偏二甲肼分子化学键解离能的理论计算

利用量子化学组合从头算方法和密度泛函理论方法计算了偏二甲肼分子的准确化学键解离能。结果表明,除N—C键外,组合从头算方法对该分子其余键解离能的计算值与文献值都很接近;密度泛函理论中BMK方法的计算结果与组合从头算方法的结果很接近,对于N—H和C—H键,B3P86方法的计算结果稍优于BMK方法,而B3LYP方法则普遍低估了键解离能。由于自旋污染的原因,限制性开壳层方法要优于非限制性方法。计算结果表明,偏二甲肼分子中N—N和N—C键的键解离能最低。     

Nitroarenes as Antitubercular Agents: Stereoelectronic Modulation to Mitigate Mutagenicity

Nitroarenes are less preferred in drug discovery due to their potential to be mutagenic. However, several nitroarenes were shown to be promising antitubercular agents with specific modes of action, namely, nitroimidazoles and benzothiazinones. The nitro group in these compounds is activated through different mechanisms, both enzymatic and non‐enzymatic, in mycobacteria prior to binding to the target of interest. From a whole‐cell screening program, we identified a novel lead nitrobenzothiazole (BT) series that acts by inhibition of decaprenylphosphoryl‐β‐d ‐ribose 2′‐epimerase (DprE1) of Mycobacterium tuberculosis (Mtb). The lead was found to be mutagenic to start with. Our efforts to mitigate mutagenicity resulted in the identification of 6‐methyl‐7‐nitro‐5‐(trifluoromethyl)‐1,3‐benzothiazoles (cBTs), a novel class of antitubercular agents that are non‐mutagenic and exhibit an improved safety profile. The methyl group ortho to the nitro group decreases the electron affinity of the series, and is hence responsible for the non‐mutagenic nature of these compounds. Additionally, the co‐crystal structure of cBT in complex with Mtb DprE1 established the mode of binding. This investigation led to a new non‐mutagenic antitubercular agent and demonstrates that the mutagenic nature of nitroarenes can be solved by modulation of stereoelectronic properties.     

Insights from ab initio molecular dynamics simulations for a multicomponent oxide glass

It remains a challenge to establish structural models of multicomponent oxide glass systems. In this study, we have investigated 68.3SiO₂–16.1B₂O₃–4.2Al₂O₃–11.4Na₂O glass and melt structures by ab initio molecular dynamics (AIMD) simulations. The atomic configurations obtained from AIMD simulations were validated against ¹⁷O solid‐state NMR spectrum under 24.0 T and neutron diffraction data, and excellent agreement was achieved. The bond lengths, angles, and coordination geometries were statistically analyzed for each atomic species. Here we particularly address the role of minor atomic species such as five‐coordinate Si (Si^V) and Al (Al^V). The Si^V–O bond lengths and O–Si^V–O angle distribution in the glass indicated 1.718 Å and three peaks at 90°, 120°, and 175°, which are assigned to a coordination geometry of the trigonal bipyramidal structure. Ring statistic analysis revealed that Si^V and Al^V were found to preferentially contribute to the formation of small ring sizes.     

Conformational Analysis of Thioether Musks Using Density Functional Theory

A conformational analysis of nine macrocyclic thioether musks has been carried out using molecular mechanics (MMFF), density functional theory (DFT) using both B3LYP and M06 functionals, as well as Hartree-Fock and post-Hartree-Fock (MP2) ab initio methods. 6-Thia-, 10-thia- and 4-methyl-5-thia-14-tetradecananolide, 4-thia-, 7-thia-, 11-thia- and 12-thia-15-pentadecanolide and 6-thia- and 12-thia-16-hexadecanolide were modeled. Unfortunately, there was little agreement between the computational methods at the levels of theory used in this study.     

Transition metals supported on oxides: density functional cluster studies of palladium deposition on MgO(001)

The interaction of isolated Pd atoms and of a square Pd₄ cluster with the (001) surface of MgO is investigated by means of density functional (DF) calculations. The oxide surface is represented by various model clusters and the effect of the surrounding is taken into account by embedding the cluster in point charges and total ion model potentials. The calculations are performed at the relativistic level using the Becke–Perdew exchange-correlation functional. The adsorption properties determined with this computational scheme are compared with other DF results. The bonding of the Pd atoms and clusters with the surface is analyzed in terms of charge density difference plots. It is found that the polarization of the metal adsorbate due to the surface electric field provides an important contribution to the metal–oxide adhesion energy. This revised version was published online in June 2006 with corrections to the Cover Date.     

3‐Heterocycle‐Phenyl N‐Alkylcarbamates as FAAH Inhibitors: Design,Synthesis and 3D‐QSAR Studies

Carbamates are a well‐established class of fatty acid amide hydrolase (FAAH) inhibitors. Here we describe the synthesis of meta‐substituted phenolic N‐alkyl/aryl carbamates and their in vitro FAAH inhibitory activities. The most potent compound, 3‐(oxazol‐2yl)phenyl cyclohexylcarbamate ( 2 a ), inhibited FAAH with a sub‐nanomolar IC₅₀ value (IC₅₀=0.74 nM ). Additionally, we developed and validated three‐dimensional quantitative structure–activity relationships (QSAR) models of FAAH inhibition combining the newly disclosed carbamates with our previously published inhibitors to give a total set of 99 compounds. Prior to 3D‐QSAR modeling, the degree of correlation between FAAH inhibition and in silico reactivity was also established. Both 3D‐QSAR methods used, CoMSIA and GRID/GOLPE, produced statistically significant models with coefficient of correlation for external prediction (R²_PRED) values of 0.732 and 0.760, respectively. These models could be of high value in further FAAH inhibitor design.     

Synthesis and photovoltaic properties of an alternating phenylenevinylene copolymer with substituted-triphenylamine units along the backbone for bulk heterojunction and dye-sensitized solar cells

We have fabricated bulk heterojunction (BHJ) photovoltaic devices based on the as cast and thermally annealed P:[6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) blends and found that these devices gave power conversion efficiency (PCE) of about 1.15 and 1.60% respectively. P is a novel alternating phenylenevinylene copolymer which contains 2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid units along the backbone and was synthesized by Heck coupling. This copolymer was soluble in common organic solvents and showed long-wavelength absorption maximum at 390-420 nm with optical band gap of 1.94 eV. The improvement of PCE after thermal annealing of the device based on the P:PCBM blend was attributed to the increase in hole mobility due to the enhanced crystallinity of P induced by thermal treatment. In addition, we have fabricated BHJ photovoltaic devices based on the as cast and thermally annealed PB:P:PCBM ternary blend. PB is a low band gap alternating phenylenevinylene copolymer with BF₂-azopyrrole complex units, which has been previously synthesized in our laboratory. We found that the device based on this ternary blend exhibited higher PCE (2.56%) as compared to either P:PCBM (1.15%) or PB:PCBM (1.57%) blend. This feature was associated with the well energy level alignment of P, PB and PCBM, the higher donor-acceptor interfaces for the exciton dissociation and the improved light harvesting property of the ternary blend. The further increase in the PCE with thermally annealed ternary blend (3.48%) has been correlated with the increase in the crystallinity of both P and PB. Finally, we used copolymer P as sensitizer for quasi solid state dye-sensitized solar cell and we achieved PCE of approximately 3.78%.     

A Puzzle of Quantum Phase Transition on Gd-IMC by Tuning of Conduction Electron Concentration

Based on the critical unstable of both crystal and magnetic structure of Gd-intermetallic compound near the competition of two strongly independent subsystem （＂local 4f7＂ and ＂conduction electron concentration＂）, a new QPT （quantum point transition） is predicted by calculation of： （1） The band structure and density of state by density functional theory where a strong narrowing fluidity of fermions around EF with shifted to negative value ＂-0.8 eV ＂is observable in the Gd-intermetalliccompound system while in the Y-case, it is not dominated. An antiferromagnetic state on the fluidity of conduction band can be investigated; （2） The internal magnetic field due to short range exchange interaction Jij between the nearest neighbor of local magnetic moment of stable s-state of Gd （L = 0） through the mean field approximation and of Eigenvalue-Eigenfunction ~.（k） are calculated. While a strong negative value of Jy is predicted, the eigenvalue L（k） of the system shows a strong antiferromagnetic phase in the reciprocal lattice direction 〈010〉, 〈001〉 in the correlation length 3.38 ~A. Although the antiferromagnetic state at Rc 〈_ 3.38 °A is a puzzle but it is completely dominated at Rc = 9 °A after passing through the competition between ）.λmin（O） and λmin（π） in the ranger of 3.2 °A 〈 Rc 〈 9 °A. Since both of the antiferromagnetic subsystems are sensitive to the predicted KF, the effect of decreasing of conduction electron is proposed to investigate, the change of the antiferromagnetic ordering state to the competition of ferromagnetic state （in direction 〈010〉） and antiferromagnetic state （in direction 〈001 〉 and 〈 100〉） resulted to paramagnetic state in the long range Rc = 9 °A.     

从头算法对甲基磺酸拉曼光谱振动频率指认

对液态的甲基磺酸进行了拉曼光谱测定。采取从头算法用各种不同的基组 (最大的基组为MP2 / 6 -311+G( 2d ,2 p) )对甲基磺酸的结构和光谱进行了计算 ,得到了甲基磺酸的结构参数及稳定构象信息。采用一个具有Ci 对称的二聚体模型解释了甲基磺酸的液态光谱。对单体和二聚体的甲基磺酸进行了简正坐标计算 ,结果表明二聚体结构是液态甲基磺酸聚积态分子的合理模型。