密度泛函理论和从头算方法对四唑负离子的比较研究

运用多种密度泛函理论(DFT)方法和从头算(abinitio)方法研究了四唑负离子的分子几何、电子结构、红外光谱和热力学性质.结果表明,B3LYP-DFT法与MP2-abinitio法计算结果较吻合,故可用于对四唑衍生物及其配合物的系统研究.     

四唑及其衍生物的理论研究：II.一氯代四唑负离子的从头算

用从头计算法，取６－３１Ｇ基组，在ＭＰ２水平上，计算研究了１Ｈ－和２Ｈ－四唑一氯取代物三种负离子的全优化几何构型和电子结构，比较讨论了它们的芳香性和稳定性，发现三者均取平面构型，其芳香性和稳定性次序为５－氯四唑负离子〉２－氯四唑负离子〉１－氯四唑负离子，预示了形成金属配俣物时５－氯四唑作为配体的重要性和配位方式。     

N_2O与氧负离子微观反应机理的理论研究

采用G3B3//B3LYP理论水平对反应O-+N2O的双重电子态势能面反应机理进行了详细的理论研究.该反应涉及的各个稳定点的构型、振动频率是在B3LYP/6-311++G(d,p)理论水平下计算的.计算结果表明,得到的反应焓变与已有实验值相吻合,该反应主反应通道是O-+N2O→NO+NO-,而生成O2-+N2的反应通道是次反应通道.     

铂二硫氰(2,2’)二联吡啶三种异构体吸收与发射光谱的理论研究

采用密度泛函与依时密度泛函理论(Density Functional Theory and Time-dependent Density Functional Theory, DFT/TDDFT)对铂二硫氰(2,2’)二联吡啶三种异构体[Pt(SCN)₂(bpy)]，[Pt(SCN)(NCS)(bpy)]和[Pt(NCS)₂(bpy)]的分子与电子结构，吸收与发射光谱进行了理论研究。研究不同异构体对此类化合物吸收与发射性质的影响。     

气相中环丁烯负离子与N2O反应机理的理论研究

采用B3LYP 和MP2两种计算方法,在6-31++G(d, p)的基组下,对气相中环丁烯负离子与N2O反应的微观机理进行了较为系统的计算研究。结果表明,该反应存在两条反应通道,每条反应通道又包含着三条反应路径,产物分别为乙烯基重氮甲基负离子与甲醛,同时也应能检测到少量的环丁烯酮负离子及N2等产物。其中,通道1是主反应通道,路径1为主反应路径,路径3是路径1、2的竞争反应。理论计算结果与实验预测基本一致。     

气相中环丁烯负离子与N2O反应机理的理论研究

采用MP2和B3LYP两种计算方法,在6-31 G(d,p)的基组下,对气相中环丁烯负离子与N2O反应的微观机理进行了较为系统的计算研究,并在相同基组下进一步用QCISD方法在MP2优化构型的基础上进行了单点能校正.结果表明,该反应存在两条反应通道,每条反应通道又包含着三条反应路径,产物分别为乙烯基重氮甲基负离子与甲醛,同时也应能检测到少量的环丁烯酮负离子及N2等产物.其中,通道1是主反应通道,路径1为主反应路径,路径3是路径1和2的竞争反应.理论计算结果与实验预测基本一致.     

四唑及其衍生物的理论研究 2: 氯代四唑负离子的从头算

用从头计算法, 取6-21G基组, 在MP2水平上, 计算研究了1H-和2H-四唑一氯取代物三种负离子的全优化几何构型和电子结构, 比较讨论了它们的芳香性和稳定性。发现三者均取平面构型, 其芳香性和稳定性次序为: 5-氯四唑负离子>2-氯四唑负离子>1-氯四唑负离子。预示了形成金属配合物时5-氯四唑作为配体的重要性和配位方式。     

密度泛函理论研究Gd（H2O）n^3＋（n=8，9）化合物的结构及相对稳定性

用密度泛函理论方法研究了气相和水溶液中Gd（H2O）n^3＋（n=8，9）化合物的结构和相对稳定性，其中水溶剂效应利用极化连续介质方法结合多种溶质空腔模型进行模拟．气相计算得到的化合物结构与实验观察结果一致．计算结果表明，在气相中9配位Gd（H2O）9^3＋比8配位Gd（H2O）8^3＋稳定，而在水溶液中稳定顺序刚好相反，这一结果不依赖于计算中采用的空腔模型种类，而且也与实验结果吻合．最后，通过采用各种空腔模型计算Gd^3＋的水合自由能，并与实验值比较，发现当化合物只包含第一层配位水分子时，UA0、UAHF及UAKS空腔模型最适合研究Gd^3＋在水溶液中的性质．     

四唑及其衍生物的理论研究 2: 氯代四唑负离子的从头算

用从头计算法, 取6-21G基组, 在MP2水平上, 计算研究了1H-和2H-四唑一氯取代物三种负离子的全优化几何构型和电子结构, 比较讨论了它们的芳香性和稳定性。发现三者均取平面构型, 其芳香性和稳定性次序为: 5-氯四唑负离子>2-氯四唑负离子>1-氯四唑负离子。预示了形成金属配合物时5-氯四唑作为配体的重要性和配位方式。     

具有生物活性的N-苯基-N'-(1,3-噻唑-2-基)-1,2,3-苯并噻二唑-7-甲脒的 晶体结构与理论计算

本文设计合成了一种新的植物激活剂先导化合物的衍生物N-苯基-N′-(1,3-噻唑-2-基)-1,2,3-苯并噻二唑-7-甲脒,并进行了元素分析、1HNMR、IR和MS测定。采用密度泛函理论在B3LYP/6-311 +G*水平上对该化合物进行了分子几何结构全优化和频率计算,计算表明,该分子结构中存在N－H···N分子内氢键,从而使分子更加稳定;计算结果还得到分子的红外与拉曼光谱以及不同溶剂相下的电子吸收光谱和不同温度下的热力学性质,为该类化合物构效关系的研究奠定了基础。     

Ag_2~-催化CO氧化反应机理的理论研究

用密度泛函理论B3LYP方法详细研究了Ag_2~-催化CO氧化反应的机理.计算结果表明,O2分子在Ag_2~-和Au_2~-上吸附能相差不大,而CO分子在Ag_2~-上吸附要比在Ag_2~-上弱得多.Ag_2~-催化CO氧化反应共有四条反应途径.最可能反应通道为CO插入Ag2O_2~-中的Ag—O键形成中间体[Ag—AgC(O—O)O]-,然后直接分解形成产物CO2和Ag2O-,或另一分子CO进攻中间体[Ag—AgC(O—O)O]-形成两分子产物CO2和Ag_2~-.在动力学上最难进行的反应通道为经历碳酸根双银中间体,需要克服约0.24eV的能垒.Ag_2~-催化CO氧化反应活性要高于Au_2~-.     

Theoretical Investigation on the Absorption and Emission Properties of the Three Isomers of Bis（thiocyanato）（2,2^1-bipyridyl）platinum（ll）

This paper presents a Density Functional or Time Dependent Density Functional （DFT/TDDFT） study of the molecular and electronic structures, optical absorption and emission spectra of three linkage isomers： bis（isothiocyanato-S）（2,2^1-bipyridyl） platinum（II） （[Pt（SCN）2（bpy）]）, （isothiocyanato-S）（thiocyanato-N）-（2,2^1-bipy- ridyl） platinum（II） （[Pt（SCN）（NCS）（bpy）]）, and bis（thiocyanato-N）（2,2^1）-bipyridyl）platinum（II） （[Pt（NCS）2（bpy）]）, in which different coordination ligands based on the N- and S-coordination of the thiocyanato ligands control the luminescent color. The electronic structures were studied using the B3LYP functional. Optimized geometries Were compared to the experimentally observed structures. TDDFT calculation was carded out to investigate the excited singlet and triplet states. Calculations have been performed both in vacuo and in solvents, using a polarized continuum model （PCM） to account for solute-solvent interactions. Inclusion of the solvent led to a significant energy change, and as a consequence, the computed spectrum calculated in the presence of the solvent was in good agree- ment with the experimental determinations. The first two absorptions were found to originate from mixed plati- num-SCN （or NSC） to bipyridyl-n＊ transitions rather than pure metal-to-ligand-charge-transfer （MLCT） transitions, whereas the higher-energy bands arose from intraligand n→π＊ transitions. The stretching frequencies of C≡N have been calculated both in the ground and excited states, which are relative to the charge transition during the excitation. In addition, different sizes of basis sets were also discussed in this paper.     

胞嘧啶…NO复合物结构与性质的理论研究

用密度泛函理论在BL3YP/6-311＋G*基组水平上对胞嘧啶…NO复合物体系进行了理论计算, 发现了6个能量极小的复合物. 其结合方式是NO的N或O原子与胞嘧啶的N—H键形成氢键, 最稳定的复合物的结合能为－9.65 kJ/mol. NO的N原子与胞嘧啶的结合具有更强的优势, N结合的复合物中NO的键长缩短, 而O结合的复合物中NO键长伸长. 同时, 对复合物的振动分析发现, 在胞嘧啶中所有的与NO结合的N—H键的伸缩频率下降, 而所有氨基的面内弯曲振动频率是增加的.     

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.     

Mycoepoxydiene核磁共振谱的理论研究

用密度泛涵理论(Density Functional Theory,DFT)的B3PW 91方法在6-311G**基组下优化了标题化合物mycoepoxyd iene的几何构型,同时计算了红外光谱.并用规范不变原子轨道(gauge independent atom ic orb ital)G IAO/B3PW 91以及G IAO/HF方法分别在6-311G**,6-311++G**等基组进行了核磁共振谱研究,计算结果与实验结果吻合很好.     

Theoretical Study of Ethanethiol Adsorption on HZSM-5 Zeolite

The density functional theory and the cluster model methods have been employed to investigate the interactions between ethanethiol and HZSM-5 zeolites. Molecular complexes formed by the adsorption of ethanethiol on silanol H3SiOH with two coordination forms, model Bronsted acid sites of zeolite cluster H3Si(OH)Al(OH)2SiH3 interaction with ethanethiol, aluminum species adsorbed ethanethiol have been comparatively studied. Full optimization and frequency analysis of all cluster models have been carried out using B3LYP hybrid method at 3-21G basis level for hydrogen atoms and 6-31G(d) basis set level for silicon, aluminum, oxygen, carbon, and sulfur atoms. The structures and energy changes of different coordination forms of H3Si(OH)Al(OH)2SiH3-ethanethiol, silanol-ethanethiol and Al(OH)3-ethanethiol have been studied. The calculated results showed the nature of interactions was van der Waals force as exhibited by not much change in geometric structures and properties. The preference order of ethanethiol adsorbed on HZSM-5 zeolite may be residual aluminum species, bridging hydroxyl groups and silanol OH groups from the adsorption heat. The adsorbed models of protonized ethanethiol on bridging hydroxyl OH groups and linear hydrogen bonded ethanethiol on bridging OH groups suggested in literature might not exist as revealed by this theoretical calculation. Possible adsorption models were obtained for the first time.     

Study of conformational and optical rotation for the alaninamide

Six stationary points of alaninamide have been located on the potential surface energy (PES) at the B3LYP/6‐311++G(2d,2p) level of theory both in the gas phase and in aqueous solution. In the aqueous solution, to take the water solvent effect into account, the polarizable continuum model (PCM) method has been used. Accurate geometric structures and their relative stabilities have been investigated. The results show that the intramolecular hydrogen bond plays a very important role in stabilizing the global minimum of the alaninamide. Moreover, the consistent result in relative energy using high‐level computations, including the MP2 and MP3 methods with the same basis set [6‐311++G(2d,2p)], indicates that the B3LYP/6‐311++G(d,p) level may be applied to the analogue system. More importantly, the optical rotation of the optimized conformers (both in the gas phase and in aqueous solution) of alaninamide have been calculated using the density functional theory (DFT) and Hartree–Fock (HF) method at various basis sets (6‐31+G*, 6‐311++G(d,p), 6‐311++G(2d,2p) and aug‐cc‐pvdz). The results show that the selection of the computation method and the basis set in calculation has great influence on the results of the optical rotations. The reliability of the HF method is less than that of DFT, and selecting the basis set of 6‐311++G(2d,2p) and aug‐cc‐pvDZ produces relative reliable results. Analysis of the computational results of the structure parameters and the optical rotations yields the conclusion that just the helixes in molecules caused the chiral molecules to be optical active. The Boltzmann equilibrium distributions for the six conformers (both in the gas phase and in the aqueous solution) are also carried out. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

肝醇脱氢酶催化乙醇氧化生成乙醛反应机理的理论研究

 采用 B3LYP 方法研究了肝醇脱氢酶催化烟酰胺腺嘌呤二核苷酸氧化乙醇生成乙醛的反应机理. 优化得到了反应物、过渡态、中间体和产物的几何构型, 并计算了在蛋白质或水环境下有或没有肝醇脱氢酶时的反应势垒. 结果表明, 没有催化剂时, 乙醇负离子的形成及其被氧化生成乙醛的反应势垒都很高, 常温下反应难以进行; 当肝醇脱氢酶存在时, 乙醇负离子可以与肝醇脱氢酶中的 Zn2+配位形成络合物, 从而极大地降低了这两步的反应势垒, 使得反应在常温下容易进行.