AgPd双金属纳米空心球的合成及其催化性能

以Ag纳米颗粒为牺牲模板,H₂PdCl₄为前驱体,抗坏血酸为还原剂,聚乙烯吡咯烷酮为表面活性剂,在70℃下采用电偶置换法结合还原法制备出AgPd双金属纳米空心球。采用紫外可见光谱、粉末X射线衍射、透射电镜结合能量色散等手段对由不同体积的0.01 mol·L^-1 H₂PdCl₄溶液制备的产物进行结构表征。结果表明,随着H₂PdCl₄溶液体积的增加,产物的空心化程度逐渐升高,晶粒的尺寸逐渐增大。当H₂PdCl₄溶液体积为120 μL时,合成的AgPd双金属纳米空心球组成和结构较为均匀,其粒径约为25 nm,壳层厚度2~3 nm。双金属中,由于Ag和Pd电负性的差异,电子从Ag转移到了Pd,使Pd表面出现电子富集区,显著提高了其催化效率。将所合成的AgPd双金属以及纯金属Ag和Pd作为催化剂,分别用于硼氢化钠催化还原4-硝基苯酚的反应,发现AgPd双金属的催化性能远高于纯金属Ag和Pd,其中AgPd-120纳米空心球(H₂PdCl₄溶液体积120 μL)作催化剂时的反应速率常数最高,是同等尺寸纯Ag纳米球的24.0倍,纯Pd纳米立方体的14.7倍。     

低负载量的双金属Au@Pt核壳催化剂催化氧化甲苯

采用液相氢气两步还原法制备了双金属Au@Pt核壳纳米粒子,通过直接吸附法将纳米粒子均匀地分散于载体上,制备出低负载量的双金属Au@Pt/Al₂O₃催化剂,并且评价了催化剂对甲苯的催化氧化性能。通过TEM、XRD、XPS、N₂吸附-脱附和H₂-TPR等对催化剂进行了表征。结果表明,与单金属Au和Pt催化剂相比,双金属Au@Pt核壳催化剂表现出更高的催化活性,具有很好的稳定性和选择性,在甲苯体积分数为1×10^-3,气体空速为18 L·g^-1·h^-1的条件下,Au₁@Pt₂/Al₂O₃核壳催化剂具有优异的催化氧化性能,其中甲苯实现98%的转化率的温度（T₉₈）为195℃。由XPS结果可知,在Au和Pt之间存在电子转移促进了Pt上活性氧物种的形成,催化剂的活性组分主要以Au⁰和Pt⁰的形式存在,并广泛分布在载体的表面上。Au@Pt纳米粒子与载体Al₂O₃之间的强相互作用也是提高甲苯催化氧化活性的重要因素。     

PdCl42-配离子插层类水滑石的组装及其结构特征

以Mg_0.76Al_0.24(OH)₂(NO₃)_{0.24·0.32H2O LDHs为前体，由离子交换法实现了层间为含Pd阴离子LDHs的插层组装。用XRD、FT-IR、TG-DTA和ICP等手段对样品进行表征和分析，结果表明Pd以PdCl4^2-的形式位于层间，反应24 h达到最大插层限度，配离子平面平行于层板排布，3个PdCl4^2-配离子构成的几何空间的中心存在1个NO3-离子以维持插层结构能量最低。所得插层产物的化学组成式为Mg0.74Al0.26(OH)2(PdCl4)0.11(NO3)0.04·0.62H2O。}     

改进液相还原法制备的Pd/C催化剂对甲酸氧化的电能

用液相还原法制备炭载Pd(Pd/C)催化剂时,先用Na₂CO₃调节溶液pH值至8～9,然后加入还原剂还原PdCl₂,由于PdCl₂能与Na₂CO₃形成配合物,降低了得到的Pd粒子聚集倾向,使制得的Pd/C催化剂中Pd粒子的平均粒径和相对结晶度都较小,分别为3.57 nm和1.37。而没有加Na₂CO₃制得的Pd/C催化剂中Pd粒子的     

软模板法六边形纳米Pd粒子的超声制备与表征

在微量十六烷基三甲基溴化铵(CTAB)存在下,超声还原PdCl₂水溶液,没有气氛保护且不加还原剂制得了纳米Pd粒子,用XRD、TEM、选区电子衍射(SAED)、UV、HRTEM和低温氮吸附-脱附等进行了表征。结果表明,纳米Pd晶粒的粒径分布集中,约为8 nm,呈六边形,(111)晶面的晶面间距为0.22 nm,晶格条纹清晰均匀。研究了纳米粒子的生长过程,揭示了NR₄X-Pd²⁺配合物的生成,分析了可能的超声反应机理。利用CTAB模板控制得到的纳米粒子比未添加CTAB样品的比表面积增大了10 m²·g^-1,有利于催化性能的提高。     

PdCl2-CuCl2/Al2O3催化剂低温催化CO氧化的失活机理

采用X射线衍射、N₂吸-脱附、X射线光电子能谱分析、氢气-程序升温还原和原位红外漫反射等方法对新鲜和失活的PdCl₂-CuCl₂/Al₂O₃低温催化CO氧化催化剂进行表征,研究了高相对湿度(100%)下催化剂的失活机理.结果表明,催化剂表面沉积的水使得活性铜物种容易从催化剂表面向载体孔道内部迁移,由于Pd、Cu相互作用弱化从而减弱了Pd与Cu物种间的相互作用,使得催化剂的氧化还原性能受到影响,抑制了Pd⁰再氧化为Pd²⁺的过程,从而因CO氧化反应中催化剂氧化还原循环受阻而导致失活.     

磁性纳米Fe3O4的氧化共沉淀法制备及催化性能

以单一 Fe²⁺作为铁源,0.4% 的 H₂O₂为氧化剂,NaOH 为沉淀剂,采用氧化共沉淀法制备了尺寸为 7 nm的 Fe₃O₄颗粒。为进一步体外模拟肿瘤饥饿治疗,设计了一个包含5 mL(10 μg·mL^-1)的葡萄糖氧化酶和15 mL(5 mg·mL^-1)葡萄糖溶液的体系,以探究纳米 Fe₃O₄的类过氧化氢酶(CAT)与类过氧化物酶(POD)催化性能的最适条件。结果表明：在 1 mg·mL^-1 pH=5.0 时,纳米Fe₃O₄的类CAT活性能推动葡萄糖氧化反应的反应速度增加、限度增大;pH=5.0时,纳米Fe₃O₄的类POD活性更好,能高效率催化H₂O₂产生活性氧。     

磁性纳米Fe3O4的氧化共沉淀法制备及催化性能

以单一 Fe²⁺作为铁源,0.4% 的 H₂O₂为氧化剂,NaOH 为沉淀剂,采用氧化共沉淀法制备了尺寸为 7 nm的 Fe₃O₄颗粒。为进一步体外模拟肿瘤饥饿治疗,设计了一个包含5 mL(10 μg·mL^-1)的葡萄糖氧化酶和15 mL(5 mg·mL^-1)葡萄糖溶液的体系,以探究纳米 Fe₃O₄的类过氧化氢酶(CAT)与类过氧化物酶(POD)催化性能的最适条件。结果表明：在 1 mg·mL^-1 pH=5.0 时,纳米Fe₃O₄的类CAT活性能推动葡萄糖氧化反应的反应速度增加、限度增大;pH=5.0时,纳米Fe₃O₄的类POD活性更好,能高效率催化H₂O₂产生活性氧。     

牺牲模板法制备空心结构钯纳米粒子/石墨烯复合体及其甲酸电氧化性能研究

通过PdCl₄^2-与Co之间发生简单的置换反应,在表面活性剂PVP的作用下,成功地制备出由3nm的Pd纳米粒子组成的空心结构Pd纳米球结构,将其命名为Pd-NS。随后,以石墨烯（GN）作为载体,将Pd-NS负载在GN的表面制备了Pd-NS/GN催化剂。在甲酸电氧化催化反应中,Pd-NS/GN催化剂表现出较大的电化学比表面积、良好的电催化性能以及较高的稳定性。     

纳米晶态硼化钴的合成及其催化氨硼烷高效制氢

采用简单的煅烧工艺合成了纳米硼化钴(CoB)晶体,并首次研究了纳米CoB晶体在氨硼烷溶液水解制氢过程中的催化活性。研究发现,纳米CoB晶体具有较高的催化活性,在室温条件下其转换频率(TOF)为35.3mol_H2·mol_cat^-1·min^-1,优于同等条件下贵金属Pt催化剂(TOF=29.3mol_H2·mol_cat^-1·min^-1)。此外,循环测试8次后纳米硼化物晶体的催化制氢性能没有发生衰减。进一步研究发现CoB表面的Co⁰物种是催化制氢的活性位点,而表面的B物种位点能够有效辅助Co⁰位点实现协同催化氨硼烷制氢。     

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.     

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.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

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.