定向Monte Carlo格点搜索算法用于氧化铝团簇(Al2O3)n (n=1~50)的结构搜索

氧化铝纳米团簇在众多技术应用中日益受到重视, 找到其最优结构对进一步的研究非常重要. 本工作提出了一种定向Monte Carlo格点搜索算法用于搜索不同氧化铝晶体(α, θ和δ)内的不同尺寸的氧化铝纳米团簇的结构, 并对结构进行了分析比较. 通过定向移动策略, 定向Monte Carlo格点搜索中每一步都是“有效”移动, 极大地增加了搜索效率. 研究结果发现α氧化铝团簇形成一种多层结构, θ和δ氧化铝团簇形成一种单层薄膜结构. θ和δ氧化铝团簇的二阶能量差分存在奇偶震荡, 偶数尺寸的氧化铝团簇具有相对更高的稳定性. 通过相对能量比较发现相同尺寸下θ和δ氧化铝团簇薄膜结构比α氧化铝团簇结构更稳定, 在对这种薄膜进行第一性原理计算后进一步验证这种薄膜具有良好的稳定性和抗氧化性.     

基于多层结构设计的高储能密度氧化石墨烯/聚酰亚胺复合材料

采用逐层涂布、 分层控制固化程度的方法, 利用聚酰胺酸(PAA, 聚酰亚胺前体)溶液和含有氧化石墨烯（GO）的PAA溶液制备了一系列由高绝缘性PI层与GO@PI介电层交替组合而成的界面清晰且紧密衔接的多层复合薄膜. 通过调控介电层中GO含量及分层结构, 使多层复合薄膜兼具高介电常数和高击穿强度特征. 结果表明, 三层复合薄膜PI/1.0GO@PI/PI的击穿强度为261.5 kV/mm, 储能密度达到1.27 J/cm³, 与相同介电层厚度的单层薄膜相比, 击穿强度和储能密度分别提高了97%和144%, 同时, 其介电损耗也保持在较低水平(tanδ=0.0079). 绝缘层和高介电常数层的协同作用提升了氧化石墨烯/聚酰亚胺复合薄膜的储能密度. 这种简单的多层结构设计有利于氧化石墨烯/聚合物复合材料在介质储能领域的应用.     

α,β,γ,δ,ε,η-Bi2O3电子结构和光学性质的第一性原理研究

基于密度泛函理论的CASTEP模块研究了α, β, γ, δ, ε和η-Bi₂O₃晶型, 计算分析了其几何结构、 能带结构、 电子态密度和光学性质. 结果表明, α, ε和η相均为层状结构, 其中, α和ε相为单层—Bi—O—结构, 而η相为双层—Bi—O—结构; β, γ和δ相为—Bi_m—O_n—交错结构, 其中δ相交错尤为密集, 呈现导体特性. 各晶相的导带均由Bi 6p态构成, 价带由O_2p态起主导作用. 电势电位分析结果表明, 6种晶相价带电位均在H₂O/O₂之下, 具有强氧化能力, 与实验报道的光催化氧化能力大小顺序γ-Bi₂O₃>β-Bi₂O₃>α-Bi₂O₃>δ-Bi₂O₃一致, 而导带还原电位低于H₂/H₂O, 预测纯Bi₂O₃很难具备催化产氢能力. 光学性质分析发现, γ和δ相的起始响应波长较大, 说明其应具备红外激发的性质. 这些结果可为获得偏红外激发和较宽光谱响应的Bi₂O₃材料研究提供理论基础, 为研发和应用Bi₂O₃及其复合物提供重要的指导.     

七水合三氯化铈-碘化钠催化氨基苯硫酚与高位阻α, β-不饱和酮的迈克尔加成反应

对七水合三氯化铈-碘化钠(CeCl₃·7H₂O-NaI)化邻氨基苯硫酚、 对氯邻氨基苯硫酚、 间氨基苯硫酚、 对氨基苯硫酚和对甲基苯硫酚与α,β-不饱和酮(1a~1o)的迈克尔加成反应进行了系统研究. 结果表明, CeCl₃·7H₂O-NaI-SiO₂复合催化剂能有效催化邻氨基苯硫酚及对氯邻氨基苯硫酚与α,β-不饱和酮(1a~1o)的迈克尔加成反应. 在优化的反应条件下, 即n(CeCl₃·7H₂O):n(NaI):n(α,β-不饱和酮)=1:2:2, m(CeCl₃·7H₂O):m(SiO₂)=1:1.6, 三氯甲烷作溶剂, 反应温度为回流温度, 反应时间为2 h, 反应可达到中等产率(43.1%~58.8%). 催化剂重复使用4次基本稳定. 此外, 提出了可能的催化机理.     

黑果枸杞叶多糖LRLP3的结构、抗氧化活性及免疫活性

黑果枸杞叶经水提醇沉, 离子交换柱层析和凝胶柱层析分离纯化, 得到平均分子量为79400的均一多糖组分LRLP3. 对该多糖的理化性质、 结构、 抗氧化活性及免疫活性的研究结果表明, LRLP3为多分支结构, 主链为(1→3)βGalp, 大部分半乳糖6位存在分支; 支链由(1→6)βGalp, (1→4)βGalp, (1→3)βAraf, (1→3)αArap, (1→5)βAraf和(1→2,4)αRhap组成, 非还原末端由αAraf, βGalp和βGlcp组成. LRLP3具有较强的还原能力, 可显著清除1,1-二苯基-2-三硝基苯肼(DPPH)自由基、 羟自由基和超氧阴离子自由基, 有效抑制Cu²⁺/H₂O₂诱导的蛋白氧化损伤和H₂O₂诱导的细胞氧化损伤. LRLP3在体外对未经诱导和经刀豆蛋白(ConA)或脂多糖(LPS)诱导的小鼠脾细胞增殖均有促进作用.     

白山毛桃根抗脑胶质瘤活性成分及其纳米胶束的制备

采用溶剂提取和萃取方法得到白山毛桃根乙酸乙酯、 正丁醇和水层萃取物. 通过噻唑蓝(MTT)比色法考察了各萃取物对脑胶质瘤细胞U87MG活性的抑制作用. 采用高效液相色谱(HPLC)指纹图谱法比对确认活性部位的主要化学成分为2α,3α,24-三羟基-12-烯-28-乌苏酸. 采用溶剂挥发法制备了2α,3α,24-三羟基-12-烯-28-乌苏酸纳米胶束, 对其包封率、 粒径及ζ电位等进行了表征, 并考察了其抗肿瘤活性. 体外细胞实验结果表明, 白山毛桃根乙酸乙酯萃取物对脑胶质瘤细胞U87MG具有抑制作用, 通过与标准品比对确认2α,3α,24-三羟基-12-烯-28-乌苏酸为乙酸乙酯部位的主要成分, 且该成分对脑胶质瘤细胞活性具有较强抑制作用. 通过溶剂挥发法制备的2α,3α,4-三羟基-12-烯-28-乌苏酸纳米胶束包封率为64.7%, 粒径为20 nm, 粒径分布宽度(PDI)为0.246, ζ电位为-5.7 mV. 细胞实验结果进一步证明, 与单体化合物相比, 2α,3α,24-三羟基-12-烯-28-乌苏酸纳米胶束对脑胶质瘤细胞活性具有更强的抑制作用, 为白山毛桃根在脑胶质瘤治疗中的应用提供了实验依据.     

剪切速率对等规聚丙烯的结晶和形貌的影响

利用同步辐射小角X射线散射、 广角X射线衍射和差示扫描量热法研究了不同剪切速率下等规聚丙烯的结晶结构. 结果表明, 施加剪切会导致β晶生成, 但基本不改变样品总结晶度. β晶含量随着剪切速率的提高先升高后降低, 与α晶具有竞争关系. 当剪切速率在10~32 s^-1之间时, α晶和β晶共存, 并存在分属于两种晶型的两组长周期, 其中较大的长周期属于β晶.     

金属串配合物[MM′M″(dpa)4(Cl)2](M=Co,Ni;M′,M″=Co,Rh)电子输运的理论研究

采用密度泛函理论DFT/BP86方法研究金属串配合物[MM'M″(dpa)₄(Cl)₂] [MM'M″=CoCoCo(1), CoCoRh(2), CoRhRh(3), NiCoRh(4)] 的结构和电子输运性质. 结果表明, 配合物1, 2和4的最稳定自旋态均存在1个(MM'M″)⁶⁺的离域$\sigma_{3}^{3}$键($\sigma^{2}\sigma_{nb}^{1}\sigma^{*0}$); 但配合物3具有1个(MM'M″)⁶⁺的离域$\sigma_{3}^{4}$键($\sigma^{2}\sigma_{nb}^{2}\sigma^{*0}$)和2个$\pi_{3}^{5}$键($\pi^{4}\pi_{nb}^{4}\pi^{*2}$), 故Rh—Rh键和Co—Rh键较强; Rh的引入使M—M键增强, Ni的引入则使M—M键减弱, 键强次序为Rh—Rh>Co—Rh>Co—Co>Ni—Co. 配合物14的传输通道均含有π和σ型轨道. 正偏压下, 配合物2和3的电流大于配合物1和4的. 负偏压下, 配合物4中出现负微分电阻效应. 配合物3中形成传输通道的σ_nbα/β和π^*α/β轨道能级分裂明显, (MM'M″)⁶⁺对β自旋的π^*轨道的贡献(88%)比α自旋(74%)的大, 使β自旋的电子更易传输, 具有较好的自旋过滤效应(70%80%).     

新型咪唑[2,1-b][1,3,4]噻二唑衍生物的合成及生物活性

合成了18个新型含苯并噁/噻唑啉酮结构的2,6-二取代咪唑[2,1-b][1,3,4]噻二唑衍生物5a~5i', 即2-[(2-苯并噁/噻唑啉酮-3-基)甲基]-6-芳基-咪唑[2,1-b][1,3,4]噻二唑. 利用红外光谱、 核磁共振和元素分析对化合物的结构进行了表征. β2-肾上腺素受体(β2-AR)拮抗剂钙流筛选结果表明, 部分目标化合物对β2-AR具有明显的拮抗作用, 其中化合物5c'的拮抗效果最高, 为70%. 这些化合物可作为潜在的β2-AR拮抗剂.     

改性钛基PbO2电极的制备及其对COD的快速检测

通过制备Ti/α/β-PbO₂、Ti/Ag/β-PbO₂这两种含有不同中间层的钛基二氧化铅电极来探究电催化氧化技术快速测定葡萄糖模拟废水中有机物(COD)含量的可行性。为了评估两种电极的各项性能,首先采用扫描电镜(SEM)、X射线衍射(XRD)对电极进行形貌表征,其次进行电化学性能测试包括线性伏安曲线(LSV)、塔菲尔曲线(Tafel)、循环伏安曲线(CV)以及交流阻抗测量分析。结果表明,Ti/α/β-PbO₂电极表面晶体结构更加均匀,晶粒尺寸偏小,具有更大的电活性表面积。Ti/α/β-PbO₂电极的析氧电位为1.77 V,为·OH的产生提供良好条件。在Tafel、CV测试中,Ti/α/β-PbO₂电极的交换电流密度i₀及比电容C_p分别为0.0995 A·cm^-1、0.004098 F·cm^-1均高于Ti/Ag/β-PbO₂电极,说明Ti/α/β-PbO₂电极的耐腐蚀性以及释放电子的能力优异。最终选用Ti/α/β-PbO₂电极为工作电极。Ti/α/β-PbO₂电极检测COD的最佳条件为：氧化电位1.30 V、电解时间150 s、电解液浓度0.03 mol·L^-1 硝酸钠(NaNO₃)。电化学法与比色消解法测定COD的相关系数可达0.9909,同时具有良好的重现性与相关性,COD的检测范围为0 mg·L^-1 ~ 500 mg·L^-1。在误差允许的范围内可以替代标准的重铬酸钾法,为实现COD的在线快速检测提供参考价值。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.