Density Functional Theory Study on Hydrogen Bonding Interaction of Catechin-(H2O)n

Density functional theory B3LYP method with 6‐31G* basis set has been used to optimize the geometries of the catechin, water and catechin‐(H₂O)_n complexes. The vibrational frequencies have been studied at the same level to analyze these complexes. Six and eleven stable structures for the catechin‐H₂O and catechin‐(H₂O)₂ have been found, respectively. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) have been utilized to investigate the hydrogen bonds involved in all the systems. The interaction energies of all the complexes corrected by basis set superposition error, are from ?13.27 to ?83.56 kJ/mol. All calculations also indicate that there are strong hydrogen‐bonding interactions in catechin‐water complexes. The strong hydrogen‐bonding contributes to the interaction energies dominantly. The O–H stretching motions in all the complexes are red‐shifted relative to that of the monomer.     

N—O键解离焓的密度泛函理论研究

在高精度计算方法G3和G3B3的基础上,比较了密度泛函理论(DFT)十几种方法对N—O键解离焓(BDE)相对于实验值的计算精度,发现用B3P86方法计算15种化合物N—O键的BDE,均方根误差最小,仅为6.36kJ·mol-1,计算值与实验值的线性相关系数为0.991.在此基础上,用该方法分别计算了非芳香化合物及芳香化合物的N—O键BDE.通过自然键轨道分析,发现部分N—O键的BDE与N—O键的键长、原子电荷密度及键级之间存在定量关系.此外,在B3P86方法的基础上预测了几种典型的杂环芳香化合物N—O键BDE值.     

Lindqvist型[M6-nMonO19]p-阴离子（M=W,Nb,Ta）电子性质的密度泛函理论研究

采用密度泛函理论方法探讨了取代Mo原子对[W6-nMonO19]2-,[Nb6-nMonO19]p-和[Ta6-nMonO19]p-体系的M—Ot(M=W,Nb,Ta)键的活化作用.计算结果表明,随着取代Mo原子数的增多,[M6-nMonO19]2-(M=W,Nb,Ta)中M—Ot键的键能逐渐减小,因此Mo原子的引入使M—Ot键活化.在[W6-nMonO19]2-中,Mo—Ot键的键能小于W—Ot键的键能,因此,Mo—Ot键比W—Ot键易断裂,与实验结果一致.而在[Nb6-nMonO19]p-和[Ta6-nMonO19]p-体系中,Mo—Ot键的键能大于M—Ot(M=Nb,Ta)键的键能.Nb和Ta原子的端氧Ot的电荷大于Mo原子的端氧Ot的电荷,初步预测,当[Nb6-nMonO19]p-和[Ta6-nMonO19]p-与有机胺反应时,Nb—Ot和Ta—Ot键优先断裂,易与有机胺的氮原子成键.     

在Rh(111)面上NO+CO反应机理的密度泛函理论研究

应用基于密度泛函理论赝势平面波方法的CASTEP程序, 对Rh(111)上的NO+CO反应机理进行研究. 对于反应中的各个关键步骤: NO离解、CO2生成、通过N2O离解生成N2以及通过N+N反应生成N2都进行了详细讨论, 计算得到各反应步骤的过渡态以及活化能, 从而确立了各步骤的反应路径.     

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．     

Density Functional Studies on Isonicotinato Lead(II) Complex [Pb(C5H4NCOO)2]

1 INTRODUCTION Recently, the chemistry of lead is of interest in relation to its toxicity and effects on intelligence in human populations[1~3]. The design of drugs to coun- teract the effects of lead poisoning requires estab- lishing the preferred ligands of Pb(II) and their ste- reochemistry. Consequently, synthesis of chelated- form antidotes for lead(II) ion toxicosis has attracted more and more attention, and numerous reports con- cerning experimental coordination chemistry of lead(…     

Adsorption of H2O,OH, and O on CuCl(111) Surface: A Density Functional Theory Study

The adsorption of H2O molecule and its dissociation products, O and OH, on CuCl(111) surface was studied with periodic slab model by PW91 approach of GGA within the framework of density functional theory. The results of geometry optimization indicate that the top site is stable energetically for H2O adsorbed over the CuCl(111) surface. The threefold hollow site is found to be the most stable adsorption site for OH and O, and the calculated adsorption energies are 309.5 and 416.5 kJ/mol, respectively. Adsorption of H2O on oxygen-precovered CuCl(111) surface to form surface hydroxyl groups is predicted to be exothermic by 180.1 kJ/mol. The stretching vibrational frequencies, Mulliken population analysis and density of states analysis are employed to interpret the possible mechanism for the computed results.     

酚氧桥联铜钴异双核配合物的密度泛函研究

用密度泛函方法,在ROB3LYP/SDD//ROB3LYP/LanL2MB水平上,对酚氧桥联CuⅡ-CoⅡ异双核配合物CuCo(TS)(H2O),进行了理论计算.优化得到了它的单、三重态的平衡几何构型,计算了它们的谐振动频率.结果表明,该配合物分子的三重态比单重态稳定;电子自旋布居高度集中在Co(6)及其周围的配体原子上,而Cu（1）则没有发现电子自旋布居; 体系中存在较强的自旋离域效应.体系的前线分子轨道主要由Co(6)的d轨道和配体原子的p轨道组成,这有利于配体原子与Co(6)之间的电子转移.计算结果与实验符合得很好.     

Early Relaxation Dynamics in the Photoswitchable Complex trans-[RuCl(NO)(py)4]2+

The design of photoswitchable transition metal complexes with tailored properties is one of the most important challenges in chemistry. Studies explaining the underlying mechanisms are, however, scarce. Herein, the early relaxation dynamics towards NO photoisomerization in trans-[RuCl(NO)(py)₄]²⁺ is elucidated by means of non-adiabatic dynamics, which provided time-resolved information and branching ratios. Three deactivation mechanisms (I, II, III) in the ratio 3:2:4 were identified. Pathways I and III involve ultrafast intersystem crossing and internal conversion, whereas pathway II involves only internal conversion.     

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.     

配合物[Fe(CO)x(Ph2Ppy)y(HgCl2)z](x=3, 4; y=1, 2; z=0, 1, 2)的Fe-Hg相互作用及31P化学位移的理论研究

用密度泛函理论PBE0法计算配合物[Fe(CO)x(Ph2Ppy)y(HgCl2)z](1: x=4, y=1, z=0; 2: x=3, y=2, z=0; 3: x=4, y=1, z=1; 4: x=3, y=2, z=1; 5: x=4, y=1, z=2; 6: x=3, y=2, z=2)的几何构型, 用PBE0-GIAO法计算配合物1~6的31P化学位移. 计算结果表明, 含2个Ph2Ppy的配合物5和6的Fe—Hg相互作用略大于含单个Ph2Ppy的配合物3和4. 含2个HgCl2的配合物4和6存在Fe—Hg σ键, 比含单个HgCl2的配合物3和5的Fe—Hg相互作用强, 配合物3和5的Fe—Hg相互作用以Fe→Hg和Fe←Hg离域为主. 配合物3中Fe的负电荷比5的小, 故配合物5的Fe—Hg相互作用比配合物3的强且Fe→Hg离域比较显著, 而配合物3的Fe←Hg离域更显著. Fe—Hg相互作用增大了双核配合物中P核周围的电子密度, 其31P化学位移比相应的单核配合物小, 且含2个HgCl2的双核配合物的31P化学位移更小. 含单个Ph2Ppy的配合物的31P化学位移小于含2个Ph2Ppy的配合物.     

CO在SnO2(110)面吸附特性的密度泛函研究

根据密度泛函理论, 采用广义密度近似和总体能量平面波赝势方法, 以6层Slab周期结构为模型, 计算了CO以4种不同方式在SnO2(110)表面的吸附, 研究了CO吸附对表面特性的影响. 计算结果表明, CO以C端向下在低配位Sn5C位置的顶位吸附为稳定的吸附方式, 该吸附对表面的驰豫现象有所改善. CO吸附并未明显改变表面电子态密度分布, 但造成了费米能1.06 eV的升高. 吸附后CO分子向表面转移了0.07个电子, 使表面电阻下降. 理论计算的结果支持了气体传感器气敏机理中的表面电导模型.     

Synthesis and Kinetic Study on the Chromium(III) Complex [Cr(ASA)(en)2]Cl·2H2O

In order to explore the transfer mechanism of chromium(III) in mammals, a novel complex [Cr(ASA)(en)₂]Cl· 2H₂O, bis(ethylenediamine‐ κ ² N,N′)(4‐aminosalicylic acid‐ κ ² O,O′) chromium(III) monochloride dihydrate was synthesized (4‐aminosalicylic acid=H₂ASA, ethylenediamine=en). The crystal structure belongs to orthorhombic system with the space group P2₁2₁2₁ by means of X‐ray diffraction. The characteristic for transfer of Cr³⁺ from the compound to the low‐molecular‐mass chelator EDTA and the iron‐binding protein apoovotransferrin (apoOTf) was followed by UV‐visible (UV‐Vis) and fluorescence spectra in 0.01 mol·L^?1 Hepes at pH 7.4. The second order rate constants were calculated. Those spectra in conjunction were used to obtain more accurate information about the interaction of chromium complex with apoOTf. The experimental results indicate that Cr³⁺ can be transferred from the complex to apoOTf with the retention of the 4‐aminosalicylic acid acting as a synergistic anion.     

[EPy]Cl和[EPy]Br离子对的气相和液相结构及阴阳离子间的相互作用

采用密度泛函理论B3LYP/6-31+G(d,p)方法对氯化乙基吡啶([EPy]Cl)、溴化乙基吡啶([EPy]Br)的离子对进行了结构优化和频率分析, 并利用自洽反应场(SCRF)的导体极化连续模型(CPCM)考察了离子液体液相下的结构及相互作用. 得到了两种离子液体的离子对在气相、液相下最稳定结构及气相红外光谱特征值, 两种离子液体的离子对结构存在相似性, 红外光谱特征值与文献值比较吻合. 应用自然键轨道(NBO)理论分析了离子对中原子电荷分布及电荷转移情况, 结果证明两种离子液体中阴阳离子间除了静电相互作用外还存在着氢键作用. 通过对比气相及液相下的几何参数、相互作用能及NBO分析结果, 发现液相下阴阳离子的相互作用明显降低. 液相环境抵消了大部分阴阳离子间的静电作用, 导致液相下阴阳离子间相互作用的减小.     

(CH2)2N和(CH3)2NH+的密度泛函理论计算

用密度泛函理论UB3LYP／6-31G（d,p）方法研究了二甲胺自由基（CH3）2N及其质子化离子（CH3）2NH 的构象和超精细结构．在由构象研究得到的两种自由基的最稳定结构上,用密度泛函的UB3LYP和UB3PW91方法及从头计算的UHF、UMP2（FULL）方法计算了α-质子、β-质子和N核上的超精细偶合常数A（Hα）、A（Hβ）和A（N）结果表明：两种自由基中甲基内旋转的位垒均很低,分别为0．46kJ·mol-1（（CH3）2NH ）和2．6kJ·mol-1（（CH3）2N）．UB3LYP／6-31G（d,p）和UB3PW91／6-31G（d,p）计算的A（Hα）、A（Hβ）和A（N）与ESR实验结果符合得很好,UMP2／6-31G（d,p）方法的计算值与实验值符合得也较好．     

I2-环己烯复合物的共振拉曼光谱和密度泛函理论计算研究

实验得到I2-环己烯电荷转移复合物的电子吸收光谱和共振拉曼光谱.用密度泛函方法计算了复合物的基态结构、振动频率和电子跃迁能.计算和吸收光谱实验结果表明,I2-烯烃复合物在约300nm处的强吸收带为pz(I17)→π*(C=C)跃迁,即由靠近C=C双键端的碘原子(I17)上的一个pz电子向C=C双键反键轨道跃迁引起的吸收.在约300nm共振拉曼光谱的强度模式表现为I—I伸缩振动模和C=C伸缩振动模的基频、泛频及其组合频,表明在该激发态上I2-环己烯复合物经历了显著的I—I和C=C的价键变化.     

Study on Chromium‐Containing Aluminophosphate CrAPO‐5 via Density Functional Theory

Various structures of CrAPO‐5 clusters are studied via density functional B3LYP exchange‐correlation method. The optimized structures are compared with data from X‐ray absorption. Their total energies and atomic net charges are also analyzed. Results indicate that the substitution of the aluminum site of an AFI framework by chromium is in general not feasible. The chromium ion is more likely docked in between two neighboring 12‐membered rings of the framework of AFI. To further verify our claim, the excitation energies of the representative chromium structures of CrAPO‐5 clusters are calculated via the TDDFT method. The results for excitation energies further support that Cr³⁺ is not incorporated into the framework.     

MgF2表面结构稳定性及电子特性的密度泛函理论研究

用密度泛函理论(DFT)研究了MgF₂(010)、MgF₂(001)、MgF₂(011)及MgF₂(110)四种表面10种构型的稳定性和电子特性. 结果表明: 四种表面的邻近表面几层原子均出现了明显的驰豫现象, 终止于单层F原子的表面相对稳定; 进一步对比分析四种表面(终止于单层F原子的稳定构型)的表面能发现, 稳定性依次减弱排列为MgF₂(110)、MgF₂(011)、MgF₂(010)、MgF₂(001); 最稳定的MgF₂(110)表面的态密度显示在费米能级以下较多的成键电子处于低能级区, 同时由于表面的影响, 导致表面F原子电荷聚集显负电性, 促使表面活性增加.     

硅氧团簇(SiO2)nO2H4的密度泛函理论研究

提出硅氧团簇(SiO2)nO2H4的两种新构型: 基于笼状结构和环状结构的构型, 并与链状构型相比较, 用密度泛函理论的B3LYP方法在6-31G(d)基组水平上计算了三种构型n=2～22(n取偶数)的几何结构、平均结合能、能隙以及能量的二次差分. 分析计算结果发现, 笼状构型不但在n=4和8处存在幻数团簇(实验上已经观察到), 而且预测在n=14处也存在类似的幻数团簇; 此外, 与(SiO2)n团簇不同的是, (SiO2)nO2H4团簇的环状构型的稳定性从n=4开始大于链状构型, 意味着水的加成对硅氧团簇的稳定性有着重要的影响.