6-羟基-5,12-萘并萘醌及其CH3, C6H5取代衍生物的光致变色理论研究

用密度泛函理论的B3LYP/6-31G方法和从头算的CIS/6-31G方法分别研究了6-羟基-5,12-萘并萘醌及其CH₃, C₆H₅取代衍生物基态和激发态的异构化反应，.对反应势能面的研究发现, 在光异构化反应中化合物M21和M21、M31的基态和激发态虽然都可以构成四能级反应过程, 但由于M21异构化过程的活化能较高, 使其所构成的四能级反应难以进行, 这就从理论上解释了迁移基团为甲基的M21变色性能低于迁移基团为苯基的M31的实验结果. 此外用TD/B3LYP方法在溶剂存在下计算了上述化合物的紫外吸收光谱和荧光发射光谱, 计算所得到的光谱数据与实验值基本一致, 与光异构化反应的光激发条件相符合.     

丙交酯合成过程的理论及实验研究

采用密度泛函方法研究了丙交酯的合成过程, 优化了合成过程中可能出现的化合物的几何构型, 分析了各化合物的振动频率和偶极矩. 在B3LYP/6-31G*和B3LYP/6-311＋G*水平上进行了各化合物的能量计算, 得到了所设计的各模型反应的焓变和吉布斯自由能变. 结果表明, 所选择的各模型反应为吸热反应且近似可逆, 水的控制对丙交酯的形成很重要. 根据量化计算结果与丙交酯合成实验中不同阶段反应体系红外谱图的变化, 提出了丙交酯合成的可能机理.     

Photochromic reactions of 6-hydroxy-5,12-naphthacenequinone and its derivatives bearing methyl or phenyl groups

Photoisomerizations of 6-hydroxy-5,12-naphthacenequinone and its derivatives bearing methyl and phenyl group were theoretically investigated with density functional theory and ab initio CIS method at the B3LYP 6-31G basis set, respectively. The obtained potential energy curves revealed that a four-state cycle existed in the ground and excited states. It was also found that the activation energy for the methyl transfer was higher compared to that for the phenyl transfer, and this was consistent with the experimental results that the photoisomerization of the phenyl substituted derivative was more rapid than that of the methyl substituted derivatives. Further hybrid time-dependent density functional theory (TD-DFT) was used to investigate the absorption and fluorescence spectra of these compounds under solvent effect condition. The calculated values were in agreement with the experimental results and the excitation condition of photochromic reactions. __________ Translated from Acta Chimica Sinica, 2007, 65(24): 2821–2826     

笼状碳氢化合物五环[5.4.0.02，6.03，10.05，9]十一烷的密度泛函理论研究

运用密度泛函理论,在B3LYP/6-31G**水平上,对典型高能量密度笼状化合物五环[5.4.0.02,6.03,10.05,9]十一烷（PCU）进行了理论计算。基于上述水平全优化分子结构的键长、键角及二面角求得PCU分子的张力能;用Monte-Carlo方法得到化合物的理论密度;由简谐振动分析求得IR谱,计算结果与实验良好相符;基于振动分析,由统计热力学求得PCU的热力学性质;采用GIAO方法求得PCU的13C-NMR和1H-NMR谱的化学位移,计算结果与实验结果的线性相关性均大于0.99,计算结果可辅助解析PCU的NMR谱。     

First-principles study of the phonon vibrational spectra and thermal properties of hexagonal MoS2

The phonon spectra and thermal properties of the hexagonal MoS₂ are investigated by using first-principles calculations within the density functional theory (DFT). Finite displacement method is used to calculate the phonon vibrational spectra and phonon density of states. The vibrational modes at the Gamma point are analyzed by using group theory. The temperature and pressure dependence of its thermal quantities such as the thermal expansion, the heat capacity at constant volume, the Gibbs energy and entropy are obtained based on the quasi-harmonic approximation (QHA). Our results show that both the thermal expansion coefficient α and the heat capacity C_V increase with T³ at low temperatures and gradually turn almost linear as the temperature increases. It is found that the entropy is sensitive to the temperature while the Gibbs free energy is more sensitive to the pressure change.     

Density functional theory study of vibrational spectra and assignment of fundamental vibrational modes of 1-methyl-4-piperidone

The FT-IR and FT-Raman spectra of 1-methyl-4-piperidone was recorded and the observed bands were interpreted with the aid of normal coordinate analysis following a full structure optimization and force field calculation based on the density functional theory (DFT) using the standard B3LYP/6-311G** method and basis set combinations. A very good agreement obtained between the simulated and experimental spectra was established and unambiguous vibrational assignments of various modes were proposed based on the results of potential energy distribution (PED) calculations.     

Structural and solvent effects on the spectroscopic properties of 1, 8‐naphthalimide derivatives: A density functional study

The molecular structures of 1, 8‐naphthalimide derivatives were investigated at density functional theory level within framework of PBE1PBE/6‐31G*. The vertical ionization potential and their delocalization energy of the X‐ray solid structure and gas‐phase optimized structure were explored. The configuration difference between them was attributed to the π‐π interaction of the solid effect, which has negligible effect on their absorption spectra. Solid effect also weakens the intramolecular interaction. Their absorption and luminescent spectra in gas and solvent phase were calculated by time‐dependent density functional theory (TDDFT) and conductor polarizable continuum models (CPCM)‐TDDFT approaches. Obvious red shifts from the solvent effect were found. Substituents on the imides will not improve their spectra properties a lot, whereas substituents on the naphthalene of naphthalimide would modify their properties to emit different spectra. Systematical deviation of vertical excitation energy from absorption and emission spectra, obtained by CPCM‐PBEPBE/6‐31G* and CIS‐CPCM‐PBEPBE/6‐31G* models, were about 0.05 eV and 0.02 eV compared with the experimental values. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

对苯二甲酸二苯酯类液晶化合物光谱和二阶非线性光学性质的理论研究

在密度泛函理论B3LYP/6-31G*水平上计算对苯二甲酸二苯酯类液晶化合物分子的几何结构、振动光谱、电子光谱和非线性光学性质, 分析讨论端接基对其光谱与非线性光学性质的影响. 结果表明, 端接基的引入对该类分子的几何结构影响不大. 烷氧基的链长对分子振动光谱的影响很小, 端基引入CN时, C＝O的伸缩振动频率蓝移9 cm^－1. TD-DFT计算表明, 最大吸收光谱源于分子中HOMO→LUMO的p→p*跃迁, 对应的最大吸收波长值在313～375 nm之间, 属于紫外区. 端接强供电子基团可以提高分子的二阶非线性光学性质.     

外电场对甲醛分子的结构与电子光谱的影响

采用密度泛函理论(DFT)在B3LYP/6-311++G(d,p)基组水平上,计算了不同外加电场(-8.22×10~9~8.22×10~9 V/m)下甲醛分子基态稳定构型、分子键长、电荷分布、能级分布、能隙、红外光谱、拉曼光谱和分子的总能量.在此基础上利用TDDFT/B3LYP/6-311++G(d,p)方法研究了甲醛分子由基态跃迁到前25个激发态的激发能E、谐振强度f、吸收波长λ受外电场的影响.结果表明:随着C=O连线方向外电场的增加,C=O键键长、氢原子电荷、偶极矩和能隙递增;C—H键键长、C,O原子电荷递减,总能量降低.振动频率与红外强度及拉曼强度由于不同振动有不同变化.甲醛分子UV-Vis光谱随外电场的增加,不同的吸收峰发生了不同程度的蓝移或者红移;外电场对甲醛分子的激发能、谐振强度和吸收波长的强度有一定影响,但随电场变化比较复杂.     

Electron Momentum Spectroscopy of Ethanethiol Complete Valence Shell

The binding energy spectra and electron momentum distributions for the complete valence orbitals of ethanethiol were measured for the first time by binary (e, 2e) electron momentum spectroscopy employing non-coplanar symmetric kinematics at an impact energy of 1200 eV plus binding energy. The experimental results are generally consistent with the theoretical calculations using density functional theory and Hartree-Fock methods with various basis sets. A possible satellite line at 17.8 eV in binding energy spectrum was observed and studied by electron momentum spectroscopy.     

氰乙基对几种芳胺结构和光谱的影响

采用量子化学中密度泛函理论(DFT)的B3LYP方法分别用6-31G*和6-311+G*基组对苯胺、对氯苯胺和对甲苯胺及其氰乙基衍生物的几何构型进行全优化, 探讨了氨基上氰乙基的引入对分子电荷转移、前线轨道能量和电子光谱等性质的影响规律. 在此基础上采用含时密度泛函方法(TD-DFT)计算了分子第一激发态的电子跃迁能, 得到最大吸收波长λmax. 计算结果表明, 氨基上氰乙基的引入, 对前线分子轨道组成影响虽然小, 但使得最大吸收波长红移, 与实验值λmax有较好的一致性, 发现该类物质主要吸收光谱源于分子内的π→π*的电子跃迁.     

Theoretical approaches for predicting the color of rigid dyes in solution

Aiming at developing an affordable and easily implementable computational protocol for routine prediction of spectral properties of rigid molecular dyes, density functional theory, and time‐dependent density functional theory were used in conjunction with a vibronic coupling scheme for band shape estimate. To predict the perceived color of molecules in solution, a model has been setup linking the UV‐vis spectra predicted at ab initio level to the L *a *b * colorimetric parameters. The results show that a mixed protocol, implying the use of a global hybrid functional for the prediction of adiabatic energy differences and a range separated hybrid for the prediction of potential energy curvature, allows perceived colors to be quantitatively predicted, as demonstrated by the comparison of L *a *b * colorimetric parameters obtained from computed and experimental spectra. © 2017 Wiley Periodicals, Inc.     

Spectroscopic and quantum chemical study of cyclopropylmethylphosphine, a candidate for intramolecular hydrogen bonding

The properties of the novel compound cyclopropylmethylphosphine (C3H5CH2PH2) have been investigated by means of Stark-modulation microwave spectroscopy and high-level quantum chemical calculations. Spectra attributable to the three conformers of the molecule with a synclinal arrangement of the H-C-C-P atoms were recorded and assigned. The experimental rotational constants obtained for these conformers were found to be in good agreement with those generated by ab initio geometry optimizations at the MP2/aug-cc-pVTZ level of theory. An estimate of the relative energies of the three conformers with observable spectra, by means of relative intensity measurements, compared favorably with the results of G3 energy calculations performed for the molecule. In addition to the observation of ground-state rotational spectra for three conformers, spectra belonging to a number of vibrationally excited states were also assigned with the aid of radio frequency microwave double-resonance experiments. A tentative assignment of these excited-state spectra was proposed by appealing to the results of density functional theory vibrational frequency calculations performed at the B3LYP/6-311++(3df,2pd) level. The energetically preferred conformer of the molecule allowed a close approach between a hydrogen atom belonging to the phosphino group and the edge of the cyclopropyl ring. The possibility of the formation of an intramolecular hydrogen bond to electron density associated with so-called banana bonds is discussed.     

(BN)n团簇的结构和稳定性

用HF方法、密度泛函理论的B3LYP以及微扰理论的MP2方法，在6—31G(d)基组 水平上，对(BN)n(n=1-16)团簇的各种可能结构进行了优化．讨论了环状与笼状稳 定团簇的几何构型、自然键轨道(NBO）、振动频率、结合能、核独立化学位移 (NICS)和能量二次差分，得到了(BN)n(n＝1-16)团簇结构的稳定性信息．比较了 HF，B3LYP以及MP2三种理论方法对(BN)n团簇的适应性所表现出的差异．     

Photoelectron spectroscopy of fullerene dianions C76(2-), C78(2-), and C84(2-)

We report laser photoelectron spectra of the doubly negatively charged fullerenes C(76) (2-), C(78) (2-), and C(84) (2-) at 2.33, 3.49, and 4.66 eV photon energy. From these spectra, second electron affinities and vertical detachment energies, as well as estimates for the repulsive Coulomb barriers are obtained. These results are discussed in the context of electrostatic models. They reveal that fullerenes are similar to conducting spheres, with electronic properties scaling with their size. The experimental spectra are compared with the accessible excited states of the respective singly charged product ions calculated in the framework of time dependent density functional theory.     

苯乙烯基吡啶类化合物几何结构与光谱的理论研究

采用量子化学密度泛函理论(DFT)方法分别在B3LYP/6-31G*, 6-31G**, 6-31＋G*水平上对苯乙烯基吡啶类化合物进行计算研究. 通过在相同水平下的振动频率分析发现苯乙烯基吡啶类化合物具有C₁对称性, 酯基的碳氧原子与苯环形成不同的离域大π键, 空间位阻和共轭效应使得两苯环处于两个不同平面, 二面角在60°与62°之间. 使用含时密度泛函理论(TD-DFT)方法计算第一激发态的电子垂直跃迁能, 得到最大吸收波长λ_max. 计算结果表明末端烷基链的长度对该类化合物的几何结构与振动光谱、电子光谱无影响.     

Hydrogen bonding and molecular vibrations of 3,5-diamino-1,2,4-triazole

This work deals with the analysis of hydrogen bonding and the vibrational spectroscopy of 3,5-diamino-1,2,4-triazole by means of quantum chemical calculations. The mid and far FTIR and FT-Raman spectra were measured in the condensed state. The fundamental vibrational frequencies were calculated under different possible symmetries by applying the density functional theory with the B3LYP functional and the 6-31G* basis set. The results of the calculations obtained under C(2) symmetry produces the global minimum on the potential energy surface. The vibrational spectra were interpreted with the aid of normal coordinate analysis based on scaled density functional force field. The infrared and Raman spectra were also predicted from the calculated intensities.     

Ab initio calculations of optical absorption spectra: solution of the Bethe-Salpeter equation within density matrix perturbation theory

We describe an ab initio approach to compute the optical absorption spectra of molecules and solids, which is suitable for the study of large systems and gives access to spectra within a wide energy range. In this approach, the quantum Liouville equation is solved iteratively within first order perturbation theory, with a Hamiltonian containing a static self-energy operator. This procedure is equivalent to solving the statically screened Bethe-Salpeter equation. Explicit calculations of single particle excited states and inversion of dielectric matrices are avoided using techniques based on density functional perturbation theory. In this way, full absorption spectra may be obtained with a computational workload comparable to ground state Hartree-Fock calculations. We present results for small molecules, for the spectra of a 1 nm Si cluster in a wide energy range (20 eV), and for a dipeptide exhibiting charge transfer excitations.     

Electron Momentum Spectroscopy Investigation on Electronic Structure of Iso-dichloroethylene Valence Shell

Here an electron momentum spectroscopy study on the electronic structure of valence shell of iso-dichloroethylene molecule is reported. The experiment is carried out with a binary (e, 2e) spectrometer at incident electron energy of 1200 eV, employing noncoplanar symmetric arrangement. The binding energy spectra and electron momentum distributions (EMDs) of iso-dichloroethylene valence shell have been obtained. Theoretical EMDs are predicted with both Hartree-Fock and density functional theory methods, generally indicating good agreements with the measurement results. The interference effect is observed to significantly influence the EMDs of 2a₂ and 5b₂ Cl lone-pair orbitals.     

Improvement of anti-inflammatory and anticancer activities of poly(lactic-co-glycolic acid)-sulfasalazine microparticle via density functional theory,molecular docking and ADMET analysis

In the present study, we assessed improvement of anti-inflammatory activity and drug delivery of sulfasalazine (SSZ) by the poly(lactic-co-glycolic acid), (PLGA), in H₂O and dichloromethane (DCM) environments via density functional theory (DFT), ADMET, and molecular docking. Our calculated results based on binding energy and thermodynamic parameter represents that the interaction between SSZ and PLGA in Complex A via double hydrogen bonds is stronger in comparison with Complex B. The analysis of Ultraviolet–visible (UV–VIS) spectra proved the interaction of SSZ with PLGA by time-dependent density functional theory (TDDFT). Infrared (IR) spectra demonstrated that the structure of PLGA was shifted in the presence of the SSZ. The interaction of SSZ with PLGA leads to an increase in dipole moment and higher solubility with more negative Gibbs free solvation energy (ΔG_solv) values and lowering of the energy gap (E_g). The obtained results by Molecular docking demonstrates that the interaction of SSZ via its carboxylate group with PLGA (complex A) had a strong interaction towards the binding pocket of the target and as a potential inhibitor of the COX-2, TNF-α, and IL-1 receptors at the binding site as compared with the complex B.