Complex formation of silver(I) with 18-crown-6 in methanol-DMF binary mixtures

Dependence of the stability of the silver(I)-18-crown-6 complex on the composition of the binary methanol-DMF solvent was studied potentiometrically. It was found that the increase in DMF content in the binary mixture decreased the stability of the coordination compound. New approach to analysis of the solvation contributions of reagents in the variation of Gibbs energy while substitution of solvent with another one was suggested. It was shown that the shift in the complex formation equilibrium is determined by variation in the solvate state of the central ion.     

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.     

A europium(II) complex with bis-pyridino-18-crown-6

A new Eu(II) complex, bis(perchlorato)(bis-pyridino-18-crown)europium(II), has been obtained in the crystalline form by electrolytic reduction. The metal ion is 10-coordinated and its surrounding consists of four macrocycle O atoms, two N ones and four O atoms from perchlorate anions. The compound shows a very broad absorption band, starting gently from 600 nm towards the UV region, and two weak luminescence bands with maxima at 430 and 500 nm. The performed density functional theory (DFT) calculations have shown that the absorption results from mixed f–d, f–s and charge transfer transitions. The possible mechanism of luminescence is also discussed.     

Tetrakis(isothiocyanato)manganese(II) bis[aqua(18-crown-6)potassium] (18-crown-6)(thiocyanato)potassium

A new complex compound, i.e., tetrakis(isothiocyanato)manganese(II) bis[aqua(18-crown-6)potassium] (18-crown-6)(thiocyanato)potassium, was synthesized and its crystal structure was studied by X-ray diffraction (space group P2₁/m, a = 13.377, b = 14.690, c = 17.499 Å, β = 108.96°, Z = 2) and refined by the least-squares method in anisotropic approximation to R = 0.060 for 4715 independent reflections (CAD-4 automated diffractometer, λMoK _α). In the crystal, infinite chains are formed through the coordination bonds between its components. The monomer fragment of a chain [Mn(NCS)₅K₃(18-crown-6)₃(H₂O)₂] lies in plane m; three of the five SCN^? ligands and one of the two water molecules behave as bridges. The [Mn(NCS)₄]^2? anion has the tetrahedral structure. The coordination polyhedron of each of the three K⁺ cations is a distorted hexagonal bipyramid with six O atom of the corresponding crown ligand in a base. Three 18-crown-6 ligands have standard crown conformation.     

Synthesis and crystal structure of aqua(dibenzo-18-crown-6)potassium (dibenzo-18-crown-6)-(tetrachlorocuprato(II)-Cl)potassium

New mixed complex compound aqua(dibenzo-18-crown-6)potassium (dibenzo-18-crown-6)(tetrachlorocuprato(II)-Cl)potassium, [K(CuCl₄)(Db18C6)]^? · [K(Db18C6)(H₂O)]⁺, is synthesized and its crystal structure is studied by the method of x-ray structural analysis. The structure includes two independent complex ions, both of guest-host type: two cations K⁺ are located in the respective cavities of the Db18C6 crown-ligand (one in each) and each is coordinated by all its six O atoms and one Cl atom of the anion-ligand [CuCl₄]^2? or O atom of the ligand water molecule. Coordination of these two K⁺ cations is completed to hexagonal pyramidal one by formation by each of unusually weak coordination bond K⁺ → π(\(C\dddot - C\)) with two C atoms of respective benzene ring in the neighboring Db18C6 ligand. In this crystal structure the complex anions and cations form dual infinite chains via these coordination bonds and interionic O-H?Cl hydrogen bonds.     

Synthesis and crystal structure of triaqua(18-crown-6)calcium bis(perchlorate) 18-crown-6 monohydrate

A complex [Ca(18C6)(H₂O)₃]²⁺(ClO ₄ ^? · 18C6 · H₂O is synthesized and studied by X-ray diffraction analysis. The structure (space group P2₁/n, a = 11.570 Å, b = 16.024 Å, c = 22.225 Å, β = 98.89°, Z = 4) is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.075 for 5305 independent reflections (CAD4 automated diffractometer, λMoK _α radiation). In the complex cation of the host-guest type, the Ca²⁺ cation lies in the cavity of the 18-crown-6 ligand and is coordinated by all the six O atoms and three O atoms of three water molecules. In a crystal, the alternating complex anions, 18C6 molecules, and water molecules are joined by hydrogen bonds into broad infinite chains along the y axis. The disordered ClO ₄ ^? anions are bonded to these chains on the side through hydrogen bonds.     

Interaction of uranyl monoaquadiformate with diaza-18-crown-6 in aqueous ethanol

The reaction of {[UO₂(HCOO)₂(H₂O)]} with diaza-18-crown-6 (DA18C6 = C₁₂H₂₆O₄N₂) in aqueous ethanol in the presence of formic acid yields the complexes {[DA18C6H₂]·[UO₂(HCOO)₃]₂} (I), [DA18C6H₂]·[UO₂(HCOO)₄] (II), and [DA18C6H₂]·(HCOO)₂·(H₂O)₂ (III). The complexes are characterized using IR spectroscopy, chemical analysis, and powder X-ray diffraction. From the comparison of the structural and spectral characteristics of [DA18C6H₂]·An₂·(H₂O)_2n (where An = Cl^?,NO ₃ ^? ,HCOO^?,HSO ₄ ^? ; n = 0.1), correlations are derived between the conformation of the [DA18C6H₂]²⁺ units and the conformation-sensitive frequencies. On the basis of these correlations, the conformations of the N⁺CCO and OCCO units were determined in the diazonia cations of compounds I and II and in [DA18C6H₂]·[UO₂(NO₃)₄]; the latter was prepared previously by reacting [UO₂(NO₃)₂(H₂O)₂]·(H₂O)₄ with DA18C6 in ethanol in the presence of nitric acid.     

Reactions of potassium dibenzo-18-crown-6 pentacyanocobaltate(II) with some lewis bases

ESR has been applied to the interactions of [K(DBC)]₃[Co(CN)₅], in which DBC is dibenzo-18-crown-6, in methanol solution with triphenylphosphine, pyridine, and triethylamine. The ESR spectra are described for the paramagnetic [(NC)₅CoB]^3– adducts, where B is triphenylphosphine or pyridine.Translated from Teoreticheskaya i Éxperimental'naya Khimiya, Vol. 25, No. 2, pp. 234–237, March–April, 1989.     

Crystal structure of supramolecular complexes formed by 18-crown-6 andcis-anti-cis-dicyclohexano-18-crown-6 (host) with 3,4-diaminofurazane (guest)

An X-ray—diffraction study is reported for two molecular complexes containing 3,4-diamino-1,2,5-oxadiazole as guest (G) with 18-crown-6 (18-C-6) andcis-anti-cis-dicyclohexano-18-crown-6 (DCH-6B) as host. Both complexes are of the polymeric-chain structure with the guest molecule bridging two crown neighbours. ComplexI: [18-C-6*G*H₂O], 111, monoclinic,P2₁/n,a=8.171(1),b=15.042(2),c=16.209(6) Å, =101.15(2)°, finalR-factor 0.068. ComplexII: [DCH-6B*G], 11, monoclinicC2/c,a=21.212(4),b=9.380(2),c=13.049(3) Å, =108.61(3)°, finalR 0.047.     

Reaction of trimethylaluminum with crown ethers. II. The synthesis and crystal structure of (Dibenzo-18-crown-6)tris(trimethylaluminum) and of (18-crown-6)tetrakis(trimethylaluminum)

Both title compounds were prepared by adding AlMe₃ to a suspension of the appropriate crown ether in toluene, followed by reaction in a sealed tube. Both products were obtained in the form of extremely air-sensitive, colorless crystals. [AlMe₃]₃[dibenzo-18-crown-6] crystallizes in space group Pī, witha=8.898(4),b=11.848(5),c=19.060(6) Å, α=74.86(3), β=80.73(4), and γ=67.02(4)°. Refinement led to a final conventional weightedR value of 0.052 for 1800 reflections. [AlMe₃]₄[18-crown-6] belongs to space group Pbcn, witha=18.753(3),b=12.570(6), andc=15.095(6) Å. Refinement was taken toR _w =0.064 for 1320 reflections.     

Coordination-driven self-assembly of dibenzo-18-crown-6 functionalized Pt(Ⅱ) metallacycles

Coordination-driven self-assembly was used to construct two metallacycles of a dicarboxylatefunctionalized dibenzo-18-crown-6 in combination with either a 0° anthracene-based clip-type acceptor or a 60° phenanthrene-based acceptor. The angularities of these moieties make them suitable for the formation of a [2 + 2] rectangle and a [3 + 3] triangle, respectively. The synthesis, characterization and host-guest chemistry of two metallacycles were described and supported by³¹P{¹     

Lead(II) complexes with macrocyclic receptors derived from 4,13-diaza-18-crown-6

The complexation properties of three related macrocycles derived from 4,13-diaza-18-crown-6 toward lead(II) are reported. The flexible macrocycle N,N'-bis(2-aminobenzyl)-4,13-diaza-18-crown-6 (L(2)) forms stable complexes with this metal ion in the presence of different counterions (perchlorate and thiocyanate). The X-ray crystal structure of [PbL(2)](SCN)(2) indicates that, in the solid state, the lead(II) ion is eight-coordinated and fits quite well into the crown hole favoring an anti arrangement of the organic receptor, which generates a very infrequent cubic coordination polyhedron around the Pb(II) ion. In solution both complexes are fluxional and the nature of the counterion seems to affect the dynamic behavior. Ligand L(3), N,N'-bis[(2-salicylaldimino)benzyl]-4,13-diaza-18-crown-6, derives from L(2) by condensation of salicylaldehyde with the amine group of each side arm. It can be deprotonated to yield cationic complexes of formula [Pb(L(3)-H)](+) where the metal ion lies asymmetrically on the cavity of the ligand, being seven-coordinated and pushed out from the crown hole, the bibracchial lariat ether presents a syn arrangement, and one of the arms remains uncoordinated. The lead(II) ion also lies asymmetrically on the cavity of the third macrocycle (L(7)), a lateral macrobicycle incorporating a phenolyl Schiff-base spacer. Spectrophotometric titrations of L(2) and (L(3)-2H)(2)(-) with lead(II) perchlorate in acetonitrile gave values of log K[PbL(2)] = 7.7(5) and log K[Pb(L(3)-2H)] = 7.2(3), demonstrating that the stability of the lead(II) complexes with these two ligands is very similar.     

Diaquabromo(18-crown-6)rubidium and triaqua(18-crown-6)barium dibromide monohydrate: Synthesis and crystal structures

Two complexes are synthesized: diaquabromo(18-crown-6)rubidium [RbBr(18-crown-6)(H₂O)₂] (I) and triaqua(18-crown-6)barium dibromide monohydrate [Ba(18-crown-6)(H₂O)₃]²⁺ 2Br^? · H₂O (II). The orthorhombic structure of compound I (space group Pnma, a = 10.124 Å, b = 15.205 Å, c = 12.544 Å, Z = 4) and the monoclinic structure of compound II (space group C 2/c, a = 17.910 Å, b = 10.315 Å, c = 14.879 Å, β = 123.23°, Z = 4) are determined by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.063 (I) and 0.042 (II) for all 2293 (I) and 3363 (II) independent measured reflections (CAD-4 automated diffractometer, λMoK _α). The complex molecule [RbBr(18-crown-6)(H₂O)₂] in compound I and the randomly disordered cation [Ba(18-crown-6)(H₂O)₃]²⁺ in compound II are of the host-guest type: their Rb⁺ or Ba²⁺ cation (its coordination number is nine) is located in the cavity of the 18-crown-6 ligand and coordinated by all six O atoms. In structure I, the coordination polyhedron of Rb⁺ is a distorted hexagonal pyramid with a triple apex at the Br^? ligand and two O atoms of the water molecules. In structure II, the Ba²⁺ polyhedron is a distorted hexagonal bipyramid with one apex at the O atom of the water molecule and the other split apex at two O atoms of water molecules.     

Dibenzo-18-crown-6 diaqua(dibenzo-18-crown-6)potassium triiodide: Synthesis and crystal structure

A new compound, dibenzo-18-crown-6 diaqua(dibenzo-18-crown-6)potassium triiodide [K(Db18C6)(H₂O)₂)⁺ · I₃⁻ · Db18C6 (I), is synthesized and studied by X-ray crystallography. The crystals of compound I are orthorhombic: a = 22.065 ?, b = 22.140 ?, c = 9.433 ?, Z = 4, space group Pccn. Structure I is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.098 for all 5974 unique reflections. Structure I contains the following asymmetric units: a half of the I₃⁻ centrosymmetric anion and two halves of the mixed equally average [K(Db18C6)(H₂O)₂]⁺ host—guest complex cation (a) and a free Db18C6 molecule, each stacked on the axes 2 of the perpendicularly averaged plane of the eighteen-membered macroheterocycle. In complex I, both Db18C6 molecules (a and b) have a “butterfly” conformation with approximate symmetry C _2v . Original Russian Text ? A.N. Chekhlov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 3, pp. 516–520.