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离子液体中离子对结构及氢键相互作用研究
Alternative TitleStudy on the Configurations of Cation-Anion Pair and Hydrogen Bonding Interaction in Ionic Liquids
何宏艳
Subtype博士
Thesis Advisor张锁江
2013-11
Degree Grantor中国科学院研究生院
Degree Discipline应用化学
Keyword离子液体 氢键 超额红外光谱 电荷转移 电荷密度拓扑分析
Abstract离子液体作为一类环境友好介质和功能材料,其结构?性质关系的研究非常重要。氢键作用的本质和规律作为化学研究的基本问题之一,在离子液体中广泛存在,因此离子液体中的氢键作用研究十分必要。本论文采用量子化学计算、电荷密度拓扑分析、红外、超额红外、二维红外、核磁氢谱等手段,选择几种典型的、环境友好且有应用潜力的离子液体作为对象来研究其构型及氢键相互作用。主要研究内容总结如下: (1) 采用密度泛函方法(DFT)在B3LYP/6-31++g**水平上研究了一种环境友好的新型离子液体[Emim][LAC]的离子对构型及阴阳离子间的相互作用。讨论了离子对的几何结构特征、离子间相互作用能、红外光谱特征、离子间氢键作用、电荷转移、电荷密度及电子云的拓扑分析。发现每种稳定存在的离子对之间都存在着2-3个氢键,其中最强的氢键作用出现在咪唑环上的C2?H氢原子和阴离子的羧基O原子之间。参与形成氢键的C?H键键长增加,伴随着红外光谱波数的红移; *(C?H)反键轨道上电荷密度的增加、红外光谱红移波数变化值、轨道相互作用能与C?H键键长的增加量之间都有很好的线性相关性。AIM理论分析揭示了大部分的氢键相互作用都具有共价键的特征。 (2) 采用红外、超额红外、二维相关红外及量子化学计算方法研究了[Emim][LAC]和共溶剂甲醇间的氢键相互作用。发现氢键广泛存在于[Emim][LAC]和甲醇混合体系中,并对体系的稳定性及互溶性起着至关重要的作用。NBO分析表明CH3OH分子与[Emim]+阳离子及[LAC]?阴离子的作用机理有着本质的不同;超额红外光谱研究发现,随着甲醇浓度的不断增加,阳离子上C?H基团参与形成的氢键都呈减弱趋势,且?COO基团参与形成的氢键也都逐渐减弱,说明甲醇的加入可以影响到离子液体体系相互作用。二维相关红外分析表明随着甲醇加入到[Emim][LAC]中,甲醇分子将优先和[Emim]+中的芳香氢作用。量子化学计算表明包含[Emim]+, [LAC]?和甲醇分子的多种作用体的相互作用能大小关系如下:Emim?CH3OH?LAC > Emim?LAC > LAC?CH3OH > Emim?CH3OH。 (3) 采用DFT方法研究了由环烷酸类阴离子及胆碱阳离子构成可生物降解的一类新型离子液体[Ch][NA](NA=CPC, CHC, Be和Sa)的离子对构型、电子性质及阴阳离子间的相互作用,尤其是氢键相互作用。发现:[NA]?阴离子都倾向于和阳离子形成两类基本的氢键,其中形成的最稳定结构中都存在着O?H???O氢键作用。阴离子构型对不同离子液体离子对的相互作用能有着重要影响。增加[NA]?阴离子C环的C数亦或采用芳香性的基团替代饱和环烷烃基团,均可降低阴阳离子间的相互作用能。采用自然键轨道(NBO)分析、原子中的分子(AIM)理论的分析及约化电荷密度梯度(RDG)分析三种方法细致地研究了这几类离子液体中的氢键相互作用。 (4) 结合红外、超额红外、核磁共振氢谱及量子化学计算,研究了一类典型的吡啶类含有氰基阴离子的离子液体([C4Py][SCN])和二甲基亚砜(DMSO)之间的氢键相互作用,发现氢键对于体系的稳定性及互溶性有着重要作用。红外光谱及超额光谱分析表明DMSO能够与吡啶环C?H及烷基侧链C?H同时形成氢键作用,但是减弱了原来阴阳离子间的离子氢键作用。随着DMSO浓度的增加,可以增强了阴离子中C≡N参与的氢键作用。[C4Py][SCN]离子液体的加入使DMSO中甲基参与的氢键作用较原作用体本身的缔合氢键减弱。采用量子化学计算进一步验证了上述实验结果。NBO分析表明:DMSO分子与[C4Py]+及[SCN]?的作用机理有着本质的不同,DMSO分子在与阴阳离子作用过程中既是质子给体,也是质子受体。 综上所述,本文主要采用量子化学计算、电子密度拓扑分析、超额红外光谱、二维相关红外、核磁氢谱等方法,对六种离子液体及其中的两种与甲醇/DMSO共溶剂体系的微观结构、相互作用尤其是氢键相互作用进行了研究。理论计算结合实验的方法对离子液体进行的研究,为进一步探索离子液体结构?性能–相互作用之间的关系打下了一定的基础。
Other AbstractIonic liquids (ILs) are believed to have potential applications in a variety of industrial fields, while hydrogen bonds (H-bonds) between the cation/anion and cosolvents plays an important role in governing the structure and properties of the systems containing ILs. Quantum chemical calculations, topological analysis of the electron density, infrared spectroscopy, including excess infrared spectroscopy, and two-dimensional (2D) correlation infrared spectroscopy have been applied to elucidate the H-bonding interactions in a series of ILs systems and IL-solvent systems. The detail contents and innovations are listed as follows: (1) 1-ethyl-3-methylimidazolium lactate ([Emim][LAC]) is an environmental friendly ionic liquid with potential industrial applications. The geometrical characteristics, ion interaction energy, calculated IR vibrations, characterization of H-bonds, electron transfer, electron density as well as topology analysis of [Emim][LAC] ion pair were calculated by DFT at B3LYP/6-31++G** level. The natural bond orbital (NBO) and atoms in molecule (AIM) analyses were employed to understand the nature of the interactions between cation and anion. The five most stable geometries were verified by analyzing the interaction energies. It was found that the most of the C?H???O intermolecular H-bonds interactions in five stable conformers have some covalent character in nature. The elongation and red shift in IR spectrum of C?H bonds which involve in H-bonds is proved by electron transfers from the lone pairs of the carbonyl O atom of [LAC]? anion to the C?H antibonding orbital of the [Emim]+ cation. The interaction modes are more favorable when the carbonyl O atoms of [LAC]? anion interact with the C2?H of the imidazolium ring and the C?H of the ethyl group through the formation of triple H-bonds. (2) Attenuated total reflectance infrared spectroscopy (ATR-IR) and DFT calculations were employed to investigate the molecular interactions between methanol and [Emim][LAC] ionic liquid. The infrared spectra were analyzed by two methods: excess spectroscopy and 2D correlation spectroscopy. In the ATR-FTIR spectra, v(C4,5?H), v(C2?H), v(alkyl), v(?OD), and v(?COO) all show blue shifts upon addition of methanol. 2D correlation analysis indicated that the v(imidazolium ring C?H) band varies before that of v(alkyl C?H) with increasing CD3OD content. The following sequential order of interaction strength was established by DFT calculations at B3LYP/6-31++G** level: Emim?methanol?LAC>Emim?LAC>LAC?methanol>Emim?methanol. (3) Cation-anion pair configurations, electronic properties, and intermolecular interactions, especially H-bond interactions, in biodegradable ionic liquids (bio-ILs) composed of naphthenate anion and choline cation ([Ch][NA]) (NA= CPC, CHC, Be and Sa) were investigated by DFT calculations at B3LYP/6-311++G** level. The results indicated that multiple H-bonds are the major intermolecular structural feature between the cation and anion. These H-bonds were analyzed by NBO, AIM and reduced density gradient (RDG) function. The influence of anionic structure on the interaction energy was studied. Based on the canonical orbital analysis, it was found that the σ-type orbital overlap and the partial charges transfer between the anion and cation, finally, result in the decrease of the energy and rationalize the location of the anion. Additionally, linear relationships between second-order interaction energies and the increment of electron density, as well as the interaction energies and the sum of the electron density at bond critical points for all studied [Ch][NA] ion pairs were found. (4) ATR-IR, excess spectroscopy, 1H NMR and DFT calculations were used to study the H-bonding interactions in a [C4Py][SCN]-DMSO system. It was found that H-bonds are universally involved in the system, which may play an important role for the miscibility of DMSO with [C4Py][SCN] ionic liquid and for keeping the stability of this system. ATR-IR
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/15504
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
何宏艳. 离子液体中离子对结构及氢键相互作用研究[D]. 中国科学院研究生院,2013.
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