【作者】 王素纹；

【导师】 黎安勇；

【作者基本信息】 西南大学 ， 物理化学， 2007， 硕士

【摘要】 本工作运用量子化学从头算计算方法，以吡啶、呋喃、噻吩和吡咯等典型杂环芳香烃为质子受体，HCl、C₂H₂和HCX₃（X=F，Cl，Br，I）等典型分子为质子供体，比较系统地研究了它们之间形成分子间红移和蓝移氢键本质。本论文主要包括以下三部分：1．用量子化学从头算（ab initio）方法MP2，采用6-31G（d，p），6-311+G（d，p），6-311++G（d，p），6-311++G（2df，2p）、AUG-cc-pVDZ基组研究了以吡啶为质子受体，HCl和HCCl₃为质子供体的分子间氢键。研究表明，在MP2／6-31G（d，p）水平下，吡啶与HCl分子之间仅形成了Cl—H...N氢键，分子间的氢键作用使Cl—H键伸长0.0495 （?），振动频率减小了725.1cm^-1，表现为红移氢键。吡啶与HCCl₃间形成两种类型的氢键，在MP2／6-31G（d，p）水平下，C—H...N氢键使HCCl₃中的C—H键伸长0.0049 （?），振动频率减小了79.1cm^-1，表现为红移氢键；而C—H...π相互作用使CHCl₃中的C—H键缩短0.003 （?），振动频率增大了58 cm^-1，表现为蓝移氢键。所有这些氢键复合物中，不论是红移还是蓝移氢键，C—H或Cl—H的伸缩振动红外强度相对于单体来说都增大，且质子供体固有偶极矩导数都大于零。自然键轨道（NBO）分析表明，超共轭和重杂化理论以及Hobza等提出的观点都能很好的解释这些氢键的形成原因。包含电子相关的Hartree-Fock理论能很好的解释复合物形成分子间C—H...N氢键本质。2．运用量子化学从头算方法研究了复合物C₅H₅N...HCX₃（X=F，Cl，Br，I）分子间C—H...N和C—H...π氢键。研究表明，在MP2／SDD水平下，分子间C—H...N氢键的形成均使HCX₃分子中C—H键伸长，伸缩振动频率减小，形成红移氢键；分子间C—H...π氢键的形成均使HCX₃分子中C—H键收缩，伸缩振动频率增大，形成蓝移氢键。振动光谱分析表明，不能根据质子供体分子HCX₃的固有偶极矩对C—H键长的导数来判断红移氢键和蓝移氢键。NBO分析表明，超共轭效应占优势，因此形成C—H...N红移氢键；重杂化效应占优势，因此形成C—H...π蓝移氢键。3．用量子化学从头算（ab initio）方法MP2，分别在B3LYP／6-311++G（d，p），MP2／6-31G（d，p），MP2／6-31+G（d，p），MP2／6-311++G（d，p）理论水平下对以呋喃、噻吩、吡咯和吡啶为质子受体，氟仿和乙炔为质子供体的C—H...π型氢键复合物进行了研究。计算表明：当以氟仿为质子供体时，所形成的C—H...π型氢键均为蓝移氢键，表现为C—H键收缩，而以乙炔为质子供体时，所形成的C—H...π型氢键均为红移氢键，表现为C—H键伸长。自然键轨道（NBO）分析表明，影响氢键红移和氢键蓝移主要有三个因素：π→σ^*（C—H）超共轭作用、C—H键轨道再杂化和质子供体电子密度重排。其中，超共轭作用属于键伸长效应，电子密度重排和轨道再杂化属于键收缩效应。在以乙炔为质子供体复合物中，由于键伸长效应处于优势地位导致形成红移氢键；在以氟仿为质子供体的复合物中，由于键收缩效应处于优势地位导致形成蓝移氢键。更多还原

【Abstract】 In present paper, ab initio quantum mechanics method is employed to investigate the origin of red-shifting and blue-shifting hydrogen bond between furan, thiophene, pyrole, pyridine and HCl, C₂H₂, HCX₃（X=F, Cl, Br, I）. The main contents are the following:1. The hydrogen bonds of HCl and HCCl₃ as the proton donors with pyridine as the acceptor were studied at the MP2 level of theory using the five basis sets 6-31G（d,p）, 6-311+G（d,p）, 6-311++G（d,p）, 6-311++G（2df,2p） and AUG-cc-pVDZ. Pyridine and HCl can only form a Cl—H...N H-bond, which causes a large frequency red shift of 725 cm^-1 for the Cl—H vibration and an elongation 0.0495 A of this bond using the basis set 6-31G（d,p）. Two H-bonds are formed between pyridine and HCCl₃: the C—H...N hydrogen bond with an elongation 0.0049 A of the C—H bond and a red shift of 80 cm^-1 for the C—H stretch vibration of HCCl₃, and the C—H...πinteraction with a contraction 0.003 A of the C—H bond and a blue shift of 58 cm^-1 for the C—H stretch vibration of HCCl₃ using the basis set 6-31G（d,p）. In these H-bonds, regardless of which are red-shifted or blue-shifted, the IR intensities of the C—H and Cl—H stretch vibrations increase, and the permanent dipole moment derivatives of the proton donors are positive. The natural bond orbital analysis was carried out, and the concepts of hyperconjugation and rehybridization and the theory of Hobza were applied to account for the origin of these hydrogen bonds. A post Hartree-Fock wavefunction containing electron correlation in the analysis of the natural bond orbital is required for interpreting the C—H...N H-bond in pyridine—HCCl₃.2. The C—H...N and C—H...πinteraction between pyridine and HCX₃（X=F, Cl,Br, I） was investigated by means of quantum chemical method of high level ab initio calculations. For the C—H...N interaction classical H-bonds are formed with an elongation of C—H and a red shift. However, for the C—H...πinteraction blue shifting H-bonds are identified with a contraction of C—H and a blue shift. The result of vibrational spectral analysis indicates that it is impossible to confirm blue shifting or red shifting H-bonds by the derivative of permanent dipole moment with respect to C—H stretch of the proton donor only. The NBO analysis show that the competitions of hyperconjugation and rehybridization result in two kinds of H-bonds.3. Ab initio quantum mechanics method is employed to investigate intermolecular interactions between furan, thiophene, pyrole and pyridine as proton acceptor and acetylene and trifluoromethane at B3LYP/6-311++G（d, p）, MP2/6-31G（d, p）, MP2/6-31+G（d, p）, MP2/6-311++G（d, p） levels. For compounds containing acetylene C—H...πred shifting H-bond is formed with C—H bond elongation and a concomitant red shift. However, for compounds containing trifluoromethane, C—H...πblue shifting H-bond is formed with C—H bond contraction and concomitant blue shift. The NBO analysis shows that the C—H bond length in C—H...πis controlled by a balance of three main factors. C—H bond lengthening due toπ→σ*（C—H） hyperconjugative interaction is balanced by C—H bond shortening due to increase of s-character and polarization of the C—H bond and redistribution of electron density in proton donor. In compounds containing acetylene, hyperconjugative interaction dominates which results in red shifting H-bonds. In compounds containing trifluoromethane, the condition is reverse which results in blue shifting H-bonds.更多还原