Complexes of Lanthanoid Nitrates with 15-Crown-5 and 18-Crown-6 Ethers

Complexes between the heavier lanthanoid nitrates Ln(NO₃)₃ and 15-crown-5 ( 1 ) and 18-crown-6 ( 2 ) ethers were isolated and characterized. Both 1:1 and 4:3 complexes are formed with each Ln(III) ion, except in the case of Gd and 2 . The thermal transformation of the 1:1 complexes into the corresponding 4:3 complexes was studied by thermogravimetry and by DSC, X-ray and vibrational data provide information about the structure of these complexes. The interaction between Ln(III) ions and ligands 1 and 2 in non-aqueous solutions is discussed on the basis of conductometric, fluorescence, UV./VIS. and ¹H-NMR. data. Only 1:1 complexes of 2 formed in solution and their formation constants range from logK_f = 4.4 (Ln = La) to 2.4 (Ln = Yb); for Eu, K_f of the 15-crown-5 and 18-crown-6 ether complexes are of the same order of magnitude. For La, Pr, Nd, Eu, Yb, a variable temperature NMR. study gave some indications about the chemical exchanges in solution. The factors which determine the stoichiometry of the complexes are discussed.     

Stability of Complexes of NH4 + with 18-Crown-6, Dicyclohexyl-18-Crown-6, Dibenzo-18-Crown-6 and Dibenzo-24-Crown-8 in Water Saturated Nitrobenzene

From extraction experiments with ²²Na tracer, the exchange extraction constants corresponding to the NH₄ ⁺(aq) + NaL⁺ (nb)NH₄L⁺(nb) + Na⁺ (aq) equilibrium taking place in the two-phase water-nitrobenzene system (L = 18-crown-6, dicyclohexyl-18-crown-6, dibenzo-18-crown-6 and dibenzo-24-crown-8; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the NH₄L⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the order dibenzo-24-crown-8 (DB24C8) < dibenzo-18-crown-6 (DB18C6) < dicyclohexyl-18-crown-6 (DCH18C6) < 18-crown-6 (18C6).     

Structure of the 18-Crown-6 Complex with Ammonium Hexafluorosilicate and Water

The crystalline host–guest type complex [(18-crown-6NH₄)₂][SiF₆]4H₂Ohas been obtained as the result of the interaction of SiF₄2NH₃ with 18-crown-6 (18C6) in an aqueous medium. Crystal data: monoclinic, space groupC 2 c, a=26.541(2), b=8.363(2), c=20.469(2) Å, = 122.43(1)°and Z=4. The final R-value is 0.070 for 3253 reflections with I 2(I).The crystals consist of the complex [NH₄18C6]⁺ cations, [SiF₆]^2-anions and water molecules. The ammonium cation is hydrogen bonded by three of its H-atoms to the crown ether oxygen atoms with N(1) O separations2.923(5)–2.940(5) Å and by the fourth H-atom to the fluorine atom of thehexafluorosilicate anion, the N(1)F(4) distance being 2.797(6) Å.The conformation of the macrocycle and the hydrogen-bond geometry in thecomplex cation closely resemble those in related adducts between 18-crown-6and ammonium salts. All crystal components are connected via a system of hydrogen bonds into a ribbon along the b axis in the unit cell.     

二苯并18－冠－6铵与硫氰酸银配合物的晶体结构

标题化合物［（ＮＨ_４）（ＤＢ１８Ｃ６）］_２［Ａｇ（ＳＣＮ）_２］_２其晶体属三斜晶系，空间群为Ｐ１。晶胞参数：ａ＝１４．００３（２），ｂ＝１４．４６１（３），ｃ＝１４．８８７（２），ａ＝６６．５１（２），β＝６６．７０（１），γ＝７６．０９（２）°，Ｖ＝２５２７．１３　３，Ｍ_ｒ＝１２０５．０，Ｚ＝２，Ｄ_ｘ＝１．５８ｇ／ｃｍ~３，μ＝９．８８ｃｍ~（－１）。偏差因子Ｒ_ｗ＝０．０８１，独立可观测点数［Ｉ＞３σ（Ｉ）］为３３５１个，在配合物分子中，二苯并１８－冠－６与ＮＨ４~＋形成配阳离子，Ａｇ~＋与硫氰酸根形成配阴离子，二者以静电力形成配合物。银原子被两个ＳＣＮ~－的Ｓ原子桥联和硫氰酸根上的硫，氮杂配，使整个分子形成一条高分子长链。     

二苯并18－冠－6铵与硫氰酸银配合物的晶体结构

标题化合物［（ＮＨ_４）（ＤＢ１８Ｃ６）］_２［Ａｇ（ＳＣＮ）_２］_２其晶体属三斜晶系，空间群为Ｐ１。晶胞参数：ａ＝１４．００３（２），ｂ＝１４．４６１（３），ｃ＝１４．８８７（２），ａ＝６６．５１（２），β＝６６．７０（１），γ＝７６．０９（２）°，Ｖ＝２５２７．１３　３，Ｍ_ｒ＝１２０５．０，Ｚ＝２，Ｄ_ｘ＝１．５８ｇ／ｃｍ~３，μ＝９．８８ｃｍ~（－１）。偏差因子Ｒ_ｗ＝０．０８１，独立可观测点数［Ｉ＞３σ（Ｉ）］为３３５１个，在配合物分子中，二苯并１８－冠－６与ＮＨ４~＋形成配阳离子，Ａｇ~＋与硫氰酸根形成配阴离子，二者以静电力形成配合物。银原子被两个ＳＣＮ~－的Ｓ原子桥联和硫氰酸根上的硫，氮杂配，使整个分子形成一条高分子长链。     

Complex Formation of Potassium Hexachloroplatinate with 18-Crown-6 and Dibenzo-18-Crown-6 in Acetonitrile

The products of the reactions between potassium hexachloroplatinate {K₂PtCl₆} and 18-crown-6 or dibenzo-18-crown-6 in acetonitrile were studied. Pure crystalline compounds [2K·2(18-crown-6)· 2CH₃CN]²⁺·[PtCl₆]^2-·2H₂O, [2K·dibenzo-18-crown-6·CH₃CN]^{2 +}·[PtCl₆]^{2 -}, and [2K·dibenzo-18-crown-6·CH₃CN]^{2 +}·[Pt₂Cl₁₀]^{2 -} were obtained. Physicochemical properties of these compounds were studied, and their near- and far-IR IR spectra and thermogravimetric curves were considered. The composition of the complexes is determined by metal:ligand molar ratio and crown ether nature. It was found that acetonitrile is coordinated via the nitrogen atom.     

Structures of 18-Crown-6 Complexes with Alkali Cations in Methanolic Solution as Studied by X-ray Absorption Fine Structure

The structures of 18-crown-6 (18C6) complexes with K⁺ and Rb⁺ in methanolic solutions have been studied by X-ray absorption fine structure (XAFS) at the Br K-edge as well as at the K and Rb K-edges. The XAFS spectrum at the K or Rb K-edge has indicated that either Br⁻ or solvent (methanol) molecules are present in the first coordination shell of K⁺ or Rb⁺ complexed by 18C6. However, the spectra obtained at the Br-K edge have strongly suggested that the alkali cations do not exist in the vicinity of Br⁻, indicating that no direct ion-pairing occurs between the 18C6 complex and Br⁻. The 18C6-K⁺ complex maintains D _3d symmetry even in methanol, and two methanol molecules coordinate the cation possibly from above and below the crown plane. In contrast, the corresponding Rb⁺ complex possibly forms an umbrella-shaped complex, in which Rb⁺ is situated slightly off the crown plane and three solvent molecules bind With the cation.     

Crown Inclusion Compounds with 3,4-Diamino-1,2,5-Oxadiazole. X-Ray Structures of Its 1:1 Inclusion Complexes with 15-Crown-5 and Benzo-15-crown-5

The X-ray crystal structures of two closely related molecular complexes of 15-crown-5 and benzo-15-crown-5 with 3,4-diamino-1,2,5-oxadiazole are reported (I and II). Both complexes are of 1:1 stoichiometry with the host–guest alternation in the infinitechains formed due to the unsymmetrical H-bonding patterns between the components. Crystals of I are monoclinic, P2_1/c, a = 7.856(3), b = 12.994(1), c = 16.033(1) , = 94.79(2)°, Z = 4, final R-factor is 0.0488. Crystals of II are orthorhombic, P2₁2₁2₁, a = 8.260(4), b = 15.692(5),c = 13.955(7) , Z = 4, final R-factor is 0.0522.     

Chemical Processes Involving 18-Crown-6-Ether in Activated Noncovalent Complexes with Protonated Peptides

These last decades, it has been widely assumed that 18-crown-6-ether (CE) plays a spectator role during the chemical processes occurring in isolated host-guest complexes between peptides or proteins and CE after activation in mass spectrometers. Our present experimental and theoretical results challenge this hypothesis by showing that CE can abstract a proton or a protonated molecule from protonated peptides after activation by collisions in argon or electron capture/transfer. Furthermore, thanks to comparison between experimental and calculated values of collision cross-sections, we demonstrate that CE can change binding site after electron transfer. We also propose detailed mechanisms for these processes.     

Structure of Dibenzocrown Ethers and their H-Bonded Adducts.1. [1.5]Dibenzo-18-Crown-6 and Biphenyl-20-Crown-6: Complexes with Amidosulfuric Acid

The interaction of the amidosulfuric acid NH ₃ SO ₃ with 15 distal and proximal dibenzocrown ethers, including diphenyloxide, diphenylsulfide and biphenyl ones leads to the stable (1:1) complexes only in the case of [2.4]- and [1.5]dibenzo-18-crown-6 and biphenyl-20-crown-6. According to the data of the X-ray analysis, in the two last adducts the amidosulfuric acid coordinates to hexadentate crown ethers in a zwitterion form through a near-ideal ‘tripod’ arrangement to alternate crown oxygen atoms. The conformations of crown molecules are different in complexes and in initial macrocyclic ligands.This revised version was published online in July 2005 with a corrected issue number.     

Relative Ammonium Ion Affinities of 18-Crown-6 and the Isomers of Dicyclohexano-18-Crown-6

Complexes of cis-syn-cis- and cis-anti-cis-dicyclohexano-18-crown-6(DC18C6) with ammonium, methylammonium, propylammonium, isopropylammonium,butylammonium, isobutylammonium, and tert-butylammonium were generated andstudied in the gas phase using Fourier transform ion cyclotron resonancemass spectrometry to measure exchange equilibrium constants of the guestswith unsubstituted 18-crown-6 (18C6). Semiempirical calculations at the PM3level were also performed for all the complexes. Both the experiments andthe calculations indicate that sterically unhindered ammonium cations bindDC18C6 in preference to 18C6, but that preference decreases or vanishes forammonium cations branched at the carbon. The cis-syn-cis isomer hashigher ammonium affinities than the cis-anti-cis isomer. The experiments andthe calculations both suggest that in the cis-syn-cis isomer the ammoniumcations preferentially bind on the face of the macroring enclosed by thecyclohexano units, but again this preference decreases for stericallycrowded ammonium substituents. These trends are explained in terms of theability of the substituents in the host to stabilize the charge of the guest.     

Complexation of Amino Acids with 18-Crown-6

In complexation of 18-crown-6 with glycine, L-alanine, L-serine, L-threonine, L-asparagine, L-glutamine, L-histidine, L-phenylalanine, and diglycine in D₂O at 298 K, side groups of the amino acids are not involved in additional interactions with the macrocycle, except the OH group of threonine.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 3, 2005, pp. 445–447.Original Russian Text Copyright © 2005 by Terekhova, Kulikov, Kumeev, Nikiforov, Al’per.     

The Synthesis and Formation of Complexes between Derivatives of Chiral Aza-18-Crown-6 Ethers and Chiral Primary Organic Ammonium Salts

Chiral mono aza-18-crown-6 derivatives have been prepared in optically active form and high yield from amino alcohols via a cyclization reaction with tetraethylene glycol ditosylate.The enantiomeric recognition by these chiral aza-crown ethers between chiral primary ammonium perchlorate salts has been characterized by UV–Vis at 25 °C in chloroform.     

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.     

四Schiff碱(二苯并-18-冠-6)及其钾(Ⅰ)/钴(Ⅱ)配合物的合成和性质

由二苯并-18-冠-6出发,合成了4′,4″,5′,5"-四(2-羟基苯亚甲基亚氨基)二苯并-18-冠-6(L1H4)及其5位取代衍生物(取代基R=CH3,OH,OCH3,Cl,NO2)L2H4～L6H4.它们依次与硝酸钾和醋酸钴反应,制得1:1:2的钾(Ⅰ)/双钴(Ⅱ)配合物LCo2·2H2O·KNO3(L=L5,L6)或其某些二氧加合物LCo2(2O2)·2H2O·KNO3(L=L1～L4).考察了取代基R和冠醚环配合的钾离子对二氧加合物形成及稳定性的影响.结果表明,含吸电子基(R=Cl,NO2)的钾(Ⅰ)/双钴(Ⅱ)配合物不能形成二氧加合物;冠环中的钾离子会导致二氧加合物中两个Co-O2键热稳定性的差异.     

18-冠醚-6的构象研究

以柔性大分子１８－冠醚－６为研究对象，将ＭＮＤＯ法所得的三种构象的静电势电荷用于分子力学计算，得到了三种构象的能量，同时计算了电负性电荷，亦将其用于分子力学计算，将两种计算结果进行比较发现，有可能将电负性作为分子力学、分子动力学计算的力场参数。     

Synthesis and Cation Binding Ability of the Phosphonoalkyl- and Phosphinoylalkyl Derivatives of Monoaza-18-Crown-6

Azacrown ethers with phosphonoalkyl-and phosphinoylalkyl side chains of two to five carbonatoms (2–4, 7 and 5–6, 8,respectively) were synthesized in acceptable yields.The cation binding ability of the new lariat etherswas evaluated by the picrate extraction method.Introduction of the P-functionalised N-substituentresulted in a decrease in the cation extractionability in most cases, but the discrimination betweenthe cations examined was, in some instances,significantly increased.     

Solubilization of Benzene and Several Benzene Derivatives in Dilute Aqueous Solution of 18-Crown-6

Solubilities of benzene, toluene, nitrobenzene, p-and o-nitrotoluene in dilute aqueous solutions of 18-crown-6 have been determined by UV-spectrometry at 15, 25, and 35°C. The saturation concentration of each aromatic solute depends linearly on the l8-crown-6 concentration. Experimental results show that 18-crown-6 molecules form host-guest complexes (with 1:1 stoichiometry) with the aromatic molecules, which supports the assumption that the force of combination between the crown ether and the aromatic molecules is a weak hydrophobic interaction.     

Molecular Complexes of Crown Ethers: Part 7. Effect of Surfactant on the Charge-Transfer Complex between Dibenzo-18-Crown-6 and Tetracyanoethylene

The charge transfer complexes (CTC) of dibenzo-18-crown-6 (DB 1 8C6) andtetracyanoethylene (TCNE) were studied in the presence of the surfactant TritonX-100. It was found that the stability of the CTC increases with increasingconcentration of the donor, acceptor and the surfactant. This suggests that thecharge transfer complex is encapsulated in the micelle structure. Results of theeffect of time on the complex stability are also presented.