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| 18-Crown-6 is an organic compound with the formula [C2H4O]6 and the IUPAC name of 1,4,7,10,13,16-hexaoxacyclooctadecane. It is a white, hygroscopic crystalline solid with a low melting point. Like other crown ethers, 18-crown-6 functions as a ligand for some metal cations with a particular affinity for potassium cations (binding constant in methanol: 106 M−1). The point group of 18-crown-6 is S6. The dipole moment of 18-crown-6 is solvent- and temperature-dependent. Below 25 °C, the dipole moment of 18-crown-6 is 2.76 ± 0.06 D in cyclohexane and 2.73 ± 0.02 in benzene. The synthesis of the crown ethers led to the awarding of the Nobel Prize in Chemistry to Charles J. Pedersen. |
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| InChI=1S/C12H24O6/c1-2-14-5-6-16-9-10-18-12-11-17-8-7-15-4-3-13-1/h1-12H2 |
| XEZNGIUYQVAUSS-UHFFFAOYSA-N |
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phase-transfer catalyst
A catalyst that facilitates the migration of a reactant from one phase into another phase where reaction occurs.
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View more via ChEBI Ontology
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1,4,7,10,13,16-hexaoxacyclooctadecane
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18-crown-6
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IUPAC
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18-crown-6 ether
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NIST Chemistry WebBook
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ethylene oxide cyclic hexamer
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NIST Chemistry WebBook
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1619616
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Beilstein Registry Number
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Beilstein
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17455-13-9
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CAS Registry Number
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ChemIDplus
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17455-13-9
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CAS Registry Number
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NIST Chemistry WebBook
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4535
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Gmelin Registry Number
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Gmelin
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Ghasemisarabbadieh M, Gizurarson S, Sveinbjornsson BR (2021)
Effect of 18-Crown-6 on Oxytocin Stability in Aqueous Buffer Solutions.
ACS omega 6, 5805-5811 [PubMed:33681619]
[show Abstract]
In this study, the effect of 18-crown-6 on the stability of oxytocin in aqueous solution was explored. The study found that while 12-crown-4 and 15-crown-5 do not stabilize oxytocin, 18-crown-6 does have a stabilizing effect in citrate/phosphate buffer at pH 4.5. However, in acetate buffer at the same pH, the presence of 18-crown-6 had a destabilizing effect, possibly leading to a different degradation pathway. Both the stabilizing and destabilizing effects, depending on the buffer used, are concentration dependent where a higher concentration of 18-crown-6 is linked to a stronger effect. It is hypothesized that this effect may be linked to 18-crown-6 binding to the protonated ammonium group of oxytocin. Upon changing the mobile phase used in high-performance liquid chromatography experiments, we observed evidence supporting this binding hypothesis. When an acidic mobile phase was used (0.01% trifluoroacetic acid (TFA)), a partial shift in oxytocin retention time was observed for samples in acetate buffers in the presence of 18-crown-6 when using a 150 mm column (C18). The amount of the peak that shifted depended on the 18-crown-6 concentration used. A similar shift in oxytocin peak retention time was observed for samples in both acetate and citrate/phosphate buffers when using a 250 mm column (C18), but the peak completely shifted in those samples. When using an even more acidic mobile phase (0.1% TFA), the oxytocin peaks all had the same retention time again. Ultraviolet and nuclear magnetic resonance spectroscopy experiments also showed that the presence of 18-crown-6 has an observable effect on the resulting oxytocin spectra. | Merzlyakova E, Wolf S, Lebedkin S, Bayarjargal L, Neumeier BL, Bartenbach D, Holzer C, Klopper W, Winkler B, Kappes M, Feldmann C (2021)
18-Crown-6 Coordinated Metal Halides with Bright Luminescence and Nonlinear Optical Effects.
Journal of the American Chemical Society 143, 798-804 [PubMed:33405904]
[show Abstract]
The crown-ether coordination compounds ZnX2(18-crown-6), EuX2(18-crown-6) (X: Cl, Br, I), MnI2(18-crown-6), Mn3Cl6(18-crown-6)2, Mn3I6(18-crown-6)2, and Mn2I4(18-crown-6) are obtained by ionic-liquid-based synthesis. Whereas MX2(18-crown-6) (M: Zn, Eu) show conventional structural motives, Mn3Cl6(18-crown-6)2, Mn3I6(18-crown-6)2, and Mn2I4(18-crown-6) exhibit unusual single MnX4 tetrahedra coordinated to the crown-ether complex. Surprisingly, some compounds show outstanding photoluminescence. Thus, rare Zn2+-based luminescence is observed and unexpectedly efficient for ZnI2(18-crown-6) with a quantum yield of 54%. Unprecedented quantum yields are also observed for Mn3I6(18-crown-6)2, EuBr2(18-crown-6), and EuI2(18-crown-6) with values of 98, 72, and 82%, respectively, which can be rationalized based on the specific structural features. Most remarkable, however, is Mn2I4(18-crown-6). Its specific structural features with finite sensitizer-activator couples result in an extremely strong emission with an outstanding quantum yield of 100%. Consistent with its structural features, moreover, anisotropic angle-dependent emission under polarized light and nonlinear optical (NLO) effects occur, including second-harmonic generation (SHG). The title compounds and their optical properties are characterized by single-crystal structure analysis, X-ray powder diffraction, chemical analysis, density functional theory (DFT) calculations, and advanced spectroscopic methods. | Balakrishnan C, Manonmani M, Rafi Ahamed S, Vinitha G, Meenakshisundaram SP, Sockalingam RM (2020)
Supramolecular cocrystals of O-H...O hydrogen-bonded 18-crown-6 with isophthalic acid derivatives: Hirshfeld surface analysis and third-order nonlinear optical properties.
Acta crystallographica Section B, Structural science, crystal engineering and materials 76, 241-251 [PubMed:32831226]
[show Abstract]
Two cocrystals of 18-crown-6 with isophthalic acid derivatives, 5-hydroxyisophthalic acid and trimesic acid, have been successfully grown by the slow evaporation solution growth technique. Crystal structures of (18-crown-6)·6(5-hydroxyisophthalic acid)·10(H2O) (I) and (18-crown-6)·2(trimesic acid)·2(H2O) (II) elucidated by single crystal X-ray diffraction reveal that both cocrystals pack the centrosymmetric triclinic space group P{\overline 1}. The molecules are associated by strong/weak hydrogen bonds, π...π and H...H stacking interactions. Powder X-ray diffraction analyses, experimental and simulated from single-crystal diffractogram data have been matched. The vibrational patterns in FT-IR spectra are used to identify the functional groups. The band gap energy is estimated by the application of the Kubelka-Munk algorithm. Hirshfeld surfaces derived from X-ray diffraction analysis reveal the type of molecular interactions and their relative contributions. The constructed supramolecular assembly of crown ether cocrystal is thoroughly described. Both cocrystals exhibit a significant third-order nonlinear optical response and it is observed that (I) possesses a significant first-order molecular hyperpolarizability whereas it is negligible for (II). | Sellin M, Malischewski M (2019)
Crystal structure of [K(18-crown-6)]+ 2[Pt(CN)4]2.
Acta crystallographica. Section E, Crystallographic communications 75, 1871-1874 [PubMed:31871748]
[show Abstract]
In the title compound, di-μ-cyanato-1:2κ2 N:C;2:3κ2 C:N-di-cyanato-2κ2 C-bis-(1,4,7,10,13,16-hexa-oxa-cyclo-octa-deca-ne)-1κ6 O;3κ6 O-1,3-dipotassium(I)-2-platinum(II), [K2Pt(CN)4(C12H24O6)2] or [K(18-crown-6)]2·[Pt(CN)4], two trans-orientated cyano groups of the square-planar [Pt(CN)4]2- dianion (Pt site symmetry ) bind to one potassium ion each, which are additionally coordinated by the six O atoms of 18-crown-6. No Pt⋯Pt inter-actions occur in the crystal, but very weak Pt⋯H contacts (2.79 Å) are observed. | Li J, Gómez-Coca S, Dolinar BS, Yang L, Yu F, Kong M, Zhang YQ, Song Y, Dunbar KR (2019)
Hexagonal Bipyramidal Dy(III) Complexes as a Structural Archetype for Single-Molecule Magnets.
Inorganic chemistry 58, 2610-2617 [PubMed:30694042]
[show Abstract]
Single-molecule magnets (SMMs), are regarded as excellent nanomaterials for high-density information storage and quantum computing. The local symmetry of the crystal field for the metal ion plays an important role in pursuing a high-performance SMM. Herein, two highly stable distorted hexagonal bipyramidal (quasi- D6 h) Dy complexes exhibiting slow relaxation of the magnetization are reported. A hexagonal bipyramidal Dy model complex with 18-crown-6 was also designed to study the relationship between magnetic anisotropy and symmetry. The combined experimental and theoretical results indicate that quantum tunneling is highly dependent on the local symmetries of the crystal field. The magnetic anisotropy becomes much stronger when the symmetry is closer to a standard D6 h geometry. These results support the conclusion that the hexagonal bipyramidal geometry is a viable one for the design of new classes of SMMs. | Shi MW, Thomas SP, Hathwar VR, Edwards AJ, Piltz RO, Jayatilaka D, Koutsantonis GA, Overgaard J, Nishibori E, Iversen BB, Spackman MA (2019)
Measurement of Electric Fields Experienced by Urea Guest Molecules in the 18-Crown-6/Urea (1:5) Host-Guest Complex: An Experimental Reference Point for Electric-Field-Assisted Catalysis.
Journal of the American Chemical Society 141, 3965-3976 [PubMed:30761898]
[show Abstract]
High-resolution synchrotron and neutron single-crystal diffraction data of 18-crown-6/(pentakis)urea measured at 30 K are combined, with the aim of better appreciating the electrostatics associated with intermolecular interactions in condensed matter. With two 18-crown-6 molecules and five different urea molecules in the crystal, this represents the most ambitious combined X-ray/synchrotron and neutron experimental charge density analysis to date on a cocrystal or host-guest system incorporating such a large number of unique molecules. The dipole moments of the five urea guest molecules in the crystal are enhanced considerably compared to values determined for isolated molecules, and 2D maps of the electrostatic potential and electric field show clearly how the urea molecules are oriented with dipole moments aligned along the electric field exerted by their molecular neighbors. Experimental electric fields in the range of 10-19 GV m-1, obtained for the five different urea environments, corroborate independent measurements of electric fields in the active sites of enzymes and provide an important experimental reference point for recent discussions focused on electric-field-assisted catalysis. | Liebing P, Zaeni A, Olbrich F, Edelmann FT (2016)
Crystal structures of two solvates of (18-crown-6)potassium acetate.
Acta crystallographica. Section E, Crystallographic communications 72, 1757-1761 [PubMed:27980824]
[show Abstract]
The crystal and mol-ecular strutures of two solvated forms of [K(18c6)]OAc (18c6 = 18-crown-6 = 1,4,7,10,13,16-hexa-oxa-cyclo-octa-decane and OAc = acetate) were determined by single-crystal X-ray diffraction, namely (acetato-κ2O,O')(1,4,7,10,13,16-hexa-oxa-cyclo-octa-decane-κ6O)potassium dihydrate, [K(CH3COO)(C12H24O6)]·2H2O (1) and (acetato-κ2O,O')aqua-(1,4,7,10,13,16-hexa-oxa-cyclo-octa-decane-κ6O)potassium acetic acid monosolvate [K(CH3COO)(C12H24O6)(H2O)]·CH3COOH (2). In both compounds, the acetate anion is bonded to the potassium ion in a chelating fashion and the metal atom is consequently slightly displaced from the O6 plane of the crown ether. In the crystals, O-H⋯O hydrogen bonds lead to a polymeric ladder structure in the dihydrate 1, while the acetic acid hydrate 2 features inversion dimers. | Rodgers MT, Armentrout PB (2016)
Cationic Noncovalent Interactions: Energetics and Periodic Trends.
Chemical reviews 116, 5642-5687 [PubMed:26953819]
[show Abstract]
In this review, noncovalent interactions of ions with neutral molecules are discussed. After defining the scope of the article, which excludes anionic and most protonated systems, methods associated with measuring thermodynamic information for such systems are briefly recounted. An extensive set of tables detailing available thermodynamic information for the noncovalent interactions of metal cations with a host of ligands is provided. Ligands include small molecules (H2, NH3, CO, CS, H2O, CH3CN, and others), organic ligands (O- and N-donors, crown ethers and related molecules, MALDI matrix molecules), π-ligands (alkenes, alkynes, benzene, and substituted benzenes), miscellaneous inorganic ligands, and biological systems (amino acids, peptides, sugars, nucleobases, nucleosides, and nucleotides). Hydration of metalated biological systems is also included along with selected proton-based systems: 18-crown-6 polyether with protonated peptides and base-pairing energies of nucleobases. In all cases, the literature thermochemistry is evaluated and, in many cases, reanchored or adjusted to 0 K bond dissociation energies. Trends in these values are discussed and related to a variety of simple molecular concepts. | Hausmann D, Kuzmanoski A, Feldmann C (2016)
MnBr₂/18-crown-6 coordination complexes showing high room temperature luminescence and quantum yield.
Dalton transactions (Cambridge, England : 2003) 45, 6541-6547 [PubMed:26956783]
[show Abstract]
The reaction of manganese(ii) bromide and the crown ether 18-crown-6 in the ionic liquid [(n-Bu)3MeN][N(Tf)2] under mild conditions (80-130 °C) resulted in the formation of three different coordination compounds: MnBr2(18-crown-6) (), Mn3Br6(18-crown-6)2 () and Mn3Br6(18-crown-6) (). In general, the local coordination and the crystal structure of all compounds are driven by the mismatch between the small radius of the Mn(2+) cation (83 pm) and the ring opening of 18-crown-6 as a chelating ligand (about 300 pm). This improper situation leads to different types of coordination and bonding. MnBr2(18-crown-6) represents a molecular compound with Mn(2+) coordinated by two bromine atoms and only five oxygen atoms of 18-crown-6. Mn3Br6(18-crown-6)2 falls into a [MnBr(18-crown-6)](+) cation - with Mn(2+) coordinated by six oxygen atoms and Br - and a [MnBr(18-crown-6)MnBr4](-) anion. In this anion, Mn(2+) is coordinated by five oxygen atoms of the crown ether as well as by two bromine atoms, one of them bridging to an isolated (MnBr4) tetrahedron. Mn3Br6(18-crown-6), finally, forms an infinite, non-charged [Mn2(18-crown-6)(MnBr6)] chain. Herein, 18-crown-6 is exocyclically coordinated by two Mn(2+) cations. All compounds show intense luminescence in the yellow to red spectral range and exhibit remarkable quantum yields of 70% (Mn3Br6(18-crown-6)) and 98% (Mn3Br6(18-crown-6)2). The excellent quantum yield of Mn3Br6(18-crown-6)2 and its differentiation from MnBr2(18-crown-6) and Mn3Br6(18-crown-6) can be directly correlated to the local coordination. | Ponomarova VV, Rusanova JA, Rusanov EB, Domasevitch KV (2015)
Unusual centrosymmetric structure of [M(18-crown-6)](+) (M = Rb, Cs and NH4) complexes stabilized in an environment of hexachloridoantimonate(V) anions.
Acta crystallographica. Section C, Structural chemistry 71, 867-872 [PubMed:26422213]
[show Abstract]
In (1,4,7,10,13,16-hexaoxacyclooctadecane)rubidium hexachloridoantimonate(V), [Rb(C12H24O6)][SbCl6], (1), and its isomorphous caesium {(1,4,7,10,13,16-hexaoxacyclooctadecane)caesium hexachloridoantimonate(V), [Cs(C12H24O6)][SbCl6]}, (2), and ammonium {ammonium hexachloridoantimonate(V)-1,4,7,10,13,16-hexaoxacyclooctadecane (1/1), (NH4)[SbCl6]·C12H24O6}, (3), analogues, the hexachloridoantimonate(V) anions and 18-crown-6 molecules reside across -3 axes passing through the Sb atoms and the centroids of the 18-crown-6 groups, both of which coincide with centres of inversion. The Rb(+) [in (1)], Cs(+) [in (2)] and NH4(+) [in (3)] cations are situated inside the cavity of the 18-crown-6 ring; they are situated on -3 axes and are equally disordered about centres of inversion, deviating from the centroid of the 18-crown-6 molecule by 0.4808 (13), 0.9344 (7) and 0.515 (8) Å, respectively. Interaction of the ammonium cation and the 18-crown-6 group is supported by three equivalent hydrogen bonds [N...O = 2.928 (3) Å and N-H...O = 162°]. The centrosymmetric structure of [Cs(18-crown-6)](+), with the large Cs(+) cation approaching the centre of the ligand cavity, is unprecedented and accompanied by unusually short Cs-O bonds [2.939 (2) and 3.091 (2) Å]. For all three compounds, the [M(18-crown-6)](+) cations and [SbCl6](-) anions afford linear stacks along the c axis, with the cationic complexes embedded between pairs of inversion-related anions. | Brennessel WW, Ellis JE (2015)
Crystal structure of (18-crown-6)potassium(I) [(1,2,3,4,5-η)-cyclo-hepta-dien-yl][(1,2,3-η)-cyclo-hepta-trien-yl]cobalt(I).
Acta crystallographica. Section E, Crystallographic communications 71, 291-295 [PubMed:25844191]
[show Abstract]
The reaction of bis-(anthracene)cobaltate(-I) with excess cyclo-hepta-triene, C7H8, resulted in a new 18-electron cobaltate containing two different seven-membered ring ligands, based on single-crystal X-ray diffraction. The asymmetric unit of this structure contains two independent cation-anion pairs of the title complex, [K(18-crown-6)][Co(η(3)-C7H7)(η(5)-C7H9)], where 18-crown-6 stands for 1,4,7,10,13,16-hexa-oxa-cyclo-octa-decane (C12H24O6), in general positions and well separated. Each (18-crown-6)potassium cation is in contact with the η(3)-coordinating ligand of one cobaltate complex. Each η(3)-coordinating ligand behaves as an allylic anion whose exo-diene moiety is bent away from the allylic plane, and thus is not involved directly in the bonding. The metal-coordinating portions of the anionic η(5) ligands are planar and one of these ligands is modeled as disordered over two positions, with occupancy ratio 0.699 (5):0.301 (5), such that one orientation is rotated by one carbon atom with respect to the other. The diffraction intensities were integrated according to non-merohedral twin law [-1 0 0/0 -1 0/0.064 0 1], a 180° rotation about reciprocal lattice axis [001], and the masses of the twin domains refined to equal amounts. As both ligands are formally coordinated as anions, the cobalt atom is best considered to be Co(I). This compound is of inter-est as the first to possess cyclo-hepta-trienyl and cyclo-hepta-dienyl ligands in an anionic metal complex. | Boardman ND, Munshi T, Scowen IJ, Seaton CC (2014)
Creation of a ternary complex between a crown ether, 4-aminobenzoic acid and 3,5-dinitrobenzoic acid.
Acta crystallographica Section B, Structural science, crystal engineering and materials 70, 132-140 [PubMed:24441136]
[show Abstract]
The creation of ternary multi-component crystals through the introduction of 18-crown-6 to direct the hydrogen-bonding motifs of the other molecular components was investigated for 3,5-dinitrobenzoic acid (3,5-dnba) with 4-aminobenzoic acid (4-aba). The creation of a binary complex between 18-crown-6 and 4-aba (C12H24O6·2C7H7NO2)2 and a ternary salt between 3,5-dnba, 18-crown-6 and 4-aba (C12H24O6·C7H8NO2(+)·C7H3N2O6(-)·C7H4N2O6) were confirmed by single-crystal structure determination. In both structures, the amino molecules bind to the crown ether through N-H...O hydrogen bonds, leaving available only a single O atom site on the crown with restricted geometry to potentially accept a hydrogen bond from 3,5-dnba. While 3,5-dnba and 4-aba form a binary co-crystal containing neutral molecules, the shape-selective nature of 18-crown-6 preferentially binds protonated amino molecules, thereby leading to the formation of the ternary salt, despite the predicted low concentration of the protonated species in the crystallizing solution. Thus, through the choice of crown ether it may be possible to control both location and nature of the available bonding sites for the designed creation of ternary crystals. | Belghith Y, Toumi H, Daran JC, Nasri H (2014)
A one-dimensional polymeric cobalt(III)-potassium complex with 18-crown-6, cyanide and porphyrinate ligands.
Acta crystallographica. Section E, Structure reports online 70, m104-5 [PubMed:24764938]
[show Abstract]
The reaction of Co(II)(TpivPP) {TpivPP is the dianion of 5,10,15,20-tetra-kis-[2-(2,2-di-methyl-propanamido)-phen-yl]por-ph-yrin} with an excess of KCN salts and an excess of the 18-crown-6 in chloro-benzene leads to the polymeric title compound catena-poly[[dicyanido-2κ(2) C-(1,4,7,10,13,16-hexa-oxa-cyclo-octa-decane-1κ(6) O){μ3-(2α,2β)-5,10,15,20-tetra-kis-[2-(2,2-di-methyl-propanamido)-phen-yl]porphyrinato-1κO (5):2κ(4) N,N',N'',N''':1'κO (15)}cobalt(III)potassium] dihydrate], {[CoK(CN)2(C12H24O6)(C64H64N8O4]·2H2O} n . The Co(III) ion lies on an inversion center, and the asymmetric unit contains one half of a [Co(III)(2α,2β-TpivPP)(CN)2](-) ion complex and one half of a [K(18-C-6](+) counter-ion (18-C-6 is 1,4,7,10,13,16-hexa-oxa-cyclo-octa-deca-ne), where the K(I) ion lies on an inversion center. The Co(III) ion is hexa-coordinated by two C-bonded axial cyanide ligands and the four pyrrole N atoms of the porphyrin ligand. The K(I) ion is chelated by the six O atoms of the 18-crown-6 mol-ecule and is further coordinated by two O atoms of pivalamido groups of the porphyrin ligands, leading to the formation of polymeric chains running along [011]. In the crystal, the polymeric chains and the lattice water mol-ecules are linked by N-H⋯O and O-H⋯N hydrogen bonds, as well as weak C-H⋯O, O-H⋯π and C-H⋯π inter-actions into a three-dimensional supra-molecular architecture. | Kaas M, Friedrich U, Korber N (2014)
(18-Crown-6)potassium(I) di-phenyl-stibate(-1).
Acta crystallographica. Section E, Structure reports online 70, m260 [PubMed:25161524]
[show Abstract]
Red crystals of the title salt, [K(C12H24O6)][Sb(C6H5)2], were obtained by the reaction of SbPh3, KSnBi and 18-crown-6 in liquid ammonia. The asymmetric unit contains one half of a [K(18-crown-6)](+) cation and one half of an SbPh2 (-) anion, with the central element lying on a twofold axis and a centre of inversion, respectively. In the crystal structure, the sequestered potassium cations show weak inter-actions with the π-electrons of the phenyl groups of the SbPh2 (-) anion [shortest K⋯C distances = 3.190 (2) and 3.441 (2) Å], leading to one-dimensional strands along the crystallographic c axis. These strands are aligned in a pseudo-hexa-gonal packing perpendicular to the ab plane. | Lee CC, Maestre-Reyna M, Hsu KC, Wang HC, Liu CI, Jeng WY, Lin LL, Wood R, Chou CC, Yang JM, Wang AH (2014)
Crowning proteins: modulating the protein surface properties using crown ethers.
Angewandte Chemie (International ed. in English) 53, 13054-13058 [PubMed:25287606]
[show Abstract]
Crown ethers are small, cyclic polyethers that have found wide-spread use in phase-transfer catalysis and, to a certain degree, in protein chemistry. Crown ethers readily bind metallic and organic cations, including positively charged amino acid side chains. We elucidated the crystal structures of several protein-crown ether co-crystals grown in the presence of 18-crown-6. We then employed biophysical methods and molecular dynamics simulations to compare these complexes with the corresponding apoproteins and with similar complexes with ring-shaped low-molecular-weight polyethylene glycols. Our studies show that crown ethers can modify protein surface behavior dramatically by stabilizing either intra- or intermolecular interactions. Consequently, we propose that crown ethers can be used to modulate a wide variety of protein surface behaviors, such as oligomerization, domain-domain interactions, stabilization in organic solvents, and crystallization. | Engel ER, Smith VJ, Bezuidenhout CX, Barbour LJ (2014)
Uniaxial negative thermal expansion facilitated by weak host-guest interactions.
Chemical communications (Cambridge, England) 50, 4238-4241 [PubMed:24633431]
[show Abstract]
A nitromethane solvate of 18-crown-6 was investigated by means of variable-temperature single-crystal X-ray diffraction in response to a report of abnormal unit cell contraction. Exceptionally large positive thermal expansion in two axial directions and negative thermal expansion along the third was confirmed. The underlying mechanism relies exclusively on weak electrostatic interactions to yield a linear thermal expansion coefficient of -129 × 10(-6) K(-1), the largest negative value yet observed for an organic inclusion compound. | Mihelj T, Tomašić V, Biliškov N, Liu F (2014)
Temperature-dependent IR spectroscopic and structural study of 18-crown-6 chelating ligand in the complexation with sodium surfactant salts and potassium picrate.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy 124, 12-20 [PubMed:24457933]
[show Abstract]
18-crown-6 ether (18C6) complexes with the following anionic surfactants: sodium n-dodecylsulfate (18C6-NaDS), sodium 4-(1-pentylheptyl)benzenesulfonate (18C6-NaDBS); and potassium picrate (18C6-KP) were synthesized and studied in terms of their thermal and structural properties. Physico-chemical properties of new solid 1:1 coordination complexes were characterized by infrared (IR) spectroscopy, thermogravimetry and differential thermal analysis, differential scanning calorimetry, X-ray diffraction and microscopic observations. The strength of coordination between Na(+) and oxygen atoms of 18C6 ligand does not depend on anionic part of the surfactant, as established by thermodynamical parameters obtained by temperature-dependent IR spectroscopy. Each of these complexes exhibit different kinds of endothermic transitions in heating scan. Diffraction maxima obtained by SAXS and WAXS, refer the behavior of the compounds 18C6-NaDS and 18C6-NaDBS as smectic liquid crystalline. Distortion of 18C6-NaDS and 18C6-KP complexes occurs in two steps. Temperature of the decomplexation of solid crystal complex 18C6-KP is considerably higher than of mesophase complexes, 18C6-NaDS, and 18C6-NaDBS. The structural and liquid crystalline properties of novel 18-crown-ether complexes are function of anionic molecule geometry, type of chosen cation (Na(+), K(+)), as well as architecture of self-organized aggregates. A good combination of crown ether unit and amphiphile may provide a possibility for preparing new functionalized materials, opening the research field of ion complexation and of host-guest type behavior. | Zhang Y (2013)
Butan-1-aminium tetra-chlorido-ferrate(III)-18-crown-6 (1/1).
Acta crystallographica. Section E, Structure reports online 69, m38 [PubMed:23476335]
[show Abstract]
In the crystal of the title compound, (C4H12N)[FeCl4]·C12H24O6, the butan-1-aminium cation and the tetra-chloridoferrate(III) anion have m symmetry: in the cation, the non-H atoms are located on the mirror plane and in the anion, the Fe(III) atom and two Cl atoms are located on the mirror plane. The 18-crown-6 mol-ecule also has m symmetry, with two O atoms located on the mirror plane. The butan-1-amine cation and the 18-crown-6 mol-ecule are connected by N-H⋯O hydrogen bonds. | Gjikaj M, Pook NP, Qarri F (2013)
μ-Hexa-thio-metadiphosphato-bis-[(1,4,7,10,13,16-hexa-oxa-cyclo-octa-decane-κ(6) O)rubidium] aceto-nitrile disolvate.
Acta crystallographica. Section E, Structure reports online 69, m689 [PubMed:24860286]
[show Abstract]
The asymmetric unit of the title compound, [Rb2(P2S6)(C12H24O6)2]·2CH3CN, contains one half of an [Rb(18-crown-6)2]2[P2S6] unit and one aceto-nitrile solvent mol-ecule. The [Rb(18-crown-6)]2[P2S6] unit is completed by inversion symmetry. Its Rb(+) ion is situated near the centre of the macrocyclic cavity, but is displaced by 0.8972 (1) Å from the O atoms of the crown in the direction of the [P2S6](2-) moiety. The overall coordination number of the cation is eight, defined by the six crown ether O atoms and by two terminal S atoms of the [P2S6](2-) anion. The hexa-thio-metadiphosphate anion is built up from two tetra-hedral PS4 units joined together by a common edge. The crystal structure is characterized by alternating layers of [Rb(18-crown-6)]2[P2S6] and aceto-nitrile solvent mol-ecules stacked along [010]. | Kleeberg C (2013)
On the structural diversity of [K(18-crown-6)EPh3] complexes (E = C, Si, Ge, Sn, Pb): synthesis, crystal structures and NOESY NMR study.
Dalton transactions (Cambridge, England : 2003) 42, 8276-8287 [PubMed:23599065]
[show Abstract]
A series of homologous potassium triphenylelement complexes [K(18-crown-6)EPh3] 6a-e of group 14 elements (E = C, Si, Ge, Sn, Pb) was synthesised by alkoxide induced heterolytic cleavage of boron-element compounds. The complexes 6a-e are isolated as storable solids possibly useful as sources of nucleophilic [EPh3](-) moieties. The solid state structures of 6a-e were established by X-ray crystal structure determination. Whilst all structures can be described as polymeric chains consisting of alternating [K(18-crown-6)](+) and [EPh3](-) units, the interaction within each chain varies systematically with the coordination properties of E. For Si and Ge, classical E-K coordination along with secondary phenyl-K interactions are characteristic, whilst for Sn and Pb, potassium coordination via the phenyl π-system is observed due to inefficient coordination by the free electron pair localised in an 'inert' s-orbital. The carbon derivative is exceptional as the central sp(2)-hybridised carbon atom gives rise to extensive charge delocalisation and coordination via these partially charged π-systems. A (1)H-(1)H NOESY NMR spectroscopic study in THF-d8 suggests appreciable anion/cation interactions for Si to Pb and hence the presence of contact ion pairs. | Beattie C, Farina P, Levason W, Reid G (2013)
Oxa-thia-, oxa-selena and crown ether macrocyclic complexes of tin(II) tetrafluoroborate and hexafluorophosphate--synthesis, properties and structures.
Dalton transactions (Cambridge, England : 2003) 42, 15183-15190 [PubMed:24000049]
[show Abstract]
The reactions of Sn(BF4)2 and Sn(PF6)2 with crown ethers and oxa-thia- or oxa-selena-macrocycles are complex, with examples of fragmentation of the fluoroanions, and cleavage of the ligands observed, in addition to adduct formation. The reaction of Sn(BF4)2 with 15-crown-5 or 18-crown-6 produced the sandwich complex [Sn(15-crown-5)2][BF4]2 with 10-coordinate tin, and [Sn(18-crown-6)(H2O)][BF4]2·2H2O which has an hexagonal pyramidal tin centre with two long contacts to lattice water molecules (overall 7 + 2 coordination). [Sn(18-crown-6)(PF6)][PF6] is formed from 18-crown-6 and Sn(PF6)2, but the hexafluorophosphate ions hydrolyse readily in these systems to produce F(-) which coordinates to the tin to produce [Sn(18-crown-6)F][PF6], which can also be made directly from Sn(PF6)2, 18-crown-6 and KF in MeCN. The structure contains a hexagonal pyramidal coordinated Sn(II) cation with an apical fluoride. The oxa-thia macrocycle [18]aneO4S2 forms [Sn([18]aneO4S2)(H2O)2(PF6)][PF6], from which some crystals of composition [Sn([18]aneO4S2)(H2O)2(PF6)]2[PF6][F] were obtained. The cation contains an approximately planar O4S2 coordinated macrocycle, with two coordinated water molecules on one side of the plane and a weakly bound (κ(2)) PF6(-) group on the opposite face, and with the fluoride ion hydrogen bonded to the coordinated water molecules. In contrast, the oxa-selena macrocycle, [18]aneO4Se2, produces an anhydrous complex [Sn([18]aneO4Se2)(PF6)2] which probably contains coordinated anions, although it decomposes quite rapidly in solution, depositing elemental Se, and hence crystals for an X-ray study were not obtained. Reacting Sn(BF4)2 and [18]aneO4Se2 or [18]aneO4S2 also causes rapid decomposition, but from the latter reaction crystals of the 1,2-ethanediol complex [Sn([18]aneO4S2){C2H4(OH)2}][BF4]2 were isolated. The structure reveals the coordinated macrocycle and a chelating diol, with the O-H protons of the latter hydrogen bonded to the [BF4](-) anions. This is a very rare, structurally authenticated example of ring opening/cleavage of an oxa-thia macrocycle. The new complexes were characterised by microanalysis, IR, (1)H, (19)F{(1)H} and (31)P{(1)H} NMR spectroscopy as appropriate, and X-ray structures are reported for [Sn(15-crown-5)2][BF4]3[H3O]·H2O, [Sn(18-crown-6)(H2O)][BF4]2·2H2O, [Sn(18-crown-6)F][PF6], [Sn([18]aneO4S2)(H2O)2(PF6)]2[PF6][F] and [Sn([18]aneO4S2){C2H4(OH)2}][BF4]2. The complexes are compared and contrasted with chloro-tin(II) complexes of crown ethers, germanium(II) and lead(II) analogues. | Shi PP, Zhang L, Ye Q (2012)
4-Carboxypyridinium perchlorate 18-crown-6 dihydrate clathrate and 4-carboxypyridinium tetrafluoroborate 18-crown-6 dihydrate clathrate.
Acta crystallographica. Section C, Crystal structure communications 68, o266-9 [PubMed:22763694]
[show Abstract]
Mixtures of 4-carboxypyridinium perchlorate or 4-carboxypyridinium tetrafluoroborate and 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) in ethanol and water solution yielded the title supramolecular salts, C(6)H(6)NO(2)(+)·ClO(4)(-)·C(12)H(24)O(6)·2H(2)O and C(6)H(6)NO(2)(+)·BF(4)(-)·C(12)H(24)O(6)·2H(2)O. Based on their similar crystal symmetries, unit cells and supramolecular assemblies, the salts are essentially isostructural. The asymmetric unit in each structure includes one protonated isonicotinic acid cation and one crown ether molecule, which together give a [(C(6)H(6)NO(2))(18-crown-6)](+) supramolecular cation. N-H···O hydrogen bonds between the protonated N atoms and a single O atom of each crown ether result in the 4-carboxypyridinium cations `perching' on the 18-crown-6 molecules. Further hydrogen-bonding interactions involving the supramolecular cation and both water molecules form a one-dimensional zigzag chain that propagates along the crystallographic c direction. O-H···O or O-H···F hydrogen bonds between one of the water molecules and the anions fix the anion positions as pendant upon this chain, without further increasing the dimensionality of the supramolecular network. | Zhao MM (2012)
Triaqua-chlorido(18-crown-6)barium chloride.
Acta crystallographica. Section E, Structure reports online 68, m286 [PubMed:22412432]
[show Abstract]
In the title compound, [BaCl(C(12)H(24)O(6))(H(2)O)(3)]Cl, the Ba(II) atom, the coordinating and free Cl(-) anions, one coordinating water mol-ecule and two O atoms of an 18-crown-6 mol-ecule lie on a mirror plane. The environment of the ten-coordinate Ba(2+) ion is defined by one Cl atom, three water mol-ecules and six O atoms from the macrocyclic ether. The macrocycle adopts a conformation with an approximate D(3d) symmetry. In the crystal, O-H⋯Cl hydrogen bonds link the complex cations and Cl(-) anions into a two-dimensional network parallel to (010). An intra-molecular O-H⋯Cl hydrogen bond is also present. | Sun SW (2012)
(1H-Benzimidazol-2-yl)methanaminium perchlorate-18-crown-6-water (1/1/1).
Acta crystallographica. Section E, Structure reports online 68, o25 [PubMed:22259530]
[show Abstract]
The crystal structure of the title compound C(8)H(10)N(3) (+)·ClO(4) (-)·C(12)H(24)O(6)·H(2)O, consists of an organic (1H-benzimidazol-2-yl)methanaminium cation, an inorganic ClO(4) (-) anion, one 18-crown-6 mol-ecule and one water mol-ecule. In the crystal, the cations and 18-crown-6 mol-ecules are linked by N-H⋯O hydrogen bonds. The crystal packing is stabilized by inter-molecular O-H⋯O, O-H⋯N and O-H⋯Cl hydrogen bonds between anions and the water mol-ecules. One 18-crown-6 C atom and a perchlorate O atom are disordered; both have an occupancy factor ratio of 0.60 (2) and 0.40 (2). | Wei B (2012)
Bis-(guanidinium) naphthalene-1,5-di-sulfonate-18-crown-6 (1/1).
Acta crystallographica. Section E, Structure reports online 68, o990 [PubMed:22590041]
[show Abstract]
In the crystal of the title compound, 2CH(6)N(3) (+)·C(10)H(6)O(6)S(2) (2-)·C(12)H(24)O(6), the 1,5-naphthnalenedisulfonate anion and the 18-crown-6 mol-ecule lie across inversion centers. The guanidin-ium cation links with the 1,5-naphthnalenedisulfonate anion and 18-crown-6 mol-ecule via N-H⋯O hydrogen bonds. | Wei B (2012)
Guanidinium chloride-18-crown-6 (2/1).
Acta crystallographica. Section E, Structure reports online 68, o1490 [PubMed:22590362]
[show Abstract]
In the crystal of the title compound, 2CH(6)N(3) (+)·2Cl(-)·C(12)H(24)O(6), the 18-crown-6 mol-ecule is located across an inversion center. The guanidinium cation links to the 18-crown-6 mol-ecule and chloride anion via N-H⋯O and N-H⋯Cl hydrogen bonds. | Grassl T, Hamberger M, Korber N (2012)
Acetyl-ene-ammonia-18-crown-6 (1/2/1).
Acta crystallographica. Section E, Structure reports online 68, o2933 [PubMed:23125720]
[show Abstract]
The title compound, C(2)H(2)·C(12)H(24)O(6)·2NH(3), was formed by co-crystallization of 18-crown-6 and acetyl-ene in liquid ammonia. The 18-crown-6 mol-ecule has threefold rotoinversion symmetry. The acteylene mol-ecule lies on the threefold axis and the whole mol-ecule is generated by an inversion center. The two ammonia mol-ecules are also located on the threefold axis and are related by inversion symmetry. In the crystal, the ammonia mol-ecules are located below and above the crown ether plane and are connected by inter-molecular N-H⋯O hydrogen bonds. The acetyl-ene mol-ecules are additionally linked by weak C-H⋯N inter-actions into chains that propagate in the direction of the crystallographic c axis. The 18-crown-6 mol-ecule [occupancy ratio 0.830 (4):0.170 (4)] is disordered and was refined using a split model. | Higelin A, Haber C, Meier S, Krossing I (2012)
Isolated cationic crown ether complexes of gallium(I) and indium(I).
Dalton transactions (Cambridge, England : 2003) 41, 12011-12015 [PubMed:22777160]
[show Abstract]
The recently reported homologous low-valent indium and gallium salts M(+)[Al(OR(F))(4)](-) (M = Ga, In; R(F) = C(CF(3))(3)) were used to extend the coordination chemistry of Ga(I) and In(I) to the isolated [18]crown-6 complexes [M([18]crown-6)(PhF)(2)](+)[Al(OR(F))(4)](-) in fluorobenzene solution (PhF = C(6)H(5)F). In contrast to known ion-paired compounds for M = In, our complexes are undisturbed and in the solid state free of contacts to the anion. A peculiar combination of very weak η(1)- and η(6)-coordination to the PhF-solvent was observed that allows speculation about the presence of a stereochemically active lone pair at M(I). Structure and energetics of these novel salts were rationalized on the basis of DFT calculations. | Hu JG (2011)
2-Meth-oxy-ethanaminium periodate 18-crown-6 clathrate.
Acta crystallographica. Section E, Structure reports online 67, o472-3 [PubMed:21523131]
[show Abstract]
In the crystal structure of the title organic salt, C(3)H(10)NO(+)·IO(4) (-)·C(12)H(24)O(6), the protonated 2-meth-oxy-ethanaminium (CH(3)OC(2)H(4)-NH(3) (+)) cation forms a 1:1 supra-molecular rotator-stator complex with the 18-crown-6 mol-ecule via N-H⋯O hydrogen bonds. The (CH(3)OC(2)H(4)-NH(3) (+)) group is attached from the convex side of the bowl-shaped crown, in contrast to similar ammonium cations that nest in the curvature of the bowl. The cations are associated via N-H⋯O inter-actions, while the cations and anions are linked by weak C-H⋯O hydrogen bonds, forming cation-crown-anion chains parallel to [010]. | Mutzbauer F, Korber N (2011)
Tris[(1,4,7,10,13,16-hexa-oxacyclo-octa-deca-ne)rubidium] heptaantimonide-ammonia (1/4).
Acta crystallographica. Section E, Structure reports online 67, m1551 [PubMed:22219792]
[show Abstract]
The crystal structure of the title compound, [Rb(C(12)H(24)O(6))](3)[Sb(7)]·4NH(3), fills the gap between the already known Zintl anion ammoniates {[Cs(18-crown-6)](3)Sb(7)}(2)·9NH(3) [Wiesler (2007 ▶). Dissertation, Universität Regensburg, Germany] and [K(18-crown-6)](3)Sb(7)·4NH(3) [Hanauer (2007 ▶). Dissertation, Universität Regensburg, Germany]. As in the two known compounds, the anti-mony cage anion in this crystal structure is coordinated by three alkali cations. The coordination spheres of each of the cations are saturated by 18-crown-6 mol-ecules. The ammonia mol-ecules of crystallization are situated between the crown ethers. The neutral, mol-ecular [Rb(18-crown-6)](3)Sb(7) units are inter-connected by multiple dipole-dipole interactions between ammonia and 18-crown-6. | Mansour A, Belkhiria MS, Daran JC, Nasri H (2010)
(5,10,15,20-Tetra-phenyl-porphyrinato-κN)cobalt(II)-18-crown-6 (1/1).
Acta crystallographica. Section E, Structure reports online 66, m509-10 [PubMed:21579007]
[show Abstract]
The asymmetric unit of the title compound, [Co(C(44)H(28)N(4))]·C(12)H(24)O(6), contains one half of a Co(II)(TPP) (TPP is tetra-phenyl-porphyrin) complex and one half of an 18-crown-6 mol-ecule of crystallization, both lying on inversion centers. The Co(II)(TPP) complex exhibits a nearly planar conformation of the porphyrinate core [maximum deviation = 0.069 (2) Å] with an average Co-N distance of 1.971 (4) Å. The distance between the Co atom and the closest O atom of the 18-crown-6 mol-ecule is 2.533 (2) Å, indicating a short non-bonded contact between the Co atom and the crown ether mol-ecule. An ethyl-ene group of the 18-crown-6 mol-ecule is disordered over two sites with occupancies of 0.565 (7) and 0.435 (7). | Ravindran Durai Nayagam B, Jebas SR, Shakina J, Murugesan R, Schollmeyer D (2010)
catena-Poly[[(18-crown-6-κO)potassium]-μ-chlorido-[(1H-benzotriazol-1-ol-κN)chloridoplatinum(II)]-μ-(benzotriazol-1-olato-κN:O)].
Acta crystallographica. Section E, Structure reports online 66, m631 [PubMed:21579285]
[show Abstract]
In the structure of the title compound, [KPt(C(6)H(4)N(3)O)Cl(2)(C(6)H(5)N(3)O)(C(12)H(24)O(6))], the Pt(II) atom is in a distorted square-planar geometry. The crystal structure is consolidated by O-H⋯O hydrogen bonds. The measured crystal was a non-merohedral twin with four components. | Wang B (2010)
Diaqua-bromido-copper(II)-18-crown-6-water (1/1/2).
Acta crystallographica. Section E, Structure reports online 66, m836 [PubMed:21587748]
[show Abstract]
In the title compound, [CuBr(2)(H(2)O)(2)]·C(12)H(24)O(6)·2H(2)O, the Cu(II) atom, which is situated on an inversion centre and has a slightly distorted square-planar geometry, and the two coordinated water mol-ecules are linked to the 18-crown-6 macrocycles by O-H⋯O hydrogen bonds. The water mol-ecule of crystallization further links the metal complex and the crown ether macrocycles into a chain along the c axis. | Shi PP, Zhao MM (2010)
Dimethyl-ammonium tetra-chloridoferrate(III) 18-crown-6 clathrate.
Acta crystallographica. Section E, Structure reports online 66, m728 [PubMed:21587672]
[show Abstract]
The reaction of dimethyl-amine hydro-chloride, 18-crown-6 and ferric chloride in ethanol yields the title compound, (C(2)H(8)N)[FeCl(4)]·C(12)H(24)O(6), which exhibits an unusual supramolecular structure. The protonated dimethyl-amine contains one NH(2) (+) group, resulting in a 1:1 supra-molecular rotator-stator structure (CH(3)-NH(2) (+)-CH(3))(18-crown-6), through N-H⋯O hydrogen-bonding inter-actions between the ammonium group of the cation and the O atoms of the crown ether. In the crystal, all three components lie on a common crystallographic mirror plane normal to [010]. | Ge JZ, Zhao MM, Shi PP (2010)
Dimethyl-ammonium perchlorate 18-crown-6 monohydrate clathrate.
Acta crystallographica. Section E, Structure reports online 66, o1740 [PubMed:21587957]
[show Abstract]
The reaction of dimethyl-amine, 18-crown-6, and perchloric acid in methanol yields the title compound, C(2)H(8)N(+)·ClO(4) (-)·C(12)H(24)O(6)·H(2)O. The dimethyl-ammonium cation and the water mol-ecule inter-act with the 18-crown-6 unit: N-H⋯O hydrogen bonds are formed between the ammonium NH(2) (+) group and four O atoms of the crown ether, while the water mol-ecule on the other side of 18-crown-6 ring forms O-H⋯O hydrogen bonds with two other O atoms of the crown ether. All conventional donors and acceptors in the cations are thus engaged in hydrogen bonding. The ClO(4) (-) anion is disordered over two sites, and occupancies for the disordered O atoms were fixed at 0.5. In the crystal, the cations and anions are arranged in alternating layers. | Wu DH, Wu QQ (2010)
Ammonium hexa-fluorido-phosphate-18-crown-6 (1/1).
Acta crystallographica. Section E, Structure reports online 66, o2132 [PubMed:21588421]
[show Abstract]
In the crystal structure of the title compound, NH(4) (+)·PF(6) (-)·C(12)H(24)O(6), the cation is situated in the 18-crown-6 ring, forming a supra-molecular rotator-stator-like structure held by N-H⋯O hydrogen bonds. The six O atoms of the crown ether lie approximately in a plane [mean deviation 0.2129 (3) Å]; the N atom is displaced by 0.864 (3)Å from the centroid of the 18-crown-6 ring. The slightly distorted tetra-hedral cations further inter-act with the slightly distorted octa-hedral anions via inter-molecular N-H⋯F hydrogen bonds. | Wu DH (2010)
4-Ethyl-anilinium perchlorate-18-crown-6 (1/1).
Acta crystallographica. Section E, Structure reports online 66, o2278 [PubMed:21588633]
[show Abstract]
The asymmetric unit of the title compound, C(8)H(12)N(+)·ClO(4) (-.)C(12)H(24)O(6), contains one half of the cationic [(C(2)H(5)-C(6)H(4)-NH(3))(18-crown-6)](+) moiety and one half of the ClO(4) (-) anion. Two O atoms of the crown ether, four C atoms and the N atom of the ethylanilinium unit and the Cl and two O atoms of the anion lie on a mirror plane. In the crystal structure, the -NH(3) (+) group lies in the 18-crown-6 ring, forming a supra-molecular rotator-stator-like structure linked by intra-molecular N-H⋯O hydrogen bonds. The six O atoms of the crown ether lie approximately in a plane, the mean deviation being 0.1771 (3) Å; the N atom lies approximately 0.855 (3) Å from the centroid of the crown ether ring. | Tun ZM, Panzner MJ, Scionti V, Medvetz D, Wesdemiotis C, Youngs WJ, Tessier C (2010)
Crown ether complexes of HPCl6.
Journal of the American Chemical Society 132, 17059-17061 [PubMed:21080621]
[show Abstract]
The reactions of HCl, PCl5, and a crown ether (12-crown-4 or 18-crown-6) in CHCl3 under anaerobic conditions give complexes of the superacid HPCl6: [H(12-crown-4)][PCl6 ] and [H(18-crown-6)2][PCl6]. The crystal structures indicate that the proton lies roughly in the center of the 12-crown-4 molecule in [H(12-crown-4)][PCl6 ] whereas it lies between two oxygen atoms of two different 18-crown-6 molecules in [H(18-crown-6)2][PCl6]. | Kong L (2009)
Bis[(18-crown-6-κO)sodium] (18-crown-6-1κO)-μ-thiocyanato-1:2κS:N-pentathio-cyanato-2κN-indate(III)sodium 1,2-dichloro-ethane sesquisolvate.
Acta crystallographica. Section E, Structure reports online 65, m1312 [PubMed:21578075]
[show Abstract]
The title complex, [Na(C(12)H(24)O(6))](2)[InNa(NCS)(6)(C(12)H(24)O(6))]·1.5C(2)H(4)Cl(2), has been synthesized by the reaction of 18-crown-6 with InCl(3) and NaSCN. The In atom has a six-coordinate octa-hedral environment, being bonded to the N atoms of six thio-cyanate groups. The bond lengths and angles show normal values. The crystal packing exhibits no significantly short inter-molecular contacts. | Misra P, Koner R, Nayak M, Mohanta S, Low JN, Ferguson G, Glidewell C (2007)
Hydrated hexacyanometallate(III) salts of triaqua(18-crown-6)lanthanoid(III) and tetraaqua(18-crown-6)lanthanoid(III) cations containing nine- and ten-coordinate lanthanoids.
Acta crystallographica. Section C, Crystal structure communications 63, m440-4 [PubMed:17917212]
[show Abstract]
Tetraaqua(18-crown-6)cerium(III) hexacyanoferrate(III) dihydrate, [Ce(C(12)H(24)O(6))(H(2)O)(4)][Fe(CN)(6)].2H(2)O, and tetraaqua(18-crown-6)neodymium(III) hexacyanoferrate(III) dihydrate, [Nd(C(12)H(24)O(6))(H(2)O)(4)][Fe(CN)(6)].2H(2)O, are isomorphous and isostructural in the C2/c space group, where the cations, which contain ten-coordinate lanthanoid centres, lie across twofold rotation axes and the anions lie across inversion centres. In these compounds, an extensive series of O-H...O and O-H...N hydrogen bonds links the components into a continuous three-dimensional framework. Triaqua(18-crown-6)lanthanoid(III) hexacyanoferrate(III) dihydrate, [Ln(C(12)H(24)O(6))(H(2)O)(3)][Fe(CN)(6)].2H(2)O, where Ln = Sm, Eu, Gd or Tb, are all isomorphous and isostructural in the P\overline{1} space group, as are triaqua(18-crown-6)gadolinium(III) hexacyanochromate(III) dihydrate, [Gd(C(12)H(24)O(6))(H(2)O)(3)][Cr(CN)(6)].2H(2)O, and triaqua(18-crown-6)gadolinium(III) hexacyanocobaltate(III) dihydrate, [Gd(C(12)H(24)O(6))(H(2)O)(3)][Co(CN)(6)].2H(2)O. In these compounds, there are two independent anions, both lying across inversion centres, and the lanthanoid centres exhibit nine-coordination; in the crystal structures, an extensive series of hydrogen bonds links the components into a three-dimensional framework. | Endicott C, Strauss HL (2007)
Infrared hole burning of crown ether 18-c-6 ammonium ion complexes.
The journal of physical chemistry. A 111, 1236-1244 [PubMed:17256920]
[show Abstract]
Crystals of the complexes of 18-crown-6 with a number of ammonium salts (bromide, chloride, two forms of iodide, nitrate) and with amminetrifluoroboron have been prepared, analyzed with X-ray diffraction, and then investigated by infrared hole burning. The complexes all have similar hydrogen-bonding arrangements between the crown ether ring and the ammonium nitrogen. Hole burning of the infrared bands at low temperature identifies the N-D hydrogen bonds of the compounds that have been doped with a small amount of deuterium. The patterns of N-D bands from different complexes are often quite overlapped, with a few notable exceptions. The hole burning reveals a wide variety of phenomena, including monotonic decay and kinetic interchange among the holes and antiholes, a variety similar to that observed in previous hole-burning experiments. | Schlueter JA, Geiser U (2003)
Potassium dicyanoargentate(I) 1,4,7,10,13,16-hexaoxacyclooctadecane.
Acta crystallographica. Section C, Crystal structure communications 59, m325-7 [PubMed:12909757]
[show Abstract]
The crystal structure of the title compound, K[Ag(CN)(2)].C(12)H(24)O(6), conventionally denoted K(18-crown-6)Ag(CN)(2), where 18-crown-6 is 1,4,7,10,13,16-hexaoxacyclooctadecane, is characterized by closely packed linear chains formed by the coordination of the nitrile N atoms of the [Ag(CN)(2)](-) anions to the K(+) cations. The K atoms lie on centers of inversion and are additionally bound to the six O atoms of the crown ether. | Munro OQ, Pearson N (2003)
The isothiocyanate complex of triphenylborane forms an unusual coordination polymer with [K(18-crown-6)](+), both in the solid state and in solution.
Acta crystallographica. Section C, Crystal structure communications 59, M407-12 [PubMed:14532657]
[show Abstract]
The title salt, (1,4,7,10,13,16-hexaoxacyclooctadecane-kappa(6)O)[(isothiocyanato)triphenylborato-kappaS]potassium(I), [K(C(19)H(15)BNS)(C(12)H(24)O(6))] or [K(SCNBPh(3))(18-crown-6)], where 18-crown-6 is 1,4,7,10,13,16-hexaoxacyclooctadecane and [SCNBPh(3)](-) is the (isothiocyanato)triphenylborate anion, exhibits a supramolecular structure that is best described as a helical coordination polymer or molecular screw. This unusual supramolecular structure is based on a framework in which the SCN(-) ion bridges the chelated K(+) ion and the B atom of BPh(3) in a micro(2) fashion. The X-ray crystal structure of the title salt has been determined at 100 (1) and 293 (2) K. The K(+) ion exhibits axial ligation by the S atom of the [SCNBPh(3)](-) anion, with a K-S distance of 3.2617 (17) A (100 K). The trans-axial ligand is an unexpected eta(2)-bound C=C bond of a phenyl group (meta- and para-C atoms) that belongs to the BPh(3) moiety of a neighboring molecule. The K-C bond distances span the range 3.099 (3)-3.310 (3) A (100 K) and are apparently retained in CDCl(3) solution (as evidenced by (13)C NMR spectroscopy). By virtue of the latter interaction, the supramolecular structure is a helical coordination polymer, with the helix axis parallel to the b axis of the unit cell. IR spectroscopy and semi-empirical molecular orbital (AM1) calculations have been used to investigate further the electronic structure of the [SCNBPh(3)](-) ion. | Al-Kahtani AA (2002)
Structural and vibrational study of the Ci(1) conformation of 18-crown-6.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy 58, 2877-2884 [PubMed:12477032]
[show Abstract]
Optimized geometry, vibrational frequencies and IR absorption intensities were calculated for the Ci(1) conformation of 18c6. Optimized geometry was compared with the experimental geometry and that of the Ci(2) conformation of 18c6. The Ci(1) conformation is more planer than the Ci(2) conformation of 18c6, which provides an explanation that free 18c6 in the crystal phase has a Ci(1) conformation. Vibrational frequencies were scaled using an unvaried one-scale-factor scaling of 0.928. Calculated vibrational frequencies were compared with the experimental vibrational frequencies. The root-mean-square deviation of the difference between the calculated and experimental frequencies was only 15 cm(-1). This excellent agreement between the calculated and experimental frequencies is an indication of the proper assignment of the fundamental vibrational frequencies of the Ci(1) conformation of 18c6. | Kim Y, Kim SJ, Nam W (2001)
A ferric-cyanide-bridged one-dimensional dirhodium complex with (18-crown-6)potassium cations.
Acta crystallographica. Section C, Crystal structure communications 57, 266-268 [PubMed:11250572]
[show Abstract]
The crystal structure of the title compound, catena-poly[bis[aqua(18-crown-6)potassium] diaqua(18-crown-6)potassium [[tetra-mu-benzoato-2:3 kappa(8)O:O'-mu-cyano-1:2 kappa(2)C:N-tetracyano-1 kappa C-irondirhodium(Rh-Rh)]-mu-cyano-1 kappa C:3' kappa N] octahydrate], [K(18-crown-6)(H(2)O)](2)[K(18-crown-6)(H(2)O)(2)][FeRh(2)(C(7)H(5)O(2))(4)(CN)(6)] x 8H(2)O, where (18-crown-6) is 1,4,7,10,13,16-hexaoxacyclooctadecane (C(12)H(24)O(6)), has been determined. Ferric cyanides connect the dirhodium units to form a one-dimensional chain compound. [K(18-crown-6-ether)(H(2)O)(2)] cations (with inversion symmetry) and [K(18-crown-6-ether)(H(2)O)] cations (in general positions) are located between the chains. | Kim TH, Lee SS, Kim JS, Kim J (2001)
Crystal structure of Cs(18-crown-6)I x 2H2O.
Analytical sciences : the international journal of the Japan Society for Analytical Chemistry 17, 573-574 [PubMed:11990584] | Ermer O, Neudörfl J (2001)
Comparative supramolecular chemistry of coronene, hexahelicene, and [18]crown-6: hydrated and solvated molecular complexes of [18]crown-6 with 5-hydroxyisophthalic acid and related di- and tricarboxylic acids.
Chemistry (Weinheim an der Bergstrasse, Germany) 7, 4961-4980 [PubMed:11763465]
[show Abstract]
The outer rim of C-H bonds of coronene (COR) and hexahelicene (HEL) is similar to that of the crown conformation of [18]crown-6 (CRO), which is exploited for crystal engineering of molecular complexes of CRO. However, although CRO does form the adduct (TMA)2 x CRO x (H2O)2 (TMA = trimesic acid = 1,3,5-benzenetricarboxylic acid), its structure does not correspond to the H-bonded, three-connected honeycomb sheet architectures of (TMA)2 x COR and (TMA)2 x HEL. Instead, porous, but noninterpenetrating, H-bonded four-connected sheets are observed, with the dihydrated, crown-shaped CRO molecules functioning as spacers rather than molecular guests. In the adduct (CHTA)2 x CRO x (H2O)5 (CHTA = cis,cis-1,3,5-cyclohexanetricarboxylic acid), the tetrahydrated CRO molecules again take up the crown conformation and act as spacers, this time within porous, noninterpenetrating H-bonded three-connected sheets. The engineering goal of CRO-filled H-bonded, hexagonal honeycomb cavities similar to the COR- and HEL-filled TMA honeycomb pores in (TMA)2 x COR and (TMA)2 x HEL was met in the adduct (HIPA)6 x CRO x (H2O)10 (HIPA = 5-hydroxyisophthalic acid), crystallized from aqueous EtOH. The crystal structure of this complex is on the one hand built up of isolated hexagonal honeycomb cavities established by six HIPA molecules cyclically linked through pairwise intercarboxylic H bonds. These cavities accommodate the crown-shaped CRO molecules, oriented such that maximally straight C-H...O contacts are enabled between its 12 equatorial H atoms and the surrounding 12 carboxylic groups of HIPA, in complete analogy to the situation prevailing in (TMA)2 x HEL and (probably) (TMA)2 xCOR. The second building block of (HIPA)6 x CRO x (H2O)10 is represented by a centrosymmetric decameric water cluster, which has the connectivity of the carbon skeleton of a bishomocubane with opposite methylene bridges, in agreement with vibrational spectroscopic evidence on gaseous (H2O)10. The crystal architecture of the adduct as a whole may either be likened to a severely distorted NaCl-type lattice, with the (HIPA)6 x CRO units replacing, for example, the Na+ ions, and the water clusters substituting the Cl- ions, or else to a system of stacked host sheets set up by C-H...O bonded (HIPA)6 macrorings, which give rise to perpendicular channels taking up guest columns of alternating, H-bonded CRO and (H2O)10 units. Crystals of another, solvated HIPA-CRO adduct of the composition (HIPA)4 x CRO x (EtOH)2 were obtained from aqueous EtOH. Their crystal structure is related to those of (TMA)2 x HEL and (TMA)2 x COR inasmuch distorted HIPA honeycomb sheets are adopted, which may be developed from the hexagonal TMA sheets by replacing one third of the pairwise intercarboxylic linkages by single interphenolic H bonds. The cavities in the HIPA sheets are thus smaller than those of the TMA honeycomb sheets and elliptically shaped. The HIPA sheets associate in pairs yielding twin cavities which take up one CRO and two EtOH molecules. The CRO molecules are suspended in the twin HIPA cages through H bonds extended from the phenolic OH groups and relayed by interposed EtOH "bridges". In keeping with the elliptic shape of the pores in (HIPA)4 x CRO x (EtOH)2, the CRO molecules are not crown-shaped, but rather adopt the more rectangular form as observed in crystalline CRO itself. The crystal structure of a dihydrate of HIPA itself was analysed, too, which assembles in a complex three-dimensional H-bonded network. It is finally concluded that hydrated CRO appears to be an avid H-bond acceptor, in particular towards carboxylic acids functioning as H-bond donors. | Dye JL (1990)
Electrides: ionic salts with electrons as the anions.
Science (New York, N.Y.) 247, 663-668 [PubMed:17771882]
[show Abstract]
Electrides are ionic compounds that have alkali metal cations complexed by a crown ether or cryptand, with trapped electrons as counterions. The crystal structures and properties of two electrides illustrate the diversity that is encountered. One Cs(+) (18-crown-6)(z)e(-), has relatively isolated, trapped electrons apparently centered at each anionic site. It has a low conductivity consistent with electron localization, with an activation energy for conductivity of at least 0.45 electron volt. The other, K(+) (cryptand[2.2.2])e(-), has electron pairs trapped in an elongated cavity in a singlet ground state, but there is also a thermally accessible paramagnetic state available. This electride is much more conducting, with an activation energy of only 0.02 electron volt. |
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