Crystal Structure,Photoluminescence and Theoretical Studies of Diethyl 4,5-di(thienyl)-3,6-bis(trimethylsilyl)phthalate

The crystal structure of the title compound, diethyl 4,5-di（thienyl）-3,6-bis（trime- thylsilyl）phthalate （C26H3404S2Si2, Mr = 530.83）, has been determined by single-crystal X-ray diffraction. The crystal belongs to the orthorhombic system, space group Pccn with a = 43.008（5）, b = 10.9000（12）, c = 11.9357（14） A, V= 5595.3（11） A3, Z = 8, F（000） = 2256, Dc= 1.260 mg/m3, p = 0.305 mm-1, T = 113（2） K, S = 1.090, R = 0.0413 and wR = 0.0969 for 5952 observed reflections with 1 〉 2o（/）. The benzene ring system is planar and makes dihedral angles of 63.7（2） and 72.5（4） with the two thienyl rings A （C（23）-C（26）, S（2）） and B （C（19）-C（22）, S（1））, respectively. The UV-vis absorption and fluorescence of the title compound were discussed. The molecular structure of the title compound has been optimized using DFT method at the B3LYP/6-31G（d） level. The computational results showed that the optimized geometer parameters are consistent well with the experiment data. The vertical ionization potential, vertical electron affinity and frontier orbitals were also discussed.

DFT Study on the Structural, Electronic, and Spectroscopic Properties of the Highest Epoxygenated Fullerene C_(36)O_(18)

Theoretical investigation on the highest epoxygenated fullerene C36018 formed from the initial C36 fullerene with D6h symmetry has been performed at the B3LYP/6-31G（d） level. Their equilibrium structures, thermal stabilities, electronic structures, vertical ionization potentials, vertical electron affinities, vibrational frequencies and 13C NMR chemical shifts have been studied. The calculation results showed that C36O18 isomers have higher LUMO-HOMO energy gaps than the fullerene C36 and should be more stable. Compared with C36, it is less possible for C36O18 to accept or donate electrons from reduced VEAs and enhanced VIPs. It has been found that C36O18 isomers are not aromatic at all or antiaromatic on analyzing the NICS values. The present study will encourage further theoretical and experimental analyses of this system in future.

N-(3-苯丙基)哌嗪类σ_1受体配体的3D-QSAR研究

采用比较分子力场(CoMFA)分析法和比较分子相似性指数(CoMSIA)分析法,对34个N-(3-苯丙基)哌嗪类σ1受体配体进行三维定量构效关系(3D-QSAR)研究,建立了具有较强预测能力的3D-QSAR模型.并利用Gaussian 03程序,采用B3LYP/6-31G(d)方法,探索了化合物分子的前线轨道与分子结构的关系.新设计的化合物的体外受体结合分析结果与该模型预测的数据一致,此结果为进一步研究σ1受体-配体的相互作用模型以及设计高亲和力的哌嗪类σ1受体配体提供了参考.

DFT Studies on Thermal Stabilities,Electronic Structures,and ^(13)C Chemical Shifts of C_(24)O_2 Based on Fullerene C_(24)(D_6)

Quantum chemical calculations on some possible equilibrium geometries of C24O2 isomers derived from C24 （D6） and C24O have been performed using density functional theory （DFT） method. The geometric and electronic structures as well as the relative energies and thermal stabilities of various C24O2 isomers at the ground state have been calculated at the B3LYP/6-31G（d） level of theory. And the 1,4,2,5-C24O2 isomer was found to be the most stable geometry where two oxygen atoms were added to the longest carbon-carbon bonds in the same pentagon from a thermodynamic point of view. Based on the optimized neutral geometries, the vertical ionization potential and vertical electron affinity have been obtained. Meanwhile, the vibrational frequencies, IR spectrum, and 13C chemical shifts of various C24O2 isomers have been calculated and analyzed.

Synthesis,Crystal Structure and Spectroscopic Properties of 1,2-Benzothiazine Derivatives:An Experimental and DFT Study

1,2-Benzothiazine derivatives methyl 3-methoxy-4-oxo-3,4-dihydro-2H-benzo[e] [1,2]thiazine-3-carboxylate 1,1-dioxide（1） and methyl 2-ethyl-3-hydroxy-4-oxo-3,4-dihydro-2Hbenzo[e][1,2]thiazine-3-carboxylate 1,1-dioxide（2） were synthesized, and characterized by spectroscopic techniques; 1H-NMR and infrared（IR） spectroscopy. Crystals of 1 and 2 were grown by slow evaporation of methanol and ethyl acetate, respectively and their crystal structures were investigated by single-crystal X-ray diffraction analysis. Geometric properties were calculated by the B3 LYP method of density functional theory（DFT） at the 6-31G＋（d） basis set to compare with the experimental data. Simulated properties were found in strong agreement with the experimental ones. Intermolecular forces have also been modeled in order to investigate the strength of packing and strong hydrogen bonding was observed in both compounds 1 and 2. Electronic properties such as Ionization Potential（IP）, Electron Affinities（EA） and coefficients of the highest occupied molecular orbital（HOMO） and the lowest unoccupied molecular orbital（LUMO） of com- pounds 1 and 2 were simulated for the first time.

Ab initio Study on Structures and Isomerization of Magnesium Fluorosilylenoid H2SiFMgF

The structures and isomerization of magnesium fluorosilylenoid H2SiFMgF were investigated by ab initio molecular orbital theory. Four equilibrium structures and three isomeric transition states were located and fully optimized at the B3LYP/6-31G（d,p） and G3MP2B3 levels, respectively. Based on the B3LYP/6- 31G（d,p） optimized geometries, harmonic frequencies of various structures were obtained and 29Si chemical shifts were calculated. The solvent effects were investigated by means of the polarizable continuum model using THF as a solvent at B3LYP/6-31G（d,p） level. Isomerization paths for isomers were confirmed by intrinsic reaction coordinate calculations. The calculated results show that tetrahedral structure has the lowest energy and is the most stable; tetrahedral, three-membered ring, and p-complex structures are suggested to be the experimentally detectable ones; and a-complex structure has the highest energy and will not exist.

2D-QSAR Studies on Phenoxybenzoic Acid Derivatives: A Novel Class of 5a-Reductase Inhibitors

The quantitative structure-activity relationship （QSAR） of 14 phenoxybenzoic acid derivatives was studied by ab initio method at the HF/6-31G level using Guassian03 software. The optimized structures together with some characteristic and electric parameters of the title compounds were obtained; some stereo-parameters were calculated by HyperChem software. Stepwise multiple regression and principal component regression methods are adopted to establish multi-parametric models between biological activity and parameters. The results indicated that the lager Ehomo, M, V and LogP, the smaller Etumo and S, and the higher biological activity. A theoretical direction was provided to synthesize some compounds with high activity.

Studies on the Structures and Spectra of Benzothiophene Oligomers

Theoretical studies on a series of oligobenzothiophenes were carded out with the AM 1 and DFT methods. Based on B3LYP/6-31G（D） optimized geometries, the electronic spectra, IR spectra and NMR spectra of the oligomers were calculated by INDO/CIS, AM1 and B3LYP/6-31G（D） methods, respectively. The energy gaps decrease, and the absorption in elec- tronic spectra exhibits a red-shift as polymerization increases. The IR frequencies are little affected by the polymerization and substituents. The ^13C chemical shifts are changed to be upfield since the electron-donating groups increase the electron density of carbon atoms but remain unchanged with the increase of polymerization.

Molecular Dipole Moment Computed with Ab Initio MKS Charges

Molecular dipole moments computed at the levels of HF/STO-3G, HF/6-31G(d, p), HF/6-311+G(2d, 2p), MP2/6-31G(d, p) and MP2/6-311+G(2d, 2p) have been investigated. HF/6-311+G(2d, 2p) was found to be the relatively good choice to compute MKS charges for reproducing the experimental values of molecular dipole moments. Root mean square deviation of computed dipole moments for 21 small polar molecules is about 0.1969 D.

DFT Study of the Solvent Effects on the Structure, UV-Vis Spectra and the Antioxidant Activity of Caffeic Acid Phenethyl Ester and Some of Its Derivatives

In this study, the antioxidative （3-methyl-2-butenyl caffeate）, BC efficiency of CAPE （caffeic acid phenethyl ester） and four of its derivatives （MBC （benzoic caffeate）, P3HC （phenethyl-3-hydroxy-cinnamate） and P4HC （phenethyl-4-hydroxy-cinnamate）） are compared in vacuum and in seven solvents. It turned out that the AA （antioxidant activity） in increasing order was P3HC 〈 P4HC 〈 CAPE 〈 MBC. Effects of solvents on the structure and the antioxidant activity of P3HC, P4HC, BC, MBC and CAPE, were studied at 133LYP/6-31G （d, p） then B3LYP/6-3 I＋G （d, p） level of theory using the conductor polarized continuum model methods. Thermodynamically, the authors showed that solvent effects on bond dissociation enthalpy are very weak （within 25 kJ/mol）, but sufficient to influence hydrogen bonds, O-H bond lengths and showed the preferential sites of hydrogen atom cleavage. In addition, solvent notably influences and changes the nature of the scavenging process of ROS （reactive oxygen species）, favouring by this way the HHAT （homolytic hydrogen atom transfer） in non polar solvents, the SPLET （sequential proton loss electron transfer） in polar solvents. Moreover, in chloroform and for the five molecules studied the SET-PT （sequential electron transfer proton transfer） mechanism is preferred compared to the HHAT, because in this solvent the IP is lower than the BDE. TD-DFT calculations revealed that solvent induce a bathochromic effect （red-shift of the wavelengths） coupled to hyperchromic or hypochromic effects.

一种3,4-二氢嘧啶-2-酮合成及性质的理论研究

对5-甲氧羰基-4,6-二甲基-3,4-二氢嘧啶-2(1H)-酮的合成过程进行了理论计算研究。在HF/6-31G(d)和B3LYP/6-31G(d)水平优化各物种的构型,得到了较为精确的结构和能量。分析了某些分子的前线轨道HOMO和LUMO,讨论了它们的反应活性中心及可能的反应机理。计算了各反应的热力学函数熵变、焓变以及吉布斯自由能的变化,对产物进行了频率分析。

高能炸药CL-20分子结构的理论模拟方法探究

采用量子化学方法,在HF/6-31G,DFT-B3LYP/6-31G和MP2/6-31G基组水平下全优化ε-CL-20分子的结构,对ε-CL-20的结构(包括键长、键角、二面角)分析得出B3LYP/6-31G水平下的理论值更接近实验值。采用B3LYP方法,不同基组3-21G,6-31G,6-31++G,6-311++G,6-31++G**水平下全优化ε-CL-20分子,基组选取基本不影响计算结果,表明B3LYP/6-31G基组水平下的计算结果能够满足ε-CL-20的结构优化要求。采用HF、B3LYP、MP2方法不同基组计算ε-CL-20原子的净电荷分布,结果表明充分考虑电子相关性的B3LYP方法计算结果最合理。

2,4-苯基咪唑方酸衍生物非线性光学性质的从头算研究

用HF/6-31G方法优化2,4—苯基咪唑方酸衍生物几何构型,在获得稳定构型基础上,用CPHF方法研究了该系列衍生物的二阶非线性光学系数vβec,并对βvec影响因素进行探讨.计算结果表明,此类体系具有较大的βvec,其非线性光学性质与其分子结构有着密切的关系,是一类具有很好应用前景的非线性光学材料.

DFT Study on the Heterofullerene C_(48)O_(12) with Rare T_h Symmetry

The molecule with Th symmetry is rare. A novel C60-1ike molecule C48O12 with rare Th symmetry has been studied at the B3LYP/6-31G（d） level of theory. Its structural, electronic, vibrational, NMR, and thermodynamic properties have been calculated at the B3LYP/6-31G（d） level of theory. Vibrational modes have been assigned according to their symmetry. There are 73 independent vibrational modes： 22 IR-active modes with Tu symmetry and 37 Raman-active modes with Ag, Eg and Tg symmetry, respectively. The heat of formation has been calculated by using isodesmic reactions, 765.7 kJ mol-1. According to the heat of formation and the HOMO-LUMO gap, C48O12 with rare Th symmetry is more stable than C6o.

Intelligence Way from Eco-friendly Synthesis Strategy of New Heterocyclic Pyrazolic Carboxylic a-Amino Esters

The a-amino acid derivatives constitute a class of compounds of particular medicinal and synthetic attention and considerable interest has been devoted to their synthesis in recent years.In the present work,we develop the computational study of the synthesis reaction of new pyrazolyl a-amino esters derivatives using the Gaussian 09based on the DET/B3LYP density functional theorv method,with the base 6-31G(d.p)to ensure the possibility of carrying out these reactions within the laboratory of synthesis.Indeed,this research has encouraged us to establish an economical synthesis strategy of these products in overall vields of 73.5%to 87%to have access to new active biomolecule through the O-alkvlation reaction between methyl a-azidoglycinate N-benzoylated and primary pyrazole alcohols(3,5-dimethyl-1 H-pyrazol-1-yl)methanol,(1H-pyrazol-1-yl)methanol and(3-ethoxy-5-methyl-1H-pyrazol-1yl)methanoll under different operating conditions.The structure of the prepared heterocyclic systems was characterized by conventional spectroscopic techniques,like H NMR.I3℃NMR,and MS.The results revealed that the experimental study is in good correlation with the computational one.

Heterofullerenes C_(48)N_(12) and C_(48)B_(12) with Rare T_h Symmetry: a DFT Study

The molecule with Th symmetry is rare. Two C60-1ike molecules C48N12 and C48B12 with rare Th symmetry have been reported here, which is an approach to seek for the molecule with rare Th symmetry. Their structural, electronic, vibrational, NMR, and thermodynamic properties have been calculated at the B3LYP/6-31G（d） level of theory. Vibrational modes have been assigned according to their symmetry. They all have 73 independent vibrational modes： 22 IR-active modes with Tu symmetry and 37 Raman-active modes with Ag, Eg and Tg symmetry, respectively. The heats of formation have been calculated using isodesmic reactions, and the values of C48N12 and C48B12 are 3812.0 and 3423.8 kJ mo1-1, respectively. According to the estimated band gaps for their fcc solid, they are all semiconducting materials, like C60, especially C48B12-based fcc solid.

Computational evaluation concerning the deviation of the atoms in 1-and 4-postions on the six-member ring and the effects on ^(1)HNMR chemical shift

Density functional theory(DFT)calculations were carried out on some cyclohexane derivatives to investigate the deviation atoms on the 1-and 4-positions of chair plane.The deviations of chair plane of two position in the cyclohexane derivatives were calculated at the B3LYP/6–31++G(d,p)level.Furthermore,we investigated the correlation between deviations of two positions from chair plane on the chemical shift hydrogen atoms on the 4-position.

基于不同功能的苯并噻二唑为受体单元和低聚噻吩为给体单元的D-A-D-A-D型有机小分子光伏材料的理论计算研究

设计了四个以四联噻吩为中心给电子单元,联二噻吩为末端给电子单元,不同功能的苯并噻二唑(DOBT,BT,FBT和FFBT)为吸电子单元的有机小分子太阳能电池给体材料,分别称为DOBT-8T,BT-8T,FBT-8T和FFBT-8T.在B3LYP/6-31G(d)基组的水平上利用密度泛函和含时密度泛函理论对四个小分子进行了理论计算.详细分析了吸电子单元苯并噻二唑的结构修饰对小分子给体材料性能的影响.理论计算结果显示,不同功能的苯并噻二唑单元的引入对小分子给体材料的几何结构、禁带宽度、HOMO与LUMO能级、轨道电子密度分配、能量驱动力、开路电压和分子中的原子电荷(NPA)都有重要调节作用.相比于其它分子,以FBT为吸电子单元的FBT-8T,显示了最窄的带隙和较低的HOMO能级值.以FFBT为吸电子单元的FFBT-8T,获得了最低的HOMO能级和较为合适的禁带宽度.利用Scharber模型分别计算了基于小分子/PC61BM为活性层的光伏器件的能量转换效率(PCE),基于FBT-8T/PC61BM和FFBT-8T/PC61BM的光伏器件,将获得的PCE分别高达约4.7%和5.2%.在以上研究的基础上,推测FBT-8T和FFBT-8T是潜在的高性能的有机小分子体异质结光伏给体材料.

二苯醚衍生物的第一超极化率的理论研究

研究的二苯醚衍生物是氧桥Λ型分子,它含有两个D-π-A轴,属于典型的二维电荷转移体系,且它们的βxxx/βyxx<1.我们利用HF/6-31G(d)//TDHF/6-31G(d)方法得到的二苯醚衍生物的第一超额级化率β计算值与可利用的实验值之间存在近似的线性关系.优化得到的此类分子的结构不对称,通过自然键轨道(NBO)分析发现,取代基和桥原子氧对分子的非线性光学性质有一定的影响.需要指出的是,这类分子的βtot在10-29esu左右,但是这类分子的透光性和热稳定性较好.

C_4O_7团簇的密度泛函理论研究

利用理论计算方法设计高能量密度材料(HEDM)分子是目前材料科学领域的研究热点之一。本文利用密度泛函理论(DFT)在B3LYP/6-31G(d)水平上对C4O7团簇异构体几何结构进行优化,找到了C4O7团簇的27种稳定结构。以一个C4O7团簇分子分解为3个CO2和一个CO计算,C4O7团簇分子的解离能在7.312×103～2.958×103kJ/kg之间,放出的能量较多,是用做高能量密度材料的潜在资源。