电荷辅助氢键的形成机制及环境效应研究进展
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摘要
氢键(Hydrogen bond)作为分子间一种常见的相互作用力,在物理、化学和生物过程中起着重要作用,这种所谓的"弱相互作用"已经被广泛研究。因独特的键合方向性和成键特异性,该键合作用能够在分子聚集过程中提供最佳的控制,被应用于晶体材料合成工艺领域。尤其是离子或电荷辅助下形成的氢键,即电荷辅助氢键(Charge-assisted hydrogen bond,CAHB),其键合强度相当于共价键,引起了研究者的关注。CAHB是指相对于普通的氢键作用,形成氢键作用的两个物质之间存在电荷分布,能够直接形成CAHB。实际上,在给定的共振结构中,电荷的分布是间接导致相对较强的CAHB形成的主要原因。此外,两性离子组分与携带相反电荷的载体之间伴随着库仑相互作用,由于存在两个能量等价的价键共振形式,进而形成具有更强结合作用的CAHB。其中,与质子供体原子上正电荷之间形成(+) CAHB,与质子接受基团上的负电荷之间形成(-) CAHB。研究发现CAHB作为一类低阻氢键,或类似于阳离子桥的盐桥,普遍存在于环境过程中。其键强比普通的氢键强得多,具有与共价键相当的特性,该特性有助于环境中许多介质自组装过程的发生。CAHB作用下形成的超级大分子结构就是天然有机质在环境中的主要存在形式。吸附是常用于去除水环境中可解离的两性有机污染物的技术手段。研究发现,碳基吸附剂和离子型化合物之间的静电相互作用可能是去除诸多离子型化合物的主要吸附机制。然而,一些其他研究已经注意到,单独的静电相互作用不能解释pH值对发生解离后的离子型污染物吸附的影响,这表明存在额外的物理或化学相互作用机制需要进一步研究。CAHB作为负电荷吸附质和吸附剂之间强的作用力,能较好地解释吸附实验中出现的一些异常现象。本文综述了CAHB在环境中的成键机理以及产生的环境效应。结合部分实验数据,着重论述了CAHB作为天然有机质(包括腐殖质和溶解性有机质)共轭形成超级大分子的重要作用机理。最后,对CAHB参与的复杂水质条件下的环境行为及其受天然有机质的影响,以及碳基吸附剂去除离子型有机污染物的选择和制备方面的研究提出了展望。
As a common intermolecular interaction force,hydrogen bonds play a significant role in physical,chemical and biological processes. And this so-called"weak interaction"has long been studied extensively. Thanks to its unique orientation and specificity of bonding,hydrogen bonding effect can regulate molecular aggregation perfectly,which has been widely applied in synthesis of crystal materials. Especially,the hydrogen bonds formed with the assist of ion or charge,namely the charge-assisted hydrogen bonds( CAHB),exhibit a binding strength stronger than ordinary hydrogen bond,and equivalent to covalent bond,which has aroused numerous interests of researchers.Different from ordinary hydrogen bonds,there is a charge distribution between the two substances that form the CAHB. Actually,just the distribution of charge in a given resonance structure dominant the formation of the relatively strong CAHB. In addition,there is also Coulomb interaction between the amphoteric ion component and the carrier carrying the opposite charge. The existence of two energy-equivalent valence bond resonance forms result in the stronger binding CAHB. Specifically,( +) CAHB is formed between the positive charge on the proton donor atom; and(-) CAHB is formed between the formal negative charge on the proton accepting group.It has been also found that CAHB,as a kind of low-resistance hydrogen bond or a salt bridge similar to a cation bridge,is ubiquitous in environmental processes. They possess not only bonding strength much stronger than ordinary hydrogen bonds,but also characteristics similar to covalent bonds,which is beneficial to the self-assembly process of many environmental media. The super macromolecular structure formed by CAHB is the main form of natural organic matter( NOM) in the environment. Adsorption is commonly used to remove the dissociable amphoteric organic pollutants in water environments. The electrostatic interaction between carbon-based adsorbents and ionic compounds may be the main adsorption mechanism for the removal of these ionic compounds. However,a number of other studies have noted that individual electrostatic interaction alone is not able to explain the effect of p H on the adsorption of dissociated ionic contaminants. Apparently,there exists additional physical or chemical interaction mechanisms that need to be further investigated. While CAHB can be well used to explain some abnormal phenomena in adsorption experiments,such as the strong interaction between the negatively charged adsorbates and the adsorbents.In this article,the key formation mechanism of CAHB in the environment and their environmental effects are summarized. Combining with some experimental data,the important mechanism of natural organic matter( including humic substances and dissolved organic matter) conjugating and forming supramolecules via CAHB is discussed with emphasis. Finally,the environment behavior of ionic compounds affected by natural organic matter under the complex water quality conditions with the participation of CAHB is mentioned. The selection and preparation of carbon-based adsorbents for the removal of ionic compounds are also suggested.
As a common intermolecular interaction force,hydrogen bonds play a significant role in physical,chemical and biological processes. And this so-called"weak interaction"has long been studied extensively. Thanks to its unique orientation and specificity of bonding,hydrogen bonding effect can regulate molecular aggregation perfectly,which has been widely applied in synthesis of crystal materials. Especially,the hydrogen bonds formed with the assist of ion or charge,namely the charge-assisted hydrogen bonds( CAHB),exhibit a binding strength stronger than ordinary hydrogen bond,and equivalent to covalent bond,which has aroused numerous interests of researchers.Different from ordinary hydrogen bonds,there is a charge distribution between the two substances that form the CAHB. Actually,just the distribution of charge in a given resonance structure dominant the formation of the relatively strong CAHB. In addition,there is also Coulomb interaction between the amphoteric ion component and the carrier carrying the opposite charge. The existence of two energy-equivalent valence bond resonance forms result in the stronger binding CAHB. Specifically,( +) CAHB is formed between the positive charge on the proton donor atom; and(-) CAHB is formed between the formal negative charge on the proton accepting group.It has been also found that CAHB,as a kind of low-resistance hydrogen bond or a salt bridge similar to a cation bridge,is ubiquitous in environmental processes. They possess not only bonding strength much stronger than ordinary hydrogen bonds,but also characteristics similar to covalent bonds,which is beneficial to the self-assembly process of many environmental media. The super macromolecular structure formed by CAHB is the main form of natural organic matter( NOM) in the environment. Adsorption is commonly used to remove the dissociable amphoteric organic pollutants in water environments. The electrostatic interaction between carbon-based adsorbents and ionic compounds may be the main adsorption mechanism for the removal of these ionic compounds. However,a number of other studies have noted that individual electrostatic interaction alone is not able to explain the effect of p H on the adsorption of dissociated ionic contaminants. Apparently,there exists additional physical or chemical interaction mechanisms that need to be further investigated. While CAHB can be well used to explain some abnormal phenomena in adsorption experiments,such as the strong interaction between the negatively charged adsorbates and the adsorbents.In this article,the key formation mechanism of CAHB in the environment and their environmental effects are summarized. Combining with some experimental data,the important mechanism of natural organic matter( including humic substances and dissolved organic matter) conjugating and forming supramolecules via CAHB is discussed with emphasis. Finally,the environment behavior of ionic compounds affected by natural organic matter under the complex water quality conditions with the participation of CAHB is mentioned. The selection and preparation of carbon-based adsorbents for the removal of ionic compounds are also suggested.
引文
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2 Braga D,Grepioni F.Accounts of Chemical Research,2000,33,601.
3 Gilli P,Bertolasi V,Ferretti V,et al.Journal of the American Chemical Society,1994,116,909.
4 Gilli G,Gilli P.The nature of the hydrogen bond,Oxford University Press,UK,2009.
5 Son S U,Reingold J A,Carpenter G B,et al.Organometallics,2006,25,5276.
6 Piccolo A.Advances in agronomy,Elsevier,US,2002.
7 Piccolo A.Humic substances in terrestrial ecosystems,Elsevier,Netherlands,1996.
8 Xie M,Chen W,Xu Z,et al.Environmental Pollution,2014,186,187.
9 Gilli G,Gilli P.Journal of Molecular Structure,2000,552,1.
10 Xiao F,Pignatello J J.Environmental Science&Technology,2016,50,6276.
11 Lehn J M.Supramolecular chemistry,Vch,Weinheim,GER,1995.
12 Adachi K,Sugiyama Y,Yoneda K,et al.Chemistry-A European Journal,2005,11,6616.
13 Prins L J,Reinhoudt D N,Timmerman P.Angewandte Chemie International Edition,2001,40,2382.
14 Arunan E,Desiraju G R,Klein R A,et al.Pure and Applied Chemistry,2011,83,1637.
15 Desiraju G R,Steiner T.International Union of Crystal,Oxford University Press,UK,2001.
16 Sobczyk L,Grabowski S J,Krygowski T M.Chemical Reviews,2005,105,3513.
17 Adams H,Carver F J,Hunter C A,et al.Angewandte Chemie International Edition,1996,35,1542.
18 Corbin P S,Zimmerman S C.Journal of the American Chemical Society,2000,122,3779.
19 Gilli G,Bellucci F,Ferretti V,et al.Journal of the American Chemical Society,1989,111,1023.
20 Gilli P,Bertolasi V,Ferretti V,et al.Journal of the American Chemical Society,1994,116,909.
21 Bankiewicz B,Palusiak M.Computational and Theoretical Chemistry,2011,966,113.
22 Ward M D.Chemical Communications,DOI:10.1039/b513077h.
23 Schmuck C.Chemical Communications,DOI:10.1039/A901126I.
24 Braga D,Polito M,Bracaccini M,et al.Organometallics,2003,22,2142.
25 Kononova M M.Soil organic matter:Its nature,its role in soil formation and in soil fertility,Pergamon Press,US,1966.
26 Stevenson F J.Humus chemistry:Genesis,composition,reactions,Wiley,US,1994.
27 Dubach P,Mehta N C.Soils Fertil,1963,26,293.
28 Conte P,Piccolo A.Environmental Science&Technology,1999,33,1682.
29 Piccolo A,Nardi S,Concheri G.European Journal of Soil Science,1996,47,319.
30 Piccolo A,Nardi S,Concheri G.Chemosphere,1996,33,595.
31 Piccolo A,Conte P,Cozzolino A.European Journal of Soil Science,1999,50,687.
32 Cozzolino A,Piccolo A.Soil Biology&Biochemistry,2002,33,563.
33 Zhao J,Chu G,Pan B,et al.Environmental Science&Technology,2018,52,5173.
34 Li X,Pignatello J J,Wang Y,et al.Environmental Science&Technology,2013,47,8334.
35 Franz M,Arafat H A,Pinto N G.Carbon,2000,38,1807.
36 Lian F,Sun B,Song Z,et al.Chemical Engineering Journal,2014,248,128.
37 Moreno-Castilla C.Carbon,2004,42,83.
38 Gilli P,Pretto L,Bertolasi V,et al.Accounts of Chemical Research,2008,42,33.
39 TeixidóM,Pignatello J J,Beltrán J L,et al.Environmental Science&Technology,2011,45,10020.
40 Lee J W,Kidder M,Evans B R,et al.Environmental Science&Technology,2010,44,7970.
41 Silber A,Levkovitch I,Graber E.Environmental Science&Technology,2010,44,9318.
42 Fang Q,Chen B,Lin Y,et al.Environmental Science&Technology,2013,48,279.
43 Li H,Cao Y,Zhang D,et al.Science of the Total Environment,2018,618,269.