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.     

Synthesis and crystal structure of hexaaquamagnesium 18-crown-6 dibromide dihydrate

A new complex compound [Mg(H₂O)₆]Br₂ · 18-crown-6 · 2H₂O(I) is synthesized, and its structure is studied by X-ray diffraction analysis. The crystals are monoclinic: space group P2₁/c, a = 7.128 Å, b = 18.584 Å, c = 9.598 Å, Å = 103.01°, Z = 2; R = 0.039 for 2180 independent reflections (CAD-4 automated diffractometer, λMoK _α radiation). The coordination polyhedron of the Mg²⁺ cation is a slightly distorted octahedron. The 18-crown-6 molecule has the conformation of a distorted crown with the approximate D _3d symmetry. The crystal contains a branched three-dimensional network of intermolecular (interionic) hydrogen bonds.     

Synthesis and crystal structure of dibenzo-18-crown-6 oxonium perchlorate

An ionized crystalline adduct of dibenzo-18-crown-6, perchloric acid, and water (H₃O)[DB 18K6](ClO₄) is synthesized and structurally studied by X-ray diffraction. The crystals are triclinic: a = 8.582 Å, b = 10.486 Å, c = 26.293 Å, α = 79.45°, β = 82.00°, γ = 79.36°, Z = 4, space group P \(\bar 1\). The structure is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.098 for 5936 independent reflections (CAD4 automated diffractometer, λMoK _α radiation). The structure contains two independent DB18C6 molecules, two independent H₃O⁺ ions, and two independent ClO ₄ ^? ions. The H₃O⁺ ions each lie in the cavity of each of the two DB18C6 molecules and are retained there by three strong hydrogen bonds. Two DB18C6 molecules have close geometric parameters and a butterfly conformation with approximate symmetry C _2v . One of the two independent ClO ₄ ^? anions is disordered over two orientations.     

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.     

Synthesis and crystal structure of dibenzo-18-crown-6 oxonium perchlorate trihydrate

A hydrated crystalline ionized adduct of dibenzo-18-crown-6 and perchloric acid DB18C6 · H₃O⁺ · CiO ₄ ^? · 3H₂O (I) is synthesized and characterized by X-ray diffraction. The crystals of I are monoclinic: a = 17.760 Å, b = 12.922 Å, β = 124.27°, Z = 4, space group Cc. The structure of I is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.079 for 3294 independent reflections (CAD4 automated diffractometer, λMoK _α radiation). A DB18C6 molecule has a butterfly conformation with the rough symmetry C _2v . An H₃O⁺ · H₂O dimer is situated on one side of the DB18C6 macrocycle, and the ClO ₄ ^? anion and two other water molecules are on the other side. In the crystal of I, the DB18C6 molecules, H₃O⁺ and ClO ₄ ^? ions, and water molecules are linked through intermolecular (interionic) hydrogen bonds to form broad infinite chains running along the z axis.     

Synthesis and crystal structure of aqua(dibenzo-18-crown-6)potassium (dibenzo-18-crown-6)(perchlorato-O)potassium perchlorate

A new compound, aqua(dibenzo-18-crown-6)potassium (dibenzo-18-crown-6)(perchlorato-O)potassium perchlorate ([K(DB18C6)(H₂O)]⁺ · [K(ClO₄)(DB18C6)] · ClO ₄ ^? ; compound I) is synthesized and studied by X-ray crystallography. The crystals are triclinic: a = 9.050 Å, b = 9.848 Å, c = 26.484 Å, α = 82.87°, β = 84.16°, γ = 77.93°, Z = 2, space group P $\bar 1$ . The structure is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.058 for 5960 independent reflections (CAD4 diffractometer, λMoK _α radiation). A complex cation [K(DB18C6)(H₂O)]⁺ and a complex molecule [K(ClO₄)(DB18C6)] are of the host-guest type; they are linked into a dimer through two K⁺ → π(C) bonds formed by one of the two K⁺ cations with two C atoms of the benzene ring of the DB18C6 ligand from the adjacent complex. Both DB18C6 ligands in I have a butterfly conformation with approximate symmetry C _2v .     

Reaction of lead halides with 18-crown-6 and dicyclohexano-18-crown-6: Solvent extraction,synthesis and crystal structure of [Pb(18-crown-6)I2]

Abstract

Solvent extraction of lead halides with 18-crown-6 (18C6), dicyclohexano-18-crown-6 (DC18C6, cis-syn-cis and cis-anti-cis isomers) in chloroform was studied, and the extraction constants corrected for side reactions and ionic strength effects were obtained. The compounds of the same composition as those being extracted were also isolated in crystal form. The molecular structure of the [Pb(18C6)I₂] complex has been determined. Crystals are monoclinic, P2₁/n, a = 11.237(2), b = 10.992(2), c = 8.139(2)Å, β = 97.32(3)°, V = 997.1(7)ų, D_calc = 2.416(2)gcm^?3, Z = 2 for the composition C₁₂H₂₄O₆PbI₂. The final R-factor is 0.043 for 558 unique reflections. The lead atom is coordinated to six oxygen atoms of the crown ether and two iodine atoms forming a hexagonal bipyramidal coordination polyhedron. The 18C6 molecule and the two halogen atoms form a hydrophobic coating for the lead atom which may be assumed to be the main reason of high extraction constants of the iodine complexes. For 10-coordinate lead ion (bidentate counter ions) the cis-syn-cis isomer of DC18C6 appears to be the best extraction reagent, while for 8-coordinate lead ion (monodentate halide anion) no difference between isomers was observed.     

On the protonation of dibenzo-18-crown-6

Abstract  

The stability constant of the dibenzo-18-crown-6·H₃O⁺ cationic complex species dissolved in nitrobenzene saturated with water has been determined from extraction experiments in the two-phase water–nitrobenzene system and from γ-activity measurements. Various structures of protonated dibenzo-18-crown-6 are discussed.     

Preparation and disordered crystal structure of (18-crown-6)ammonium isothiocyanate hemihydrate

A crystalline complex salt, (18-crown-6)ammonium isothiocyanate hemihydrate [NH ₄ ⁺ (18C6)]·SCN^?·0.5H₂O, was prepared and studied by single-crystal X-ray diffraction. The crystal structure of this salt is highly disordered: Almost all the constituents (except the water molecule) are disordered over two different orientations: major and less occupied or weakly occupied. The geometric parameters (bond lengths, bond angles, etc.) of the molecular and ionic constituents of the salt were determined with reasonable accuracy, and the crystal packing was elucidated. The sale forms in the crystal a complex tetrahedral supramolecular hydrogen-bonded structure consisting of one water molecule, two complex cations [NH ₄ ⁺ (18C6)], and two SCN^? anions.     

On the protonation of dibenzo-18-crown-6

Abstract  The stability constant of the dibenzo-18-crown-6·H₃O⁺ cationic complex species dissolved in nitrobenzene saturated with water has been determined from extraction experiments in the two-phase water–nitrobenzene system and from γ-activity measurements. Various structures of protonated dibenzo-18-crown-6 are discussed. Graphical abstract        

Second crystal modification of 1,10-diazonia-18-crown-6 dichloride

The second crystal modification (II) of 1,10-diazonia-18-crown-6 dichloride [H₂DA18C6]²⁺·2Cl^?, where [H₂DA18C6]²⁺ is the 1,10-diaza-18-crown-6 dication (DA18C6) with two protonated nitrogen atoms, was investigated by XRD. The monoclinic modification (II) (space group P2₁/n, a = 9.600 Å, b = 5.689 Å, c = 15.749 Å, β = 91.03°, Z = 2) was solved by direct methods and refined by full-matrix least squares analysis in an anisotropic approximation to R = 0.032 for all 2494 independent reflections collected (CAD-4 automatic diffractometer, λMoK _α). In modification II, the conformation of the DA18C6 dication and the ion packing differ from those in triclinic modification I investigated previously.     

Synthesis and crystal structure of ammonium (picrate) (dibenzo-18-crown-6)

NH₄(Pic)(DB18C6) (Pic=picrate and DB18C6=dibenzo-18-crown-6), (C₂₆H₃₀N₄O₁₃) FW 606.56, arthorhombic,Pmn2₁,a=26.045(5),b=12.055(3),c=8.982(3) Å,V=2820(1) ų,Z=4,D _c =1.429 g/cm³, CuK, =1.54184 Å, (CuK)=9.5 cm^–1,F(000)=1272,T=298 K. The structure has been refined toR=0.0475 for 2617 unique observed reflections. In the lattice the 1:1 complex exists as a 2:2 dimer in which the crown are coupled through the Pic anions and NH₄ ⁺ cations. The asymmetric unit consists of two independent half crown ethers of which two opposite O atoms are on the mirror plane, two half ammonium cations of which the N and two H atoms are also on the mirror plane while the Pic anion is in a general position. Relative to each other, the corwn ethers are shifted by about 7.3 Å alongb and 1 Å alongc. The 1:1 sandwich of NH₄ with DB18C6 and Pic on dimerisation becomes a club pseudo-sandwich with three phenyl rings on either side of the mirror plane, thus forming a nearly parallel stack with a 3.6 Å inter-ring distance. The NH₄ ions hold the structure; two H atoms on the mirror plane are hydrogen-bonded to the opposite oxygens of the crown located on the purely aliphatic part of the ring (2.10(1), 2.06(3) and 2.26(3), 2.05(1) Å) for the two independent crowns, respectively, while the other two H atoms form mirror-related bifurcated hydrogen bonds with the phenoxide oxygen (1.99(1) and 2.01(1) Å) and theo-nitrogen oxygen (2.44(2) and 2.34(1) Å) of the picrates. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82037 (29 pages)     

Selective transport of silver ion through a supported liquid membrane using hexathia-18-crown-6 as carrier.

A facile supported liquid membrane (SLM) system for the selective and efficient transport of silver ion is introduced. The SLM used is a thin porous polyvinyldifluoride membrane impregnated with hexathia-18-crown-6 (HT18C6) dissolved in nitrophenyloctyl ether. HT18C6 acts as a specific carrier for the uphill transport of Ag+ ion as its picrate ion paired complex through the SLM. In the presence of thiosulfate ion as a suitable stripping agent in the strip solution, transport of silver occurs almost quantitatively after 4 h. The selectivity and efficiency of silver transport from aqueous solutions containing other Mn+ cations such as Mg2+, Ca2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+, Hg2+, Fe3+ and Cr3+ ions were investigated.     

Conformational study of the structure of free 18-crown-6

A conformational search was performed for 18-crown-6 using the CONLEX method at the MM3 level. To have a more accurate energy order of the predicted conformations, the predicted conformations were geometry optimized at the HF/STO-3G level and the 198 lowest energy conformations, according to the HF/STO-3G energy order, were geometry optimized at the HF/6-31+G level. In addition, the 47 nonredundant lowest energy conformations, according to the MP2/6-31+G energy order at the HF/6-31+G optimized geometry, hereafter the MP2/6-31+G//HF/6-31+G energy order, were geometry optimized at the B3LYP/6-31+G level. According to the MP2/6-31+G//B3LYP/6-31+G energy order, three conformations had energies lower than the experimentally known Ci conformation of 18c6. At the MP2/6-31+G//B3LYP/6-31+G level, the S6 lowest energy conformation is more stable by 1.96 kcal/mol than this Ci conformation. This was confirmed by results at the MP2/6-31+G level with an energy difference of 1.84 kcal/mol. Comparison between the structure of the S6 conformation of 18c6 and the S4 lowest energy conformation of 12-crown-4, as well as other important conformations of both molecules, is made. It is concluded that the correlation energy is necessary to have an accurate energy order of the predicted conformations. A rationalization of the conformational energy order in terms of the hydrogen bonding and conformational dihedral angles is given. It is also suggested that to have a better energy order of the predicted conformations at the MM3 level, better empirical force fields corresponding to the hydrogen bond interactions are needed.     

On the solid-state conformations of 18-crown-6 complexes

A procedure for displaying macrocylic torsion angles as a map on polar coordinates is discussed with reference to the solid-state conformations of l8-crown-6 and its complexes. The maps aid in comparisons of related structures, in the perception of pseudo-symmetry elements, and in the classification of the conformations of 18-crown-6. Only four conformational groups are found in the 1 : 1 complexes of 18-crown-6 with sodium, potassium, rubidium, cesium, thallium(I), calcium and strontium cations. The relationship of donor number, mean cavity radius and effective ionic radius combined with skeletal drawings of the donors and the polar map of the torsion angles provide a composite picture of the structures and insight into the balance between cation-donor interaction energy and conformational energy.This paper is dedicated to the memory of the late Dr C. J. Pedersen.     

Synthesis and crystal structure of (dibenzo-18-crown-6)(iodo)(trichlorometane)potassium

A new complex compound (dibenzo-18-crown-6)(iodo)(trichlorometane)potassium was obtained. Its crystal structure was studied by X-ray structural analysis. The complex molecule is built by the “guest-host” type: its K⁺ cation is in the crown ligand hollow and is coordinated via its all six O atoms, and also via the iodine ligand I and one Cl atom of the ligand CHCl₃ molecule. The coordination polyhedron of this K⁺ cation is a slightly distorted hexagonal bipyramid. In the crystal structure the complex molecules are connected in infinite chains by intercomplex hydrogen bonds Cl₃C-H?I ⁱ between the ligand molecule CHCl₃ and the iodine ligand of a neighboring complex molecule.     

Synthesis and crystal structure of (18-crown-6)(perchlorato-O)(triphenylphosphine oxide)potassium

A new complex, (18-crown-6)(perchlorato-O)(triphenylphosphine oxide)potassium, was synthesized and its structure was studied by X-ray diffraction. The crystals are trigonal: a = 14.419,c = 13.895 Å, Z = 3, space group R3m; the structure was solved by the direct method and refined by the anisotropic full-matrix least-squares method, R = 0.079 on 1930 independent reflections, CAD-4 automated diffractometer, λMoK _α . The structure contains a highly symmetric host-guest complex molecule [K(ClO₄)(18-crown-6)(Ph₃PO)] in position 3m (with three Ph rings of the Ph₃PO ligand and all the O atoms of a crown ligand lying in three m planes). The coordination polyhedron of the K⁺ cation is a distorted hexagonal bipyramid with six O atom of the 18-crown-6 ligand in a base and the O atom of the Ph₃PO ligand and disordered O atom of the ClO ₄ ^? ligand in the axial vertices.     

Synthesis and crystal structure of diaqua(trinitrato)iron(III) 18-crown-6

A novel complex adduct, diaqua(trinitrato)iron(III) 18-crown-6, [Fe(NO₃)₃(H₂O)₂] · 18-crown-6, was synthesized and its crystal structure was studied by X-ray diffraction: space group C2/c, a = 10.073, b = 18.069, c = 25.326 Å, β = 91.51°, Z = 8. The structure was solved by the direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.076 for 4090 independent reflections (CAD-4 automated diffractometer, λMoK_α). The structure contains isolated complex molecule [Fe(NO₃)₃(H₂O)₂] and two halves of independent molecules 18-crown-6, one of which is statistically disordered about axis 2, while another one is located around the inversion center and is somewhat disordered with respect to the latter. In the complex molecule, the coordination polyhedron of the Fe³⁺ cation is a distorted pentagonal bipyramid with five O atoms of three NO ₃ ^? ligands in a base and two O atoms of two water molecules in the axial vertices. The alternating complex molecules and the disordered 18-crown-6 molecules are joined by hydrogen bonds into “thick” infinite chains along the z axis.     

(Dibenzo-18-crown-6)potassium tetrachloroferrate(III): Synthesis and crystal structure

A new complex [K(Db18C6)]⁺[FeCl₄]^? (I) is synthesized and its structure is studied by X-ray diffraction analysis. The crystals are triclinic: space group P \(\bar 1\), a = 17.998, b = 18.670, c = 19.590 Å, α = 106.61°, β = 104.55°, γ = 113.87°, Z = 8. The structure is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.057 by 13 670 independent reflections (CAD-4 automated diffractometer, λMoK _α). All the four independent complex cations [K(Db18C6)]⁺ are host-guest, and in each complex cation the K⁺ cation is localized in the cavity of the Db18C6 crown ligand. The coordination polyhedron of K⁺ (coordination number nine) is a distorted hexagonal bipyramid with the base of all six O atoms of the Db18C6 ligand, the axial vertex at the Cl atom of the [FeCl₄]^? anion, and another bifurcated axial vertex at two Cl atoms of another [FeCL₄]^? anion. All the four independent [FeCL₄]^? anions are orientationally disordered and have somewhat distorted tetrahedral structure. In crystal I, the alternating complex cations [K(Db18C6)]⁺ and [FeCL₄]^? anions form infinite polymer chains by the K-Cl bonds.     

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.