scholarly journals Структура и динамика цепочек водородных связей молекул фтористого водорода внутри углеродных нанотрубок

2020 ◽  
Vol 62 (11) ◽  
pp. 1968
Author(s):  
А.В. Савин ◽  
О.И. Савина
Keyword(s):  
Hydrogen Bonds ◽  
Hydrogen Fluoride ◽  
Molecular Complexes ◽  
Thermal Fluctuations ◽  
Single Wall Carbon Nanotubes ◽  
Internal Cavity ◽  
Hydroxyl Groups ◽  
Proton Conducting ◽  
Winding Insulation

Using the method of molecular dynamics, it was shown that hydrogen fluoride molecules inside single-wall carbon nanotubes with a diameter D<0.85 nm form flat zigzag chains of hydrogen bonds F–H∙ ∙ ∙F–H∙ ∙ ∙F–H∙ ∙ ∙ . The chains structurally closest to the chain of hydrogen bonds of hydroxyl groups OH form hydrogen fluoride molecules inside nanotubes with a chirality index (6,6) and (10,0). In such open nanotubes with narrowed edges, hydrogen bond chains (FH) _N can completely fill their internal cavity forming a structure that is resistant to thermal fluctuations in a wide temperature range. The chains can have stationary orientation defects localized on 3-4 chain links separating parts of the chain having the opposite directions of FH molecules. The molecular complexes (FH)_N∈CNT(6,6) and (FH)_N∈CNT(10,0) can play the role of proton-conducting nanowires, in which the outer nanotube serves as a external winding (insulation) that protects and stabilizes the inner proton-conducting chain (FH)_N.

scholarly journals Deprotonation of resorcinarenes and novel ammonium salt complexes

2014 ◽  
Vol 70 (a1) ◽  
pp. C678-C678
Author(s):  
Ngong Beyeh ◽  
Arto Valkonen ◽  
Fanfang Pan ◽  
Kari Rissanen
Keyword(s):  
Hydrogen Bonds ◽  
Binding Sites ◽  
Molecular Complexes ◽  
Ammonium Salts ◽  
Hydroxyl Groups ◽  
Binding Modes ◽  
Intermolecular Hydrogen Bonds ◽  
Guest Molecules ◽  
Cone Conformation ◽  
Intramolecular Hydrogen

The bowl shape cavity of resorcinarenes usually stabilized by four intramolecular hydrogen bonds offers an interesting array of binding modes such as C–H...π and cation...π interactions to recognize a variety of guests. The multiple hydroxyl groups can participate in a series of intermolecular hydrogen bonds with guest molecules. This unique cone conformation of resorcinarenes has led to the synthesis of many receptors with convergent arrangement of binding sites suitable for molecular recognition in many applications. Unfunctionalized resorcinarenes are known to easily form molecular complexes with guests of varying shapes and sizes. Amines are very common bases used in many catalytic processes. A good example is the use of amines as bases in the alkylation and acylation of resorcinarenes leading to cavitands, carcerands, hemicarcerands and velcrands. The use of amines in such reactions is to deprotonate the resorcinarene hydroxyl groups, hence facilitating the alkylation and acylation processes. The subsequently protonated ammonium cation then forms interesting supramolecular complexes with the anionic and dianionic resorcinarenes. Furthermore, secondary and tertiary ammonium salts possess hydrogen bond donating -NH2 and -NH respectively and these can further enhance their complexation through intermolecular hydrogen bonds. Here we present our recent examples of supramolecular assemblies resulting from the deprotonation of resorcinarenes by mono- and dibasic amines. Also, our latest supramolecular co-crystals between resorcinarenes as the receptors and a series of secondary and tertiary mono- and diammonium cations are illustrated.

scholarly journals Crystal structure of dimethylammonium hydrogen oxalate hemi(oxalic acid)

2015 ◽  
Vol 71 (5) ◽  
pp. 473-475 ◽  
Author(s):  
Waly Diallo ◽  
Ndongo Gueye ◽  
Aurélien Crochet ◽  
Laurent Plasseraud ◽  
Hélène Cattey
Keyword(s):  
Hydrogen Bonds ◽  
Oxalic Acid ◽  
Molecular Assembly ◽  
Point Of View ◽  
Hydroxyl Groups ◽  
Inversion Center ◽  
Asymmetric Unit ◽  
Close Proximity ◽  
Polymeric Chains

Single crystals of the title salt, Me2NH2+·HC2O4−·0.5H2C2O4, were isolated as a side product from the reaction involving Me2NH, H2C2O4and Sn(n-Bu)3Cl in a 1:2 ratio in methanol or by the reaction of the (Me2NH2)2C2O4salt and Sn(CH3)3Cl in a 2:1 ratio in ethanol. The asymmetric unit comprises a dimethylammonium cation (Me2NH2+), an hydrogenoxalate anion (HC2O4−), and half a molecule of oxalic acid (H2C2O4) situated about an inversion center. From a supramolecular point of view, the three components interact togetherviahydrogen bonding. The Me2NH2+cations and the HC2O4−anions are in close proximity through bifurcated N—H...(O,O) hydrogen bonds, while the HC2O4−anions are organized into infinite chainsviaO—H...O hydrogen bonds, propagating along thea-axis direction. In addition, the oxalic acid (H2C2O4) molecules play the role of connectors between these chains. Both the carbonyl and hydroxyl groups of each diacid are involved in four intermolecular interactions with two Me2NH2+and two HC2O4−ions of four distinct polymeric chains,viatwo N—H...O and two O—H...O hydrogen bonds, respectively. The resulting molecular assembly can be viewed as a two-dimensional bilayer-like arrangement lying parallel to (010), and reinforced by a C—H...O hydrogen bond.

Role of weak hydrogen bonds in the crystal structures of phenazine, 5,10-dihydrophenazine and their 1:1 and 3:1 molecular complexes

2000 ◽  
Vol 24 (3) ◽  
pp. 143-147 ◽  
Author(s):  
Venkat R. Thalladi ◽  
Tanja Smolka ◽  
Annette Gehrke ◽  
Roland Boese ◽  
Reiner Sustmann
Keyword(s):  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Molecular Complexes ◽  
Weak Hydrogen Bonds

The role of secondary alcoholic groups of D-galacturonan in its degradation with exo-D-galacturonanase

1980 ◽  
Vol 45 (2) ◽  
pp. 427-434 ◽  
Author(s):  
Kveta Heinrichová ◽  
Rudolf Kohn
Keyword(s):  
Acetyl Derivative ◽  
Competitive Inhibitor ◽  
Hydroxyl Groups ◽  
Pectic Acid ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
The Individual ◽  
Degradation Degree ◽  
Derivatives Of

The effect of exo-D-galacturonanase from carrot on O-acetyl derivatives of pectic acid of variousacetylation degree was studied. Substitution of hydroxyl groups at C(2) and C(3) of D-galactopyranuronic acid units influences the initial rate of degradation, degree of degradation and its maximum rate, the differences being found also in the time of limit degradations of the individual O-acetyl derivatives. Value of the apparent Michaelis constant increases with increase of substitution and value of Vmax changes. O-Acetyl derivatives act as a competitive inhibitor of degradation of D-galacturonan. The extent of the inhibition effect depends on the degree of substitution. The only product of enzymic reaction is D-galactopyranuronic acid, what indicates that no degradation of the terminal substituted unit of O-acetyl derivative of pectic acid takes place. Substitution of hydroxyl groups influences the affinity of the enzyme towards the modified substrate. The results let us presume that hydroxyl groups at C(2) and C(3) of galacturonic unit of pectic acid are essential for formation of the enzyme-substrate complex.

scholarly journals F/OH ratio in a rare fluorine-poor blue topaz from Padre Paraíso (Minas Gerais, Brazil) to unravel topaz’s ambient of formation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
N. Precisvalle ◽  
A. Martucci ◽  
L. Gigli ◽  
J. R. Plaisier ◽  
T. C. Hansen ◽  
...  
Keyword(s):  
Supercritical Fluids ◽  
Fluorine Content ◽  
Minas Gerais ◽  
Hydroxyl Groups ◽  
Exchange Reactions ◽  
Silicate System ◽  
Mullite Phase ◽  
Anomalous Water

AbstractTopaz [Al2SiO4(F,OH)2] is one of the main fluorine-bearing silicates occurring in environments where variably acidic (F)/aqueous (OH) fluids saturate the silicate system. In this work we fully characterized blue topaz from Padre Paraíso (Minas Gerais, Brazil) by means of in situ synchrotron X-Ray and neutron powder diffraction measurements (temperature range 298–1273 K) combined with EDS microanalyses. Understanding the role of OH/F substitution in topaz is important in order to determine the hydrophilicity and the exchange reactions of fluorine by hydroxyl groups, and ultimately to characterize the environmental redox conditions (H2O/F) required for mineral formation. The fluorine content estimated from neutron diffraction data is ~ 1.03 a.f.u (10.34 wt%), in agreement with the chemical data (on average 10.0 wt%). The XOH [OH/(OH + F)] (0.484) is close to the maximum XOH value (0.5), and represents the OH- richest topaz composition so far analysed in the Minas Gerais district. Topaz crystallinity and fluorine content sharply decrease at 1170 K, while mullite phase starts growing. On the basis of this behaviour, we suggest that this temperature may represent the potential initial topaz’s crystallization temperature from supercritical fluids in a pegmatite system. The log(fH2O/fHF)fluid (1.27 (0.06)) is coherent with the fluorine activity calculated for hydrothermal fluids (pegmatitic stage) in equilibrium with the forming mineral (log(fH2O/fHF)fluid = 1.2–6.5) and clearly different from pure magmatic (granitic) residual melts [log(fH2O/fHF)fluid < 1]. The modelled H2O saturated fluids with the F content not exceeding 1 wt% may represent an anomalous water-dominant / fluorine-poor pegmatite lens of the Padre Paraíso Pegmatite Field.

scholarly journals Role of thermal fluctuations in biological copying mechanisms

2021 ◽  
Vol 103 (3) ◽  
Author(s):  
Moupriya Das ◽  
Holger Kantz
Keyword(s):  
Thermal Fluctuations

Investigating the role of GeO2 in enhancing the thermal stability and proton mobility of proton-conducting phosphate glasses

2021 ◽  
Author(s):  
Takahisa Omata ◽  
Aman Sharma ◽  
Takuya Kinoshita ◽  
Issei Suzuki ◽  
Tomohiro Ishiyama ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Phosphate Glasses ◽  
Proton Mobility ◽  
Proton Conducting

In this study, the effect of GeO2 on the thermal stability and proton mobility (μH) of proton-conducting phosphate glasses was experimentally investigated using 22HO1/2−3NaO1/2−(12−x)LaO3/2−xGeO2−63PO5/2 glasses. Increasing glass transition temperature (Tg)...

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