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Dr. Koichi Fumino Anne‐Marie Bonsa Benjamin Golub Dr. Dietmar Paschek Prof. Dr. Ralf Ludwig 《Chemphyschem》2015,16(2):299-304
Ionic liquids (ILs) attract interest in science and technology as a result of their unique properties. Binary and ternary mixtures of ILs significantly increase the number of possible cation/anion combinations, resulting in targeted physical and chemical properties. In this work, we study the mixing behaviour of two protic ILs: triethyl ammonium methylsulfonate [Et3NH][CH3SO3] and triethylammonium triflate [Et3NH][CF3SO3]. We find a characteristic deviation from ideal mixing by means of low‐frequency infrared spectroscopy. By using molecular dynamics simulations, we explain this behaviour as being the result of different strengths of anion/cation hydrogen bonding. This non‐ideality of non‐random H‐bond mixing is also reflected in macroscopic properties such as the viscosity. Mixing suitable ILs may, thus, result in new ILs with targeted physical properties. 相似文献
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Víctor Manuel Castor-Villegas José Manuel Guevara-Vela Wilmer E. Vallejo Narváez Ángel Martín Pendás Tomás Rocha-Rinza Alberto Fernández-Alarcón 《Journal of computational chemistry》2020,41(26):2266-2277
Hydrogen bonds (HB) are arguably the most important noncovalent interactions in chemistry. We study herein how differences in connectivity alter the strength of HBs within water clusters of different sizes. We used for this purpose the interacting quantum atoms energy partition, which allows for the quantification of HB formation energies within a molecular cluster. We could expand our previously reported hierarchy of HB strength in these systems (Phys. Chem. Chem. Phys., 2016, 18 , 19557) to include tetracoordinated monomers. Surprisingly, the HBs between tetracoordinated water molecules are not the strongest HBs despite the widespread occurrence of these motifs (e.g., in ice Ih). The strongest HBs within H2O clusters involve tricoordinated monomers. Nonetheless, HB tetracoordination is preferred in large water clusters because (a) it reduces HB anticooperativity associated with double HB donors and acceptors and (b) it results in a larger number of favorable interactions in the system. Finally, we also discuss (a) the importance of exchange-correlation to discriminate among the different examined types of HBs within H2O clusters, (b) the use of the above-mentioned scale to quickly assess the relative stability of different isomers of a given water cluster, and (c) how the findings of this research can be exploited to indagate about the formation of polymorphs in crystallography. Overall, we expect that this investigation will provide valuable insights into the subtle interplay of tri- and tetracoordination in HB donors and acceptors as well as the ensuing interaction energies within H2O clusters. 相似文献
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Controlled Sol–Gel Transitions of a Thermoresponsive Polymer in a Photoswitchable Azobenzene Ionic Liquid as a Molecular Trigger
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Dr. Caihong Wang Dr. Kei Hashimoto Dr. Ryota Tamate Dr. Hisashi Kokubo Prof. Dr. Masayoshi Watanabe 《Angewandte Chemie (International ed. in English)》2018,57(1):227-230
Producing ionic liquids (ILs) that function as molecular trigger for macroscopic change is a challenging issue. Photoisomerization of an azobenzene IL at the molecular level evokes a macroscopic response (light‐controlled mechanical sol–gel transitions) for ABA triblock copolymer solutions. The A endblocks, poly(2‐phenylethyl methacrylate), show a lower critical solution temperature in the IL mixture containing azobenzene, while the B midblock, poly(methyl methacrylate), is compatible with the mixture. In a concentrated polymer solution, different gelation temperatures were observed in it under dark and UV conditions. Light‐controlled sol–gel transitions were achieved by a photoresponsive solubility change of the A endblocks upon photoisomerization of the azobenzene IL. Therefore, an azobenzene IL as a molecular switch can tune the self‐assembly of a thermoresponsive polymer, leading to macroscopic light‐controlled sol–gel transitions. 相似文献
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Amontons' law successfully describes friction between macroscopic solid bodies for a wide range of velocities and normal forces. For the diffusion and forced sliding of adhering or entangled macromolecules, proteins, and biological complexes, temperature effects are invariably important, and a similarly successful friction law at biological length and velocity scales is missing. Hydrogen bonds (HBs) are key to the specific binding of biomatter. Here we show that friction between hydrogen-bonded matter obeys in the biologically relevant low-velocity viscous regime a simple law: the friction force is proportional to the number of HBs, the sliding velocity, and a friction coefficient γ(HB). This law is deduced from atomistic molecular dynamics simulations for short peptide chains that are laterally pulled over planar hydroxylated substrates in the presence of water and holds for widely different peptides, surface polarities, and applied normal forces. The value of γ(HB) is extrapolated from simulations at sliding velocities in the range from V = 10(-2) to 100 m/s by mapping on a simple stochastic model and turns out to be of the order of γ(HB) ? 10(-8) kg/s. The friction of a single HB thus amounts to the Stokes friction of a sphere with an equivalent radius of roughly 1 μm moving in water. Cooperativity is pronounced: roughly three HBs act collectively. 相似文献
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The phase separation of ionic liquids (ILs) in water is studied by laser light scattering (LLS). For the ILs with longer alkyl chains, such as [C(8)mim]BF(4) and [C(6)mim]BF(4) (mim = methylimidazolium), macroscopic phase separation occurs in the mixture with water. LLS also reveals the coexistence of the mesoscopic phase, the size of which is in the order of 100-800 nm. In aqueous mixtures of ILs with shorter alkyl chains, such as [C(4)mim]BF(4), only the mesoscopic phase exists. The mesoscopic phase can be effectively removed by filtration through a 0.22 μm filter. However, it reforms with time and can be enhanced by lowering the temperature, thus indicating that it is controlled by thermodynamics. The degree of mesoscopic phase separation can be used to evaluate the miscibility of ILs with water. This study helps to optimize the applications of ILs in related fields, as well as the recycling of ILs in the presence of water. 相似文献
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John W. Whitley William Jeffrey Horne Matthew S. Shannon Mary A. Andrews Kelsey L. Terrell Spenser S. Hayward Shuwen Yue Max S. Mittenthal Kathryn E. O'Harra Jason E. Bara 《Journal of polymer science. Part A, Polymer chemistry》2018,56(20):2364-2375
The use of ionic liquids (ILs) as media in radical polymerizations has demonstrated the ability of these unique solvents to improve both reaction kinetics and polymer product properties. However, the bulk of these studies have examined the polymerization behavior of common organic monomers (e.g., methyl methacrylate, styrene) dissolved in conventional ILs. There is increasing interest in polymerized ILs (poly(ILs)), which are ionomers produced from the direct polymerization of styrene-, vinyl-, and acrylate-functionalized ILs. Here, the photopolymerization kinetics of IL monomers are investigated for systems in which styrene or vinyl functionalities are pendant from the imidazolium cation. Styrene-functionalized IL monomers typically polymerized rapidly (full conversion ≤1 min) in both neat compositions or when diluted with a nonpolymerizable IL, [C2mim][Tf2N]. However, monomer conversion in vinyl-functionalized IL monomers is much more dependent on the nature of the nonpolymerizable group. ATR-FTIR analysis and molecular simulations of these monomers and monomer mixtures identified the presence of multiple intermolecular interactions (e.g., π–π stacking, IL aggregation) that contribute to the polymerization behaviors of these systems. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2364–2375 相似文献
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Dr. Dipak Kumar Sahoo Kiran Devi Tulsiyan Subhrakant Jena Dr. Himansu S. Biswal 《Chemphyschem》2020,21(23):2525-2535
Ionic liquids (ILs) are useful in pharmaceutical industries and biotechnology as alternative solvents or sources for protein extraction and purification, preservation of biomolecules and for regulating the catalytic activity of enzymes. However, the binding mechanism, the non-covalent forces responsible for protein-IL interactions and dynamics of proteins in IL need to be investigated in depth for the effective use of ILs as alternatives. Herein, we disclose the molecular level understanding of the structural intactness and reactivity of a model protein cytochrome c (Cyt c) in biocompatible threonine-based ILs with the help of experimental techniques such as isothermal titration calorimetry (ITC), fluorescence spectroscopy, transmission electron microscopy (TEM) as well as molecular docking. Hydrophobic and electrostatic forces are responsible for the structural and conformational integrity of Cyt c in IL. The ITC experiments revealed the Cyt c-IL binding free energies are in the range of 10–14 kJ/mol and the molecular docking studies demonstrated that ILs interact at the surfaces of Cyt c. The results look promising as the ILs used here are non-toxic and biocompatible, and thus may find potential applications in structural biology and biotechnology. 相似文献
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Dr. Alesia A. Tietze Prof. Dr. Frank Bordusa Dr. Ralf Giernoth Prof. Dr. Diana Imhof Prof. Dr. Thomas Lenzer Dr. Astrid Maaß Dr. Carmen Mrestani‐Klaus Prof. Dr. Ines Neundorf Dr. Kawon Oum Prof. Dr. Dirk Reith Dr. Annegret Stark 《Chemphyschem》2013,14(18):4044-4064
During the last decade, ionic liquids (ILs) have revealed promising properties and applications in many research fields, including biotechnology and biological sciences. The focus of this contribution is to give a critical review of the phenomena observed and current knowledge of the interactions occurring on a molecular basis. As opposed to the huge advances made in understanding the properties of proteins in ILs, complementary investigations dealing with interactions between ILs and peptides or oligopeptides are underrepresented and are mostly only of phenomenological nature. However, the field has received more attention in the last few years. This Review features a meta‐analysis of the available data and findings and should, therefore, provide a basis for a scientifically profound understanding of the nature and mechanisms of interactions between ILs and structured or nonstructured peptides. Fundamental aspects of the interactions between different peptides/oligopeptides and ILs are complemented by sections on the experimental (spectroscopy, structural biology) and theoretical (computational chemistry) possibilities to explain the phenomena reported so far in the literature. In effect, this should lead to the development of novel applications and support the understanding of IL–solute interactions in general. 相似文献
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Saeedreza Emamian Tian Lu Holger Kruse Hamidreza Emamian 《Journal of computational chemistry》2019,40(32):2868-2881
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The structure of the vapor/ethanol-aqueous-solution interface has been carefully investigated focusing on an intermolecular hydrogen bond (HB) and molecular clusters bound by HBs. This paper is a continuation of our previous molecular dynamics (MD) study (Langmuir 2005, 21, 10885), and all analysis was performed based on five independent adsorption-equilibrated configurations of a slab of ethanol solution at 298.15 K, where the ethanol mole fraction of the solution, chi(e), is 0.0052, 0.012, 0.024, 0.057, and 0.12, respectively. The geometrical definition of HB enabled the detection of the HB between ethanol-ethanol, ethanol-water, and water-water molecules. The variations of the density of HB and the coordination number of HB across the vapor/solution interface were analyzed. Analysis on the density of HB reveals that a monolayer of adsorbed ethanol can be classified into two parts where ethanol molecules prefer to form HBs with each other and ethanol molecules prefer to form HBs with water molecules. Despite chi(e), the coordination number of ethanol-ethanol HB monotonically increases toward the vapor region, while those of ethanol-water and water-water HBs monotonically decrease. In addition, the variation of the mean size of both ethanol one-component clusters and ethanol/water binary clusters across the interface were analyzed. The mean size of an ethanol one-component cluster and that of an ethanol/water binary cluster are expressed as a maximum at the interface. These behaviors are linked with the size distributions of both one-component and binary clusters. A relatively large system in this calculation also enables detailed discussion about the molar dependency of the bulk structural properties of an ethanol solution. 相似文献
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The molecular interactions of the ionic liquids (ILs) 1‐butyl‐3‐methylimidazolium tetrafluoroborate [C4mim][BF4], 3‐methyl‐1‐octylimidazolium tetrafluoroborate [C8mim][BF4] and 1‐butyl‐3‐methylimidazolium octylsulfate [C4mim][C8OSO3] are investigated in ethylene glycol (EG) over the whole mole fraction range using fluorescence (steady‐state and time‐resolved), Fourier transform infrared and nuclear magnetic resonance (NMR) spectroscopy. The cybotactic region surrounding the pyrene fluorescent probe exhibits peculiar characteristics for different ILs in the EG‐rich region. The extent of solute–solvent interactions is assessed by determining the deviations of experimentally observed vibronic band intensity ratios of peak 1 to peak 3 of pyrene fluorescence (I1/I3) from a composite I1/I3 value obtained using a preferential solvation model. A distinct vibrational frequency shift for various stretching modes of EG (O? H) or ILs (C? H of ring protons, B? F and S?O of anions) indicates specific interactional preferences of EG toward the IL protons/anion. Splitting of the O? H vibration band of EG at 3000–3700 cm?1 into three separate bands, and analysis of the changes in location and area of these bands as a function of concentration enable precise determination of the effect of ILs on hydrogen bridges of EG. NMR chemical shifts and their deviations from ideality show multiple hydrogen‐bonding interactions of varying strengths between unlike molecules in the mixtures. A comparison of spectroscopic results with thermodynamic properties shows that the mixing microscopic behaviour of the investigated systems is completely different from the macroscopic behaviour, which is primarily governed by the difference in shape, size and nature of the molecules. 相似文献
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首先通过两步法合成了具有双咪唑环阳离子结构的离子液体(DIL),并将其与单咪唑环离子液体(MIL)进行混合以调控黏度变化,混合离子液体(ILs)的黏度符合对数混合规则且随温度变化呈现Arrhenius型流体行为.进一步通过动态流变、示差扫描量热(DSC)、电化学测试等方法研究了混合离子液体中DIL比例对聚甲基丙烯酸甲酯(PMMA)链缠结和松弛行为的影响,并讨论了PMMA/ILs体系热稳定性、玻璃化转变及离子电导率等的变化.结果表明,DIL独特的双咪唑环结构可与PMMA分子形成更多相互作用位点,从而导致凝聚缠结的形成,很大程度上限制了PMMA分子链的运动和松弛.随DIL含量增加,PMMA/ILs体系的松弛时间、热分解温度、玻璃化转变温度等参数均呈增大趋势,但其离子电导率有所损失,这与DIL较大的分子尺寸和运动能力有关. 相似文献
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Alexander E. Khudozhitkov Jan Neumann Thomas Niemann Dzmitry Zaitsau Peter Stange Dietmar Paschek Alexander G. Stepanov Daniil I. Kolokolov Ralf Ludwig 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(49):18027-18035
We present deuteron quadrupole coupling constants (DQCC) for hydroxyl‐functionalized ionic liquids (ILs) in the crystalline or glassy states characterizing two types of hydrogen bonding: The regular Coulomb‐enhanced hydrogen bonds between cation and anion (c–a), and the unusual hydrogen bonds between cation and cation (c–c), which are present despite repulsive Coulomb forces. We measure these sensitive probes of hydrogen bonding by means of solid‐state NMR spectroscopy. The DQCCs of (c–a) ion pairs and (c–c) H‐bonds are compared to those of salt bridges in supramolecular complexes and those present in molecular liquids. At low temperatures, the (c–c) species successfully compete with the (c–a) ion pairs and dominate the cluster populations. Equilibrium constants obtained from molecular‐dynamics (MD) simulations show van't Hoff behavior with small transition enthalpies between the differently H‐bonded species. We show that cationic‐cluster formation prevents these ILs from crystallizing. With cooling, the (c–c) hydrogen bonds persist, resulting in supercooling and glass formation. 相似文献
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We give a perspective on the relations between inorganic and organic cation ionic liquids (ILs), including members with melting points that overlap around the borderline 100 degrees C. We then present data on the synthesis and properties (melting, boiling, glass temperatures, etc.) of a large number of an intermediate group of liquids that cover the ground between equimolar molecular mixtures and ILs, depending on the energetics of transfer of a proton from one member of the pair to the other. These proton-transfer ILs have interesting properties, including the ability to serve as electrolytes in solvent-free fuel cell systems. We provide a basis for assessing their relation to aprotic ILs by means of a Gurney-type proton-transfer free energy level diagram, with approximate values of the energy levels based on free energy of formation and pK(a) data. The energy level scheme allows us to verify the relation between solvent-free acidic and basic electrolytes, and the familiar aqueous variety, and to identify neutral protic electrolytes that are unavailable in the case of aqueous systems. 相似文献
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《International journal of quantum chemistry》2018,118(14)
Proton dynamics of hydrogen bonds (HBs) in the α and γ form of Nylon 6 were investigated by Born–Oppenheimer molecular dynamics (BOMD). Our results show differences in the dynamic effects of interchain HB interactions between the α form and the γ form of Nylon 6. Analysis of the time course of the geometrical parameters of HBs along the BOMD simulations has shown that HBs are dynamically favored in the γ form of Nylon. The quantization of the N H stretching mode enables a detailed discussion of the strengths of HB interactions. Solving the Schrödinger equation for the snapshots of one‐dimensional proton potentials, extracted from the ab initio MD, enables the consideration of anharmonicity, thermodynamics, and approximate quantum effects on proton movement. A larger red shift of the N H stretching band was observed in the γ form compared with the α form. Our study shows that HBs are more stabilized in the γ form than in the α form, which is mainly due to the higher number of HBs. The distribution of HBs along the trajectory clearly reveals the preference of the γ form. The quantization of the N H motion enables the discussion of the differences in the IR spectra between the two forms. 相似文献
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《Journal of computational chemistry》2017,38(8):530-540
Ionic liquids (ILs) play a key role in many chemical applications. As regards the theoretical approach, ILs show added difficulties in calculations due to the composition of the ion pair and to the fact that they are liquids. Although density functional theory (DFT) can treat this kind of systems to predict physico–chemical properties, common versions of these methods fail to perform accurate predictions of geometries, interaction energies, dipole moments, and other properties related to the molecular structure. In these cases, dispersion and self‐interaction error (SIE) corrections need to be introduced to improve DFT calculations involving ILs. We show that the inclusion of dispersion is needed to obtain good geometries and accurate interaction energies. SIE needs to be corrected to describe the charges and dipoles in the ion pair correctly. The use of range–separated functionals allows us to obtain interaction energies close to the CCSD(T) level. © 2017 Wiley Periodicals, Inc. 相似文献
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离子液体与气体、溶剂等物质组成的多相体系为吸收、萃取、两相催化等技术的发展提供了新的平台。离子液体的表/界面性质与结构是含离子液体多相体系的重要科学问题,可在介观尺度下显著影响多相体系反应和分离过程的效率。近年来,离子液体表/界面性质和结构的研究得到了广泛的关注。本文综述了离子液体及其与水、有机溶剂组成的混合物的表/界面张力及结构研究进展,介绍了现有的研究方法、研究对象与研究成果,归纳了离子液体及其混合物表/界面张力及结构的变化规律,分析了表/界面结构与表/界面张力之间的关系,探讨了离子液体表/界面研究存在的问题和未来的发展方向。 相似文献
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Nicolás Ríos‐Lombardía Eduardo Busto Dr. Vicente Gotor‐Fernández Dr. Vicente Gotor Prof. Raúl Porcar Eduardo García‐Verdugo Dr. Santiago V. Luis Prof. Ignacio Alfonso Dr. Santiago García‐Granda Prof. Amador Menéndez‐Velázquez Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(3):836-847
This paper reports a simple and robust modular synthetic strategy that leads to a large variety of configurationally and structurally diverse imidazole‐based chiral ionic liquids (CILs) by lipase‐catalyzed resolution. The intimate microscopic interactions of the supramolecular ionic network of these imidazolium chiral salts at the molecular level are investigated both spectroscopically (NMR, FT‐IR‐ATR) and theoretically, and a topological analysis of the experimental electron densities obtained by X‐ray dif fr action of single crystals is performed. Our results support the key role played by the relative configuration of the ‐OR group on the hydrogen‐bonding pattern and its strong influence on the final physical properties of the imidazolium salt. We also obtained a reasonable correlation between the observed melting point and the non‐covalent interactions. The spectroscopic data and the topological analysis reflect the key role played by hydrogen bonds between the OH and imidazolium C2H groups in both cation–anion and cation–cation interactions, with the presence of an OH group leading to an additional inter‐cation interaction. This interaction significantly affects the properties of stereoisomeric salts. Even more interestingly, we also studied the effect of the chirality by comparing enantiopure CILs with their racemic mixtures and found that, with the exception of trans‐Cy6‐OH‐Im‐Bn‐Br, the melting points of the racemic mixtures are higher than those of the corresponding enantiomerically pure forms. For stereoisomeric examples, we have successfully explained the differences in melting temperatures in light of the corresponding structural data. Chirality should therefore be taken into account as a highly attractive design vector in the preparation of ILs with specifically desired properties. 相似文献