚中,苯环的1,3位有二个亚甲基单元占据时,处于2位上的甲氧基、羟基、硝基、卤素等带孤对电子的中心功能基,可以用来调节冠醚环的空腔大小,致使其对金属离子的络合选择性有所改变。由于氧杂冠醚对碱金属和碱土金属离子具有较好的络合作用,而对过渡金属和重金属离子等的络合行为则不甚满意。因此,以氮、硫等杂原子代替冠醚环中的氧原子时,会对过渡金属和重金属离子产生明显的络合效果。 相似文献
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亲脂性强的冠醚化合物对金属离子选择性高、络合性能好,是高效率的相转移催化剂。对于二苯并型大环冠醚,在其芳环上引入烷基是增强冠醚脂溶性的一种有效途径;在其冠醚的脂环上引入烷氧基是提高冠醚脂溶性的又一方便的方法。为此,我们将开链冠醚(Ⅰ)与环氧氯丙烷反应得到6-羟基二苯并-16-冠-5(Ⅰ)。(Ⅱ)转化为钠盐。钠盐分别和硫酸二甲酯及7种卤代烃缩合成一组带有6-烷氧基的二苯并型冠醚化合物Ⅲ_(a—h)。反应为: 相似文献
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本文报道以大环中性配体作为大块液膜载体时,冠醚结构对金属离子的传质选择性,以及迁移速度与配合物稳定常数之间的关系。实验结果表明,在一定的配合物稳定常数范围,其稳定常数越高,迁移速度也越快。对于4-取代苯并-15-冠-5类型的冠醚与Na~+的配合物,其配合物的稳定常数顺序与取代基的给电子或吸电子效应的强弱一致,而迁移速度与稳定常数的大小顺序一致。在影响着冠醚醚氧碱度的取代基效应的Hammett常数(δm+δ_P)同配合物稳定常数logk及离子迁移通量logJ之间存在着线性关系。对于其空腔直径与N_a~+相匹配的苯并-15-冠-5及空腔直径与K~+相匹配的苯并-18冠-6,当冠醚中的一个或两个1,2-亚乙基被1,3-亚丙基所代替而变成苯并-17-冠-5及苯并-19-冠-6时,其配合物的稳定常数减小,迁移速度也相应减小。 相似文献
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2,6-二羟甲基-4-氯苯甲醚(3)和2,6-二羟甲基-4-苯基苯甲醇(4)与三缩四乙二醇和四缩五乙二醇的二对甲苯磺酸酯在含有叔丁醇钾的无水四氢呋喃中反应生成甲氧基冠醚5—7。后者与过量无水碘化锂在无水吡啶中廻流有选择性地除去甲基而不影响大环苄醚基的破裂生成三种2’-羟基-1’,3’-亚苯基二甲基冠醚8—10,产率为85—89%。 相似文献
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用量热滴定法测定了2,3-二苯基-烯-[2]-1,4,7,10,13-五氧杂环十五烷(以下称2,3-二苯基-烯-[2]-15-冠-5)与稀土(Ⅲ)硝酸盐(La,Ce,Pr,Nd,Sm,Eu)在无水乙腈溶液中,298.15 K时配位作用的热力学性质.化学计量法表明,所有的稀土硝酸盐均与不饱和冠醚形成了1:1的配合物.实验中,由联接的计算机直接算出了配位物的稳定常数和配合作用的焓,进而算出了吉布斯自由能和配位熵. 结果表明,2,3-二苯基-烯-[2]-15-冠-5与Pr(NO_3)_3形成的配位化合物,其稳定常数最高,并与15-冠-5的实验结果作了比较.从热力学的观点讨论了不饱和冠醚分子结构和阳离子的性质对配位稳定性的影响. 相似文献
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H. D. Inerowicz J. Chojnacki A. Merz T. Futterer 《Journal of inclusion phenomena and macrocyclic chemistry》2000,38(1-4):123-132
The complexation reactions between the macrocyclic polyethers dibenzo-18-crown-6, benzo-18-crown-6, benzo-15-crown-5 and polyethers bearing a stilbene unit with alkali metal and silver cations have been studied conductometrically in nitromethane. The formation constants of 1 : 1 and 1 : 2 (metal : ligand) complexes were determined and found to decrease with increasing cation diameter. The stability of the stilbene crown – metal cation complexes is lower than for complexes of other investigated crown ethers with analogous cations. There seem to be some effects of double bond-silver ion interactions. 相似文献
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研究一种方法以测定二苯并-18-冠-6在氯仿中与碱金属苦味酸盐相互作用的若干参数。这些参数是:络合物的无限稀释摩尔电导 A_0,络合物的解离常数 K_d(或 k_d),络合物中冠醚与盐的分子比,冠醚对苦味酸盐的络合常数 K_c(或 k_c),以及冠醚存在下苦味酸盐紧密离子对的饱和浓度[MA]等。 相似文献
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H.-J. Buschmann E. Cleve L. Mutihac E. Schollmeyer 《Journal of solution chemistry》1998,27(8):755-759
The stability constants for the complexation of a diprotonated diamine, a diaza crown ether, and a cryptand with dibenzo-18-crown-6 and dibenzo-24-crown-8, have been studied in aqueous solution using a new spectrophotometric technique. Because of the complex formation, the solubility of the dibenzocrown ethers increases. Complex formation is possible between diamines and dibenzocrown ethers with both 1:1 and 2:1 stoichiometry. However, experimental data are insufficient to decide on the actual stoichiometry of the complexes formed. By computing the stability constants and comparing them with the corresponding results for monoamines, it is possible to decide on the actual stoichiometry of the complexes. Under the experimental conditions only 1:1 complexes with diamines are formed. 相似文献
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Wang Z Chang SH Kang TJ 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(2):313-317
Pyrene- and anthracene-appended new crown ether derivatives have been synthesized by Schiff's base reaction, and cation complexation behavior was investigated by fluorescence spectroscopy measurements. Based on photo-induced electron transfer and intramolecular charge transfer mechanism, the host molecules emit stronger fluorescence in the presence of various cations Na(+), K(+), Rb(+), Cs(+) and NH(4)(+) since the complexation between guest cations and crown ether compounds inhibit partial electron transfer from the nitrogen atom to the chromophores and subsequently fluorescence is enhanced. The binding constants were estimated from the plots of the fraction of binding sites filled for crown ether compound as a function of free-ion concentration. Results show that 15-crown-5 derivatives exhibit higher binding ability with sodium cations while 18-crown-6 derivatives had higher affinity for potassium cations, which is consistent with the hole-size relationship of the crown ethers. Ammonium ion complexation caused largest fluorescence enhancement. It is understood that ammonium ion cannot only complex with crown ether, but also interact directly with the lone pair electrons of nitrogen atom in C=N bond so that electron transfer from the nitrogen atom to chromophores is further inhibited. 相似文献
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Tzeli D Petsalakis ID Theodorakopoulos G 《Physical chemistry chemical physics : PCCP》2011,13(3):954-965
The electronic and geometric structures of dibenzo-12-crown-4, dibenzo-18-crown-6, and dibenzo-24-crown-8 ethers, and dibenzo-18-crown-6 ether of fullero-N-methylpyrrolidine and their complexes with (CH(3))(x)NH+(4-x), x = 0-4 were investigated by employing density functional theory (B3LYP, M05-2X, M06-2X, MPWBIK and B2PLYP-D) in conjunction with three basis sets. Different energetic minima have been identified for all of the above molecules and complexes in the gas phase as well as in CHCl(3) solvent. We report geometries, complexation energies and some thermochemical data. For increasing values of x, the complexation energies, corrected for the basis set superposition error range from 3.29 to 0.73 eV in the gas phase and from 1.56 to 0.13 eV in the CHCl(3) solvent. In the case of the largest crown ethers, the 24-crown-8 ethers are folded around the ammonium cation so as to maximize the number of hydrogen bonds formed and present the largest complexation energies. Finally, the presence of fullero-N-methylpyrrolidine, attached to the crown ethers, does not change the complexation energies substantially. 相似文献
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Rahul M. KOTKAR 《Supramolecular chemistry》2013,25(6):545-552
The complexation behavior of nicotinamide with macrocyclic polyethers viz, 15-crown-5, benzo-15-crown-5, 18-crown-6, dicyclohexano-18-crown-6, dibenzo-18-crown-6, dibenzo-24-crown-8, 1,4,7,10,13,16-hexathiacyclooctadecane, monoaza-15-crown-5, 1,4,10-trioxa-7,13-diaza-cyclopentadecane, 5,6,14,15-dibenzo-1,4-dioxa-8,12-diazacyclopentadecane, 7,16-dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane, 1,4,7-tritosyl-1,4,7-triazacyclononane, 1,4,7,10-tetratosyl-1,4,7,10-tetraazacyclododecane and 1,4,8,11-tetraazacyclooctadecane has been studied in dimethylsulphoxide (DMSO) and 90% DMSO + water using differential pulse polarography and complexation constants have been reported. Nicotinamide forms stable complexes with six-membered coronand rings of the crown ethers. The nature of the atoms (oxygen, sulfur and nitrogen) in the coronand ring is observed to affect the stability of the complex. The stoichiometry and stability constants of the complexes were determined by monitoring the shifts in peak potentials of the polarograms of nicotinamide against the ligand concentration. The Gibbs free energy change turns out to be negative at 25°C, which indicates the spontaneity of the binding of nicotinamide with crown ethers. The mole ratio of nicotinamide to the macrocyclic compound was also determined and it was found that the complexes were of 1:1 type with respect to crown ethers. The tendency of nicotinamide to form complexes with macrocycles is found to be greater in DMSO than in DMSO + water. 相似文献
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双冠醚配位作用的热力学性质V. 双(苯并-15-冠-5)与稀土(III)硝酸盐在无水乙腈溶液中分子内夹心配位作用 总被引:1,自引:1,他引:0
本文用分光光度滴定法测定了双(苯并-15-冠-5)(1)与轻稀土(III)硝酸盐在无水乙腈溶液中, 20.0-35.0℃时分子内夹心配位作用的稳定常数, 进而计算了配位焓和配位熵, 并与母体苯并15-冠-5(2)的实验结果作了比较。化学计量法表明, 所有稀土硝酸盐均与双(苯并-15-冠-5)形成了1 : 1的配合物。从热力学的观点, 讨论了双冠醚分子结构、尺寸效应和空间构型等配位稳定性的影响。研究结果发现, 双冠醚(1)对于Eu^3^+具有较强的配位能力和配位选择性, Nd^3^+次之。配合物的稳定性主要来自于熵的贡献。 相似文献
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The overall extraction equilibrium constants (K(ex)) of picrates of Li(+), Na(+), K(+), Rb(+), Cs(+), Ag(+), Tl(+), and Sr(2+)with 19-crown-6 (19C6) were determined between benzene and water at 25 degrees C. The K(ex) values were analyzed into the constituent equilibrium constants, i.e. the extraction constant of picric acid, the distribution constant of the crown ether, the formation constant of the metal ion-crown ether complex in water, and the ion-pair extraction constant of the complex cation with the picrate anion. The effects of an extra methylene group of 19C6 on the extraction ability and selectivity are discussed in detail by comparing the constituent equilibrium constants of 19C6 with those of 18-crown-6 (18C6). The K(ex) value of 19C6 for each metal ion is lower than that of 18C6, which is mostly attributed to the higher lipophilicity of 19C6. The extraction ability of 19C6 for the univalent metal ions decreases in the order Tl(+)>K(+)>Rb(+)>Ag(+)>Cs(+)>Na(+)Li(+), which is the same as that observed for 18C6. The difference in logK(ex) between the univalent metals is generally smaller for 19C6 than for 18C6. The extraction selectivity of 19C6 is governed by the selectivity in the ion-pair extraction, whereas that of 18C6 depends on both the selectivities in the ion-pair extraction and in the complexation in water. 相似文献