氢键相互作用等体系的结构,相互作用及其性质的理论研究/

2019-04-20 00:05:33

HF interaction HCl NH3 BH3



氢键相互作用等体系的结构,相互作用及其性质的理论研究

专 业:物理化学
指导教师:李志儒 教授
摘 要
无论在气体,液体还是在固体中,氢键都是一种非常重要的相互作用,并且在化学,物理学以及生物学中都扮演着十分重要的角色。本论文对几个具有代表性的氢键相互作用等体系的结构,相互作用和性质进行了理论研究,得到了新的结构和新的分子间相互作用形式。丰富了分子间氢键等弱相互作用的知识,揭示了某些新的分子间相互作用的本质。本论文主要包括以下五个方面:
(1)从头计算研究分子间相互作用体系HCN-HF和HNC-HF的相互作用超极化率:在有限场近似条件下计算分子间相互作用对HCN-HF和HNC-HF的偶极矩μ,平均极化率α,各向异性极化率Δα,第一超极化率β以及第二超极化率γ的影响。使用基函数x-aug-cc-pVXZ (x = s, d, t; X = D, T, Q)研究了它们的基组效应。在CCSD(T)/ d-aug-cc-pVTZ水平上给出了HCN-HF和HNC-HF的电学性质(μ, α, β和γ)。对于饱和分子二聚体(HF)2,β值相当于两个HF单体的β值和的1/4左右;对于含有π键的二聚体HCN-HF,β值大约是单体HCN和单体HF的β值和的3/5。含有键的氢键二聚体和有机分子类似,键的存在明显的提高了体系的第一超极化率。讨论了电学性质的电子相关效应。HCN-HF的每一个电学性质的值都小于HNC-HF的相应的的电学性质值。HCN-HF的μ= 2.2918 a.u., α = 23.186 a.u., Δα =14.393 a.u., β = -6.03 a.u. 和 γ = 2553.4 a.u.;HNC-HF的μ= 2.3338 a.u., α = 24.383 a.u., Δα = 14.875 a.u., β = 7.60 a.u. 和 γ = 3049.3 a.u.。来自于相互作用部分的电学性质是:μint = 0.3908 a.u.(17.1 %), αint = 0.181 a.u.(0.8 %), Δαint = 4.300 a.u.(29.9 %), βint = 6.02.(-99.8 % ) a.u. 和 γint = -492.0 a.u.(-19.3 %)(HCN-HF);μint = 0.4080 a.u.(17.5 %), αint = -0.084 a.u.(0.3 %), Δαint = 5.041 a.u.(33.9 %), βint = -7.20 a.u. (-94.7 % ) and γint = -931.7 a.u.(-30.6 %) (HNC-HF),这表明相互作用对电学性质的影响是非常重要的。电子相关效应分别是βcorr = 6.59 a.u., γcorr = 549.2 a.u.(HCN-HF)和βcorr = -9.49 a.u., γcorr = 1056.5 a.u. (HNC-HF),这说明这些分子间体系电学性质研究中电子相关效应是很大的。
(2)密度泛函研究NH3–HCl–(H2O)n (n= 0–4)体系的结构和相互作用超极化率:使用B3LYP/ d-aug-cc-pVDZ 方法计算得到了NH3-HCl-(H2O) n (n = 0 ~ 4)的几何结构。我们发现n = 1的结构发生质子转移,这与文献[Chem. Phys. Lett. 1998, 287, 549; J. Phys. Chem. A 1998, 102, 5117; Chem. Phys. Lett. 1999, 313, 366]上报道的小基函数的计算结果不同,从而,使人们认识到NH3–HCl–(H2O)n (n= 0–4)发生质子转移的最小结构是n = 1,而不是文献上的n = 2。使用基函数aug-cc-pVDZ, aug-cc-pVDZ+BF, aug-cc-pVTZ, d-aug-cc-pVDZ和t-aug-cc-pVDZ对优化好的几何结构计算了静态偶极矩μ,极化率α,第一超极化率β,并且研究了基函数效应对物理性质(μ, α 和 β)的影响。NH3–HCl的电学性质的溶剂化效应为:随着水分子数的增加,体系的μ和β减小,α值增加。NH3-HCl的性质(μ, α 和 β)随着质子转移程度的增加而增大。质子转移程度与水分子的溶剂化效应有关。提出了影响电学性质的新的因素——质子转移。
(3)单分子催化NH3-HCl的质子转移:研究可能发生质子转移的最小单元,仅在单分子催化下的NH3-HCl的质子转移研究使用MP2方法和较大基函数6-311++G(2d,2p)。优化得到18个可能发生从HCl到NH3的质子转移的最小单元(NH3-HCl-A三聚体结构),最终发现,在15个环形结构(A = H2SO4, H2SO3, HCOOH (a), HF, H2O2, HNO3, HNO2 (a), CH3OH, HCl, HNC, H2O, HNO2 (b), NH3, HCOOH (b) 和 HCHO)中有质子转移发生,而另外三个三聚体结构A = HCN, H2S 和 PH3不发生质子转移。计算分析结果显示,在环形氢键结构中,当催化剂分子A(酸性,中性和碱性均可)不仅作为质子的给体强烈地给质子到Cl原子上,同时作为受体强烈地接受来自于NH3分子的质子时,从HCl到NH3的质子转移发生。提议用质子环流模型解释质子转移的机理。我们发现,当两个氢键长的和(R = R1 + R2)小于5.0 Å时,分子A具有催化质子转移的能力。另外我们还发现,NH3-HCl 和 A之间的相互作用能Eint和质子转移程度(RH1-Cl)密切相关,相互作用能Eint随着质子转移程度(RH1-Cl)的增大而增加。
(4)BH3-HY (HY = HCCH, HCCF, HCN, HCl 和 HNC)二聚体的三氢原子相互作用:使用MP2/aug-cc-pVTZ方法优化得到5个新的存在三氢原子相互作用的最小结构:BH3-HCCH,BH3-FCCH,BH3-HCN,BH3-HCl和BH3-HNC。除BH3-HCl外,其余4个复合物都是C2v对称结构。使用基函数aug-cc-pVTZ在7个水平[HF, MP2, MP3, MP4(SDQ), MP4(SDTQ),CCSD和 CCSD(T)]上计算了三氢原子相互作用能Eint。在BH3-HCCH,BH3-FCCH,BH3-HCN,BH3-HCl和BH3-HNC中,相互作用能Eint最大的是-1.73 kcal/mol (BH3-HNC,RH1…H2最小,2.207 Å ),最小值是-0.72 kcal/mol (BH3-HCCH,RH1…H2最大,2.523 Å)。三氢原子之间的相互作用能是很小的,三氢原子相互作用是一种很弱的分子间氢键相互作用。
(5)在甲基自由基络合物H3C-BH3, H3C-AlH3 和 H3C-BF3中的单电子给予-接受键的从头算研究:预言了甲基自由基H3C 和分子YZ3 (YZ3 = 硼烷 BH3,铝烷 AlH3 和 三氟化硼 BF3)形成的一种新型的给予-接受络合物。在这种甲基络合物中发现了分子间单电子给予-接受键。这种单电子给予-接受络合物的结构和频率是在MP2/aug-cc-pVDZ水平上得到的。H3C-BH3, H3C-AlH3 和 H3C-BF3的单电子给予-接受键长分别是2.181 Å, 2.594 Å 和 2.823 Å。使用CCSD(T)/aug-cc-pVDZ方法和Counterpoise校正计算得到了分子间单电子给予-接受络合物的键能。H3C-BH3, H3C-AlH3 和 H3C-BF3分子间单电子给予-接受键能分别为-6.3 kcal/mol, -6.8 kcal/mol 和 -1.8 kcal/mol。很明显,这种由不成对电子作为电子给体的给予-接受络合物的单电子给予-接受键比传统的给予-接受络合物的给予-接受键弱,粗略地接近于较弱的传统给予-接受键(相互作用能特征范围3-9 kcal/mol)。
综上所述,本文的主要贡献在于:1. 对于氢键体系,找到了15个可发生质子转移的三聚体结构,这表明发生质子转移的最小结构是三聚体结构,氢键二聚体间发生质子转移至少需要一个分子催化。对NH3–HCl–A体系,建议了发生质子转移的质子环流机理;给出了分子具有催化质子转移能力的判据。丰富了关于质子转移的知识。2. 对于新的分子间相互作用力的研究,得到了5个具有三氢键的二聚体结构;3个具有单电子给予-接受键的二聚体结构,并研究了它们的性质。建议了两种新的分子间作用方式,丰富了分子间相互作用的新知识。3. 对于分子间相互作用体系的电学性质的研究,对于NH3–HCl–(H2O)n (n= 0–4)体系,给出了分子间相互作用电学性质的新贡献,展示了NH3–HCl的电学性质的溶剂化效应,特别是研究了一个新的因素——质子转移作用对NH3–HCl的电学性质的影响。含有键的氢键二聚体和有机分子类似,键的存在明显的提高了体系的第一超极化率。发现了电子相关作用对氢键体系的电学性质的计算是重要的。丰富了关于分子间体系电学性质的新知识,对于非线性光学材料的设计提供了新思想。



Theoretical studies of structures, interactions and properties in some hydrogen bonds and other interaction systems

Major: Physical chemistry
Advisor: Zhi-Ru Li Professor
Abstract
Hydrogen bond is one of the most important interactions encountered in gas, liquid, and solid phases. It plays a crucial role in chemistry, physics and biology. The theoretical studies were performed on the structures, interactions and properties of some representative systems containing hydrogen bond and other interactions in this thesis. The results obtained on new structures and intermolecular interactions may be valuable for improving our understanding of the nature of intermolecular interaction, and enriching our knowledge of hydrogen bonds and other weak intermolecular interactions. There are five main aspects included in this thesis:
(1) Ab initio study of the interaction hyperpolarizabilities of HCN-HF and HNC-HF complexes: The effects of the intermolecular interaction on dipole moment (μ), the mean (α) and anisotropy (Δα) of the polarizability, the first and second hyperpolarizabilities (β and γ respectively) of HCN-HF and HNC-HF complexes have been calculated using finite-field approximate approach. The augmented correlation consistent basis sets x-aug-cc-pVXZ (x = s, d, t; X = D, T, Q) are employed to study the effects of the basis sets. With the d-aug-cc-pVTZ basis set, the electric properties are obtained at the coupled-cluster theory with single, double substitutions and perturbatively linked triple excitations CCSD(T) level. For the saturated molecules HF dimer, the β value is about 1/4 of the sum of two monomers. For the dimer HCN-HF containing π-bond, the β value is about 3/5 of the sum of two monomers. Similar to the organic systems, the existence of π-bond obviously enhances the first hyperpolarizability of the hydrogen-bonded dimer. The electron correlation effects for those electric properties are discussed. The value of each electric property calculated for HCN-HF is less than that for HNC-HF. The μ= 2.2918 a.u., α = 23.186 a.u., Δα =14.393 a.u., β = -6.03 a.u. and γ = 2553.4 a.u. for HCN-HF; μ= 2.3338 a.u., α = 24.383 a.u., Δα = 14.875 a.u., β = 7.60 a.u. and γ = 3049.3 a.u. for HNC-HF. The electric properties comes from the interaction parts are: μint = 0.3908 a.u.(17.1 %), αint = 0.181 a.u.(0.8 %), Δαint = 4.300 a.u.(29.9 %), βint = 6.02.(-99.8 % ) a.u. and γint = -492.0 a.u.(-19.3 %) for HCN-HF; μint = 0.4080 a.u.(17.5 %), αint = -0.084 a.u.(0.3 %), Δαint = 5.041 a.u.(33.9 %), βint = -7.20 a.u. (-94.7 % ) and γint = -931.7 a.u.(-30.6 %) for HNC-HF. The data above indicate significant effect of intermolecular interaction on the electric properties. The estimated electron correlation corrections are βcorr = 6.59 a.u., γcorr = 549.2 a.u. for HCN-HF and βcorr = -9.49 a.u., γcorr = 1056.5 a.u. for HNC-HF, which show large electron correlation effects in the electric properties of intermolecular interaction systems.
(2) DFT (Density functional theory) study on structures and interaction hyperpolaribilities of NH3-HCl-(H2O) n (n = 0 ~ 4) clusters: The optimized structures of NH3-HCl-(H2O)n (n = 0 ~ 4) clusters have been obtained by B3LYP/d-aug-cc-PVDZ method. It is found that, in the structure for n = 1 proton transfer occurs. It is different from the results by smaller basis sets from the references [Chem. Phys. Lett. 1998, 287, 549, J. Phys. Chem. A 1998, 102, 5117, Chem. Phys. Lett. 1999, 313, 366], in which it is concluded that the proton transfer occurs in the NH3-HCl-(H2O)n (n = 0 ~ 4) clusters only for n=2. Using the optimized structures, the static dipole moments (μ), polarizabilities (α) and the first hyperpolarizabilities (β) of the clusters were calculated and the basis set effects on the physical properties (μ, α and β) were also studied with aug-cc-pVDZ, aug-cc-pVDZ+BF, aug-cc-pVTZ, d-aug-cc-pVDZ, t-aug-cc-pVDZ basis sets. The solvent effects on the electric properties of the NH3–HCl cluster are as follows: the μ and β value reduce, and the α value increases with the number of water molecules. For the NH3-HCl, the properties (μ, α and β) all increase with the strength of proton transfer, which is related to the solvent effects of water molecules. Consequently, the proton transfer is brought forward as a new factor in influencing electric properties.
(3) Proton transfer of the NH3-HCl by only one molecule catalyze: The smallest units with proton transfer occurring were studied. The proton transfer in NH3-HCl by only one molecule catalyze was studied using MP2 method with the large 6-311++G(2d,2p) basis set. The 18 structures are obtained for the smallest units, NH3-HCl-A trimers, for which the proton transfer maybe occurred. The final results show that the proton transfers have occurred in the 15 cyclic shape structures for A = H2SO4, H2SO3, HCOOH (a), HF, H2O2, HNO3, HNO2 (a), CH3OH, HCl, HNC, H2O, HNO2 (b), NH3, HCOOH (b) and HCHO, and not occurred in another 3 trimer structures for A = HCN, H2S and PH3. These results show that the proton transfer occurs from HCl to NH3 when catalyst molecule A (acidic, neutral or basic) not only as a proton donor strongly donates the proton to the Cl atom but as an acceptor strongly accepts the proton from the NH3 molecule in the cyclic H-bond structure. In this work, a proton circumfluence model is proposed to explain the mechanism of the proton transfer. We find that, for the trimer, when the sum of two hydrogen bond lengths (R = R1 + R2) is shorter than 5.0 Å, the molecule A has the ability of catalyzing the proton transfer. In addition, we also find that the interaction energy Eint between NH3-HCl and A is nearly related to the extent (RH1-Cl) of proton transfer, that is, the interaction energy Eint increases with the proton transfer.
(4) Ab Initio study on three hydrogen atoms interaction in the dimers BH3-HY (HY = HCCH, HCCF, HCN, HCl and HNC): The new geometrical structures of BH3-HCCH, BH3-FCCH BH3-HCN, BH3-HCl and BH3-HNC dimers were optimized at the MP2/aug-cc-pVTZ level, and the five dimers are the smallest structures including three hydrogen atoms interaction. Each structure of these dimers has C2v symmetry, except BH3-HCl. With aug-cc-pVTZ basis set the interaction energies Eint between three hydrogen atoms were calculated at seven levels of theory [HF, MP2, MP3, MP4(SDQ), MP4(SDTQ), CCSD and CCSD(T) ]. In the BH3-HY (HY = HCCH, HCCF, HCN, HCl and HNC) the largest interaction energy Eint is -1.73 kcal/mol (BH3-HNC, the corresponding RH1•••H2 is the shortest, 2.207Å), the smallest interaction energy Eint is -0.72 kcal/mol (BH3-HCCH, the corresponding RH1•••H2 is the longest, 2.523Å). The interaction between three hydrogen atoms is rather weak; it is a very weak intermolecular hydrogen-bonded interaction.
(5) Single electron donor-acceptor bonds in the methyl radical complexes H3C-BH3, H3C-AlH3 and H3C-BF3: an ab initio study: A new kind of donor-acceptor complexes between methyl radical H3C and YZ3 (YZ3 = borane BH3, alane AlH3 and boron trifluoride BF3) molecules is predicted and intermolecular single electron donor-acceptor bonds in these methyl radical complexes are found. The optimized structures and harmonic vibrational frequencies (all real) of those methyl radical complexes are obtained by MP2/aug-cc-pVDZ approach. The single electron bond lengths of H3C-BH3, H3C-AlH3 and H3C-BF3 complexes are 2.181 Å, 2.594 Å and 2.823 Å, respectively. The intermolecular single electron donor-acceptor bond energies are calculated by the CCSD(T)/aug-cc-pVDZ method with Counterpoise procedure. The interaction energies of the H3C-BH3, H3C-AlH3 and H3C-BF3 complexes are -6.3 kcal/mol, -6.8 kcal/mol and -1.8 kcal/mol, respectively. Obviously, the intermolecular single electron donor-acceptor bond with an unpaired electron as the electron donor is weaker than strongly conventional donor-acceptor bond and roughly close to weakly conventional donor-acceptor bond (characteristic interaction energies of 3-9 kcal/mol).
As stated above, the main contributions of this thesis are: 1. Study on hydrogen-bonded systems. Fifteen trimers with proton transfer occurring were found, which indicated that the smallest structure with proton transfer occurring is trimer, and the proton transfer in hydrogen-bonded dimer needs at least a molecule catalyze. 2. Study on the new intermolecular interaction. Five new dimers including three hydrogen atoms interaction and three dimers possessing single electron donor-acceptor bond were obtained, and their properties were studied. This thesis put forward two new kinds of intermolecular interaction manner, and thereby enriched our knowledge in intermolecular interaction. 3. Study on the interaction electric properties of intermolecular interaction systems. For the NH3–HCl–(H2O)n (n= 0–4)clusters, the new contribution of intermolecular interaction on electric properties were obtained, the solvent effects on the electric properties of the NH3–HCl complex were exhibited, and a new factor as proton transfer effect on the electric properties of the NH3–HCl complex was specially studied. Similar to the organic systems, the existence of π-bond obviously enhances the first hyperpolarizability of the hydrogen-bonded dimer. The electron correlation contribution was found to be important in the calculations of the electric properties of the hydrogen-bonded systems. This work enrichs our knowledge on the electric properties of the intermolecular interaction systems, and provides new idea on the designing of the NLO materials.