共查询到20条相似文献,搜索用时 15 毫秒
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Alexander B. A. Rupp Petra Klose Dr. Harald Scherer Prof. Dr. Ingo Krossing 《Chemphyschem》2014,15(17):3729-3731
Several new ionic liquids (ILs) were prepared from Na[B(tfe)4] (tfe=OCH2CF3) via metathesis, including one room temperature IL (RTIL). Prior to synthesis, suitable cations were chosen via predictive quantum‐chemical calculations. Nuclear magnetic resonance monitoring over almost a month showed a total stability of the anion in the presence of water. The temperature‐dependent viscosities and melting points of all the new ILs were determined. The data indicate that [B(tfe)4]? ILs may be too viscous for electrochemical applications, but are interesting candidates for lubricant research. 相似文献
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Raman Spectroscopic Study on Alkyl Chain Conformation in 1‐Butyl‐3‐methylimidazolium Ionic Liquids and their Aqueous Mixtures 下载免费PDF全文
Dr. Dheeraj K. Singh Dr. Seoncheol Cha Dr. Dahyun Nam Prof. Dr. Hyeonsik Cheong Prof. Dr. Sang‐Woo Joo Prof. Dr. Doseok Kim 《Chemphyschem》2016,17(19):3040-3046
Ionic liquids of 1‐butyl‐3‐methylimidazolium ([BMIM]) cation with different anions (Cl?, Br?, I?, and BF4?), and their aqueous mixtures were investigated by using Raman spectroscopy and dispersion‐included density functional theory (DFT). The characteristic Raman bands at 600 and 624 cm?1 for two isomers of the butyl chain in the imidazolium cation showed significant changes in intensity for different anions as well as in aqueous solutions. The area ratio of these two bands followed the order I?>Br?>Cl?>BF4? (in terms of the anion X in [BMIM]X), indicating that the butyl chain of [BMIM]I tends to adopt the trans conformation. The butyl chain was found to adopt the gauche conformation upon dilution, irrespective of the anion type. The Raman bands in the butyl C?H stretch region for [BMIM]X (X=Cl?, Br?, and I?) blueshifted significantly with the increase in the water concentration, whereas that for [BMIM]BF4 changed very little upon dilution. The blueshift in the C?H stretch region upon dilution also followed the order: [BMIM]I>[BMIM]Br>[BMIM]Cl>[BMIM]BF4, the same order as the above trans conformation preference of the butyl chain in pure imidazolium ionic liquids, which suggested that the cation‐anion interaction plays a role in determining the conformation of the chain. 相似文献
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Formation of “Quasi” Contact or Solvent‐separated Ion Pairs in the Local Environment of Probe Molecules Dissolved in Ionic Liquids 下载免费PDF全文
Matthias Strauch Dr. Christian Roth Falk Kubatzki Prof. Dr. Ralf Ludwig 《Chemphyschem》2014,15(2):265-270
The change from “quasi” contact to “quasi” solvent‐separated ion‐pair configuration in the local environment of a probe molecule in ionic liquids depends on the varying interaction strength of the chosen anions. The ion speciation in these Coulomb fluids could be shown by combining infrared spectroscopy, density functional theory calculations, and natural bond orbital analysis using a low‐self‐clustering probe molecule. 相似文献
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Transformation of Atmospheric CO2 Catalyzed by Protic Ionic Liquids: Efficient Synthesis of 2‐Oxazolidinones 下载免费PDF全文
Jiayin Hu Jun Ma Qinggong Zhu Zhaofu Zhang Congyi Wu Prof. Buxing Han 《Angewandte Chemie (International ed. in English)》2015,54(18):5399-5403
Protic ionic liquids (PILs), such as 1,8‐diazabicyclo[5.4.0]‐7‐undecenium 2‐methylimidazolide [DBUH][MIm], can catalyze the reaction of atmospheric CO2 with a broad range of propargylic amines to form the corresponding 2‐oxazolidinones. The products are formed in high yields under mild, metal‐free conditions. The cheaper and greener PILs can be easily recycled and reused at least five times without a decrease in the catalytic activity and selectivity. A reaction mechanism was proposed on the basis of a detailed DFT study which indicates that both the cation and anion of the PIL play key synergistic roles in accelerating the reaction. 相似文献
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Damla Yaprak Dr. Eike T. Spielberg Dr. Tobias Bäcker Mark Richter Dr. Bert Mallick Prof. Dr. Axel Klein Prof. Dr. Anja‐Verena Mudring 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(21):6482-6493
In the search for uranium‐based ionic liquids, tris(N,N‐dialkyldithiocarbamato)uranylates have been synthesized as salts of the 1‐butyl‐3‐methylimidazolium (C4mim) cation. As dithiocarbamate ligands binding to the UO22+ unit, tetra‐, penta‐, hexa‐, and heptamethylenedithiocarbamates, N,N‐diethyldithiocarbamate, N‐methyl‐N‐propyldithiocarbamate, N‐ethyl‐N‐propyldithiocarbamate, and N‐methyl‐N‐butyldithiocarbamate have been explored. X‐ray single‐crystal diffraction allowed unambiguous structural characterization of all compounds except N‐methyl‐N‐butyldithiocarbamate, which is obtained as a glassy material only. In addition, powder X‐ray diffraction as well as vibrational and UV/Vis spectroscopy, supported by computational methods, were used to characterize the products. Differential scanning calorimetry was employed to investigate the phase‐transition behavior depending on the N,N‐dialkyldithiocarbamato ligand with the aim to establish structure–property relationships regarding the ionic liquid formation capability. Compounds with the least symmetric N,N‐dialkyldithiocarbamato ligand and hence the least symmetric anions, tris(N‐methyl‐N‐propyldithiocarbamato)uranylate, tris(N‐ethyl‐N‐propyldithiocarbamato)uranylate, and tris(N‐methyl‐N‐butyldithiocarbamato)uranylate, lead to the formation of (room‐temperature) ionic liquids, which confirms that low‐symmetry ions are indeed suitable to suppress crystallization. These materials combine low melting points, stable complex formation, and hydrophobicity and are therefore excellent candidates for nuclear fuel purification and recovery. 相似文献
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Comparative Investigation of the Ionicity of Aprotic and Protic Ionic Liquids in Molecular Solvents by using Conductometry and NMR Spectroscopy 下载免费PDF全文
Electrical conductivity (σ), viscosity (η), and self‐diffusion coefficient (D) measurements of binary mixtures of aprotic and protic imidazolium‐based ionic liquids with water, dimethyl sulfoxide, and ethylene glycol were measured from 293.15 to 323.15 K. The temperature dependence study reveals typical Arrhenius behavior. The ionicities of aprotic ionic liquids were observed to be higher than those of protic ionic liquids in these solvents. The aprotic ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafluoroborate, [bmIm][BF4], displays 100 % ionicity in both water and ethylene glycol. The protic ionic liquids in both water and ethylene glycol are classed as good ionic candidates, whereas in DMSO they are classed as having a poor ionic nature. The solvation dynamics of the ionic species of the ionic liquids are illustrated on the basis of the 1H NMR chemical shifts of the ionic liquids. The self‐diffusion coefficients D of the cation and anion of [HmIm][CH3COO] in D2O and in [D6]DMSO are determined by using 1H nuclei with pulsed field gradient spin‐echo NMR spectroscopy. 相似文献
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Gerhard Schwaab Federico Sebastiani Martina Havenith 《Angewandte Chemie (International ed. in English)》2019,58(10):3000-3013
Ion hydration is of pivotal importance for many fundamental processes. Various spectroscopic methods are used to study the retardation of the hydration bond dynamics in the vicinity of anions and cations. Here we introduce THz‐FTIR spectroscopy as a powerful method to answer the open questions. We show through dissection of THz spectra that we can pinpoint characteristic absorption features that can be attributed to the rattling modes of strongly hydrating ions within their hydration cages as well as vibrationally induced charge fluctuations in the case of weakly hydrating ions. Further analysis yields information on anion–cation cooperativity, the size of the dynamic hydration shell, as well as the lifetimes of these collective ion‐hydration water modes and their connecting thermal bath states. Our study provides evidence for a non‐additive behavior, thus questioning the simplified Hofmeister model. THz spectroscopy enables ion pairing to be observed and quantified at a high salt concentration. 相似文献
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Yanqiang Zhang Dr. Haixiang Gao Dr. Yong Guo Young‐Hyuk Joo Jean'ne M. Shreeve Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(10):3114-3120
N,N‐Dimethylhydrazinium dicyanamide and nitrocyanamide ionic liquids (ILs) were prepared by quaterization of N,N‐dimethylhydrazine with alkyl halides followed by metathesis reactions with silver dicyanamide or silver nitrocyanamide. The key physicochemical properties, such as melting point and decomposition temperatures, density, viscosity, heat of formation, detonation pressure and velocity, and specific impulse were measured/calculated. The impact of anions and alkyl‐substituted cations on these properties is demonstrated. Droplet tests with white‐fuming nitric acid (WFNA) as an oxidizer were utilized to show that the 14 new N,N‐dimethylhydrazinium salts are hypergolic with ignition delay (ID) times ranging from 22 to 1642 ms, thereby suggesting that some may have potential as bipropellants. 相似文献
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Harald Brand Dr. Jörn Martens Peter Mayer Dr. Axel Schulz Prof. Dr. Markus Seibald Thomas Soller 《化学:亚洲杂志》2009,4(10):1588-1603
The synthesis, structure, and bonding of alkali salts of resonance stabilized amides, such as diformylamide (dfa), formylcyanoamide (fca), nitrocyanoamide (nca), and for comparision, the well‐known dicyanoamide (dca), are discussed on the basis of experimental and theoretical data. The first structural reports of K(18‐crown‐6)+dfa?, K(18‐crown‐6)+fca?, Na+nca?, and Li(TMEDA)+dca? are presented. Examination of the X‐ray data reveals almost planar anions with strong cation–anion interactions resulting in network‐like structures in the solid state. For comparison, the X‐ray structures of covalently bound phenyldicyanoamide and diformamide are also discussed. The thermal behavior of the alkali salts of these amides is studied by thermoanalytical experiments. Moreover, several novel ionic liquids based on resonance stabilized amides have been prepared and were fully characterized, namely the dfa, fca, and nca salts of EMIM (1‐ethyl‐3‐methyl‐imidazolium), BMIM (1‐butyl‐3‐methyl‐imidazolium), and HMIM (1‐hexyl‐3‐methyl‐imidazolium). Most of them are liquid at room temperature, except BMIM+fca? that melts at 32 °C. These ionic liquids are neither heat nor shock sensitive, are thermally stable up to over 200 °C, and can be prepared easily in large quantities. 相似文献
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Till Cremer Claudia Kolbeck Kevin R. J. Lovelock Dr. Natalia Paape René Wölfel Peter S. Schulz Dr. Peter Wasserscheid Prof. Dr. Henry Weber Jens Thar Barbara Kirchner Prof. Dr. Florian Maier Dr. Hans‐Peter Steinrück Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(30):9018-9033
Ten [C8C1Im]+ (1‐methyl‐3‐octylimidazolium)‐based ionic liquids with anions Cl?, Br?, I?, [NO3]?, [BF4]?, [TfO]?, [PF6]?, [Tf2N]?, [Pf2N]?, and [FAP]? (TfO=trifluoromethylsulfonate, Tf2N=bis(trifluoromethylsulfonyl)imide, Pf2N=bis(pentafluoroethylsulfonyl)imide, FAP=tris(pentafluoroethyl)trifluorophosphate) and two [C8C1C1Im]+ (1,2‐dimethyl‐3‐octylimidazolium)‐based ionic liquids with anions Br? and [Tf2N]? were investigated by using X‐ray photoelectron spectroscopy (XPS), NMR spectroscopy and theoretical calculations. While 1H NMR spectroscopy is found to probe very specifically the strongest hydrogen‐bond interaction between the hydrogen attached to the C2 position and the anion, a comparative XPS study provides first direct experimental evidence for cation–anion charge‐transfer phenomena in ionic liquids as a function of the ionic liquid’s anion. These charge‐transfer effects are found to be surprisingly similar for [C8C1Im]+ and [C8C1C1Im]+ salts of the same anion, which in combination with theoretical calculations leads to the conclusion that hydrogen bonding and charge transfer occur independently from each other, but are both more pronounced for small and more strongly coordinating anions, and are greatly reduced in the case of large and weakly coordinating anions. 相似文献
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Prof. Dr. Xiaoqing Liu Xue Li Prof. Dr. Xiaoqian Yao Prof. Dr. Weizhen Zhao Prof. Dr. Lei Liu 《Chemphyschem》2021,22(10):968-974
Nowadays, hydrogen activation by frustrated Lewis pairs (FLPs) and their applications are one of the emerging research topics in the field of catalysis. Previous studies have shown that the thermodynamics of this reaction is determined by electronic structures of FLPs and solvents. Herein, we investigated systems consisting of typical FLPs and ionic liquids (ILs), which are well known by their large number of types and excellent solvent effects. The density functional theory (DFT) calculations were performed to study the thermodynamics for H2 activation by both inter- and intra-molecular FLPs, as well as the individual components. The results show that the computed overall Gibbs free energies in ILs are more negative than that computed in toluene. Through the thermodynamics partitioning, we find that ILs favor the H−H cleavage elemental step over the elemental steps of proton attachment, hydride attachment and zwitterionic stabilization. Moreover, the results show that these effects are strongly dependent on the type of FLPs, where intra-molecular FLPs are more affected compared to the inter-molecular FLPs. 相似文献
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Veronika Strehmel Dr. Hans Rexhausen Dr. Peter Strauch Prof. Eckhard Görnitz Dr. Bernd Strehmel Dr. 《Chemphyschem》2008,9(9):1294-1302
2,2,6,6‐Tetramethylpiperidine‐1‐yloxyl derivatives substituted with either hydrogen bonding [‐OH, ‐OSO3H] or ionic [‐OSO3?Na+, ‐OSO3?K+, N+(CH3)3I?, N+(CH3)3 N?(SO2‐CF3)2] substituents are investigated in 1‐butyl‐3‐methylimidazolium tetrafluoroborate over a wide temperature range covering both glassy and viscous states. The Vogel–Fulcher–Tammann equation describes the temperature dependence of the ionic liquid viscosity. Quantum chemical calculations of the spin probes at the UB3LYP/6‐311(2d,p++) level are done to describe the dependence of the spin density on nitrogen on the substitution pattern of the 4‐position of the probe. The results of these calculations are also used to understand the experimental results obtained by applying the Spernol–Gierer–Wirtz theory to analyze the viscosity dependence of the rotational correlation time of the spin probes. Significant differences are found between 2,2,6,6‐tetramethylpiperidine‐1‐yloxyl and its derivatives containing substituents that are able to form hydrogen bonds with the ionic liquid. Moreover, derivatives substituted with ionic groups at the 4‐position have a large effect on temperature‐induced solvent viscosity, as this is particularly dependent on the nature of the substituent at the 4‐position. These dependencies include the temperature region that can be used to describe interactions between the spin probes and the ionic liquid, diffusion into the free volume during non‐activated (neutral spin probes) and activated (charged spin probes) processes. Additional parameters are the radii of the ionic liquid and the spin probes, which are calculated and measured approximately. In addition, the temperature dependence of the isotropic hyperfine coupling constants of the spin probes results in information about the micropolarity of the ionic liquid. At room temperature, this is comparable to that of the solvent dimethylsulfoxide. 相似文献
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Jalal Z. A. Laloo Dr. Lydia Rhyman Prof. Dr. Ponnadurai Ramasami Prof. Dr. F. Matthias Bickelhaupt Dr. Abel de Cózar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4431-4439
The ion‐pair SN2 reactions of model systems MnFn?1+CH3Cl (M+=Li+, Na+, K+, and MgCl+; n=0, 1) have been quantum chemically explored by using DFT at the OLYP/6‐31++G(d,p) level. The purpose of this study is threefold: 1) to elucidate how the counterion M+ modifies ion‐pair SN2 reactivity relative to the parent reaction F?+CH3Cl; 2) to determine how this influences stereochemical competition between the backside and frontside attacks; and 3) to examine the effect of solvation on these ion‐pair SN2 pathways. Trends in reactivity are analyzed and explained by using the activation strain model (ASM) of chemical reactivity. The ASM has been extended to treat reactivity in solution. These findings contribute to a more rational design of tailor‐made substitution reactions. 相似文献