顺式效应的起源: 双取代乙烯衍生物的密度泛函理论研究

一般情况下双取代乙烯衍生物的反式构象要比顺式构象稳定. 但是例外也存在, 例如1,2-二氟乙烯和1,2-二氯乙烯. 这种双取代乙烯衍生物顺式构象的超常稳定性被称之为顺式效应. 该效应的起源和本质目前仍没有定论. 本文以12 个体系(XHC=CHY (X, Y=F, Cl, Br, CN, CH₃, C₂H₆, OCH₃))为例, 对顺式效应的有效性、起源和本质进行系统的密度泛函理论研究, 其中9个体系存在顺式效应, 另外3个为正常体系没有该效应. 采用一系列泛函和基组研究其有效性, 并运用四种分析手段, 如自然键轨道(NBO)、能量分量分析(EDA)、密度泛函活性理论(DFRT)和非共价相互作用(NCI)分析, 剖析该效应的起源和本质. 发现在顺式构象的两个取代基之间存在一种微弱的非共价相互吸引作用. 能量分析表明, 静电效应、立体效应等对顺式效应的存在都起着重要作用, 但是它们均不能单独用来解释顺式效应的起源. 也就是说顺式效应没有一个简单的起源, 它是多种作用合力的结果. 本文采用双变量解释得到比较合理的相关回归系数R²=0.86-0.87,较好地解释了顺式效应的本质和起源.     

6,12-二乙炔基茚并[1,2-b]芴系列衍生物的非线性光学性质

采用密度泛函理论(DFT) CAM-B3LYP方法对6,12-二乙炔基茚并[1,2-b]芴系列衍生物的极化率(α_s)和第二超极化率(γ_s)进行研究. 结果表明, 此类分子具有较大的γ_s值. 用乙炔基硅烷基和氧原子取代茚并[1,2-b]芴分子6,12位的氢原子后, 分子的几何构型发生改变, 进而影响其非线性光学(NLO)性质. 连接乙炔基硅烷基的分子α_s值和γ_s值均增大, 而连接氧原子的分子α_s值和γ_s值均减小. 茚并[1,2-b]芴环2,8位取代基R(R=H, F, CH₃)的不同, 对分子的γ_s值也有一定的影响, R为CH₃时分子的α_s值和γ_s值均较大. 由含时密度泛函理论(TD-DFT)方法计算的吸收光谱分析可知, 与茚并[1,2-b]芴系列分子相比, 引入乙炔基硅烷基的分子共轭性增强, 最大吸收波长红移; 引入氧原子的分子几何结构扭曲, 共轭性降低, 最大吸收波长蓝移.     

Structure elucidation and NMR assignments of a new dihydrochalcone from Empetrum nigrum subsp. asiaticum (Nakai ex H.Ito) Kuvaev

Abstract

A new dihydrochalcone, namely 2',5'-dimethyl-3'-methoxy-4',6'-dihydroxyl-dihydrochalcone (1) together with five known compounds were isolated from the CHCl₃ extract from Empetrum nigrum L. var. japonicum K. Koch (E. nigrum). The structures of 1 was elucidated by spectroscopic methods, including UV, IR, HR-ESI-MS and extensive 1D and 2D NMR techniques.     

连续在线原位ATR-FTIR技术测定介孔CuAl2O4对黄药的吸附

以丁胺和正十二醇为混合模板剂, 采用共沉淀法制备了介孔纳米CuAl₂O₄. 用X射线粉末衍射(XRD)、傅里叶变换红外(FTIR)光谱、N₂吸附-脱附对产物的结构进行了表征. 采用连续在线原位衰减全反射傅里叶变换红外(ATR-FTIR)光谱技术研究了水溶液中丁基和辛基黄药在介孔CuAl₂O₄表面的吸附. 随着吸附时间的延长,1200 和1040 cm^-1两处黄药特征峰的高度逐渐增加, 根据1200 cm^-1处C-O-C伸缩振动峰的变化来评价黄药在CuAl₂O₄表面的吸附动力学过程. 结果表明, 介孔纳米CuAl₂O₄对黄药有很强的吸附能力, 在100 min 的时间内, CuAl₂O₄样品对丁基和辛基黄药的吸附量分别达到了236 和300 mg·g^-1, 且属于化学吸附. 对实验数据进行理论模拟, 发现吸附过程更接近于拟二级吸附动力学方程.     

一种铜配位聚合物的合成及其对Fe3+和对硝基苯酚的荧光传感

在水热条件下,基于H5depa配体和2,2''-bpy配体设计并合成了一个配位聚合物{[Cu₂(Hdepa)(2,2''-bpy)₂(H₂O)₂]·2H₂O}_n(H₅depa=2,2'',3,4'',5-二苯醚五羧酸,2,2''-bpy=2,2''-联吡啶)。用元素分析、红外光谱、单晶X射线衍射和热稳定性分析对其进行了结构表征。配位聚合物1中2个中心Cu²⁺离子均采用五配位模式,呈三角双锥几何构型。未完全去质子化的Hdepa^4-配体采用了μ₄-η¹-η¹-η¹-η¹配位方式。其二维层之间通过弱的氢键相互作用扩展为三维超分子网状结构。1可作为一种高灵敏度、选择性好、多响应的荧光传感器,可快速检测Fe³⁺和对硝基苯酚(4-NP),此外还研究了其荧光猝灭机理。     

基于一个四羧酸配体构筑的具有(4,8)-连接的镧系金属有机框架材料及对小分子的检测试验

以3,3’,5,5’-四-(羧基苯基)联苯为配体(H₄L),与镧系金属Ln(Ⅲ)盐反应,自组装形成了5个具有三维孔洞结构的镧系金属-有机框架材料：{[Ln₃L₂(H₂O)₇]·(OH)·10DMA}_n(Ln=Gd(1a);Ln=Ho(2a),{[Ln₃L₂(H₂O)3]·(OH)·mDMA}_n(Ln=Er,m=10(1b);Ln=Yb,m=9(2b);Ln=Lu,m=10(3b))。单晶X射线衍射分析表明,这些MOFs属于2种系列的类质同晶化合物,分别属于正交晶系Ccca空间群和单斜晶系C2/c空间群。有机小分子溶剂交换荧光研究发现,2b对小分子二氯甲烷和甲苯荧光有增强效应,表现出良好的荧光探测功能。     

基于一个四羧酸配体构筑的具有(4,8)-连接的镧系金属-有机框架材料及对小分子的检测试验

以3,3'',5,5''-四-（羧基苯基）联苯为配体（H₄L）,与镧系金属Ln（Ⅲ）盐反应,自组装形成了5个具有三维孔洞结构的镧系金属-有机框架材料：{[Ln₃L₂(H₂O)₇]·(OH)·10DMA}_n(Ln=Gd (1a); Ln=Ho(2a), {[Ln₃L₂(H₂O)₃]·(OH)·mDMA}_n (Ln=Er,m=10(1b); Ln=Yb, m=9(2b); Ln=Lu, m=10(3b))。单晶X射线衍射分析表明,这些MOFs属于2种系列的类质同晶化合物,分别属于正交晶系Ccca空间群和单斜晶系C2/c空间群。有机小分子溶剂交换荧光研究发现,2b对小分子二氯甲烷和甲苯荧光有增强效应,表现出良好的荧光探测功能。     

Framework Structure of a Synthetic High Silica Zeolite --ZSM-39 from a C_2H_4(OH)_2-H_2O Mixed Solvent System

The structural analogy of clathrate synthesized with natural zeolite framework is well known. HPF_6·6H_2O and (CH_3)_4 (OH)·5H_2O are isostructural with sodalite,melanophlogite is isostructural with the 12 cubic gas hydrate and zeolite ZSM-39 with the 17 gas hydrate. The synthesis of ZSM-39 was first reported by Brace in 1981.Schleker and Meier also obtained the crystals of ZSM-39 with size<10μm and analyzed its crystal stucture by the powder X-ray diffraction.In 1984,Gies solved the crystal structure of dodecasil 3C(ZSM-39) synthesized from an aqueous system in space group F_(ds).In the present paper,we report the framework structure of the high silica zeolite—ZSM-39 obtained from the ethylene glycol-water mixed solvent system.     

对氯硝基苯吸附在银纳米粒子上的偶联反应

表面增强拉曼光谱(SERS)具有极高的检测灵敏度, 通过检测吸附分子的SERS信号, 可以获得表面吸附分子的结构以及可能发生的反应. 在拉曼激发光源的辐射下, 在碱性溶液中, 银纳米粒子表面吸附的对氯硝基苯(PCNB)的SERS光谱与其固体的常规拉曼光谱相比, 出现异常SERS谱. 通过采用密度泛函理论(DFT)计算, 对PCNB以及可能的偶联产物p,p''-二氯偶氮苯(DCAB)进行理论分析以及谱峰归属, 发现这些异常峰来自其偶联产物DCAB的偶氮C－N＝N－C基团的基频振动.     

固定床反应器上挤条小晶粒TS-1催化丙烯环氧化反应

采用纳米TS-1母液作为晶种, 在四丙基溴化铵(TPABr)-乙胺廉价水热体系中, 合成出晶粒尺寸为600 nm×400 nm×250 nm的小晶粒钛硅分子筛(TS-1), 用挤条法将其成型, 得到的挤条小晶粒TS-1被用于催化固定床反应器中的丙烯环氧化反应. 采用X射线衍射(XRD)光谱, 傅里叶变换红外(FT-IR)光谱, 紫外-可见(UV-Vis)漫反射光谱及氮气物理吸附对挤条成型的小晶粒TS-1进行表征, 并对丙烯环氧化的最优反应条件进行考察. 其中所考察的条件包括: 反应温度, 压力, 丙烯/H₂O₂摩尔比(n(C₃H₆)/n(H₂O₂)), 丙烯、甲醇及H₂O₂的质量空速(WHSV), 以及NH₃·H₂O浓度. 在所考察的范围内, 温度对环氧丙烷(PO)收率的影响较小, 当反应压力为2.0 MPa, n(C₃H₆)/n(H₂O₂)为4时, 可以得到最高的PO收率. 当丙烯、甲醇及H₂O₂的空速分别为0.93、2.5及0.25 h^-1时, PO在产物中的含量最高. 较低的NH₃·H₂O浓度对高PO收率更有利. 在优化的反应条件下, 对比不同晶粒大小TS-1的催化性能, 并考察了挤条小晶粒TS-1的长期运转性能, 连续反应1000 h, H₂O₂转化率及PO选择性仍能维持在95%以上.     

Synthesis of a Bicyclic Diamine Derived from Kemp's Acid

A bicyclic diamine with defined and stable conformation in solution was prepared from Kemp's triacid. The efficient four-step synthesis of the Boc-protected diamine requires only a single purification by column chromatography. X-ray analysis and NMR spectroscopy confirm the structure of the diamine in the solid state and in solution.     

Inhibition of cell proliferation by a resveratrol analog in human pancreatic and breast cancer cells

Resveratrol has been reported to possess cancer preventive properties. In this study, we analyzed anti-tumor activity of a newly synthesized resveratrol analog, cis-3,4'',5-trimethoxy-3''-hydroxystilbene (hereafter called 11b) towards breast and pancreatic cancer cell lines. 11b treatments reduced the proliferation of human pancreatic and breast cancer cells, arrested cells in the G2/M phase, and increased the percentage of cells in the subG1/G0 fraction. The 11b treatments also increased the total levels of mitotic checkpoint proteins such as BubR1, Aurora B, Cyclin B, and phosphorylated histone H3. Mechanistically, 11b blocks microtubule polymerization in vitro and it disturbed microtubule networks in both pancreatic and breast cancer cell lines. Computational modeling of the 11b-tubulin interaction indicates that the dimethoxyphenyl group of 11b can bind to the colchicine binding site of tubulin. Our studies show that the 11b treatment effects occur at lower concentrations than similar effects associated with resveratrol treatments and that microtubules may be the primary target for the observed effects of 11b. These studies suggest that 11b should be further examined as a potentially potent clinical chemotherapeutic agent for treating pancreatic and breast cancer patients.     

Stereodynamics of bond rotation in tertiary 1-naphthoic acid amides: a computational study

Computations sho that independent N-CO rotation is not possible in N,N-diethyl-1-naphthamide, and that the coalescence signal corresponding to methyl equivalence observed in the VT NMR spectrum of this system is caused by a complex process whose rate-determining step implies concerted N-CO, Ar-CO, and ethyl rotations. The calculated Gibbs energy barriers for these processes in solution are in good agreement with the experimental values.     

高相转变温度的离子凝胶电解质基准固态染料敏化太阳电池

染料敏化太阳电池(DSC)以其低价、高效等优势, 成为学术界和工业界的研究热点. 传统液态电解质由于易挥发、易泄漏等问题, 导致基于液态电解质的电池难以保持长期稳定, 影响光伏技术的应用. 本文合成了N,N'-1,5-戊二基双月桂酰胺, 将其作为有机小分子胶凝剂(LMOG)胶凝离子液体电解质(ILE)制备了离子凝胶电解质(IGE)并组装成准固态电池(QS-DSCs). 差示扫描量热测试显示该凝胶电解质的相转变温度(T_gel)为104.7℃, 具有良好的本征热稳定性.利用循环伏安法、电化学阻抗谱、调制光电压/光电流谱分别研究了液态电池和准固态电池内部电子传输和复合动力学过程. 结果表明, 凝胶电解质的三维网络结构加速了TiO₂光阳极/电解质界面电子与电解质中I₃^-的复合过程, 使电子寿命降低, 导致准固态电池的光电转换效率略低于液态电池. 在AM1.5 (100 mW·cm^-2)及50℃条件下的加速老化测试结果显示, 持续老化1000 h后其光电转换效率(η)无衰减,而液态电池的光电转换效率衰减为初始值的86%, 表明准固态电池具有良好的光热稳定性.     

Aromatic hydroxylation in a copper bis(imine) complex mediated by a micro-eta2:eta2 peroxo dicopper core: a mechanistic scenario

Detailed mechanistic studies on the ligand hydroxylation reaction mediated by a copper bis(imine) complex are presented. Starting from a structural analysis of the CuI complex and the CuII product with a hydroxylated ligand, the optical absorption and vibrational spectra of starting material and product are analyzed. Kinetic analysis of the ligand hydroxylation reaction shows that O2 binding is the rate-limiting step. The reaction proceeds much faster in methanol than in acetonitrile. Moreover, an inverse kinetic isotope effect (KIE) is evidenced for the reaction in acetonitrile, which is attributed to a sterically congested transition state leading to the peroxo adduct. In methanol, however, no KIE is observed. A DFT analysis of the oxygenation reaction mediated by the micro-eta2:eta2 peroxo core demonstrates that the major barrier after O2 binding corresponds to electrophilic attack on the arene ring. The relevant orbital interaction occurs between the sigma* orbital of the Cu2O2 unit and the HOMO of the ligand. On the basis of the activation energy for the rate-limiting step (18.3 kcal mol(-1)) this reaction is thermally allowed, in agreement with the experimental observation. The calculations also predict the presence of a stable dienone intermediate which, however, escaped experimental detection so far. Reasons for these findings are considered. The implications of the results for the mechanism of tyrosinase are discussed.