N'-(2-羟基-5-甲氧基苯甲基)-4-二甲氨基苯甲酰肼及其氧钒(V)配合物:合成、晶体结构和脲酶抑制活性

制备了一个苯甲酰腙化合物N'-(2-羟基-5-甲氧基苯甲基)-4-二甲氨基苯甲酰肼(H₂L).利用H₂L、乙酰氧肟酸(HAHA)和VO(acac)₂在甲醇中反应得到了配合物[VOL(AHA)].通过元素分析、红外和紫外光谱,以及单晶X-射线衍射对H₂L和其配合物进行了表征。苯甲酰腙配体作为二价阴离子,利用其酚羟基氧原子、亚胺基氮原子、以及烯醇氧原子与V原子进行配位.乙酰氧肟酸配体利用其羰基氧原子和去质子化的羟基氧原子进行配位.配合物中的V原子为八面体配位构型。测试了H₂L、HAHA和钒配合物的脲酶抑制活性.在浓度为100 μmol·L^-1时,钒配合物对幽门螺旋杆菌脲酶的抑制率为63%,其IC₅₀值为45μmol·L^-1.还利用分子对接技术研究了配合物分子与脲酶的作用方式.     

2，7′-(乙烯基)-二-8-羟基喹啉及其金属有机配合物的密度泛函和自然键轨道理论计算

采用密度泛函理论(DFT),在B3LYP/6-31G水平上对2,7′-(乙烯基)-二-8-羟基喹啉(2,7′-Ethq₂)及其3种金属M(M=Zn,Mg,Be)有机配合物M(2,7′-Ethq₂)₂的结构进行了全优化,并用ZINDO和TDDFT方法计算了它们的吸收光谱。同时,利用自然键轨道理论(NBO)对分子内氢键进行了分析。结果表明,光谱计算值与实验值基本符合,该类化合物均具有较大的电子亲和能,改变中心金属原子对配合物吸收光谱性质影响不大。和2,7′-Ethq₂相比,M(2,7′-Ethq₂)₂的吸收光谱产生明显红移。2,7′-Ethq₂及其M(2,7′-Ethq₂)₂分子内存在较强的氢键,氢键与环上的碳原子形成五元环,分子内氢键的存在使分子的稳定性增加。     

N'-(2-羟基-5-甲氧基苯甲基)-4-二甲氨基苯甲酰肼及其氧钒(Ⅴ)配合物:合成、晶体结构和脲酶抑制活性

制备了一个苯甲酰腙化合物N'-(2-羟基-5-甲氧基苯甲基)-4-二甲氨基苯甲酰肼(H₂L)。利用H₂L、乙酰氧肟酸(HAHA)和VO(acac)₂在甲醇中反应得到了配合物[VOL(AHA)]。通过元素分析、红外和紫外光谱,以及单晶X-射线衍射对H₂L和其配合物进行了表征。苯甲酰腙配体作为二价阴离子,利用其酚羟基氧原子、亚胺基氮原子、以及烯醇氧原子与V原子进行配位。乙酰氧肟酸配体利用其羰基氧原子和去质子化的羟基氧原子进行配位。配合物中的V原子为八面体配位构型。测试了H₂L、HAHA和钒配合物的脲酶抑制活性。在浓度为100μmol·L^-1时,钒配合物对幽门螺旋杆菌脲酶的抑制率为63%,其IC₅₀值为45μmol·L^-1。还利用分子对接技术研究了配合物分子与脲酶的作用方式。     

二(2-苯基-8-羟基喹啉)锌及其衍生物的电子光谱性质的含时密度泛函理论研究

采用从头算(ab initio)和密度泛函理论(DFT B3LYP)方法。对二(2-苯基-8-羟基喹啉)锌(Zn(qPh)₂)及其衍生物的基态结构进行优化，同时用ab initio HF单激发组态相互作用(CIS)法在6-31G基组上优化其最低激发单重态几何结构，用含时密度泛函理论(TD-DFT/B3LYP)及6-31G基组计算吸收和发射光谱。计算表明，该类物质电子在基态与激发态间的跃迁，主要是电子云分布由定域化向离域化的转变。吸收及发射光谱的计算值与实验值基本符合。该类化合物的电子亲和能较大，都是优良的电子传输材料，改变中心金属原子对配合物光谱性质影响不大。而羟基氧被硫原子取代后，化合物的吸收光谱产生明显红移。     

L-谷氨酸桥连的卟啉二联体配体及其铜配合物的合成、表征和性质研究

合成了未见报道的L-谷氨酸桥连的卟啉二联体配体及其铜的金属配合物, 并用红外光谱, 电子吸收光谱, 核磁氢谱, 元素分析和质谱等对化合物的结构加以确认, 研究了配体和金属配合物的CD, 拉曼光谱和荧光光谱的变化. 结果显示在配体中没有出现劈裂的Cotton效应, 而铜配合物中出现了劈裂的正负Cotton效应, 配体的荧光强度强于铜配合物的荧光强度, 在拉曼光谱中, 由于卟啉分子平面的对称性由D_2h变为D_4h群及其铜离子d轨道的电子效应, 在卟啉配体和铜配合物之间的拉曼光谱有很大差别.     

含能配合物[Zn(DAT)6](ClO4)2(DAT＝1,5-二氨基四唑)的合成、晶体结构及性质

采用直接法合成了新型高氮含能配合物[Zn(DAT)₆](ClO₄)₂(DAT＝1,5-二氨基四唑), 并用元素分析、傅立叶变换红外光谱对其结构进行了表征. 利用缓慢蒸发溶剂法培养出其单晶, 采用X射线单晶衍射仪测定其晶体结构, 结果表明该晶体属于三方晶系, 空间群, a＝b＝1.18398(9) nm, c＝0.65700(10) nm, γ＝120°, V＝0.79760(15) nm³, Z＝1. 在目标配合物的最小不对称单元中有1个Zn^2＋, 6个DAT分子和2个. 来自6个DAT分子的6个N原子分别与中心Zn^2＋配位, 形成一个六配位、非中心对称的畸变八面体结构. 用差示扫描量热分析、热重-微分热重分析结合红外光谱研究了标题化合物的热分解机理以及分解反应动力学参数. 测定了标题配合物的感度性能, 结果表明标题配合物具有一定的摩擦感度.     

二个含水杨酰腙配体的钒配合物的合成与晶体结构研究

2种水杨酰腙配体H₂L¹(H₂L¹=邻羟基苯乙酮缩水杨酰腙)和H₂L²(H₂L²=水杨醛缩水杨酰腙)分别与VO(acac)₂反应, 合成了2个钒配合物[VOL¹(C₂H₅O)]₂ (1)和[VOL²(i-C₃H₇O)](2), 利用元素分析、红外光谱、紫外光谱和单晶衍射等手段进行表征。配合物1是由酚氧原子桥联2个金属中心形成的具有晶体学中心对称性的双核钒(Ⅴ)配合物结构, 每个V(Ⅴ)原子具有扭曲的八面体配位构型。配合物2为单核结构, 每个V(Ⅴ)原子具有扭曲的四角锥配位构型, 相邻的配合物分子通过分子间氢键作用形成一维超分子链状结构。采用循环伏安法研究了化合物2的电化学性质。     

Mn(II)配合物的晶体结构及表面光电性能

采用水热法合成3个新的Mn(II)配合物[Mn(SO₄)(H₂O)₃]_n (1), [Mn2.5(HPO₄)(PO₄)(H₂O)₂]_n (2), [Mn(phen)₂(H₂O)₂]·(C₄H₄O₄)·4H₂O (3) (phen=1,10-邻二氮杂菲). 用X射线单晶衍射、表面光电压光谱(SPS)、红外光谱(IR)、紫外-可见吸收光谱(UV-Vis)、电子顺磁共振谱(EPR)对配合物进行了表征. 结构解析表明: 配合物1是具有2D结构的配合物, 氢键将其连接成3D超分子; 配合物2是具有3D无限结构的配合物; 配合物3是单核配合物, 再由多种氢键连接, 形成3D超分子. SPS结果表明, 3个配合物在300-800 nm范围内都呈现明显的光伏响应, 表明它们均具有一定的光-电转换性能. 讨论了配合物结构, 空间维度和中心金属离子配位环境的不同对配合物表面光电性能的影响以及SPS与UV-Vis的关联: 配合物的结构维度越高、规则性越好, SPS响应强度越大; 中心金属离子的直接配位原子种类的不同、所处外晶场的强弱不同, SPS响应带的数目和位置明显不同.     

一种三核铜(Ⅱ)配合物{[Cu(HL)(EtOH)]2Cu}的合成及结构研究

通过双肟配体H₄L(H₄L=6,6′-二羟基-2,2′-[1,2-亚乙基二氧双(氮次甲基)]二酚)与水合乙酸铜反应,合成了一个新的铜配合物{[Cu(HL)(EtOH)]₂Cu},并进行了元素分析、红外光谱和X-射线单晶衍射测定。结果表明,该配合物为三核结构,由3个Cu^Ⅱ离子、2个配位的(HL)^3-单元、2个配位的乙醇分子组成。且配合物通过分子间C-H…O氢键形成了一个二维超分子结构。     

KI/NH3协同催化CO2与环氧丙烷合成碳酸丙烯酯的反应机理

采用密度泛函理论(DFT)研究了NH₃/KI、KI及无催化剂条件下, CO₂与环氧丙烷(PO)合成碳酸丙烯酯(PC)的反应机理. 在B3LYP/6-311++G^**基组水平上(I采用MIDIX基组)优化了反应过程中的反应物、中间体、过渡态和产物, 通过振动分析及内禀反应坐标(IRC)确定中间体和过渡态的真实性. 同时, 在相同基组水平应用自然键轨道(NBO)理论和分子中的原子(AIM)理论分析了这些化合物的轨道间相互作用和成键特征. 研究结果表明: 在无催化剂条件下非协同反应通道PO+CO₂→M0a→TS0c→M0c→TS0c′→PC为最有利通道, 其活化能为200.65 kJ·mol^-1; KI催化下活化能降低至187.40 kJ·mol^-1, 反应速率较小; 在KI/NH₃协同催化下, 除KI的催化作用外, NH₃中的氢原子还能与CO₂或PO中的氧原子形成氢键, 活化反应, 活化能降低至154.64 kJ·mol^-1, 大幅度提高了PO与CO₂环合生成产物PC的反应速率, 理论计算与实验结果一致.     

Quantum-mechanical analysis of the structure of phosphoric acid complexes with methyl methacrylate and methyl trimethylacetate

The structures of such model fragments of poly(methyl methacrylate) as methyl methacrylate and methyl trimethylacetate, and of its complexes with phosphoric acid, are optimized by means of density functional theory using the B3LYP hybrid functional in combination with the 6-31++G** basis set. The effect of dimethylformamide on methyl trimethylacetate complexes with phosphoric acid is considered, and the possibility of proton transfer is studied.     

儿茶素-胞嘧啶分子间相互作用的密度泛函研究

采用密度泛函理论的B3LYP方法,在6-31+G*基组水平上研究了儿茶素-胞嘧啶分子间相互作用机制,得到稳定的儿茶素-胞嘧啶复合物11个.计算结果表明氢键对于复合物的稳定性起着重要的作用,并且当复合物形成2个或更多的氢键时,氢键的类型及强度共同决定着复合物的稳定性.我们还应用了分子中的原子(AIM)理论和自然键轨道(NBO)理论对这11种复合物中氢键的性质和特征进行了分析.通过研究发现,所有的氢键复合物进行基组重叠误差(BSSE)校正后的相互作用能为-17.35～-43.27kJ/mol,相互作用能主要由氢键所贡献.振动分析显示,氢键的形成使相对应键的对称伸缩振动频率减小,说明这些复合物中形成的氢键都是正常的红移型氢键,与实验结果相一致.     

Density functional theory study on the interaction of catechin and cytosine

The interacting patterns and mechanism of the catechin and cytosine have been investigated using the density functional theory B3LYP method with 6-31+G* basis set.Eleven stable structures of the catechin-cytosine complexes have been found respectively.The results indicate that the complexes are mainly stabilized by the hydrogen bonding interactions.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 interactio...     

Chromium Bis(anthracene‐η6) Complexes – A DFT Study

Chromium bisanthracene‐η⁶ complexes are considered within the framework of density functional theory using LANL2DZ and 6‐31+G(d) basis sets and B3LYP functional. The complexation with both the same types of rings of anthracene decks (AA‐ and BB‐type complexes) and with different rings (AB‐type complex) are considered. The optimized geometries and the associated quantum chemical properties are comparatively discussed for the both types of basis sets used. LANL2DZ basis set yielded some unreasonable results. B3LYP/6‐31+G(d) level of calculations yielded the stability order as AA > BB > AB. IR spectra of AA and BB‐type complexes resemble each other. The C–H frequencies are almost the same for both of the anthracene decks, whereas they differ in the case of AB‐type complex. UV/Vis spectra of the complexes all absorb above 500 nm. AA and AB‐type complexes in contrast to BB‐type display rather complex pattern. The NICS(0) values of various rings in the complexes considered are obtained and discussed.     

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.     

四氢二嵌萘衍生物在不同环境中的电子结构及光谱特征的理论研究

采用密度泛函理论的B3LYP泛函和单激发组态相关方法(CIS)在6-31+G*基组水平下分别优化了四氢二嵌萘衍生物(THP)基态和第一单重激发态的结构,并在此基础上利用含时密度泛函理论计算了THP在不同环境中的电子结构和光谱性质.溶剂效应采用连续极化介质模型(PCM)计算.结构分析发现在酸性环境中,基态时THP二甲氨基上的N原子容易质子化.计算结果表明,尽管THP的第一单重激发态是一个电荷转移态,但是它本身并不发射双荧光.在酸性溶剂中,THP的双峰发射来源于两种物质:跃迁能为2.71eV的发射峰由激发的THP发射,而3.69eV的发射峰则来源于质子化的THP.根据计算结果,我们建议了THP在酸性溶剂中的激发与驰豫途径.理论预测的吸收和发射光谱与实验结果一致.     

Intermolecular interactions of a size‐expanded guanine analogue with gold nanoclusters

The interactions between a size‐expanded Guanine analogue x‐Guanine (xG) and gold nanoclusters, Au_n (n = 2, 4, 6, and 8), were studied theoretically using density functional theory. Geometries of neutral complexes were optimized using the B3LYP functional with the 6‐31+G(d,p) basis set for xG and the LANL2DZ basis set for gold clusters. The binding modes, interaction strength, and the charge‐transfer properties of different Au_n‐xG complexes were investigated. Natural population analysis was performed for natural bond order charges. It was found that gold nanoclusters form stable complexes with xG and these binding results in a substantial amount of electronic charge being transferred from xG to the gold clusters. The vertical first ionization potential, electron affinity, Fermi Level, and the HOMO–LUMO gap of xG and its complexes with gold nanoclusters were also analyzed. © 2013 Wiley Periodicals, Inc.     

Density Functional Theory Study of the Interaction between Guanine and Catechin

The interacting patterns and mechanism of the catechin and guanine have been investigated with the density functional theory B3LYP method by 6‐31G* basis set. Fourteen stable structures for the catechin‐guanine complexes have been found which form two hydrogen bonds at least. The results indicate that the complexes are mainly stabilized by the hydrogen bonding interactions. At the same time, the number and strength of hydrogen bond play a co‐determinant parts in the stability of the complexes which can form two or more hydrogen bonds. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) have been adopted to investigate the hydrogen bonds involved in all systems. The interaction energies of all complexes have been corrected for basis set superposition error (BSSE), ranging from ?38.86 to ?14.56 kJ/mol. The results showed that the hydrogen bonding contributes 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.     

Structure and stability of salicylic acid-water complexes and the effect of molecular hydration on the spectral properties of salicylic acid

Density functional theory with B3LYP parametrization and 6-311++G(d,p) basis set has been used to investigate the structure and stability of salicylic acid-water complexes. The vertical excitation energies for these complexes have been computed using time-dependent density functional theory (with B3LYP parametrization and a 6-311++G(d,p) basis set). It is shown that the hydrogen bond between the carboxylic hydrogen and the oxygen of water is the strongest among all possible hydrogen bonds in the system. The hydrogen bond strength in salicylic acid-water complexes seems to be nearly additive. The change in absorption maximum (lambda(max)) corresponding to the vertical excitation energy for the first three excited singlet and triplet states of the complex with 1-3 water molecules is nominal (approximately 1-3 nm). But with the addition of the fourth water molecule, the lambda(max) for S(1) and T(1) decreases by approximately 17 nm and it increases for S(2) and S(3) by about the same amount. The decrease in lambda(max) for transition to the T(2) state on the addition of the fourth water molecule is only approximately 9 nm. There seems to be an intersystem crossing between the S(1) and T(3) states that could account for the observed fluorescence quenching of salicylic acid in water.     

Density functional theory augmented with an empirical dispersion term. Interaction energies and geometries of 80 noncovalent complexes compared with ab initio quantum mechanics calculations

Standard density functional theory (DFT) is augmented with a damped empirical dispersion term. The damping function is optimized on a small, well balanced set of 22 van der Waals (vdW) complexes and verified on a validation set of 58 vdW complexes. Both sets contain biologically relevant molecules such as nucleic acid bases. Results are in remarkable agreement with reference high-level wave function data based on the CCSD(T) method. The geometries obtained by full gradient optimization are in very good agreement with the best available theoretical reference. In terms of the standard deviation and average errors, results including the empirical dispersion term are clearly superior to all pure density functionals investigated-B-LYP, B3-LYP, PBE, TPSS, TPSSh, and BH-LYP-and even surpass the MP2/cc-pVTZ method. The combination of empirical dispersion with the TPSS functional performs remarkably well. The most critical part of the empirical dispersion approach is the damping function. The damping parameters should be optimized for each density functional/basis set combination separately. To keep the method simple, we optimized mainly a single factor, s(R), scaling globally the vdW radii. For good results, a basis set of at least triple-zeta quality is required and diffuse functions are recommended, since the basis set superposition error seriously deteriorates the results. On average, the dispersion contribution to the interaction energy missing in the DFT functionals examined here is about 15 and 100% for the hydrogen-bonded and stacked complexes considered, respectively.