scholarly journals Dissolving Cellulose in 1,2,3-Triazolium- and Imidazolium-Based Ionic Liquids with Aromatic Anions

Molecules ◽  
2020 ◽  
Vol 25 (15) ◽  
pp. 3539 ◽  
Author(s):  
Martin Brehm ◽  
Julian Radicke ◽  
Martin Pulst ◽  
Farzaneh Shaabani ◽  
Daniel Sebastiani ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Ionic Liquids ◽  
Hydrogen Bonds ◽  
Md Simulations ◽  
Heterocyclic Carbenes ◽  
Quantitative Prediction ◽  
Lower Amount ◽  
New Class ◽  
Aromatic Anions ◽  
Lower Basicity

We present 1,2,3-triazolium- and imidazolium-based ionic liquids (ILs) with aromatic anions as a new class of cellulose solvents. The two anions in our study, benzoate and salicylate, possess a lower basicity when compared to acetate and therefore should lead to a lower amount of N-heterocyclic carbenes (NHCs) in the ILs. We characterize their physicochemical properties and find that all of them are liquids at room temperature. By applying force field molecular dynamics (MD) simulations, we investigate the structure and dynamics of the liquids and find strong and long-lived hydrogen bonds, as well as significant π–π stacking between the aromatic anion and cation. Our ILs dissolve up to 8.5 wt.-% cellulose. Via NMR spectroscopy of the solution, we rule out chain degradation or derivatization, even after several weeks at elevated temperature. Based on our MD simulations, we estimate the enthalpy of solvation and derive a simple model for semi-quantitative prediction of cellulose solubility in ILs. With the help of Sankey diagrams, we illustrate the hydrogen bond network topology of the solutions, which is characterized by competing hydrogen bond donors and acceptors. The hydrogen bonds between cellulose and the anions possess average lifetimes in the nanosecond range, which is longer than found in common pure ILs.

Pressure dependence of the liquid structure and the Raman noncoincidence effect of liquid methanol revisited

2004 ◽  
Vol 76 (1) ◽  
pp. 247-254 ◽  
Author(s):  
H. Torii
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Pressure Dependence ◽  
Md Simulations ◽  
Liquid Structure ◽  
Present Calculation ◽  
Number Density ◽  
Transition Dipole ◽  
Liquid Systems

Pressure dependence of the liquid structure and the Raman noncoincidence effect of liquid methanol is examined with the combination of molecular dynamics (MD) simulations and the intermolecular resonant vibrational interactions determined by the transition dipole coupling (TDC) mechanism (MD/TDC method). It is shown that the observed decrease of the Raman noncoincidence νNCE of the CO stretching band with increasing density reported in the literature is quantitatively reproduced by the present calculation. As the density increases, the hydrogen bonds get slightly shorter, but molecules belonging to different hydrogen-bond chains get closer to each other to a greater extent. This anisotropic change in the liquid structure is the reason for the behavior of νNCE. It is also shown that the concentration dependence of νNCE in the methanol/CCl4 binary mixtures reported in a previous study, and the pressure dependence of νNCE in methanol may be described in a consistent way as a function of the number density of methanol in the liquid systems.

Hydrogen bonds in the crystal structure of hydrophobic and hydrophilic COOH-functionalized imidazolium ionic liquids

CrystEngComm ◽  
2014 ◽  
Vol 16 (14) ◽  
pp. 3040-3046 ◽  
Author(s):  
Xiao-Peng Xuan ◽  
Liang-Liang Chang ◽  
Heng Zhang ◽  
Na Wang ◽  
Yang Zhao
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Ionic Liquids ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Carboxyl Group ◽  
Imidazolium Ionic Liquids

Hydrogen bonds such as the classic O–H⋯X (halide ion) hydrogen bond and the carboxyl group dimer were observed in the crystal structures of hydrophilic and hydrophobic COOH-functionalized imidazolium ionic liquids, respectively.

Two Fe3(μ3-S)2(CO)8clusters with terminal N-heterocyclic carbenes

2014 ◽  
Vol 70 (6) ◽  
pp. 528-532 ◽  
Author(s):  
Wei Yang ◽  
Qiang Fu ◽  
Jing Zhao ◽  
Huan-Ren Cheng ◽  
Yao-Cheng Shi
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Heterocyclic Carbenes ◽  
Carbonyl Ligands

The title compounds with terminal N-heterocyclic carbenes, namely octacarbonyl(imidazolidinylidene-κC2)di-μ3-sulfido-triiron(II)(2Fe—Fe), [Fe3(C3H6N2)(μ3-S)2(CO)8], (I), and octacarbonyl(1-methylimidazo[1,5-a]pyridin-3-ylidene-κC3)di-μ3-sulfido-triiron(II)(2Fe—Fe), [Fe3(C8H8N2)(μ3-S)2(CO)8], (II), have been synthesized. Each compound contains two Fe—Fe bonds and two S atoms above and below a triiron triangle. One of the eight carbonyl ligands deviates significantly from linearity. In (I), dimers generated by an N—H...S hydrogen bond are linked into [001] double chains by a second N—H...S hydrogen bond. These chains are packed by a C—H...O hydrogen bond to yield [101] sheets. In (II), dimers generated by an N—H...S hydrogen bond are linked by C—H...O hydrogen bonds to form [111] double chains.

Unveiling the peculiar hydrogen bonding behavior of solvated N-heterocyclic carbenes

2016 ◽  
Vol 18 (1) ◽  
pp. 126-140 ◽  
Author(s):  
Oldamur Hollóczki
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Force Field ◽  
Practical Importance ◽  
Md Simulations ◽  
Heterocyclic Carbenes ◽  
Mechanical Force

After fitting a molecular mechanical force field for imidazol-2-ylidenes, MD simulations revealed carbene–carbene and three-center hydrogen bonds of carbenes. The practical importance of these structures is also highlighted.

A Hydrogen Bond Between Linear Tetrapyrrole and Conserved Aspartate Causes the Far-Red Shifted Absorption of Phytochrome Photoreceptors

2020 ◽  
Author(s):  
Egle Maximowitsch ◽  
Tatiana Domratcheva
Keyword(s):  
Hydrogen Bond ◽  
Light Adaptation ◽  
Positive Charge ◽  
Pyrrole Ring ◽  
Md Simulations ◽  
Spectral Shift ◽  
Specific Domain ◽  
Study Guides ◽  
Rational Engineering ◽  
Tuning Mechanism

Photoswitching of phytochrome photoreceptors between red-absorbing (Pr) and far-red absorbing (Pfr) states triggers light adaptation of plants, bacteria and other organisms. Using quantum chemistry, we elucidate the color-tuning mechanism of phytochromes and identify the origin of the Pfr-state red-shifted spectrum. Spectral variations are explained by resonance interactions of the protonated linear tetrapyrrole chromophore. In particular, hydrogen bonding of pyrrole ring D with the strictly conserved aspartate shifts the positive charge towards ring D thereby inducing the red spectral shift. Our MD simulations demonstrate that formation of the ring D–aspartate hydrogen bond depends on interactions between the chromophore binding domain (CBD) and phytochrome specific domain (PHY). Our study guides rational engineering of fluorescent phytochromes with a far-red shifted spectrum.

Hydrogen bonds in N-(3-chloro-2-benzo[b]thienocarbonyl)- and N-(2-benzo[b]thienocarbonyl)-N'-monosubstituted thioureas

1987 ◽  
Vol 52 (11) ◽  
pp. 2673-2679 ◽  
Author(s):  
Oľga Hritzová ◽  
Peter Kutschy ◽  
Ján Imrich ◽  
Thomas Schöffmann
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Strong Hydrogen Bond ◽  
Cyclic Form ◽  
Thiourea Derivatives

N-(3-Chloro-2-benzo[b]thienocarbonyl)-N'-monosubstituted thiourea derivatives undergo photocyclizations with lower yields than those obtained from analogous N',N'-disubstituted derivatives. This decreased reactivity is caused by the existence of a six-membered cyclic form with the very strong hydrogen bond NH···O=C. The possibility of formation of various conformers has been found with N-(2-benzo[b]thienocarbonyl)-N'-monosubstituted thiourea derivatives as a consequence of the rotation around the C(2)-C(O) connecting line.

Crystal structure of tofacitinib dihydrogen citrate (Xeljanz®), (C16H21N6O)(H2C6H5O7)

2021 ◽  
pp. 1-8
Author(s):  
James A. Kaduk ◽  
Amy M. Gindhart ◽  
Thomas N. Blanton
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Carboxylic Acid ◽  
Hydrogen Bonds ◽  
Powder Diffraction ◽  
Density Functional ◽  
Acid Group ◽  
Dimensional Network ◽  
Van Der Waals Contacts ◽  
Citrate Anion

The crystal structure of tofacitinib dihydrogen citrate (tofacitinib citrate) has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Tofacitinib dihydrogen citrate crystallizes in space group P212121 (#19) with a = 5.91113(1), b = 12.93131(3), c = 30.43499(7) Å, V = 2326.411(6) Å3, and Z = 4. The crystal structure consists of corrugated layers perpendicular to the c-axis. Within the layers, cation⋯anion and anion⋯anion hydrogen bonds link the fragments into a two-dimensional network parallel to the ab-plane. Between the layers, there are only van der Waals contacts. A terminal carboxylic acid group in the citrate anion forms a strong charge-assisted hydrogen bond to the ionized central carboxylate group. The other carboxylic acid acts as a donor to the carbonyl group of the cation. The citrate hydroxy group forms an intramolecular charge-assisted hydrogen bond to the ionized central carboxylate. Two protonated nitrogen atoms in the cation act as donors to the ionized central carboxylate of the anion. These hydrogen bonds form a ring with the graph set symbol R2,2(8). The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™ (PDF®).

scholarly journals Measurement of the hydrogen bond acceptance of ionic liquids and green solvents by the 19F solvatomagnetic comparison method

2021 ◽  
Author(s):  
Christian Laurence ◽  
Sergui Mansour ◽  
Daniela Vuluga ◽  
Julien Legros
Keyword(s):  
Hydrogen Bond ◽  
Ionic Liquids ◽  
Comparison Method ◽  
Green Solvents ◽  
Reliable Measurement

A 19F solvatomagnetic comparison of 4-fluorophenol and 4-fluoroanisole yields a more reliable measurement of the hydrogen-bond acceptance of ionic liquids and green solvents than the solvatochromic comparison method.

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