2,3,7,8-四氯苯并二英分子结构与热力学性质的理论研究

用密度泛函理论(DFT)和从头算(ab initio)方法,在B3LYP/6-31G、 B3LYP/6-31G*、 B3LYP/6-311G*和MP2/6-31G*水平上全优化计算了2,3,7,8-四氯苯并二英(2,3,7,8-TCDD)的几何构型、电子结构和振动频率,并用校正后的频率计算了298～1500 K的标准热力学函数,同时用半经验的PM3 SCF-MO进行了同样的计算,计算结果与实验值及文献值较好地吻合.     

黄酮类化合物的密度泛函理论研究

在混合密度泛函B3LYP理论下,用6-31G*基函数研究了几种典型黄酮类化合物分子的几何结构、电子结构和分子的静电势,讨论了电子结构和分子活性部位的关系.     

电场作用下分子导线的理论研究

摘要利用从头计算法分别在HF/6-31G, HF/6-31G*, HF/6-31G**, HF/6-31+G, HF/6-31++G, HF/6-31+G*, HF/6-31+G**, HF/D95+*, B3LYP/6-31G*和B3LYP/6-31+G*水平上计算了5个单体的聚乙炔分子导线, 从几何构型、 SCF能量和分子轨道能级三个方面讨论了外电场对分子导线的影响, 给出了聚乙炔分子导线性质与外电场变化的定量关系.     

硝酸甲与硝酸乙酯的结构、振动频率和热力学性质的密度函数 理论(DFT)研究

用密度函数理论(DFT)的BLYP和B3LYP方法,取6-31G,6-31G^*,6-31G^*^*,6-311G,6-311G^*和6-311G^*^*六种基组,对硝酸甲酯和硝酸乙酯的几何构型和红外振动频率进行了计算研究.结果表明,B3LYP方法在采用极化基组(6-31G^*,6-31G^*^*,6-311G^*和6-311G^*^*)时计算得到的结果均较好,适用于硝酸酯类化合物的研究.而BLYP方法无论采用何种基组均不适用;运用校正后的B3LYP/6-31G^*频率(校正因子0.975)计算得到的热力学性质(C^o~p,H^o和S^o)与实验结果较吻合。     

硝酸甲与硝酸乙酯的结构、振动频率和热力学性质的密度函数 理论(DFT)研究

用密度函数理论(DFT)的BLYP和B3LYP方法,取6-31G,6-31G^*,6-31G^*^*,6-311G,6-311G^*和6-311G^*^*六种基组,对硝酸甲酯和硝酸乙酯的几何构型和红外振动频率进行了计算研究.结果表明,B3LYP方法在采用极化基组(6-31G^*,6-31G^*^*,6-311G^*和6-311G^*^*)时计算得到的结果均较好,适用于硝酸酯类化合物的研究.而BLYP方法无论采用何种基组均不适用;运用校正后的B3LYP/6-31G^*频率(校正因子0.975)计算得到的热力学性质(C^o~p,H^o和S^o)与实验结果较吻合。     

具有D~6~h对称性的C~3~6及其衍生物电子结构的密度泛函研究

运用密度泛函方法,比较不同水平的基组(HF/6-311+G^*;B3LYP/6-31G^*;B3LYP/6-311+G^*)对具有D~6~h对称性的C~3~6分子进行构型优化的结果,并分析其几何结构、电子结构、稳定性等性质;采用基组B3LYP/6-31G^*对H@C~3~6,Li@C~3~6,Na@C~3~6,K@C~3~6分子进行构型全优化,分析了不同内嵌原子对其几何结构、电子结构、稳定性等性质的影响;首次在B3LYP/6-311+G^*水平上,对C~3~6H~6,C~3~6H~1~2,X@C~3~6(X=H,Li,Na,K)几何构型及电子结构进行研究并得到其稳定性规律。     

苯和苯胺类硝基衍生物热解机理和撞击感度的理论研究

在DFT-B3LYP/6-31G*水平获得苯和苯胺类硝基衍生物的全优化分子几何和电子结构.通过非限制性(U)B3LYP/6-31G*计算求得标题物各化学键离解能(BDE).用UHF-PM3 MO方法求得引发键C-NO2键均裂反应的活化能(Ea).以静态指标(键集居数、前线轨道能级差和硝基上净电荷)和动态理论指标(BDE和Ea)阐明了热解引发机理,关联了实验撞击感度.运用SPSS程序关联静态和动态理论指标,表明它们均可以用作预示标题物的热解引发机理和撞击感度.     

藏药五脉绿绒蒿碱结构和性质的理论研究

五脉绿绒蒿碱是一种从藏药五脉绿绒蒿中提取并已确认结构的新的生物碱. 采用密度泛函理论(DFT)和从头算(ab initio)方法, 在HF/6-31G*和B3LYP/6-31G*水平下全优化计算了该化合物的分子几何构型和电子结构; 依据Onsager自恰反应场(SCRF)模型考察了五脉绿绒蒿碱在氯仿、丙酮、二甲亚砜及水等溶剂中的溶剂化作用; 基于气相优化结构进行了B3LYP/6-31G*振动分析与红外光谱计算, 进一步按照统计力学原理求得了298～1500 K温度范围内该化合物的热力学性质. 此外, 还讨论了五脉绿绒蒿碱的分子结构与药效的关系.     

一种天然产物Wangzaozin A的细胞毒活性

从总序香茶菜Isodon racemosa (Hemsl) Hara植物中分离得到一个对人类肿瘤细胞Bel-7402和HD-8910具有毒活性的对映-贝壳衫烷型二萜Wangzaozin A化合物(1). 应用密度泛函理论(DFT)B3LYP方法, 对该分子的几何构型进行优化, 结果表明用B3LYP/6-31G(d)优化的几何参数与它的X射线衍射结构参数基本一致. 在优化的几何构型基础上, 采用规范不变原子轨道(GIAO)法, 在B3LYP理论水平分别用6-31G(d), 6-31G(d,p), 6-31+G(d,p)和6-31++G(d,p)基组进行核磁共振(NMR)化学位移值计算, 预测的1H和13CNMR化学位移值与实验值吻合; 统计误差分析表明, 用B3LYP/6-31G(d)优化的分子构型接近实际的分子构型. 因此, DFT方法适用这一类型化合物的构型和NMR参数进行预测. 在几何优化的基础上, 在B3LYP/6-31G(d)水平上, 对Wangzaozin A分子的静电位(MEP)进行理论计算. MEP三维图表明, 在Wangzaozin A分子中α-亚甲基环戊酮的羰基和羟基附近出现富电子区域(负电位), 起着供电子作用, 与受体的正电子区域结合. 这些结果从理论上支持了α-亚甲基环戊酮结构是一种抗肿瘤活性中心的看法.     

Al6(OH)18(H2O)6的结构及成键方位的从头算及密度泛函分析Ⅱ

用RHF法6-31G、6-31G*、6-31G**水平的量子化学从头算及RB3LYP/6-31G、B3LYP/6-31G*,B3LYP/6-31G**水平的密度泛函方法,采用SCRF=Dipole溶剂模型,计算了三水铝石有利生长基元最优结构Al6(OH)18(H2O)6的总能量、布居数、原子静电荷等.计算结果表明,桥联OH基团更易成键,Al6(OH)18(H2O)6较为有利的成键方位是桥联OH基团方位.     

Theoretical Study on Hydrogen Interaction between 5-Fluorouracil and Glycine

The geometries,electronic structure,IR spectrum and other properties of hydrogen interaction between 5-fluorouracil and glycine were studied at the B3LYP/6-31+G* level.Single point energy calculations were executed at the B3LYP/6-311++G** and B3LYP/aug-cc-pvdz levels,and natural bond orbital (NBO) analysis was carried out at the B3LYP/6-31+G* level.Finally,the hydrogen bonds were discussed via AIM electronic density topology analysis.     

The ene reactions of nitroso compounds involve polarized diradical intermediates

The ene reactions of nitroso compounds were studied with B3LYP/6-31G* geometry optimizations and energy calculations, along with single point energy evaluations using CASPT2/6-31G** and UCCSD(T)/6-311+G* methods. Reactions of HNO with propene and of MeNO and p-NO2C6H4NO with propene or substituted alkenes were also studied. The reaction mechanism is stepwise and involves a polarized diradical intermediate. The electronic structure of this intermediate is between that of a closed shell polar species and that of a pure diradical, and it is stabilized by polar solvents. A weak C-N bonding interaction combined with a CH-O hydrogen bond leads to heightened barriers to rotation about formally single bonds compared to conventional diradicals. Consequently, rotation is slower than hydrogen abstraction and cyclization to form an aziridine N-oxide. This aziridine N-oxide does not lead to ene products without subsequent ring opening but provides a mechanism for the RNO moiety to translate from one end of the alkene to the other. B3LYP calculations are also able to reproduce kinetic isotope effects and regioselectivity.     

2-丁基-四氢噻吩亚砜~(13)C-NMR的理论研究

在RHF/6-31G和B3LYP/6-31G水平上对顺式(Cis-)与反式(Trans-)2-丁基-四氢噻吩亚砜(BTHTO)进行几何优化,应用规范不变原子轨道法(GIAO)在6-31G、6-31+G、6-31++G和6-31+G(2d,p)水平上计算了Cis-和Trans-BTHTO的13C-NMR,对13C-NMR谱进行了归属。结果表明,BTHTO噻吩五元环的稳定构象呈半椅式,Cis-和Trans-BTHTO中与硫原子直接碳原子13C-NMR的显著差异主要是由于空间构型不同引起分子的静电势场对相应碳原子的屏蔽作用不同所致。     

Fluorinated derivatives of <Emphasis Type="Italic">mer</Emphasis>-Alq3: energy decomposition analysis,optical properties,and charge transfer study

Equilibrium geometry configurations of the mono-fluorinated derivatives of the meridianal isomer of tris(8-hydroxyquinolinato)aluminum (mer-Alq3) are calculated at the B3LYP/6-31G* level. The lowest singlet excited states (S ₁) have been optimized by the singles configuration interaction (CIS/6-31G*) approach. The absorption and emission spectra were evaluated at the TD-PBE0/6-31G* level. A significant blue shift was predicted for tris(4-fluoro-8-hydroxyquinolinato)aluminum derivative (4FAlq3) while a significant red shift was observed for tris(5-fluoro-8-hydroxyquinolinato)aluminum (5FAlq3). Energy decomposition analysis has been performed at the B3LYP/DZP level. On the basis of energy decomposition analysis, we have explained the distribution pattern for frontier molecular orbitals. We have found that no contribution of improvement for intrinsic charge mobility for the mono-fluorine substituted mer-Alq3.     

1. 5-环辛二烯-3, 7-二炔(C~8H~4)结构和光谱性质的理论研究

采用量子化学从头算方法研究了1,5-环辛二烯-3,7-二炔(C~8H~4)的结构和光谱性质,根据等键反应分析和自然键轨道方法研究了它的稳定性、成键情况和共轭性。结果表明1,5-环辛二烯-3,7-二炔(C~8H~4)分子为平面刚性结构,可能稳定存在。分子中C≡C键与C=C键存在一定程度的共轭,可能具有芳香性。     

Experimental and density functional theory and ab initio Hartree-Fock study on the vibrational spectra of 2-(4-fluorobenzylideneamino)-3-mercaptopropanoic acid

2-(4-Fluorobenzylideneamino)-3-mercaptopropanoic acid (4-FC) was synthesized through the reaction of 4-fluorobenzaldehyde and l-cysteine in refluxing EtOH. Its structure was verified by (1)H NMR, FT-IR and Raman. The ground-state geometries were optimized at B3LYP/6-31G**, B3LYP/6-31G*, HF/6-31G** and HF/6-31G* levels without symmetry constrains, respectively. The vibrational wavenumbers of 4-FC were calculated at same level. The scaled theoretical spectra using B3LYP methods, which are in a good agreement with the experimental ones, are superior to those using HF methods.