水團(tuán)簇中氫鍵的電子結(jié)構(gòu)理論研究
發(fā)布時(shí)間：2018-09-18 21:07
【摘要】：水是自然界中廣泛分布的物質(zhì),其參與眾多的物理、化學(xué)過(guò)程,并為生化反應(yīng)等提供基本的環(huán)境。從原子水平認(rèn)識(shí)水體系的存在形式、性質(zhì)及行為對(duì)于從本質(zhì)上理解相關(guān)領(lǐng)域的基本問(wèn)題意義重大。水的微觀形態(tài)可被一般性的看作是由水分子通過(guò)分子間氫鍵相互作用彼此聚集而形成的氫鍵網(wǎng)絡(luò)體系,而不同尺寸的水團(tuán)簇即是氫鍵網(wǎng)絡(luò)的基本單元。水團(tuán)簇的結(jié)構(gòu)自由度及氫鍵網(wǎng)絡(luò)的復(fù)雜行為使得微觀水體系的性質(zhì)不止局限于水分子自身的屬性,而同時(shí)可以體現(xiàn)出團(tuán)簇結(jié)構(gòu)隨尺寸和對(duì)稱(chēng)性的演化特性,以及通過(guò)氫鍵網(wǎng)絡(luò)實(shí)現(xiàn)的構(gòu)象轉(zhuǎn)變、質(zhì)子轉(zhuǎn)移等過(guò)程。水分子間的氫鍵決定了氫鍵體系的結(jié)構(gòu)屬性并與水分子自身的電子結(jié)構(gòu)密切相關(guān),近年的實(shí)驗(yàn)觀測(cè)更表明分子間氫鍵具有與共價(jià)鍵類(lèi)似的電子結(jié)構(gòu),這暗示從電子結(jié)構(gòu)角度出發(fā)針對(duì)水團(tuán)簇體系進(jìn)行系統(tǒng)性的理論研究可能為上述水氫鍵體系的性質(zhì)與行為提供基礎(chǔ)層次的理解。同時(shí),水氫鍵體系的質(zhì)子轉(zhuǎn)移問(wèn)題在各學(xué)科及相互間興趣交叉的研究領(lǐng)域,也占有重要位置。本文使用量子力學(xué)第一性原理方法,從電子結(jié)構(gòu)角度出發(fā)報(bào)道了對(duì)水團(tuán)簇進(jìn)行的系統(tǒng)性研究。我們分別闡述了水分子間氫鍵類(lèi)共價(jià)特性的分子軌道表現(xiàn)、小尺寸環(huán)狀水團(tuán)簇的離域電子結(jié)構(gòu)特性、環(huán)狀水團(tuán)簇中離域分子軌道與其幾何結(jié)構(gòu)平面化間的關(guān)聯(lián)、水團(tuán)簇中心四配位水分子的四氫鍵電子結(jié)構(gòu)在中等尺寸水團(tuán)簇中隨尺寸變化的趨勢(shì),以及棱柱水團(tuán)簇協(xié)同質(zhì)子轉(zhuǎn)移過(guò)程中的手性轉(zhuǎn)變與識(shí)別這五個(gè)方面的內(nèi)容。首先,我們選取水二聚物(H2O)2這一基本模型應(yīng)用高精度第一性原理計(jì)算方法,從分子軌道角度出發(fā)研究了水分子間氫鍵的類(lèi)共價(jià)特性。分子軌道分析發(fā)現(xiàn)了兩條貫穿氫鍵區(qū)域的分子軌道,其貢獻(xiàn)主要來(lái)自于氫鍵供體一側(cè)的氧原子2p軌道。進(jìn)一步的能量分解分析表明兩個(gè)水分子之間存在不可忽略的誘導(dǎo)作用,其在兩水分子相互作用能總吸引項(xiàng)中的比例高于10%,這進(jìn)一步支持了氫鍵的類(lèi)共價(jià)特性。這一研究對(duì)理解冰、液態(tài)水、功能化材料以及生物系統(tǒng)中的氫鍵相互作用提供了新的分子軌道視角,并為本文基于電子結(jié)構(gòu)來(lái)研究水團(tuán)簇及氫鍵網(wǎng)絡(luò)提供了基礎(chǔ)指引。第二,準(zhǔn)平面小水環(huán)(H2O)n(n=3-6)是構(gòu)成更為復(fù)雜三維水團(tuán)簇和液態(tài)水模型的的基本結(jié)構(gòu)和功能單元,進(jìn)一步理解分子間氫鍵相互作用在其中的特點(diǎn)對(duì)于認(rèn)識(shí)復(fù)雜水團(tuán)簇及氫鍵網(wǎng)絡(luò)的性質(zhì)具有基礎(chǔ)性意義。我們應(yīng)用密度泛函理論結(jié)合鍵特性分析方法,研究了這類(lèi)小尺寸環(huán)狀水團(tuán)簇,結(jié)果表明n=3和4的兩種小水環(huán)均出現(xiàn)離域于整個(gè)環(huán)并覆蓋環(huán)中心區(qū)域的離域分子軌道,其貢獻(xiàn)來(lái)自于各個(gè)水分子的氫氧原子,而在n=5和6的水環(huán)中相應(yīng)離域軌道在環(huán)中心區(qū)域的軌道分布減弱。環(huán)狀水團(tuán)簇中的離域電子結(jié)構(gòu)擴(kuò)展了對(duì)水團(tuán)簇中分子間氫鍵的認(rèn)識(shí),其展示的分子間氫鍵電子結(jié)構(gòu)與體系幾何結(jié)構(gòu)間的相互影響及其隨尺寸變化的特性為后續(xù)工作提供了指引。第三,承接上一研究,我們繼續(xù)探索了n=3-6的小尺寸環(huán)狀水團(tuán)簇(H2O)n中離域電子結(jié)構(gòu)與其幾何結(jié)構(gòu)平面化之間的聯(lián)系。結(jié)果表明離域于水環(huán)氫鍵骨架中的三種離域分子軌道與體系能否形成穩(wěn)定的平面結(jié)構(gòu)密切相關(guān),它們分別為軌道(Ⅰ),主要由氧原子的孤對(duì)電子軌道O(2p)組成的分子軌道;軌道(Ⅱ),主要由O(2p)-H(1s)形成的沿氫鍵方向的成鍵軌道;以及軌道(Ⅲ),主要由O(2s)-H(1s)形成的成鍵軌道。當(dāng)水環(huán)幾何結(jié)構(gòu)為平面結(jié)構(gòu)時(shí),利于水分子單體軌道之間針對(duì)這三種離域軌道實(shí)現(xiàn)彼此重疊最大化。進(jìn)一步的能量分解分析顯示,在所有的水環(huán)中軌道項(xiàng)的貢獻(xiàn)在相互作用能總吸引項(xiàng)中的比例多于30%,這再一次凸顯了氫鍵系統(tǒng)的類(lèi)共價(jià)特性。第四,基于對(duì)小尺寸水團(tuán)簇的基本認(rèn)識(shí)及研究中體現(xiàn)出的氫鍵電子結(jié)構(gòu)隨尺寸變化的規(guī)律,同時(shí)面向水團(tuán)簇作為液態(tài)水靜態(tài)模型時(shí)需要考慮的尺寸效應(yīng)等問(wèn)題,我們研究了接近液態(tài)水中水分子性質(zhì)的4-配位水分子在團(tuán)簇(H2O)n(n=17,19,20,21,23,25)中形成的四氫鍵電子結(jié)構(gòu),隨團(tuán)簇尺寸變化的趨勢(shì)。結(jié)果表明,中心4-配位水分子與其最近鄰水分子之間的相互作用隨著團(tuán)簇水分子數(shù)增多而減弱,中心4-配位水分子與次近鄰水分子之間的相互作用能隨著水分子數(shù)目的增多而增強(qiáng)。這表明中心4-配位水分子同最近鄰和次近鄰水分子之間的相互作用存在競(jìng)爭(zhēng)關(guān)系。而光譜和電子密度分析表明中心水分子參與的最低頻分子間振動(dòng)與其和水籠之間的電子得失沒(méi)有明顯的尺寸依賴(lài)變化。此外,中心4-配位水分子四氫鍵電子結(jié)構(gòu)的類(lèi)共價(jià)特性被拓?fù)浞治鲞M(jìn)一步闡明。我們希望這一理論研究能夠?yàn)橹械瘸叽缢畧F(tuán)簇的研究及理解液態(tài)水中的氫鍵相互作用提供基本的理論參考。最后,基于以上基礎(chǔ)認(rèn)識(shí),我們進(jìn)一步探究了氫鍵網(wǎng)絡(luò)中的動(dòng)態(tài)過(guò)程。沿氫鍵的質(zhì)子轉(zhuǎn)移和手性轉(zhuǎn)換過(guò)程是物理學(xué)及其與生命科學(xué)、材料科學(xué)等學(xué)科交叉領(lǐng)域的基本問(wèn)題。其在手性識(shí)別、酶催化和藥物制備等化工生產(chǎn)方面也具有重要意義。在本部分工作中,我們?cè)诶碚撋涎芯苛丝煽醋麟p層水環(huán)的小棱柱水團(tuán)簇中單層內(nèi)質(zhì)子協(xié)同轉(zhuǎn)移過(guò)程的手性轉(zhuǎn)換和識(shí)別問(wèn)題。結(jié)果表明,雖然質(zhì)子轉(zhuǎn)移初末態(tài)的能量變化很小,僅約為0.3 kcal/mol,但是振動(dòng)圓二色譜(VCD)卻提供了一個(gè)明顯的手性特征峰區(qū)域(3000~3500 cm-1),可以用來(lái)區(qū)別具有手性特征的初末態(tài)水團(tuán)簇結(jié)構(gòu)。這個(gè)區(qū)域的振動(dòng)模式對(duì)應(yīng)于層內(nèi)氫鍵的拉伸,而且該區(qū)域的振動(dòng)模式在紅外和拉曼光譜中也具有易于觀測(cè)的較強(qiáng)信號(hào)。另外,電子圓二色性譜(ECD)也展示了類(lèi)似的識(shí)別特性。進(jìn)一步的分子軌道分析顯示,涉及兩層間相互作用的軌道主要源于氧原子的2p軌道,并且層內(nèi)協(xié)同質(zhì)子轉(zhuǎn)移過(guò)程可使相應(yīng)層間軌道的能級(jí)抬升0.1 e V。此外,我們的研究還發(fā)現(xiàn),氘原子的同位素取代能夠在VCD譜上引起明顯的特征峰移動(dòng),進(jìn)而為可能的水團(tuán)簇手性識(shí)別的實(shí)驗(yàn)探測(cè)提供了原理性設(shè)計(jì)思路。希望我們的發(fā)現(xiàn)能夠在原子水平上為水團(tuán)簇手性概念的夯實(shí),乃至手性識(shí)別觀測(cè)在相應(yīng)實(shí)驗(yàn)過(guò)程中的實(shí)現(xiàn)起到促進(jìn)作用。
[Abstract]:Water is a widely distributed substance in nature. It participates in many physical and chemical processes and provides a basic environment for biochemical reactions. It is of great significance to understand the existence form, nature and behavior of water system at the atomic level for understanding the basic problems in related fields in essence. The micro-morphology of water can be generally regarded as water. Hydrogen bond networks formed by the aggregation of molecules through hydrogen bond interactions are the basic units of hydrogen bond networks. The structural degrees of freedom of water clusters and the complex behavior of hydrogen bond networks make the properties of micro-water systems not only confined to the properties of water molecules, but also embody the properties of water clusters. The evolution of cluster structure with size and symmetry, as well as the conformational transition and proton transfer through hydrogen bonding networks. The hydrogen bonding between water molecules determines the structural properties of the hydrogen bonding system and is closely related to the electronic structure of the water molecule itself. This implies that a systematic theoretical study of water clusters from the viewpoint of electronic structure may provide a fundamental understanding of the properties and behaviors of the above-mentioned water-hydrogen bonding systems. The first-principles method of quantum mechanics reports the systematic study of water clusters from the point of view of electronic structure. The molecular orbital representations of the covalent properties of hydrogen bonds between water molecules, the characteristics of the off-domain electronic structure of small-sized ring water clusters, and the planarization of the off-domain molecular orbitals and their geometric structures in ring water clusters are described. The relationship between the four-hydrogen bond electronic structures of the four-coordinated water molecules in the center of a water cluster and the size-dependent trend of the four-hydrogen bond electronic structures in a medium-sized water cluster, as well as the chiral transition and recognition in the process of the prismatic water cluster cooperating with the proton transfer, are discussed. Firstly, we select the water dimer (H2O) 2 as the basic model to apply the high-precision first property. The molecular orbital analysis reveals that two molecular orbitals penetrate the hydrogen bond region and their contributions mainly come from the 2p orbital of the oxygen atom on the donor side of the hydrogen bond. This study provides a new molecular orbital perspective for understanding the interaction of hydrogen bonds in ice, liquid water, functionalized materials and biological systems, and for studying water based on electronic structure. Clusters and hydrogen-bonded networks provide basic guidance. Second, quasi-planar small water rings (H2O) n (n=3-6) are the basic structure and functional units of more complex three-dimensional water clusters and liquid water models. Further understanding the characteristics of hydrogen-bonded interactions among molecules is fundamental for understanding the properties of complex water clusters and hydrogen-bonded networks. The results show that both n=3 and 4 small water rings have delocalized molecular orbitals which are located in the whole ring and cover the central region of the ring. The contribution comes from the hydrogen and oxygen atoms of each water molecule, while the corresponding delocalization occurs in the water rings of n=5 and 6. The orbital distribution in the central region of the ring decreases. The detached electronic structure of the water cluster expands the understanding of the hydrogen bonds between molecules in the water cluster. The interaction between the electronic structure of the hydrogen bond and the geometric structure of the system and its size-dependent characteristics provide guidance for the follow-up work. We continue to explore the relationship between the delocalized electronic structure and the planarization of the geometric structure of the small annular water cluster (H2O) n with n=3-6. The results show that the three delocalized molecular orbitals in the hydrogen-bonded skeleton of the water ring are closely related to the formation of stable planar structures of the system, which are orbitals (I) and are mainly solitary oxygen atoms. Molecular orbitals consisting of O (2p), O (2p) - H (1s) and O (2s) - H (1s) are the main bonding orbitals, and the bonding orbitals (III) consisting mainly of O (2s) - H (1s) are the main ones. When the geometric structure of the water ring is planar, it is advantageous to achieve the maximum overlap among the three kinds of detached orbits. Further energy decomposition analysis shows that the contribution of the orbital term to the total attraction of the interaction energy is more than 30% in all water rings, which again highlights the covalent-like properties of hydrogen bonding systems. Fourthly, based on the basic understanding of small water clusters and the size-dependent variation of the electronic structure of hydrogen bonding in the study. At the same time, for the size effect of water cluster as a static model of liquid water, we studied the electronic structure of four-hydrogen bond formed in clusters (H2O) n (n = 17, 19, 20, 21, 23, 25) by 4-coordinated water molecules close to the properties of water molecules in liquid water. The interaction between the nearest neighbor water molecules decreases with the increase of the number of cluster water molecules, and the interaction between the center 4-coordination water molecules and the next nearest neighbor water molecules increases with the increase of the number of water molecules. Spectroscopic and electron density analyses show that there is no significant size-dependent change in the lowest frequency intermolecular vibrations of the central water molecule and the electron gain and loss between the central water molecule and the water cage. In addition, the covalent-like properties of the electronic structure of the tetrahydrogen bond of the central 4-coordination water molecule are further elucidated by topological analysis. Finally, based on the above basic knowledge, we further explore the dynamic process of hydrogen bond network. Proton transfer and chiral transition along hydrogen bond are the basic fields of physics, life science and material science. In this part, we theoretically study the chiral transformation and recognition of proton synergistic transfer in a small prismatic water cluster, which can be regarded as a double-layer water ring. The results show that although the initial and final states of proton transfer are energetic, the chiral transformation and recognition of proton synergistic transfer in a single-layer water cluster are also important. However, vibrational circular dichroism (VCD) provides a distinct chiral peak region (3000-3500 cm-1) that can be used to distinguish the initial and final water clusters with chiral characteristics. In addition, electron circular dichroism spectroscopy (ECD) shows similar recognition properties. Further molecular orbital analysis shows that the orbits involved in the interaction between the two layers are mainly derived from the 2p orbits of the oxygen atoms, and that the energy levels of the corresponding interlayer orbits can be raised by 0. 1 e V. In addition, we also found that the isotope substitution of deuterium atoms can cause significant characteristic peak shifts in VCD spectra, which provides a theoretical design for the possible experimental detection of chiral recognition of water clusters. Measurement plays an important role in the realization of corresponding experiments.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：O562
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本文編號(hào)：2249103
[Abstract]:Water is a widely distributed substance in nature. It participates in many physical and chemical processes and provides a basic environment for biochemical reactions. It is of great significance to understand the existence form, nature and behavior of water system at the atomic level for understanding the basic problems in related fields in essence. The micro-morphology of water can be generally regarded as water. Hydrogen bond networks formed by the aggregation of molecules through hydrogen bond interactions are the basic units of hydrogen bond networks. The structural degrees of freedom of water clusters and the complex behavior of hydrogen bond networks make the properties of micro-water systems not only confined to the properties of water molecules, but also embody the properties of water clusters. The evolution of cluster structure with size and symmetry, as well as the conformational transition and proton transfer through hydrogen bonding networks. The hydrogen bonding between water molecules determines the structural properties of the hydrogen bonding system and is closely related to the electronic structure of the water molecule itself. This implies that a systematic theoretical study of water clusters from the viewpoint of electronic structure may provide a fundamental understanding of the properties and behaviors of the above-mentioned water-hydrogen bonding systems. The first-principles method of quantum mechanics reports the systematic study of water clusters from the point of view of electronic structure. The molecular orbital representations of the covalent properties of hydrogen bonds between water molecules, the characteristics of the off-domain electronic structure of small-sized ring water clusters, and the planarization of the off-domain molecular orbitals and their geometric structures in ring water clusters are described. The relationship between the four-hydrogen bond electronic structures of the four-coordinated water molecules in the center of a water cluster and the size-dependent trend of the four-hydrogen bond electronic structures in a medium-sized water cluster, as well as the chiral transition and recognition in the process of the prismatic water cluster cooperating with the proton transfer, are discussed. Firstly, we select the water dimer (H2O) 2 as the basic model to apply the high-precision first property. The molecular orbital analysis reveals that two molecular orbitals penetrate the hydrogen bond region and their contributions mainly come from the 2p orbital of the oxygen atom on the donor side of the hydrogen bond. This study provides a new molecular orbital perspective for understanding the interaction of hydrogen bonds in ice, liquid water, functionalized materials and biological systems, and for studying water based on electronic structure. Clusters and hydrogen-bonded networks provide basic guidance. Second, quasi-planar small water rings (H2O) n (n=3-6) are the basic structure and functional units of more complex three-dimensional water clusters and liquid water models. Further understanding the characteristics of hydrogen-bonded interactions among molecules is fundamental for understanding the properties of complex water clusters and hydrogen-bonded networks. The results show that both n=3 and 4 small water rings have delocalized molecular orbitals which are located in the whole ring and cover the central region of the ring. The contribution comes from the hydrogen and oxygen atoms of each water molecule, while the corresponding delocalization occurs in the water rings of n=5 and 6. The orbital distribution in the central region of the ring decreases. The detached electronic structure of the water cluster expands the understanding of the hydrogen bonds between molecules in the water cluster. The interaction between the electronic structure of the hydrogen bond and the geometric structure of the system and its size-dependent characteristics provide guidance for the follow-up work. We continue to explore the relationship between the delocalized electronic structure and the planarization of the geometric structure of the small annular water cluster (H2O) n with n=3-6. The results show that the three delocalized molecular orbitals in the hydrogen-bonded skeleton of the water ring are closely related to the formation of stable planar structures of the system, which are orbitals (I) and are mainly solitary oxygen atoms. Molecular orbitals consisting of O (2p), O (2p) - H (1s) and O (2s) - H (1s) are the main bonding orbitals, and the bonding orbitals (III) consisting mainly of O (2s) - H (1s) are the main ones. When the geometric structure of the water ring is planar, it is advantageous to achieve the maximum overlap among the three kinds of detached orbits. Further energy decomposition analysis shows that the contribution of the orbital term to the total attraction of the interaction energy is more than 30% in all water rings, which again highlights the covalent-like properties of hydrogen bonding systems. Fourthly, based on the basic understanding of small water clusters and the size-dependent variation of the electronic structure of hydrogen bonding in the study. At the same time, for the size effect of water cluster as a static model of liquid water, we studied the electronic structure of four-hydrogen bond formed in clusters (H2O) n (n = 17, 19, 20, 21, 23, 25) by 4-coordinated water molecules close to the properties of water molecules in liquid water. The interaction between the nearest neighbor water molecules decreases with the increase of the number of cluster water molecules, and the interaction between the center 4-coordination water molecules and the next nearest neighbor water molecules increases with the increase of the number of water molecules. Spectroscopic and electron density analyses show that there is no significant size-dependent change in the lowest frequency intermolecular vibrations of the central water molecule and the electron gain and loss between the central water molecule and the water cage. In addition, the covalent-like properties of the electronic structure of the tetrahydrogen bond of the central 4-coordination water molecule are further elucidated by topological analysis. Finally, based on the above basic knowledge, we further explore the dynamic process of hydrogen bond network. Proton transfer and chiral transition along hydrogen bond are the basic fields of physics, life science and material science. In this part, we theoretically study the chiral transformation and recognition of proton synergistic transfer in a small prismatic water cluster, which can be regarded as a double-layer water ring. The results show that although the initial and final states of proton transfer are energetic, the chiral transformation and recognition of proton synergistic transfer in a single-layer water cluster are also important. However, vibrational circular dichroism (VCD) provides a distinct chiral peak region (3000-3500 cm-1) that can be used to distinguish the initial and final water clusters with chiral characteristics. In addition, electron circular dichroism spectroscopy (ECD) shows similar recognition properties. Further molecular orbital analysis shows that the orbits involved in the interaction between the two layers are mainly derived from the 2p orbits of the oxygen atoms, and that the energy levels of the corresponding interlayer orbits can be raised by 0. 1 e V. In addition, we also found that the isotope substitution of deuterium atoms can cause significant characteristic peak shifts in VCD spectra, which provides a theoretical design for the possible experimental detection of chiral recognition of water clusters. Measurement plays an important role in the realization of corresponding experiments.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：O562
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本文編號(hào)：2249103
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