scholarly journals Interaction Effects between Cellulose and Water in Nanocrystalline and Amorphous Regions: A Novel Approach Using Molecular Modeling

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Ali Chami Khazraji ◽  
Sylvain Robert
Keyword(s):  
Molecular Modeling ◽  
Hydrogen Bonds ◽  
Electrostatic Interactions ◽  
Dispersion Forces ◽  
Structural Anisotropy ◽  
Cellulose Structure ◽  
Novel Approach ◽  
Nanocrystalline And Amorphous ◽  
Hydrophobic Nature ◽  
Cellulose Crystal Structure

The hydrophilic/hydrophobic nature of cellulose is based on its structural anisotropy. Cellulose chains are arranged in a parallel manner and are organized in sheets stabilized by interchain OH–O hydrogen bonds, whereas the stacking of sheets is stabilized by both van der Waals (vdW) dispersion forces and weak CH–O hydrogen bonds. Cellulose has a strong affinity to itself and materials containing hydroxyls, especially water. Based on the preponderance of hydroxyl functional groups, cellulose polymer is very reactive with water. Water molecular smallness promotes the reaction with the cellulose chains and immediately formed hydrogen bonds. Besides that, vdW dispersion forces play an important role between these two reactive entities. They stabilize the cellulose structure according to the considerable cohesive energy in the cellulose network. Hydrogen bonding, electrostatic interactions, and vdW dispersion forces play an important role in determining the cellulose crystal structure during the cellulose-water interactions. As a result of these interactions, the volume of cellulose undergoes a meaningful change expressed not only by an exponential growth in amorphous regions, but also by an expansion in nanocrystalline regions. In addition, the volume change is associated with the swelling material expressed as a weight gain of the cellulose polymer. Molecular modeling using Accelrys Materials Studio allowed us to open a new horizon and is helpful for understanding cellulose-water interactions.

scholarly journals Cooperation/Competition between Halogen Bonds and Hydrogen Bonds in Complexes of 2,6-Diaminopyridines and X-CY3 (X = Cl, Br; Y = H, F)

Symmetry ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 766
Author(s):  
Barbara Bankiewicz ◽  
Marcin Palusiak
Keyword(s):  
Complex Formation ◽  
Hydrogen Bonds ◽  
Dft Calculations ◽  
Electrostatic Interactions ◽  
Dipole Moments ◽  
Main Role ◽  
Halogen Bonds ◽  
Topological Parameters ◽  
Leading Role ◽  
The Impact

The DFT calculations have been performed on a series of two-element complexes formed by substituted 2,6-diaminopyridine (R−PDA) and pyridine (R−Pyr) with X−CY3 molecules (where X = Cl, Br and Y = H, F). The primary aim of this study was to examine the intermolecular hydrogen and halogen bonds in the condition of their mutual coexistence. Symmetry/antisymmetry of the interrelation between three individual interactions is addressed. It appears that halogen bonds play the main role in the stabilization of the structures of the selected systems. However, the occurrence of one or two hydrogen bonds was associated with the favourable geometry of the complexes. Moreover, the impact of different substituent groups attached in the para position to the aromatic ring of the 2,6-diaminopyridine and pyridine on the character of the intermolecular hydrogen and halogen bonds was examined. The results indicate that the presence of electron-donating substituents strengthens the bonds. In turn, the presence of electron-withdrawing substituents reduces the strength of halogen bonds. Additionally, when hydrogen and halogen bonds lose their leading role in the complex formation, the nonspecific electrostatic interactions between dipole moments take their place. Analysis was based on geometric, energetic, and topological parameters of the studied systems.

scholarly journals Wetting transition of ionic liquids at metal surfaces: A computational molecular approach to electronic screening using a virtual Thomas-Fermi fluid

2020 ◽  
Author(s):  
Alexander Schlaich ◽  
Dongliang Jin ◽  
Lyderic Bocquet ◽  
Benoit Coasne
Keyword(s):  
Ionic Liquids ◽  
Energy Storage ◽  
Electrostatic Interactions ◽  
Debye Length ◽  
Wetting Transition ◽  
Molecular Fluids ◽  
Thomas Fermi ◽  
Electronic Screening ◽  
Novel Approach ◽  
The Impact

Abstract Of particular relevance to energy storage, electrochemistry and catalysis, ionic and dipolar liquids display a wealth of unexpected fundamental behaviors – in particular in confinement. Beyond now well-documented adsorption, overscreening and crowding effects1,2,3, recent experiments have highlighted novel phenomena such as unconventional screening4 and the impact of the electronic nature – metallic versus insulating – of the confining surface on wetting/phase transitions5,6. Such behaviors, which challenge existing theoretical and numerical modeling frameworks, point to the need for new powerful tools to embrace the properties of confined ionic/dipolar liquids. Here, we introduce a novel atom-scale approach which allows for a versatile description of electronic screening while capturing all molecular aspects inherent to molecular fluids in nanoconfined/interfacial environments. While state of the art molecular simulation strategies only consider perfect metal or insulator surfaces, we build on the Thomas-Fermi formalism for electronic screening to develop an effective approach that allows dealing with any imperfect metal between these asymptotes. The core of our approach is to describe electrostatic interactions within the metal through the behavior of a `virtual' Thomas-Fermi fluid of charged particles, whose Debye length sets the Thomas-Fermi screening length λ in the metal. This easy-to-implement molecular method captures the electrostatic interaction decay upon varying λ from insulator to perfect metal conditions, while describing very accurately the capacitance behavior – and hence the electrochemical properties – of the metallic confining medium. By applying this strategy to a nanoconfined ionic liquid, we demonstrate an unprecedented wetting transition upon switching the confining medium from insulating to metallic. This novel approach provides a powerful framework to predict the unsual behavior of ionic liquids, in particular inside nanoporous metallic structures, with direct applications for energy storage and electrochemistry.

scholarly journals Crystal structure from X-ray powder diffraction data, DFT-D calculation, Hirshfeld surface analysis, and energy frameworks of (RS)-trichlormethiazide

2022 ◽  
Vol 78 (2) ◽  
Author(s):  
Robert A. Toro ◽  
Analio Dugarte-Dugarte ◽  
Jacco van de Streek ◽  
José Antonio Henao ◽  
José Miguel Delgado ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Surface Analysis ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Electrostatic Interactions ◽  
Hirshfeld Surface ◽  
Hirshfeld Surface Analysis ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Π Interactions

The structure of racemic (RS)-trichlormethiazide [systematic name: (RS)-6-chloro-3-(dichloromethyl)-1,1-dioxo-3,4-dihydro-2H-1λ6,2,4-benzothiadiazine-7-sulfonamide], C8H8Cl3N3O4S2 (RS-TCMZ), a diuretic drug used in the treatment of oedema and hypertension, was determined from laboratory X-ray powder diffraction data using DASH [David et al. (2006). J. Appl. Cryst. 39, 910–915.], refined by the Rietveld method with TOPAS-Academic [Coelho (2018). J. Appl. Cryst. 51, 210–218], and optimized using DFT-D calculations. The extended structure consists of head-to-tail dimers connected by π–π interactions which, in turn, are connected by C—Cl...π interactions. They form chains propagating along [101], further connected by N—H...O hydrogen bonds to produce layers parallel to the ac plane that stack along the b-axis direction, connected by additional N—H...O hydrogen bonds. The Hirshfeld surface analysis indicates a major contribution of H...O and H...Cl interactions (32.2 and 21.7%, respectively). Energy framework calculations confirm the major contribution of electrostatic interactions (E elec) to the total energy (E tot). A comparison with the structure of S-TCMZ is also presented.

scholarly journals Synthesis and Characterization of [2-CH3CH2C6H4NH3]6P6O18⋅4H2O

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Houda Marouani ◽  
Salem Slayyem Al-Deyab ◽  
Mohamed Rzaigui
Keyword(s):  
Hydrogen Bonds ◽  
Electrostatic Interactions ◽  
Three Dimensional ◽  
Spectroscopic Studies ◽  
Monoclinic System ◽  
Dimensional Network ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Ir Spectroscopic

Single crystals of [2-CH3CH2C6H4NH3]6P6O18⋅4H2O are synthesized in aqueous solution by the interaction of cyclohexaphosphoric acid and 2-ethylaniline. This compound crystallizes in the monoclinic system with P21/c space group the unit cell dimensions are: a=16.220(4) Å, b=10.220(5) Å, c=20.328(4) Å, β=113.24(3)∘, Z=2, and V=3096.5(18) Å3. The atomic arrangement can be described by layers formed by cyclohexaphosphate anions P6O186− and water molecules connected by hydrogen bonds O–H⋯O. These inorganic layers are developed around bc planes at x=1/2 and are interconnected by the H-bonds created by ammonium groups of organic cations. All the hydrogen bonds, the van der Waals contacts and electrostatic interactions between the different entities give rise to a three-dimensional network in the structure and add stability to this compound. The thermal behaviour and the IR spectroscopic studies of this new cyclohexaphosphate are discussed.

The Difference of Serum Protein Transport between Echinosides and Verbascoside

2020 ◽  
Vol 42 (3) ◽  
pp. 369-369
Author(s):  
Ming Guo Ming Guo ◽  
Xiaoxue Zhao Xiaoxue Zhao ◽  
Peter E Brodelius Peter E Brodelius ◽  
Ling Fang Ling Fang ◽  
Zhihong Sun and Rui Wang Zhihong Sun and Rui Wang
Keyword(s):  
Molecular Modeling ◽  
Hydrogen Bonds ◽  
Serum Albumin ◽  
Protein Transport ◽  
Van Der Waals ◽  
Hydrolysis Product ◽  
Van Der Waals Forces ◽  
Molecular Structures ◽  
Hydrophobic Force ◽  
Binding Characteristics

Verbascoside (VER) is the enzymatic hydrolysis product of echinacoside (ECH). The molecular structures of ECH and VER have different glucosyl groups so they bind to serum albumin in different ways, resulting in different pharmacological actions. In this report, we have examined the binding characteristics between human serum albumin (HSA) and ECH/VER by molecular modeling and spectroscopic approaches. Molecular modeling revealed that VER bound to HSA mainly through hydrogen bonds, van der Waals forces and hydrophobic forces. The spectroscopic results showed that the interactions between HSA and VER/ECH involved a static binding process, and the bonding strength of the VER-HSA complex was stronger than that of the ECH-HSA complex. The value of the binding distances (r) was low, which indicated the occurrence of energy transfer. The reaction conformational pattern of HSA-VER and HSA-ECH gave a “two-state model” based on fluorescent phase diagram analysis. According to the thermodynamic model, the main forces between interaction of VER and HSA were hydrogen bonds and van der Waals forces, whereas the interaction between ECH and HSA was hydrophobic force. The fluorescence polarization analysis demonstrated that the interaction between HSA and VER or ECH generated a non-covalent complex. Compared with ECH, VER was more likely to bind with HSA because of its smaller molecular size and low polarity. The results of the spectral analysis concurred with the molecular modeling data, which provides a helpful reference for the study of the molecular reaction mechanism of VER/ECH binding to HSA.

scholarly journals Crystal Structure of a Cationic Bile Salt Derivative ([3,5,7,12]-3-(2-naphthyloylamino)-7,12-dihydroxycholan-24-triethylammonium iodide)

Crystals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 135
Author(s):  
Francisco Meijide ◽  
María Pilar Vázquez-Tato ◽  
Julio Seijas ◽  
Santiago de Frutos ◽  
Juan V. Trillo Novo ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Quaternary Ammonium ◽  
Electrostatic Interactions ◽  
Amide Bond ◽  
Orthorhombic Space Group ◽  
Steroid Nucleus ◽  
Quaternary Ammonium Group ◽  
Group A ◽  
Hydroxy Groups

The crystal structure of the iodide salt of a quaternary ammonium derivative of cholic acid having a naphthalene group attached to the 3rd position of the steroid nucleus through an amide bond ([3,5,7,12]-3-(2-naphthyloylamino)-7,12-dihydroxycholan-24-triethylammonium iodide) has been resolved. The compound crystallizes in the P212121 orthorhombic space group (a/Å = 10.9458(3); b/Å = 12.1625(3); c/Å = 28.4706(7)). The lateral chain adopts a fully extended tttt conformation because the quaternary ammonium group cannot participate in the formation of hydrogen bonds. The iodide ion is involved in the formation of hydrogen bonds as well as the amide group and the two steroid hydroxy groups. Hirshfeld surface analysis confirms that these contacts, as well as the electrostatic interactions, stabilize the structure. The helixes around the 21 screw axis are right-handed ones.

The evolution of self-assemblies in the mixed system of oleic acid–diethylenetriamine based on the transformation of electrostatic interactions and hydrogen bonds

Soft Matter ◽  
2014 ◽  
Vol 10 (40) ◽  
pp. 8023-8030 ◽  
Author(s):  
Chengcheng Zhou ◽  
Xinhao Cheng ◽  
Oudi Zhao ◽  
Shuai Liu ◽  
Chenjiang Liu ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Hydrogen Bonds ◽  
Electrostatic Interactions ◽  
Mixed System

scholarly journals Inside Cover: Controlling the Subtle Energy Balance in Protic Ionic Liquids: Dispersion Forces Compete with Hydrogen Bonds (Angew. Chem. Int. Ed. 9/2015)

2015 ◽  
Vol 54 (9) ◽  
pp. 2564-2564
Author(s):  
Koichi Fumino ◽  
Verlaine Fossog ◽  
Peter Stange ◽  
Dietmar Paschek ◽  
Rolf Hempelmann ◽  
...  
Keyword(s):  
Ionic Liquids ◽  
Energy Balance ◽  
Hydrogen Bonds ◽  
Dispersion Forces ◽  
Protic Ionic Liquids
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