1,4-Dioxane Hydrate: Dielectric Absorption by a Nondipolar Enclathrated Molecule

1975 ◽  
Vol 53 (15) ◽  
pp. 2217-2222 ◽  
Author(s):  
S. R. Gough ◽  
J. A. Ripmeester ◽  
D. W. Davidson
Keyword(s):  
Continuous Wave ◽  
Effective Activation Energy ◽  
Water Molecules ◽  
Effective Activation ◽  
Large Structure ◽  
Total Dipole Moment ◽  
Guest Molecules ◽  
X Ray ◽  
Dielectric Absorption ◽  
Relaxation Studies

X-Ray, continuous-wave and pulsed n.m.r., and dielectric relaxation studies show the hydrate of 1,4-dioxane (D) to be a normal clathrate hydrate of von Stackelberg's structure II with composition D·∼17H2O. The reorientation rate of the relatively large D molecule is slower and the effective activation energy(l.6 kcal/mol) larger than for other guest molecules previously studied in hydrates of the same structure. Weak dielectric absorption associated with reorientation of nondipolar D molecules is attributed mainly to the induction of a total dipole moment of ∼0.2 D in the 28 water molecules of the large structure II cage by two equal and opposed dipoles in the chair form of D.

scholarly journals Phase transformations in cucurbituril host-guest complexes

2014 ◽  
Vol 70 (a1) ◽  
pp. C646-C646
Author(s):  
Oksana Danylyuk ◽  
Karolina Kedra-Krolik ◽  
Marta Worzakowska ◽  
Joanna Osypiuk-Tomasik ◽  
Vladimir Fedin
Keyword(s):  
Single Crystal ◽  
Crystal Lattice ◽  
Supramolecular Assembly ◽  
Water Molecules ◽  
Guest Molecules ◽  
X Ray ◽  
Host Guest Complex ◽  
Crystallographic Study ◽  
Partial Dehydration ◽  
Structure Changes

The retention of crystallinity upon desolvation of molecular crystals is not common, as the molecules are rigidly and densely packed in the crystals and the original framework usually collapses once solvent is removed from the structure. However, in rare cases the host framework remains substantially unaffected by solvent (guest) removal yielding structure with open channels or discrete lattice voids that can show permanent porosity. [1] Furthermore, sometimes happens, the desolvation process proceeds as single-crystal to single-crystal transformation resulting in distortion and sliding of the structure, changes in conformation, coordination modes and/or space group. Here we would like to present crystallographic study and thermal analysis on the dehydration process of the crystalline supramolecular complex between macrocyclic host cucurbit[6]uril and dopamine. In the solid state the 1:1 host-guest complex assembles into hexameric tubes with water-filled interior channels. Another set of water channels is created between three neighboring tubes in the crystal lattice. The crystals of such supramolecular assembly are not stable when out from mother solution and immediately start to loose water upon exposure to air. However, despite severe cracking the crystals dried in air maintained their integrity and still gave satisfactory diffraction pattern. The X-ray analysis showed significant decrease in the unit cell volume of the partially dehydrated crystals that corresponds to the liberation of some of the water molecules from the channels. Moreover, the reorganization of dopamine guest molecules has occurred in the crystal lattice as a response to the escape of water molecules from the structure. The partial dehydration and reorganization of the supramolecular framework proceeds via a single-crystal to single-crystal mechanism.

Characterization of natural gas hydrates by nuclear magnetic resonance and dielectric relaxation

1977 ◽  
Vol 55 (20) ◽  
pp. 3641-3650 ◽  
Author(s):  
D. W. Davidson ◽  
S. K. Garg ◽  
S. R. Gough ◽  
R. E. Hawkins ◽  
J. A. Ripmeester
Keyword(s):  
Guest Molecule ◽  
Continuous Wave ◽  
Type I ◽  
Tetrahedral Symmetry ◽  
Guest Molecules ◽  
Line Shapes ◽  
Dielectric Absorption ◽  
Dielectric Data ◽  
First Time

Continuous-wave proton nmr spectra of the clathrate hydrates and/or deuteriohydrates of methane, ethane, propane, isobutane, and neopentane–D2S have been recorded down to 2 K. Between 50 and 200 K each H2O hydrate spectrum consists of a line 3 to 4 G wide from reorienting guest molecules and a broader band from rigid water molecules. Line shapes characteristic of non-rotating guests are obtained in D2O hydrates at low temperatures, except for methane which gives a narrow line to 2 K. Neopentane, shown for the first time to be capable of enclathration, exhibits a Resing effect and other features related to its tetrahedral symmetry. Low-temperature dielectric absorption from reorienting guest-molecule dipoles has been measured in H2S, propane, isobutane, and n-butane–H2S hydrates. For steric reasons n-butane is encaged as a gauche rather than the trans isomer. Average barriers to reorientation estimated from nmr and dielectric data are 1.2 kcal/mol for ethane in type I hydrate and 0.6, 1.2, 1.4, and 0.8 kcal/mol for propane, isobutane, n-butane, and neopentane in type II.

The Motion of Guest Molecules in Clathrate Hydrates

1971 ◽  
Vol 49 (8) ◽  
pp. 1224-1242 ◽  
Author(s):  
D. W. Davidson
Keyword(s):  
Low Temperatures ◽  
Wide Distribution ◽  
Water Molecules ◽  
Energy Calculation ◽  
Guest Molecules ◽  
Jones Potential ◽  
Dielectric Absorption ◽  
Electrostatic Fields ◽  
Cl Atoms ◽  
Range Of Variation

The reorientation of molecules encaged in hydrates of structures I and II is controlled mainly by the cage geometry and the electrostatic fields of the water molecules. Departure from spherical symmetry of the short-range interactions between the guest molecule and the water molecules which form the cages leads to preferred orientations which become increasingly occupied at low temperatures. A modified Lennard-Jones potential energy calculation shows the preferred positions of Cl2 to lie off-center and close to the equatorial plane of the tetrakaidecahedral cage with the Cl atoms near the axial planes of symmetry. In an attempt to account for the remarkable reorientational freedom of polar guest molecules, the electrostatic fields of the water molecules are treated in detail. It is shown that the geometry of the cages causes the sum of the fields of the cage water dipoles to almost vanish at points near the cage center, but that this is not true of the resultant quadrupolar fields. It is suggested that the quadrupolar fields are also relatively small because the hydrogen bonding to four neighbors considerably reduces the quadrupole moment of the water molecule. The orientational disorder of the water molecules results in a wide distribution of resultant electrostatic fields in different cages. This appears to be the origin of the great width of the dielectric absorption observed at low temperatures in tetrahydrofuran hydrate and of the wide temperature range of variation of the proton magnetic resonance (p.m.r.) line width in tetrahydrofuran deuterate.

The anomalous halogen bonding interactions between chlorine and bromine with water in clathrate hydrates

2017 ◽  
Vol 203 ◽  
pp. 61-77 ◽  
Author(s):  
Hana Dureckova ◽  
Tom K. Woo ◽  
Konstantin A. Udachin ◽  
John A. Ripmeester ◽  
Saman Alavi
Keyword(s):  
Ab Initio ◽  
Halogen Bonding ◽  
Chem Phys ◽  
Clathrate Hydrate ◽  
Clathrate Hydrates ◽  
Water Molecules ◽  
Guest Molecules ◽  
X Ray ◽  
Covalent Interaction ◽  
Water Oxygen

Clathrate hydrate phases of Cl2 and Br2 guest molecules have been known for about 200 years. The crystal structure of these phases was recently re-determined with high accuracy by single crystal X-ray diffraction. In these structures, the water oxygen–halogen atom distances are determined to be shorter than the sum of the van der Waals radii, which indicates the action of some type of non-covalent interaction between the dihalogens and water molecules. Given that in the hydrate phases both lone pairs of each water oxygen atom are engaged in hydrogen bonding with other water molecules of the lattice, the nature of the oxygen–halogen interactions may not be the standard halogen bonds characterized recently in the solid state materials and enzyme–substrate compounds. The nature of the halogen–water interactions for the Cl2 and Br2 molecules in two isolated clathrate hydrate cages has recently been studied with ab initio calculations and Natural Bond Order analysis (Ochoa-Resendiz et al. J. Chem. Phys. 2016, 145, 161104). Here we present the results of ab initio calculations and natural localized molecular orbital analysis for Cl2 and Br2 guests in all cage types observed in the cubic structure I and tetragonal structure I clathrate hydrates to characterize the orbital interactions between the dihalogen guests and water. Calculations with isolated cages and cages with one shell of coordinating molecules are considered. The computational analysis is used to understand the nature of the halogen bonding in these materials and to interpret the guest positions in the hydrate cages obtained from the X-ray crystal structures.

Structural Study of a new Compound Based on Acid 1,4-Cyclohexanedicarboxylic (1,4-CDC)

2010 ◽  
Vol 6 (1) ◽  
pp. 891-896
Author(s):  
Manel Halouani ◽  
M. Dammak ◽  
N. Audebrand ◽  
L. Ktari
Keyword(s):  
Aqueous Solution ◽  
Water Molecules ◽  
Carboxyl Group ◽  
X Ray Diffraction ◽  
Compound I ◽  
Unit Cell Parameters ◽  
Monoclinic System ◽  
X Ray ◽  
Cell Parameters ◽  
Cyclohexanedicarboxylic Acid

One nickel 1,4-cyclohexanedicarboxylate coordination polymers, Ni2 [(O10C6H4)(COO)2].2H2O  (I), was hydrothermally synthesized from an aqueous solution of Ni (NO3)2.6H2O, (1,4-CDC) (1,4-CDC = 1,4-cyclohexanedicarboxylic acid) and tetramethylammonium nitrate. Compound (I) crystallizes in the monoclinic system with the C2/m space group. The unit cell parameters are a = 20.1160 (16) Å, b = 9.9387 (10) Å, c = 6.3672 (6) Å, β = 97.007 (3) (°), V= 1263.5 (2) (Å3) and Dx= 1.751g/cm3. The refinement converged into R= 0.036 and RW = 0.092. The structure, determined by single crystal X-ray diffraction, consists of two nickel atoms Ni (1) and Ni (2). Lots of ways of which is surrounded by six oxygen atoms, a carboxyl group and two water molecules.

Synthesis and Structure of a Clathrated Two-Dimensional Metal-Organic Framework: [Cd(4,4'-bpy)2(H2O)2](ClO4)2·(L)2·H2O (L = Bis(1-pyrazinylethylidene)hydrazine)

2008 ◽  
Vol 73 (1) ◽  
pp. 24-31
Author(s):  
Dayu Wu ◽  
Genhua Wu ◽  
Wei Huang ◽  
Zhuqing Wang
Keyword(s):  
Metal Organic Framework ◽  
Channel Structure ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Square Planar ◽  
Metal Organic ◽  
Aqueous Meoh ◽  
Organic Framework

The compound [Cd(4,4'-bpy)2(H2O)2](ClO4)2·(L)2 was obtained by the reaction of Cd(ClO4)2, bis(1-pyrazinylethylidene)hydrazine (L) and 4,4'-bipyridine in aqueous MeOH. Single-crystal X-ray diffraction has revealed its two-dimensional metal-organic framework. The 2-D layers superpose on each other, giving a channel structure. The square planar grids consist of two pairs of shared edges with Cd(II) ion and a 4,4'-bipyridine molecule each vertex and side, respectively. The square cavity has a dimension of 11.817 × 11.781 Å. Two guest molecules of bis(1-pyrazinylethylidene)hydrazine are clathrated in every hydrophobic host cavity, being further stabilized by π-π stacking and hydrogen bonding. The results suggest that the hydrazine molecules present in the network serve as structure-directing templates in the formation of crystal structures.

scholarly journals Structure of aqueous sodium acetate solutions by X-Ray scattering and density functional theory

2020 ◽  
Vol 92 (10) ◽  
pp. 1627-1641
Author(s):  
Guangguo Wang ◽  
Yongquan Zhou ◽  
He Lin ◽  
Zhuanfang Jing ◽  
Hongyan Liu ◽  
...  
Keyword(s):  
Sodium Acetate ◽  
Density Functional ◽  
Hydration Shell ◽  
Ion Pair ◽  
Water Molecules ◽  
Sodium Acetate Solution ◽  
Acetate Solution ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

AbstractThe structure of aq. sodium acetate solution (CH3COONa, NaOAc) was studied by X-ray scattering and density function theory (DFT). For the first hydrated layer of Na+, coordination number (CN) between Na+ and O(W, I) decreases from 5.02 ± 0.85 at 0.976 mol/L to 3.62 ± 1.21 at 4.453 mol/L. The hydration of carbonyl oxygen (OC) and hydroxyl oxygen (OOC) of CH3COO− were investigated separately and the OC shows a stronger hydration bonds comparing with OOC. With concentrations increasing, the hydration shell structures of CH3COO− are not affected by the presence of large number of ions, each CH3COO− group binds about 6.23 ± 2.01 to 7.35 ± 1.73 water molecules, which indicates a relatively strong interaction between CH3COO− and water molecules. The larger uncertainty of the CN of Na+ and OC(OOC) reflects the relative looseness of Na-OC and Na-OOC ion pairs in aq. NaOAc solutions, even at the highest concentration (4.453 mol/L), suggesting the lack of contact ion pair (CIP) formation. In aq. NaOAc solutions, the so called “structure breaking” property of Na+ and CH3COO− become effective only for the second hydration sphere of bulk water. The DFT calculations of CH3COONa (H2O)n=5–7 clusters suggest that the solvent-shared ion pair (SIP) structures appear at n = 6 and become dominant at n = 7, which is well consistent with the result from X-ray scattering.

scholarly journals Rb1.66Cs1.34Tb[Si5.43Ge0.57O15]·H2O, a New Member of the OD-Family of Natural and Synthetic Layered Silicates: Topology-Symmetry Analysis and Structure Prediction

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 395
Author(s):  
Anastasiia Topnikova ◽  
Elena Belokoneva ◽  
Olga Dimitrova ◽  
Anatoly Volkov ◽  
Dina Deyneko
Keyword(s):  
Structure Prediction ◽  
Symmetry Analysis ◽  
Layered Silicates ◽  
Water Molecules ◽  
Structural Variants ◽  
X Ray ◽  
A Chain ◽  
Multi Component System ◽  
Tetrahedral Layer ◽  
Natural And Synthetic

Crystals of new silicate-germanate Rb1.66Cs1.34Tb[Si5.43Ge0.57O15]·H2O have been synthesized hydrothermally in a multi-component system TbCl3:GeO2:SiO2 = 1:1:5 at T = 280 °C and P = 100 atm. K2CO3, Rb2CO3 and Cs2CO3 were added to the solution as mineralizers. The crystal structure was solved using single crystal X-ray data: a = 15.9429(3), b = 14.8407(3), c = 7.2781(1) Å, sp. gr. Pbam. New Rb,Cs,Tb-silicate-germanate consists of a [Si5.43Ge0.57O15]∞∞ corrugated tetrahedral layer combined by isolated TbO6 octahedra into the mixed microporous framework as in synthetic K3Nd[Si6O15]·2H2O, K3Nd[Si6O15] and K3Eu[Si6O15]·2H2O with the cavities occupied by Cs, Rb atoms and water molecules. Luminescence spectrum on new crystals was obtained and analysed. A comparison with the other representatives of related layered natural and synthetic silicates was carried out based on the topology-symmetry analysis by the OD (order-disorder) approach. The wollastonite chain was selected as the initial structural unit. Three symmetrical ways of forming ribbon from such a chain and three ways of further connecting ribbons to each other into the layer were revealed and described with symmetry groupoids. Hypothetical structural variants of the layers and ribbons in this family were predicted.

Konkurrierende Liganden: Theophyllin als nicht- und stark koordinierender Ligand in Quecksilber(II)-Komplexen / Competing Ligands: Theophylline as Non- and Strongly Coordinating Ligand in Mercury(II) Complexes

2006 ◽  
Vol 61 (6) ◽  
pp. 758-765 ◽  
Author(s):  
Matthias Nolte ◽  
Ingo Pantenburg ◽  
Gerd Meyer
Keyword(s):  
Oxygen Atom ◽  
Water Molecule ◽  
Aqueous Solutions ◽  
Single Crystal ◽  
Coordination Polymers ◽  
Water Molecules ◽  
Slow Evaporation ◽  
Monoclinic Symmetry ◽  
X Ray ◽  
Chloride Ligand

[{Hg(CF3)2}(ThpH)(H2O)](H2O) (1), [{Hg4(Thp)4}(ClO4)4(H2O)8](H2O)4 (2), [{Hg(ThpH)2} (NO3)](NO3) (3) and {Hg(Thp)Cl}(H2O) (4) (ThpH = theophylline, C7H8N4O2) have been synthesized by slow evaporation of aqueous solutions of the mercuric salts Hg(CF3)2, Hg(ClO4)2, Hg(NO3)2, or HgCl2 and theophylline. Their crystal structures were determined on the basis of single crystal X-ray data. The coordination polymers 1 and 2 crystallize with triclinic symmetry, P1̅ (no. 2), with a = 468.8(2), b = 1256.4(5), c = 1445.5(6) pm, α = 67.15(3), β = 89.21(3), γ = 89.40(3)° and a = 833.6(1), b = 1862.7(2), c = 2182.9(2) pm, α = 111.61(1), β = 90.98(1), γ = 95.51(1)°, respectively. 3 and 4 crystallize with monoclinic symmetry, Pc (no. 7), a =1194.1(1), b=1258.8(2), c=735.5(2) pm, β =96.96(2)° and P21/n (no. 14), a=1069.0(2), b =911.6(1), c=1089.9(2) pm and β = 96.87(2)°. In 1 the theophylline molecules are non-coordinating to mercury and leave the Hg(CF3)2 molecule unchanged. Only weak electrostatic attractions to one keto-oxygen atom of theophylline and one water molecule hold this co-crystallisate together. In 2, the theophyllinate anion, Thp−, strongly coordinates with both N(7) and N(9) to HgII forming a large ring with eight Hg atoms that incorporates the water molecules. One sort of nitrate ions in 3 is weakly attached to HgII with the theophylline molecules still bound strongly through N(9). The chloride ligand and the theophyllinate ion seem to have the same strengths as ligands in 4 as they are both attached to HgII with the shortest distances possible

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