Dielectric relaxation and orientational ordering of water molecules in hexamethylenetetramine hexahydrate

1968 ◽  
Vol 46 (6) ◽  
pp. 1024-1027 ◽  
Author(s):  
D. W. Davidson
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Hydrogen Bonds ◽  
Dielectric Relaxation ◽  
Static Dielectric Constant ◽  
Water Molecules ◽  
Hydrogen Atoms ◽  
Orientational Ordering ◽  
Water Hydrogen

To account for the dielectric properties of hexamethylenetetramine hydrate, which include a static dielectric constant half that of ice, some modification is necessary of the partial orientational ordering of the water molecules proposed by Mak. It is suggested that water hydrogen atoms occupy fixed positions only in the hydrogen bonds with nitrogen.

scholarly journals Notizen: Hydrogen Bonding in MoO2Cl2 · H2O Determined by Electrostatic Energy Calculations

1977 ◽  
Vol 32 (11) ◽  
pp. 1358-1359 ◽  
Author(s):  
Werner H. Baur
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Systematic Variation ◽  
Electrostatic Energy ◽  
Water Molecules ◽  
Hydrogen Atoms ◽  
Energy Calculations ◽  
Internal Geometry

The configuration of least electrostatic energy for the hydrogen atoms in both polytypes of MoO2Cl2 · H2O was obtained by systematic variation of the orientations of the water molecules. The internal geometry of the H2O group was kept constant throughout the variation. The hydrogen bonds are of the bifurcated type: [xxx]

The crystal and molecular structure of guanine hydrochloride dehydrate

1965 ◽  
Vol 288 (1414) ◽  
pp. 418-439 ◽  
Keyword(s):  
Hydrogen Bonds ◽  
Least Squares Method ◽  
Three Dimensional ◽  
Water Molecules ◽  
Hydrogen Atoms ◽  
X Ray ◽  
Anisotropic Temperature ◽  
Chlorine Ions ◽  
Atomic Coordinates ◽  
Single Crystal Analysis

The structure of guanine hydrochloride monohydrate has been determined by X-ray single crystal analysis and the parameters (including anisotropic temperature vibrations) have been refined by the three-dimensional least squares method. The unit cell is monoclinic with a = 14.69 ± 0.01, b = 13.40 ± 0.01, c = 4.840 ± 0.005 Å; β = 93.8°± 0.1°; space group P 2 1 / a . For 1600 independent reflexions the final value of the agreement index R was 0.07 and the standard deviations of atomic coordinates are in the region of 0.0035 Å. Two guanine molecules are linked together by hydrogen bonds to form a centrosymmetrical dimer. The dimer is linked by hydrogen bonds to four water molecules which are then hydrogen bonded to two chlorine ions. It is shown that the guanine molecule has associated with it six centres of electron density corresponding to hydrogen atoms and it is therefore in the form (H guanine) + with protonation at the N 7 position.

Crystal Structure of Adeninium Trichloromercurate(II),

1975 ◽  
Vol 53 (15) ◽  
pp. 2345-2350 ◽  
Author(s):  
Monique Authier-Martin ◽  
André L. Beauchamp
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Least Squares ◽  
Title Compound ◽  
Heavy Atom ◽  
Chloride Ions ◽  
Water Molecules ◽  
Hydrogen Atoms ◽  
Space Group ◽  
Heavy Atom Method

The title compound belongs to space group P21/c with a = 23.99(1), b = 4.245(2), c = 25.98(1) Å, β = 117.58(7)°, and Z = 8. The structure was solved by the heavy-atom method and refined by block-diagonal least squares on 2589 independent observed reflections. All non-hydrogen atoms were refined anisotropically and some of the hydrogen atoms were located but their parameters were not refined. The final values of R and Rw were 0.042 and 0.047, respectively.The two nonequivalent mercury atoms have very similar environments. Two short Hg—Cl bonds (2.34–2.38 Å) at ∼ 165° define a quasi-molecular HgCl2 unit. Overall octahedral coordination is completed with two chloride ions at 2.76–2.84 Å and two chlorine atoms at 3.19–3.26 Å on neighboring HgCl2 quasi-molecules. HgCl6 octahedra share edges to form twofold ribbons in the b direction. This pattern of octahedra is identical with the onereported for β-NH4HgCl3. The cations are pairs of N(1)-protonated adenine molecules linked by two N(10)—H(10)… N(7) hydrogen bonds and stacked in the b direction. Water molecules act as acceptors in moderately strong hydrogen bonds with acidic protons H(1) and H(9) of adeninium ions. Other generally weaker hydrogen bonds exist between the various parts of the structure.

scholarly journals Origin of hydrophobicity and enhanced water hydrogen bond strength near purely hydrophobic solutes

2016 ◽  
Vol 114 (2) ◽  
pp. 322-327 ◽  
Author(s):  
Joze Grdadolnik ◽  
Franci Merzel ◽  
Franc Avbelj
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Hydrophobic Hydration ◽  
Bulk Water ◽  
Water Molecules ◽  
Classical View ◽  
Fundamental Level ◽  
Hydrophobic Solute ◽  
Hydrophobic Solutes ◽  
Water Hydrogen

Hydrophobicity plays an important role in numerous physicochemical processes from the process of dissolution in water to protein folding, but its origin at the fundamental level is still unclear. The classical view of hydrophobic hydration is that, in the presence of a hydrophobic solute, water forms transient microscopic “icebergs” arising from strengthened water hydrogen bonding, but there is no experimental evidence for enhanced hydrogen bonding and/or icebergs in such solutions. Here, we have used the redshifts and line shapes of the isotopically decoupled IR oxygen–deuterium (O-D) stretching mode of HDO water near small purely hydrophobic solutes (methane, ethane, krypton, and xenon) to study hydrophobicity at the most fundamental level. We present unequivocal and model-free experimental proof for the presence of strengthened water hydrogen bonds near four hydrophobic solutes, matching those in ice and clathrates. The water molecules involved in the enhanced hydrogen bonds display extensive structural ordering resembling that in clathrates. The number of ice-like hydrogen bonds is 10–15 per methane molecule. Ab initio molecular dynamics simulations have confirmed that water molecules in the vicinity of methane form stronger, more numerous, and more tetrahedrally oriented hydrogen bonds than those in bulk water and that their mobility is restricted. We show the absence of intercalating water molecules that cause the electrostatic screening (shielding) of hydrogen bonds in bulk water as the critical element for the enhanced hydrogen bonding around a hydrophobic solute. Our results confirm the classical view of hydrophobic hydration.

scholarly journals [rac-1,8-Bis(2-carbamoylethyl)-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane]copper(II) diacetate tetrahydrate: crystal structure and Hirshfeld surface analysis

2021 ◽  
Vol 77 (12) ◽  
Author(s):  
Sabina Yasmin ◽  
Saswata Rabi ◽  
Avijit Chakraborty ◽  
Huey Chong Kwong ◽  
Edward R. T. Tiekink ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Three Dimensional ◽  
Complex Salt ◽  
Hirshfeld Surface ◽  
Water Molecules ◽  
Coordination Geometry ◽  
Asymmetric Unit ◽  
Hirshfeld Surfaces ◽  
The Individual ◽  
Water Hydrogen

The title CuII macrocyclic complex salt tetrahydrate, [Cu(C22H46N6O2)](C2H3O2)2·4H2O, sees the metal atom located on a centre of inversion and coordinated within a 4 + 2 (N4O2) tetragonally distorted coordination geometry; the N atoms are derived from the macrocycle and the O atoms from weakly associated [3.2048 (15) Å] acetate anions. Further stability to the three-ion aggregate is provided by intramolecular amine-N—H...O(carboxylate) hydrogen bonds. Hydrogen bonding is also prominent in the molecular packing with amide-N—H...O(amide) interactions, leading to eight-membered {...HNCO}2 synthons, amide-N—H...O(water), water-O—H...O(carboxylate) and water-O—H...O(water) hydrogen bonds featuring within the three-dimensional architecture. The calculated Hirshfeld surfaces for the individual components of the asymmetric unit differentiate the water molecules owing to their distinctive supramolecular association. For each of the anion and cation, H...H contacts predominate (50.7 and 65.2%, respectively) followed by H...O/O...H contacts (44.5 and 29.9%, respectively).

The Different Organization of Water in Zeolite L and Its MOF Mimic

2019 ◽  
Author(s):  
gloria tabacchi ◽  
Ettore Fois
Keyword(s):  
Hydrogen Bonds ◽  
Metal Organic Framework ◽  
Water Molecules ◽  
One Dimensional ◽  
Zeolite L ◽  
High Proton ◽  
Metal Organic ◽  
The One ◽  
The Individual ◽  
Water Hydrogen

Abstract:<div>Confinement of molecules inside one dimensional arrays of channel-shaped cavities has led to an impressive number of technologically interesting materials. However, the interactions governing the properties of the supramolecular aggregates still remain obscure, even in the case of the most common guest molecule: water. Herein, we use computational chemistry methods (#compchem) to study the water organization inside two different channel-type environments: zeolite L – a widely used matrix for inclusion of dye molecules, and ZLMOF – the closest metal-organic-framework mimic of zeolite L. In ZLMOF, the methyl groups of the ligands protrude inside the channels, creating nearly isolated nanocavities. These cavities host well-separated ring-shaped clusters of water molecules, dominated mainly by water-water hydrogen bonds. ZLMOF channels thus provide arrays of „isolated supramolecule“ environments, which might be exploited for the individual confinement of small species with interesting optical or catalytic properties. In contrast, the one dimensional nanochannels of zeolite L contain a continuous supramolecular structure, governed by the water interactions with potassium cations and by water-water hydrogen bonds. Water molecules impart a significant energetic stabilization to both materials, which increases by increasing the water content in ZLMOF, while the opposite trend is observed in zeolite L. The water network in zeolite L contains an intriguing hyper-coordinated structure, where a water molecule is surrounded by 5 strong hydrogen bonds. Such a structure, here described for the first time in zeolites, can be considered as a water pre-dissociation complex and might explain the experimentally detected high proton activity in zeolite L nanochannels. </div>

Re-investigation of the crystal structure of whewellite [Ca(C2O4)·H2O] and the dehydration mechanism of caoxite [Ca(C2O4)·3H2O]

2005 ◽  
Vol 69 (1) ◽  
pp. 77-88 ◽  
Author(s):  
T. Echigo ◽  
M. Kimata ◽  
A. Kyono ◽  
M. Shimizu ◽  
T. Hatta
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Structure Refinement ◽  
Structural Features ◽  
Infrared Analysis ◽  
Water Molecules ◽  
Hydrogen Atoms ◽  
Direct Transformation ◽  
Dehydration Mechanism ◽  
The Difference

AbstractThe crystal structure of whewellite [Ca(C2O4)·H2O] and the dehydration mechanism of caoxite [Ca(C2O4)·3H2O] have been studied by means of differential thermal analysis, X-ray diffraction (powder and single-crystal) analysis and infrared analysis. The first and second analyses confirmed the direct transformation of caoxite into whewellite without an intermediate weddellite [Ca(C2O4)·2H2O] stage. Infrared spectra obtained from caoxite, weddellite and whewellite emphasize the similarity of the O–H-stretching band and O–C–O-stretching band in whewellite and caoxite and the unique bands of weddellite. The structure refinement at low temperature (123 K) reveals that all the hydrogen atoms of whewellite form hydrogen bonds and the two water molecules prop up the crystal structure by the hydrogen bonds that cause a strong anisotropy of the displacement parameter.Comparing the structural features of whewellite with those of weddellite and caoxite suggests that caoxite and whewellite have a sheet structure consisting of Ca2+ ions and oxalate ions although weddellite does not. It is additionally confirmed that the sheets of caoxite are corrugated by hydrogen bonds but whewellite has flat sheets. The corrugated sheets of caoxite would be flattened by dehydration so the direct transformation of caoxite into whewellite would not occur via weddellite. Essential for this transformation is the dehydration of interlayered water molecules in caoxite leading to the building of the crystal structure of whewellite on its intralayered water molecules. The difference in conformation of water molecules between those two crystal structures may explain the more common occurrence of whewellite than of caoxite in nature.

Low-temperature piezoelectric and dielectric properties of aromatic polyureas prepared by vapour deposition polymerization

1995 ◽  
Vol 7 (3) ◽  
pp. 293-301 ◽  
Author(s):  
Xian-Shan Wang ◽  
Yoshikazu Takahashi ◽  
Masayuki Lijima ◽  
Eiichi Fukada
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Low Temperature ◽  
Hydrogen Bonds ◽  
Infrared Spectra ◽  
Vapour Deposition ◽  
Piezoelectric Constant ◽  
Poling Field ◽  
Piezoelectric Activity

Thin films of aromatic polyurea were prepared by vapour deposition of a diisocyanate tmonomer and a diamine monomer. Three kinds of aromatic polyurea were synthesized by combining 4,4'-dipheny Lnethane diisocyanate (MDI) with 4,4'-diamino-3,3'-dimethyldiphenylmethane (MeMDA), 4,4'-diaminodiphenylether (ODA), and 4,4'-diamino-diphenylmethane (MDA). After poling, for example applying a field of 120 MV m -I at 210C for 10 min, these films acquired piezoelectric activity. The piezoelectric constant (13-26 x 10 3 C m' 2) and dielectric constant (3-4) were almost constant over a temperature range between -150C and 50 C. Infrared spectra observed for as-deposited, poled and annealed films indicated that CO and NH dipoles were oriented along the poling field and that hydrogen bonds were formed between adjacent molecular chains.

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