三氮杂苯-水氢键复合物的结构与性质

使用密度泛函理论B3LYP方法对三氮杂苯-水氢键复合物的基态结构与相互作用进行理论研究. 结果表明1,2,3-三氮杂苯-水, 1,2,4-三氮杂苯-水和1,3,5-三氮杂苯-水复合物基态分别具有Cs, Cs和C₁对称性和强的氢键相互作用, 经基组重叠误差和零点振动能校正后的相互作用能分别为–17.83, –17.38和–13.55 kJ/mol. 三氮杂苯-水复合物中, N∙∙∙H—O氢键的形成使水的H—O对称伸缩振动频率明显红移. 同时使用含时密度泛函理论研究了三氮杂苯单体及其与水形成的氢键复合物的第一¹(n, π^*)激发态的垂直激发能.     

二氮杂苯－水氢键复合物结构性质的理论研究

使用密度泛函理论B3LYP方法和从头算MP2方法优化二氮杂苯－水复合物的基态氢键结构和相互作用能的计算。结果表明，邻二氮杂苯－水，间二氮杂苯－水，对二氮杂苯－水复合物具有强的N∙∙∙H─O氢键相互作用，经基组重叠误差和零点能校正后的氢键相互作用能分别为-20.99, -16.73 和-15.31 kJ/mol，氢键的形成使水的H─O对称伸缩振动频率明显红移（减小）。自然键轨道NBO分析显示，氢键的形成，分子间电荷转移分别为0.0316 e，0.0255 e 和0.0265 e。另外，使用含时密度泛函理论TD-DFT (TD-B3LYP)方法计算了二氮杂苯单体与氢键复合物的第一单重态(n, p^*)激发态的垂直激发能。     

1,2,3-三氮杂苯-水复合物氢键相互作用

Density functional theory B3LYP method with 6-31++G** basis was used to optimize the geometries of the ground states for 1,2,3-triazine-(H2O)n (n=1,2,3) complexes. All calculations indicate that the 1,2,3-triazine-water complexes in the ground states have strong hydrogen-bonding interaction, and the complex having a N…H-O hydrogen bond and a chain of water molecules which is terminated by a O…H-C hydrogen bond is the most stable. The H-O stretching modes of complexes are red-shifted relative to that of the monomer. In addition, the Natural bond orbit (NBO) analysis indicates that the intermolecular charge transfer between 1,2,3-triazine and water is 0.0222e, 0.0261e and 0.0273e for the most stable 1:1, 1:2 and 1:3 complexes, respectively. The first singlet (n, π*) vertical excitation energy of the monomer 1,2,3-triazine and the hydrogen-bonding complexes of 1,2,3-triazine-(H2O)n were investigated by time-dependent density functional theory.     

1,2,3-三氮杂苯-水簇复合物氢键结构与性质的理论研究

在B3LYP/6-31 G**水平上对1,2,3-三氮杂苯和水形成1∶1,1∶2和1∶3复合物的基态氢键结构进行几何优化和性质计算,结果表明复合物之间存在较强的氢键作用。氢键的形成使水分子中H-O键振动频率减小(红移)。NBO分析表明,最稳定的1∶1,1∶2和1∶3复合物发生分子间电荷转移总量分别为0.0222e,0.0261e和0.0273e。     

1,2,4-三氮杂苯-(H2O)n复合物氢键相互作用的密度泛函理论研究

用密度泛函理论方法在B3LYP／6—31 G**水平上对1，2，4-三氮杂苯-(H2O)n(n=1，2，3)氢键复合物的基态进行了结构优化和能量计算，结果表明复合物之间存在较强的氢键作用，所有稳定复合物结构中形成一个N…H--O氢键并终止于弱O…H—C氢键的氢键水链的构型最稳定．同时，用含时密度泛函理论方法(TD—DPT)在TD—B3LYP／6—31 G**水平上计算了1,2，4-三氮杂苯单体及其氢键复合物的单重态第-1(n，π*)垂直激发能．     

1,2,4-三氮杂苯-(H2O)n复合物氢键相互作用的密度泛函理论研究

用密度泛函理论方法在B3LYP/6-31++G**水平上对1,2,4-三氮杂苯-(H₂O)_n (n＝1, 2, 3)氢键复合物的基态进行了结构优化和能量计算, 结果表明复合物之间存在较强的氢键作用, 所有稳定复合物结构中形成一个N…H—O氢键并终止于弱O…H—C氢键的氢键水链的构型最稳定. 同时, 用含时密度泛函理论方法(TD-DFT)在TD-B3LYP/6-31++G**水平上计算了1,2,4-三氮杂苯单体及其氢键复合物的单重态第一¹(n, π^*)垂直激发能.     

新型1,5-苯并二氮杂卓衍生物的结构与抑菌活性的理论分析

采用密度泛函理论(DFT)方法,在B3LYP/6-31G(d,p)水平上对一系列新型1,5-苯并二氮杂卓衍生物进行了几何结构全优化和理论计算研究,得到分子的几何结构、NPA电荷、红外振动光谱及轨道贡献。研究结果表明:1,5-苯并二氮杂卓分子的七元环是扭船式构型;分子不同位置连接不同的取代基,对分子的电荷分布有一定影响;红外光谱理论计算结果与实验结果相吻合。通过探讨前线轨道与抑菌活性的关系发现,所研究的杂卓分子对不同菌株的抑菌活性具有选择性和特异性,其中分子中的N(11)和C=N可能分别是所合成的该类化合物与细菌(枯草杆菌)和真菌(白色念珠菌和新型隐球菌)发生作用的主要活性部位。     

邻二氮杂苯-水复合物氢键相互作用的理论研究

The hydrogen bond structure and interaction energy on the ground state of pyridazine and water complex are studied with B3LYP and MP2 method. All calculations show that there are strong interactions for a hydrogen bond N…H-O and large red-shifts for the symmetric H-O stretching vibrational frequencies in the pyridazine and water complex. The first singlet 1(n, π ) and 1(π,π) vertical excitations of the monomer pyridazine and the hydrogen bond between a pyridazine molecule and a water molecule have been investigated with time-dependent density functional theory TDB3LYP method.     

1,5-苯并二氮杂的合成及其生物活性研究

采用两种方法: 以三氧化铝为载体邻苯二胺与查尔酮为原料的无溶剂合成法和以PPA(多聚磷酸)为催化剂邻苯二胺与苯乙酮的一锅合成法, 合成了1,5-苯并二氮杂, 产物收率为53.7%～74.5%. 通过¹H NMR, ¹³C NMR, MS, IR, 元素分析等手段对所合成的化合物进行了结构确定, 并测试了它们对菌和乙酰胆碱酶的抑制活性.     

锇杂苯的电子结构及芳香性

使用密度泛函理论及片段轨道相互作用分析方法,研究了典型的锇杂苯的电子结构和芳香性.结果表明,锇碳六员环具有较好的环平面性及键的离域性,占据的锇dxz轨道与碳环的3π空轨道之间的反馈π键相互作用,使得环上离域π电子数满足Hückel的4n+2规则,计算的环外质子化学位移、同键反应芳香性稳定化能、绝对硬度和磁化率增量数据均表明锇杂苯具有芳香性.     

肾上腺素与二甲亚砜氢键作用的理论研究

The hydrogen bond is one of the most important intermolecular interactions playing an important role in intermolecular recognition processes essential to most biological systems. Adrenaline is an important catecholamine neurotransmitter in the mammalian central nervous system. Dimethyl sulphoxide can carry with it drugs across membranes. The geometries of adrenaline and six stable 1 : 1 complexes formed between adrenaline and dimethyl sulphoxide were optimized by Berny method at PM3 level and thus were optimized by density functional theory（B3LYP method）at the 6-31G,6-31G*,and 6-31+G* level respectively to obtain accurate structures. Single-point energies of all optimized molecular geometries were calculated to discuss the energies and structural parameters between reactants and products. All the binding energies have been corrected by the zero point vibrational energies（ZPVE）at varied basis set levels from 6-31G to 6-31 + G*. The results indicated that stronger hydrogen-bonded complexes were formed by molecular interaction between adrenaline and dimethyl sulphoxide. The calculation results can be better used to explain some experimental phenomena.     

哒嗪裂解反应机理的密度泛函理论研究

利用密度泛函理论(DFT)方法, 以哒嗪为煤的模型化合物, 在(U)B3LYP/6-31G(d,p)水平下计算了标题化合物的键布居数和键裂解能, 并对其热解机理进行了探讨. 在(U)B3LYP/6-311++G(d,p)水平下计算了热解过程中各物种的单点能, 并对总能量进行了校正. 结果表明, 标题物N-N键的布居数和裂解能均最小, 且各键裂解能随温度变化不大, 热解最终产物为HCN和乙炔, NH₃可能是HCN经过二次转换得到的. 采用过渡态理论计算了300~1900 K温度范围内热解的速率常数, 求得lnk与1/T的线性关系.     

CH3SH与HOCl分子间氢键和卤键的结构与性质

在DFT-B3LYP及MP2/6-311＋＋G**水平上分别求得CH3SH…HOCl氢键复合物和CH3SH…ClOH卤键复合物势能面上的稳定构型. 频率分析表明, 与单体HOCl相比, 在两种复合物中, Cl(9)—O(7)和H(8)—O(7)键伸缩振动频率发生显著的红移. 经MP2/6-311＋＋G**水平计算的含基组重叠误差(BSSE)校正的气相中相互作用能分别为－19.23和－6.85 kJ•mol－1. 自然键轨道理论(NBO)分析表明, 在CH3SH…ClOH卤键复合物中, 引起Cl(9)—O(7)键变长的因素包括2种电荷转移: (i)孤对电子LP[S(1)]1→σ*[Cl(9)—O(7)]; (ii)孤对电子LP[S(1)]2→σ*[Cl(9)—O(7)], 其中孤对电子LP[S(1)]2→σ*[Cl(9)—O(7)]转移占主要作用, 总的结果是使σ*[Cl(10)—O(11)]的自然布居数增加, 同时O(7)和Cl(9)原子s成分均增加的杂化重优具有与电荷转移作用相同的“拉长效应”; 在CH3SH…HOCl氢键复合物中也存在类似的电荷转移, 但是O(7)原子的再杂化效应不同于前者. 自然键共振理论(NRT)进行键序分析表明, 在氢键复合物和卤键复合物中, H(8)—O(7)和Cl(9)—O(7)键的键序都减小. 通过分子中原子理论(AIM)分析了复合物中氢键和卤键的电子密度拓扑性质.     

水溶液中氢键寿命的定义和弛豫机理

氢键弛豫过程决定水溶液中分子的动力学行为,氢键寿命作为理论和实验结果中一个重要的参数通常用以描述溶液中的氢键动力学性质.本文采用SPC/E-P2和SPC/E-OPLS两种力场方法对二甲基亚砜(DMSO)水溶液体系进行分子动力学模拟,计算了四种不同定义下的氢键寿命,并进行了对比阐述,连续性氢键寿命Tc和基于动力学平衡方法下的氢键寿命TR较短,它们忽略了不成功的氢键交换过程,稳定态模型下的氢键寿命TPR能够真实体现氧键转换过程,可作为标度衡量其它量值.间歇性氢键寿命T相对最长,重复统计了氢键成功交换后的恢复概率.随着二甲基亚砜浓度增大,TC、TI、TR和TPR不断增大,分子平动扩散系数在中等浓度达到极小,说明氢键寿命与分子活动性无决定性关联,同类型氢键在不同浓度下的寿命差异表明氢键寿命具有分子环境依赖性;水分子和二甲基亚砜分子氢键个数降低,氢键受激角度扭曲和拉伸概率下降,TC和TR不断接近,氢键交换受体密度降低使氢键交换速率下降,TPR不断增大,氢键寿命与其周围氢键密度密切相关.TI与TPR的比值体现了氢键交换的局域性,其变化趋势与分子平动活动性趋势相同.两种力场下氢键寿命的差异也说明氢键的寿命具有明显的理论模型依赖性.     

Nature of the Hydrogen Bond Enhanced Halogen Bond

The factors responsible for the enhancement of the halogen bond by an adjacent hydrogen bond have been quantitatively explored by means of state-of-the-art computational methods. It is found that the strength of a halogen bond is enhanced by ca. 3 kcal/mol when the halogen donor simultaneously operates as a halogen bond donor and a hydrogen bond acceptor. This enhancement is the result of both stronger electrostatic and orbital interactions between the XB donor and the XB acceptor, which indicates a significant degree of covalency in these halogen bonds. In addition, the halogen bond strength can be easily tuned by modifying the electron density of the aryl group of the XB donor as well as the acidity of the hydrogen atoms responsible for the hydrogen bond.     

Theoretical Study on the Structures and Properties of Hydrogen Bonding Complexes between Diazines and Water

Density functional theory B3LYP method and second-order Moller-Plesset perturbation theory MP2 method were employed to obtain the optimized geometries of the ground state and interaction energy for diazines and water complexes. The results show that the ground state complexes have strong hydrogen bonding interaction with -20.99, -16.73 and -15.31 kJ/mol after basis set superposition error and zero-point vibration energy correction for pyridazine-water, pyrimidine-water and pyrazine-water, respectively, and large red-shift for the symmetric H-O stretching vibration frequencies due to the formation of N…H-O hydrogen bond in the diazine-water complexes. The NBO analysis indicates that intermolecular charge transfer are 0.0316, 0.0255 and 0.0265 e respectively. In addition, the first singlet （n,n＊） vertical excitation energy of the monomer and the hydrogen bonding complexes between diazines and water was investigated by time-dependent density functional theory.     

Density Functional Theory Study on Interaction between Catechin and Thymine

The interacting patterns and mechanism of the catechin and thymine have been investigated with the density functional theory Becke's three-parameter nonlocal exchange functional and the Lee, Yang, and Parr nonlocal correlation functional (B3LYP) method by 6-31+G*basis set. Thirteen stable structures for the catechin-thymine complexes have been found which form two hydrogen bonds at least. The vibrational frequencies are also studied at the same level to analyze these complexes. The results indicated that catechin interactedwith thymine by three different hydrogen bonds as N-H…O、C-H…O、O-H…O and the complexes are mainly stabilized by the hydrogen bonding interactions. Theories of atoms in molecules and natural bond orbital have been adopted to investigate the hydrogen bondsinvolved in all systems. The interaction energies of all complexes have been corrected for basis set superposition error, which are from -18.15 kJ/mol to -32.99 kJ/mol. The results showed that the hydrogen bonding contribute to the interaction energies dominantly. The corresponding bonds stretching motions in all complexes are red-shifted relative to that of the monomer, which is in agreement with experimental results.     

Hydrogen bond interactions in sulfamerazine: DFT study of the O-17, N-14, and H-2 electric field gradient tensors

Hydrogen bond (HB) interactions are studied in the real crystalline structure of sulfamerazine by density functional theory (DFT) calculations of the electric field gradient (EFG) tensors at the sites of O-17, N-14, and H-2 nuclei. One-molecule (single) and four-molecule (cluster) models of sulfamerazine are created by available crystal coordinates and the EFG tensors are calculated in both models to indicate the influence of HB interactions on the tensors. Directly relate to the experiments, the calculated EFG tensors are converted to the experimentally measurable nuclear quadrupole resonance (NQR) parameters, quadrupole coupling constant (qcc) and asymmetry parameter (η_Q). The evaluated NQR parameters reveal that due to contribution of the target molecule to N–HN and N–HO types of HB interactions, the EFG tensors at the sites of various nuclei are influenced from single model to the target molecule in cluster. Additionally, O2, N4, and H2 nuclei of the target molecule are significantly influenced by HB interactions, consequently, they have the major contributions to HB interactions in cluster model of sulfamerazine. The calculations are performed employing B3LYP method and 6-311++G** basis set using GAUSSIAN 98 suite of program.     

多肽中氢键强度的理论研究

用B3LYP/6-31G^*法优化了多肽分子的几何构型,计算了各个构型的电荷分布和氢键酸度,进而对多肽分子中的氢键强度进行了研究.结果表明,多肽分子中氢键的强度同时取决于形成氢键的H…O原子间距R和N-H…O之间的键角β;多肽分子倾向于形成R值小、β值大的大环氢键.3₁₀螺旋结构的多肽分子中的氢键具有协同效应,分子越大,分子中氢键越多,氢键的协同效应越强.