为设计硝基吡唑炸药经物理吸附方式进行废水处理的方案,借助DFT-M06-2X和MP2(full)方法在6-311++G(2d,p)基组水平上研究了Cl–···3,4-二硝基吡唑(3,4-DNP)自由基···H2O体系阴离子氢键诱导协同效应。结果...为设计硝基吡唑炸药经物理吸附方式进行废水处理的方案,借助DFT-M06-2X和MP2(full)方法在6-311++G(2d,p)基组水平上研究了Cl–···3,4-二硝基吡唑(3,4-DNP)自由基···H2O体系阴离子氢键诱导协同效应。结果表明,随着3,4-DNP自由基···H2O体系中Cl–的引入和三聚体的形成,不仅3,4-DNP自由基与H2O之间常规O–H···O和H–O···H氢键的距离、相互作用能、电子密度发生了较大改变,而且Cl–与3,4-DNP自由基或H2O之间形成的H···Cl–阴离子氢键与N···Cl–、C···Cl–、O···Cl–相互作用的相应值也发生了明显改变,从而导致了显著的阴离子氢键诱导协同或反协同效应,形成了稳定的复合物。由此可推断,依据阴离子诱导氢键协同效应,Cl–可用于硝基吡唑类炸药的废水处理。AIM (atom in molecules)、电子密度转移、RDG (reduced density gradient)和NBO (natural bonding orbital)分析揭示了协同效应的本质。展开更多
Dynamics of ammonium and ammonia in solutions is closely related to the metabolism of arnrnoniac compounds, therefore plays an important role in various biological processes. NMR measurements indicated that the reorie...Dynamics of ammonium and ammonia in solutions is closely related to the metabolism of arnrnoniac compounds, therefore plays an important role in various biological processes. NMR measurements indicated that the reorientation dynamics of NH4＋ is faster in its aqueous solution than in rnethanol, which deviates from the Stokes-Einstein-Debye rule since water has higher viscosity than methanol. To address this intriguing issue, we herein study the reorientation dynamics of ammonium ion in both solutions using numerical simulation and an extended cyclic Markov chain model. An evident decoupling between translation and ro- tation of methanol is observed in simulation, which results in the deviation of reorientation from the Stokes-Einstein-Debye rule. Slower hydrogen bond （HB） switchings of ammonium with rnethanol comparing to that with water, due to the steric effect of the rnethyl group, remarkably retards the jump rotation of ammonium. The observations herein provide useful insights into the dynamic behavior of ammonium in the heterogeneous environments including the protein surface or protein channels.展开更多
Solid-aqueous interfaces and phenomena occurring at those interfaces are ubiquitously found in a plethora of chemical systems.When it comes to heterogeneous catalysis,however,our understanding of chemical transformati...Solid-aqueous interfaces and phenomena occurring at those interfaces are ubiquitously found in a plethora of chemical systems.When it comes to heterogeneous catalysis,however,our understanding of chemical transformations at solid-aqueous interfaces is relatively limited and primitive.This review phenomenologically describes a selection of water-engendered effects on the catalytic behavior for several prototypical acid-base-catalyzed reactions over solid catalysts,and critically assesses the general and special roles of water molecules,structural moieties derived from water,and ionic species that are dissolved in it,with an aim to extract novel concepts and principles that underpin heterogeneous acid-base catalysis in the aqueous phase.For alcohol dehydration catalyzed by solid Bronsted acids,rate inhibition by water is most typically related to the decrease in the acid strength and/or the preferential solvation of adsorbed species over the transition state as water molecules progressively solvate the acid site and form extended networks wherein protons are mobilized.Water also inhibits dehydration kinetics over most Lewis acid-base catalysts by competitive adsorption,but a few scattered reports reveal substantial rate enhancements due to the conversion of Lewis acid sites to Brønsted acid sites with higher catalytic activities upon the introduction of water.For aldol condensation on catalysts exposing Lewis acid-base pairs,the addition of water is generally observed to enhance the rate when C–C coupling is rate-limiting,but may result in rate inhibition by site-blocking when the initial unimolecular deprotonation is rate-limiting.Water can also promote aldol condensation on Brønsted acidic catalysts by facilitating inter-site communication between acid sites through hydrogen-bonding interactions.For metallozeolite-catalyzed sugar isomerization in aqueous media,the nucleation and networking of intrapore waters regulated by hydrophilic entities causes characteristic enthalpy-entropy tradeoffs as these water moieties interact with kinetically relevant hydride transfer transition states.The discussed examples collectively highlight the utmost importance of hydrogen-bonding interactions and ionization of covalently bonded surface moieties as the main factors underlying the uniqueness of water-mediated interfacial acid-base chemistries and the associated solvation effects in the aqueous phase or in the presence of water.A perspective is also provided for future research in this vibrant field.展开更多
The hydrogen-bond interactions in ionic liquids have been simply described by the conventional hydrogen-bond model of A–H···B. Coupling with the strong electrostatic force, however, hydrogen bond betwe...The hydrogen-bond interactions in ionic liquids have been simply described by the conventional hydrogen-bond model of A–H···B. Coupling with the strong electrostatic force, however, hydrogen bond between the cation and anion shows particular features in the geometric, energetic, electronic, and dynamic aspects, which is inherently different from that of the conventional hydrogen bond. A general model could be expressed as +[A–H···B]-, in which A and B represent heavy atoms and "+" and "–" represent the charges of the cation containing A atom and anion containing B atom, respectively. Because the structure shows a "zig-zag" motif, this coupling interaction is defined here as the Z-bond. The new model could be generally used to describe the interactions in ionic liquids, as well as bio-systems involved in ions, ionic reaction, and ionic materials.展开更多
Ion pair speciation of ionic liquids(ILs) has an important effect on the physical and chemical properties of ILs and recognition of the structure of ion pairs in solution is essential. It has been reported that ion pa...Ion pair speciation of ionic liquids(ILs) has an important effect on the physical and chemical properties of ILs and recognition of the structure of ion pairs in solution is essential. It has been reported that ion pairs of some ILs can be formed by hydrogen bonding interactions between cations and anions of them. Considering the fact that far-IR(FIR) spectroscopy is a powerful tool in indicating the intermolecular and intramolecular hydrogen bonding, in this work, this spectroscopic technique has been combined with molecular dynamic(MD) simulation and nuclear magnetic resonance hydrogen spectroscopy(~1H NMR) to investigate ion pairs of aprotic ILs [Bmim][NO_3], [BuPy][NO_3], [Pyr_(14)][NO_3], [PP_(14)][NO_3] and [Bu-choline][NO_3] in aqueous IL mixtures. The FIR spectra have been assigned with the aid of density functional theory(DFT) calculations, and the results are used to understand the effect of cationic nature on the structure of ion pairs. It is found that contact ion pairs formed in the neat aprotic ILs by hydrogen bonding interactions between cation and anion, were still maintained in aqueous solutions up to high water mole fraction(say 0.80 for [BuPy][NO3]). When water content was increased to a critical mole fraction of water(say 0.83 for [BuPy][NO3]), the contact ion pairs could be transformed into solvent-separated ion pairs due to the formation of the hydrogen bonding between ions and water. With the further dilution of the aqueous ILs solution, the solvent-separated ion pairs was finally turned into free cations and free anions(fully hydrated cations or anions). The concentrations of the ILs at which the contact ion pairs were transformed into solvent-separated ion pairs and solvent-separated ion pairs were transformed into free ions(fully hydrated ion) were dependent on the cationic structures. These information provides direct spectral evidence for ion pair structures of the aprotic ILs in aqueous solution. MD simulation and ~1H NMR results support the conclusion drawn from FIR spectra investigations.展开更多
文摘为设计硝基吡唑炸药经物理吸附方式进行废水处理的方案,借助DFT-M06-2X和MP2(full)方法在6-311++G(2d,p)基组水平上研究了Cl–···3,4-二硝基吡唑(3,4-DNP)自由基···H2O体系阴离子氢键诱导协同效应。结果表明,随着3,4-DNP自由基···H2O体系中Cl–的引入和三聚体的形成,不仅3,4-DNP自由基与H2O之间常规O–H···O和H–O···H氢键的距离、相互作用能、电子密度发生了较大改变,而且Cl–与3,4-DNP自由基或H2O之间形成的H···Cl–阴离子氢键与N···Cl–、C···Cl–、O···Cl–相互作用的相应值也发生了明显改变,从而导致了显著的阴离子氢键诱导协同或反协同效应,形成了稳定的复合物。由此可推断,依据阴离子诱导氢键协同效应,Cl–可用于硝基吡唑类炸药的废水处理。AIM (atom in molecules)、电子密度转移、RDG (reduced density gradient)和NBO (natural bonding orbital)分析揭示了协同效应的本质。
基金supported by the National Key Research and Development Program of China(2017YFA0206801)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB20000000 and XDB10040304)the National Natural Science Foundation of China(No.21373201and No.21433014)
文摘Dynamics of ammonium and ammonia in solutions is closely related to the metabolism of arnrnoniac compounds, therefore plays an important role in various biological processes. NMR measurements indicated that the reorientation dynamics of NH4＋ is faster in its aqueous solution than in rnethanol, which deviates from the Stokes-Einstein-Debye rule since water has higher viscosity than methanol. To address this intriguing issue, we herein study the reorientation dynamics of ammonium ion in both solutions using numerical simulation and an extended cyclic Markov chain model. An evident decoupling between translation and ro- tation of methanol is observed in simulation, which results in the deviation of reorientation from the Stokes-Einstein-Debye rule. Slower hydrogen bond （HB） switchings of ammonium with rnethanol comparing to that with water, due to the steric effect of the rnethyl group, remarkably retards the jump rotation of ammonium. The observations herein provide useful insights into the dynamic behavior of ammonium in the heterogeneous environments including the protein surface or protein channels.
文摘Solid-aqueous interfaces and phenomena occurring at those interfaces are ubiquitously found in a plethora of chemical systems.When it comes to heterogeneous catalysis,however,our understanding of chemical transformations at solid-aqueous interfaces is relatively limited and primitive.This review phenomenologically describes a selection of water-engendered effects on the catalytic behavior for several prototypical acid-base-catalyzed reactions over solid catalysts,and critically assesses the general and special roles of water molecules,structural moieties derived from water,and ionic species that are dissolved in it,with an aim to extract novel concepts and principles that underpin heterogeneous acid-base catalysis in the aqueous phase.For alcohol dehydration catalyzed by solid Bronsted acids,rate inhibition by water is most typically related to the decrease in the acid strength and/or the preferential solvation of adsorbed species over the transition state as water molecules progressively solvate the acid site and form extended networks wherein protons are mobilized.Water also inhibits dehydration kinetics over most Lewis acid-base catalysts by competitive adsorption,but a few scattered reports reveal substantial rate enhancements due to the conversion of Lewis acid sites to Brønsted acid sites with higher catalytic activities upon the introduction of water.For aldol condensation on catalysts exposing Lewis acid-base pairs,the addition of water is generally observed to enhance the rate when C–C coupling is rate-limiting,but may result in rate inhibition by site-blocking when the initial unimolecular deprotonation is rate-limiting.Water can also promote aldol condensation on Brønsted acidic catalysts by facilitating inter-site communication between acid sites through hydrogen-bonding interactions.For metallozeolite-catalyzed sugar isomerization in aqueous media,the nucleation and networking of intrapore waters regulated by hydrophilic entities causes characteristic enthalpy-entropy tradeoffs as these water moieties interact with kinetically relevant hydride transfer transition states.The discussed examples collectively highlight the utmost importance of hydrogen-bonding interactions and ionization of covalently bonded surface moieties as the main factors underlying the uniqueness of water-mediated interfacial acid-base chemistries and the associated solvation effects in the aqueous phase or in the presence of water.A perspective is also provided for future research in this vibrant field.
基金supported by the National Natural Science Foundation of China(21036007)the Fund of State Key Laboratory of Multiphase Complex System,Institute of Process Engineering,Chinese Academy of Sciences(MPCS-2012-A-10)
文摘The hydrogen-bond interactions in ionic liquids have been simply described by the conventional hydrogen-bond model of A–H···B. Coupling with the strong electrostatic force, however, hydrogen bond between the cation and anion shows particular features in the geometric, energetic, electronic, and dynamic aspects, which is inherently different from that of the conventional hydrogen bond. A general model could be expressed as +[A–H···B]-, in which A and B represent heavy atoms and "+" and "–" represent the charges of the cation containing A atom and anion containing B atom, respectively. Because the structure shows a "zig-zag" motif, this coupling interaction is defined here as the Z-bond. The new model could be generally used to describe the interactions in ionic liquids, as well as bio-systems involved in ions, ionic reaction, and ionic materials.
基金supported by the National Natural Science Foundation of China(21573060,21673068)Program for Innovative Research Team in Science and Technology in University of Henan Province(16IRTSTHN002)+1 种基金Plan for Scientific Innovation Talent of Henan Province(144200510004)The High Performance Computing Center of Henan Normal University
文摘Ion pair speciation of ionic liquids(ILs) has an important effect on the physical and chemical properties of ILs and recognition of the structure of ion pairs in solution is essential. It has been reported that ion pairs of some ILs can be formed by hydrogen bonding interactions between cations and anions of them. Considering the fact that far-IR(FIR) spectroscopy is a powerful tool in indicating the intermolecular and intramolecular hydrogen bonding, in this work, this spectroscopic technique has been combined with molecular dynamic(MD) simulation and nuclear magnetic resonance hydrogen spectroscopy(~1H NMR) to investigate ion pairs of aprotic ILs [Bmim][NO_3], [BuPy][NO_3], [Pyr_(14)][NO_3], [PP_(14)][NO_3] and [Bu-choline][NO_3] in aqueous IL mixtures. The FIR spectra have been assigned with the aid of density functional theory(DFT) calculations, and the results are used to understand the effect of cationic nature on the structure of ion pairs. It is found that contact ion pairs formed in the neat aprotic ILs by hydrogen bonding interactions between cation and anion, were still maintained in aqueous solutions up to high water mole fraction(say 0.80 for [BuPy][NO3]). When water content was increased to a critical mole fraction of water(say 0.83 for [BuPy][NO3]), the contact ion pairs could be transformed into solvent-separated ion pairs due to the formation of the hydrogen bonding between ions and water. With the further dilution of the aqueous ILs solution, the solvent-separated ion pairs was finally turned into free cations and free anions(fully hydrated cations or anions). The concentrations of the ILs at which the contact ion pairs were transformed into solvent-separated ion pairs and solvent-separated ion pairs were transformed into free ions(fully hydrated ion) were dependent on the cationic structures. These information provides direct spectral evidence for ion pair structures of the aprotic ILs in aqueous solution. MD simulation and ~1H NMR results support the conclusion drawn from FIR spectra investigations.
