Thermodynamics of Solvation of 18-Crown-6 and Its Alkali-Metal Complexes in Various Solvents

Heats of solution of 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) in acetonitrile, 1,2-dichloroethane, N,N-dimethylformamide, dimethyl sulfoxide, nitromethane, propylene carbonate, pyridine and water were measured at 25 °C and the enthalpies of the transfer of 18-crown-6 from waterto the aprotic solvents were derived. The thermodynamic quantities, G₁°, H₁° and T S₁°, for the formation of the[M(18-crown-6)]⁺ (M⁺ = Na⁺, K⁺, Rb⁺, Cs⁺, NH₄ ⁺) complexeswere determined by titration calorimetry in dimethyl sulfoxide containing0.1 mol dm^-3 (C₂H₅)₄NClO₄ as a constant ionic medium at 25 °C. These thermodynamic quantities suggest that the complexationof 18-crown-6 with the alkali-metal ions mainly reflects the different solvationof 18-crown-6 and also the different degree of solvent structure.     

The Complexation of Some Amino Acids by Isomers of Dicyclohexano-18-Crown-6 and 18-Crown-6 in Methanol

The complexation of some amino acids (glycine, L-alanine,L-leucine, L-valine, and L-serine) by the cis-syn-cisand cis-anti-cis isomers of dicyclohexano-18-crown-6 (DC18C6) in methanol was studied by calorimetric titrationmeasurements. Both isomers exhibited a significant ability to bind the amino acidsmentioned above. The results obtained demonstrate that the structural isomers ofDC18C6 are significantly different in terms of thermodynamics concerning their complexationwith the amino acids. The stability constants and the thermodynamic data forthe reaction of the amino acids under study in protonated form and 18-crown-6 (18C6) are reported.     

二苯并-18-冠-6在交联聚乙烯醇微球表面的固载化

通过氯甲基化反应,将冠醚二苯并-18-冠-6(DBC)转变为氯甲基化的冠醚(CMDBC),使交联聚乙烯醇(CPVA)微球表面的羟基与CMDBC之间发生亲核取代反应,从而实现冠醚的固栽化,制得了固载有冠醚的功能微球DBC-CPVA.在建立了冠醚DBC固载量测定方法(溴百里香酚蓝-固相萃取法)的基础上,重点研究了主要因素对DBC固栽化过程的影响规律.结果表明:反应温度与溶剂性质对DBC在CPVA微球上的固载化反应有较大的影响,在70℃极性较强的N,N-二甲基甲酰胺(DMF)溶剂中,可制得冠醚DBC固载量为1.72 mmol/g的DBC-CPVA功能微球.     

醇系溶剂中冠醚与碱金属离子的配位反应

The enthalpy changes, entropy changes and equilibrium constants of coordination reactions of 18-crown-6 with the alkali ions Na+ and K+ at 298.15K were measured by using RD-496 microcalorimeter with methanol, ethanol, n-propanol and n-butanol as solvents respectively. The results indicated that the enthalpy changes △rHm, entropy changes △rSm, and the stability of the complexes are closely related with the polarity of the solvents, and the order of the stability is ethanol>methanol>n-propanol>n-butanol>H2O for the same complex in the solvents investigated. The stability order was reasonably explained by relating the stability constants of the complexes with the dielectric constants of these solvents, and by using the model of solvated-desolvated ions and ion pair in the coordination reactions.     

毛细管电泳前沿分析法研究钾离子与18-冠醚-6体系相互作用

采用毛细管电泳前沿分析(CE／FA)法，利用间接紫外检测方法，在pH为5．10，运行电压为30kV，缓冲溶液组成为咪唑和醋酸的条件下，测定了钾离子与18-冠醚-6体系的相互作用参数，结合常数对数值lgK=3．50；在同样条件下用峰漂移法作对照实验，求得体系的结合常数对数值lgK=3．40，结果与前沿分析法基本一致。验证了两种方法测定结果的正确性。     

18－冠－6修饰碳糊电极测定金的研究

本文研究了１８－冠－６修饰碳糊电极测定金的条件，金在０．５ｍｏｌ／ＬＨＣ１－０．００５ｍｏｌ／ＬＫＣ１底液中富集，介质交换到０．０１ｍｏｌ／ＬＨＣ１中进行测定。金（Ⅲ）浓度在０．１～１．０μｇ／ｍＬ范围内呈线性关系，相对标准偏差为９．７％，检出限为２０ｎｇ／ｍＬ。可不经预先分离直接测定矿样中的金，结果良好。并研究了Ａｕ（Ⅲ）在１８－冠－６碳糊修饰电极上的还原机理。     

固载化冠醚二苯并-18-冠-6在苯甲酸丁酯合成反应中的相转移催化作用

在交联聚乙烯醇(CPVA)微球表面固载冠醚二苯并-18-冠-6 (DBC), 从而制得三相相转移催化剂DBC-CPVA; 在此基础上, 以苯甲酸钾与溴代正丁烷的酯化反应为模型反应体系, 重点研究固体催化剂DBC-CPVA的相转移催化性能, 考察主要因素对液-固-液三相相转移催化反应的影响. 结果表明, 在本研究体系中, 水相中的苯甲酸钾与有机相中的溴代正丁烷可顺利地发生酯化反应, 这一结果显示出固载于DBC-CPVA表面的DBC与K+离子形成的络合物阳离子, 能有效地将苯甲酸根负离子转移至有机相, 使酯化反应顺利地进行. 有机相的极性越强, 酯化反应的速率越快, 溴代正丁烷的转化率越高; 有机相与水相体积比为1:4时, 酯化反应具有最大的速率, 溴代正丁烷的转化率可达70%. 固体催化剂DBC-CPVA循环使用8次, 催化活性保持稳定.     

Synthesis and Crystal Structures of Group 10 Metal Bis(dithiolate) Complexes Constructed by 2,3-Naphtho-15-Crown-5 or 2,3-Naphtho-18-Crown-6

Five novel 2,3-naphtho crown ether group 10 metal bis(dithiolate) complexes, [Na(N15C5)₂]₂[Pd(mnt)₂] (1), [Na(N15C5)]₂[Pd(i-mnt)₂] (2) and [K(N18C6)]₂[M(i-mnt)₂] (3 5) (where mnt = 1,2-dicyanoethylene-1,2-dithiolate, i-mnt = 1,1-dicyanoethylene-2,2-dithiolate and M = Ni, Pd, Pt for complexes 3–5, respectively), have been synthesized and characterized by elemental analysis, FT-IR, UV–Visible spectra and single crystal X-ray diffraction. X-ray diffraction analyses reveal that complexes 1 and 2 have different structural features while complexes 3–5 are structurally isomorphous. Complex 1 consists of two [Na(N15C5)₂]⁺ sandwich complex cations and one [Pd(mnt)₂]²⁻ anion, affording a zero-dimensional structure. For 2, the [Na(N15C5)]⁺ mono-capped complex cations act as the bridges linking the [Pd(i-mnt)₂]²⁻ anions into a 1D infinite chain through Na–N interactions and SȮFC and SȮFπ interactions are observed in the resulting chain. Complexes 3–5 all consist of two [K(N18C6)]⁺ complex cations and one [M(i-mnt)₂]²⁻ (M = Ni, Pd or Pt) anion and the complex molecules are linked into␣1D␣chains by the bridging K–O(ether) interactions between the adjacent [K(N18C6)]⁺ units. What’s novel is that the resulting chains are assembled into novel 2D networks through interchain π–π stacking interactions between the neighboring naphthylene moieties of N18C6. The stack model of naphthylene group in complexes 3–5 is discussed.     

Partial molar volumes of 18-crown-6 ether in organic solvents at 25°C

The partial molar volumes at infinite dilution of 18-crown-6 ether (CE) in a variety of polar and polarizable solvents with molar volumes ranging from 18 to 170 cm³-mol^–1, were measured at concentrations ranging from 0.02 to 0.1 mol-L^–1 at 25°C. The partial molar volumes of the solute at infinite dilution showed remarkable dependancy on the molar volume of the solvent. The partial molar volumes at infinite dilution for the CE increases as the solvent molar volume increases.     

Investigation of Non-covalent Interactions of 18-Crown-6 with Amino Acids in Gas Phase by Mass Spectrometry

The non-covalent interactions between 18-Crown-6 (18c6) and 20 common types of protonated amino acids were explored by electrospray ionization mass spectrometry. The mass spectra showed that 18c6 could react with amino acids to form a non-covalent complexe in a stoichiometric ratio of 1:1. The calibration curves and linear equations for the complexes of L-Phe, L-Tyr, L-Lys and L-Asp with 18c6 were established by mass spectrometric titration and used as reference values for competitive ESI-MS. Through competitive equilibria, the binding constants for the complexes of 18c6 with other L-amino acids and their D-isomers were derived. It was found that, as a general trend, lgK_a for the complexes of 18c6 with the basic amino acid and the amino acid with alkyl side chain were larger than other complexes, and among the amino acid with alkyl side chain, Gly and Ala exhibited greater 18c6 binding affinities. As for Ser and Thr, the intramolecular hydrogen bond between the nitrogen atom from terminal –NH₂ and the oxygen atom from carboxyl might impede their protonated amino-group to attack the 18c6. Furthermore, Gln and Asn exhibited lower binding affinities to 18c6, probably due to effects of electron-withdrawing group of acylamide. Finally, the chiral selectivity of 18c6 for L-amino or D-amino acids were measured by ESI-MS, and the result showed that 18c6 could only recognize some neutral amino acid isomers.     

弱相互作用构筑的二维、三维冠醚配合物{[K(18-C-6)2(C2H4Cl2)}[Ni(dmit)2]2和[K(18-C-6)][Ni(dmit)2]的合成与结构

研究了18－冠－6与NiCl·6H2O,K2dmit(dmit=4,5-dimercapto-1,3-dithiole- 2-thione,C3S5^2－）在不同溶剂中反应生成的两个标题配合物{[K(18-C-6)]2 (C2H4Cl2)}[Ni(dmit)2]2（1）和[K(18-C-6)][Ni(dmit)2](2)。通过元素分析、红 外光谱、单晶X射线衍射进行了表征。1和2均属三斜晶系,空间群P1^-.1的晶体学 数据：a=1.0272(2)nm,b=1.2282(3)nm,c=1.4205(3)nm,α=113.473(3)°,β=90. 609(3)°,γ=91.439(3)°,V=1.6430(6)nm^3,Z=2,F（000)=876,R1=0.0503。2的 晶体学数据：a=0.8502(2)nm,b=1.2178(4)nm,c=1.5118(4)nm,α=86.454(5)°,β =77.734(5)°,γ=85.364(5)°,V=1.5228(8)nm^3,Z=2,F(000)=774,R1=0.0565。配 合物1,2分别通过K…S,K…Cl,S…S和K…S,S…S弱相互作用形成二维、三维网状 结构。     

Application of affinity capillary electrophoresis and density functional theory to the investigation of benzo-18-crown-6-ether complex with ammonium cation

Affinity capillary electrophoresis (ACE) and quantum mechanical density functional theory (DFT) calculations have been employed for investigation of non-covalent interactions between macrocyclic ligand, benzo-18-crown-6-ether (B18C6) and ammonium cation, NH₄⁺. Firstly, by means of ACE, the strength of the B18C6-NH₄⁺ complex in mixed binary hydro-organic solvent system, methanol–water (50/50, v/v), was determined from the dependence of effective electrophoretic mobility of B18C6 (corrected to reference temperature 25 °C and constant ionic strength, 10 mM) on the concentration of ammonium ion in the background electrolyte (BGE) using non-linear regression analysis. The logarithmic form of the apparent binding (stability) constant (log K_b) of B18C6-NH₄⁺ complex in the above binary solvent system was found to be equal to log K_b = 1.63 ± 0.10. Secondly, the structural characteristics of B18C6-NH₄⁺ complex were described by quantum mechanical density functional theory (DFT) calculations. According to these calculations, in the energetically most favoured form of the B18C6-NH₄⁺ complex, three strong hydrogen bonds are formed between central ammonium ion and B18C6 ligand, one of them is directed to aryl-O-alkyl (Ar–O–CH₂) ethereal oxygen and the other two hydrogen bonds are oriented to alkyl-O-alkyl (CH₂–O–CH₂) ethereal oxygen atoms of the macrocyclic crown ligand.     

Application of Ionic Complex of N 2 O 4 with 18-Crown-6 as an Oxidizing Agent for the Oxidation of Organosulfur Compounds

Complexation of gaseous N 2 O 4 with 18-Crown-6 affords an ionic complex of NO + ·;18-crown-6·;H(NO 3 ) m 2 . This reagent is a nitrosating agent for conversion of thiols to thionitrites. Disulfides can be obtained from coupling of thiols via thionitrites. Moreover this reagent is an oxidizing agent for conversion of thioethers into their corresponding sulfoxides and dithianes into their carbonyl compounds in an oxidative deprotection reaction.     

Enantiomeric Separations in Capillary Electrophoresis Using 18-Crown-6-tetracarboxylic Acid (18C6H4) as Buffer Additive

An overview is presented of the applicability of the crown ether 18-crown-6-tetracarboxylic acid (18C6H₄) as buffer additive in capillary electrophoresis (CE) for the separation of enantiomers. The chiral selector 18C6H₄ is particularly useful for the separation of racemates having a primary amino function. Unfortunately, the crown ether is no longer commercially available. The synthesis and spectroscopic characterization are therefore described in detail. Moreover, a method is presented for the regeneration of the crown ether after CE application. Some new enantiomeric separations of amino acids i.e. NORLEU, ARG, GLU, m-TYR, and o-TYR are listed and the influence of the pH and temperature of the separation buffer is discussed. An intermediate in the synthetic pathway, namely 18-crown-6-tetracarboxamide, did not exhibit any enantioselectivity in CE.     

Syntheses of dibenzo-18-crown-6 lariat isomers and their complexation with lanthanoid nitrates

Two constitutional isomers of dibenzo-18-crown-6 derivatives (6 and 7) were synthesised and their binding behaviours towards trivalent lanthanoid cations (La^3 + , Ce^3 + , Pr^3 + , Nd^3 + , Sm^3 + , Eu^3 + , Gd^3 +  and Tb^3 + ) were investigated. Both isomers expressed better binding affinities towards Sm^3 +  and Tb^3 +  than a group of other lanthanoids, as measured by the ligand-to-metal charge-transfer (LMCT) band intensity at ca. 425 nm using UV–vis spectroscopic method. Additionally, the trans isomer 7 was shown to have a higher binding ability than the cis isomer 6 towards Tb^3 + .

     

Stabilities in Polar Nonaqueous Solvents and Transfer Activity Coefficients from Water to Nonaqueous Solvents of 19-Crown-6-Alkali Metal Ion Complexes

Formation constants of 1 : 1 19-crown-6(19C6) complexes with alkali metal ions weredetermined conductometrically at 25 °Cin acetonitrile(AN), propylene carbonate (PC), methanol, DMF, andDMSO. 19C6 always forms the most stable complex withK⁺. The selectivity order of 19C6 forheavy alkali metal ions isK⁺ > Rb⁺ > Cs⁺.The selectivity for Na⁺ varies withthe solvent; that for Li⁺ is the second lowest(AN, DMSO) or the lowest (PC). Transfer activity coefficients(^SH _{2 O}) of19C6 from water to the nonaqueous solvents (S) weremeasured at 25 °C. The contributions of a methylenegroup and an ether oxygen atom to thelog ^SH _{2 O}value of a crown ether wereobtained. The ^SH _{2 O}values of the 19C6–alkali metal ion complexes(^SH _{2 O} (ML⁺)) werecalculated, M⁺ and L denoting an alkali metal ionand a crown ether, respectively. For AN, PC, andCH₃OH, although the M⁺ ion is more stronglysolvated by water than by AN, PC, or CH₃OH, thelog ^SH _{2 O} (ML⁺) islarger than the correspondinglog ^SH _{2 O} (L)expect for the case of M⁺ = Li⁺.The higher lipophilicity of the19C6 complex ion is attributed to an enforcement ofthe hydrogen-bonded structure of water for the complexion caused by the greatly decreased hydrogen bondingbetween ether oxygen atoms and water uponcomplexation. For DMF and DMSO, thelog ^SH _{2 O} (ML⁺) is also greater thanthe correspondinglog ^SH _{2 O} (L).It was concluded from thisfinding that the unexpectedly lowest stability of the19C6 complex ion in water is due to the hydrogenbonding between 19C6 and water. The stabilities and thelog ^SH _{2 O}of 19C6–alkali metal ion complexes were compared with those of 18C6complexes.     

Molecular Complexes of Crown Ethers, Part 5: Complexes of DB18C6 with Some Acceptors

The UV-Visible spectra of DB18C6 as a donor with TCNE (Tetracyanoethylene), and DDQ (2,3-dichloro-5,6-dicyano-1,4- benzoquinone) as acceptors were studied. Charge transfer spectra were obtained for these systems from which it was possible to calculate the formation constant, Kc. The effects of potassium halides were studied. This study shows that in the presence of the anion there is an electron transfer from the anion to the acceptor. This process is enhanced by the presence of the crown ether, CE. The formation of the anion salt with the acceptor, in the presence of the CE, follows the trend F = I > Br > Cl. It is also indicated in this study that the interaction between DB18C6 and the acceptor follow the trend DDQ > TCNE.     

Complex formation of Ag+ with polyether 18-crown-6

The complex formation of Ag⁺ with polyether 18-crown-6 (18C6) and their solvation have been studied using calorimetric and potentiometric methods in H₂O-EtOH solvents in wide range of ethanol concentration. The standard enthalpies of dissolution AgNO₃, AgClO₄ and 18C6 in aqueous-ethanol solvents are obtained. The stability of a complex [Ag18C6]⁺ grows with increasing the EtOH content a solvent. Using the method based on the thermodynamic characteristics of solvation of metal-ion, ligand and complex-ion the interpretation of the results has been given. This revised version was published online in August 2006 with corrections to the Cover Date.     

双环己基18冠6对水／硝基苯界面离子的促进传输

Li~-和H~-因较强的亲水性,较难穿越液/液界面进行传输。本文报道了冠醚双环已基18冠6对Li~+,Na~+,Rb~-和H~-在水/硝基苯界面的促进传输行为,求得了相应促进传输过程的一系列参数,并对被传输离子在传输过程中的形态变化进行了初步的探讨。     

Dependence on pH of the Luminescent Properties of Metal Ion Complexes of 5-Chloro-8-hydroxyquinoline Appended Diaza-18-Crown-6

Luminescent properties of 5-chloro-8-hydroxyquinoline (CHQ) free and appended tothe amines in diaza-18-crown-6 (A₂18C6) were determined. These propertieswere compared to those of bivalent alkaline earth and post-transition metal ioncomplexes of the appended macrocycle (CHQ-A218C6). The luminescent properties were foundto be pH dependent. In the pH range 3 to 7, CHQ-A₂18C6 forms luminescent complexes withonly Zn²⁺ and Cd²⁺. At higher pH values, luminescent complexes wereformed with Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺. No luminescent complex was formed by Hg²⁺ over the pH range studied. This lariat macrocycle could findapplication as a chemosensor for several of the metal ions studied.