27Al核磁共振波谱法测定环境生物样品中铝研究进展

近二十年来,高分辨率²⁷Al核磁共振(²⁷Al NMR)广泛应用于研究Al(Ⅲ)离子水解过程,Al(Ⅲ)与环境生物配体的配位化学,环境与生物样品中铝含量测定和形态分析,监测铝在植物、动物、酵母菌等微生物中的转运过程,具有快速、直接、非破坏性等优点。²⁷Al NMR不仅适用于高浓度的溶液,也可应用于低浓度(10^-6mol·L^-1)的实际环境、生物样品。应用²⁷Al MASNMR可直接对固态样品中铝的存在状态和含量进行表征和测量。本文中对²⁷Al NMR的应用进展作一评述,并总结了近二十年来文献发表的²⁷Al化学位移数据。引用文献70余篇。     

介孔硅铝酸盐的合成及其在傅克反应中的催化性能

采用溶胶凝胶法合成了一系列有序性好且酸性较强的介孔硅铝酸盐材料。利用X射线粉末衍射(XRD)、透射电镜(TEM)、²⁷Al核磁共振(²⁷Al NMR)、氨气程序升温脱附(HN₃-TPD)及吡啶吸附红外光谱(Py-FT-IR)对制备的介孔硅铝酸盐材料的结构和性能进行表征,并考察了材料在苯甲醚和苯甲醇的傅克烷基化反应中的催化活性。实验结果表明：合成过程中,表面活性剂的用量、硅铝物质的量的比会影响材料结构的有序性,醋酸用量对材料结构有序性影响很小;进一步研究结果表明,n_Si / n_Al比会影响材料的酸催化活性,当n_Si / n_Al=10时材料的酸催化活性最高。氨气程序升温脱附和吡啶吸附红外光谱表明n_Si / n_Al=10的材料含有最多的B酸酸量。     

柠檬酸溶液中NaY分子筛的脱铝行为

硅铝分子筛有机酸配合脱铝是提高其稳定性、引入介孔的一种重要方法.采用X射线衍射、N₂物理吸附、高分辨透射电镜、傅里叶变换红外光谱、²⁷Al和²⁹Si固体魔角自旋核磁共振光谱等方法研究了NaY分子筛柠檬酸脱铝行为.结果表明,柠檬酸浓度对NaY分子筛骨架Al原子的脱出影响尤为显著.反应起始阶段,分子筛骨架铝原子快速脱出,其晶体结构遭到严重破坏.随着反应的进行,分子筛硅铝比和结晶度皆有所增加,表明其骨架结构可能进行了重新排列.75℃下,0.10 mol/L柠檬酸处理2 h的脱铝分子筛样品,与NaY分子筛样品相比,其骨架硅铝比增加了0.6、外表面增加了17 m²·g^-1,脱铝同时产生了大量无定形硅.     

有机-无机杂化凝胶法合成YAG∶Ce3+荧光粉的包膜及其稳定性

本文以金属硝酸盐为原料，柠檬酸为配位剂的有机-无机杂化凝胶法来合成掺杂三价铈离子的钇铝石榴石荧光粉，采用X-射线衍射法研究了杂化凝胶在煅烧过程中的相转变机制。结果表明:杂化凝胶在煅烧过程中可以通过两条途径形成Y₃Al₅O₁₂(YAG)相:一是由无定形Y₂O₃和Al₂O₃直接向YAG相的一步相转变;二是由无定型Y₂O_{3相似文献}   

系列硅铝比纳米薄层ZSM-5分子筛的合成和表征

以自制不对称双子季铵盐表面活性剂为模板, 在水热合成体系中控制合成系列硅铝比纳米薄层ZSM-5分子筛.采用X射线衍射(XRD)、N₂吸附-脱附、X射线荧光光谱(XRF)、扫描电镜(SEM)和²⁷Al魔角旋转核磁共振(²⁷Al MAS-NMR)对合成的样品进行了表征. 详细研究了晶化温度、晶化时间、结构导向剂(SDA)用量、碱度等对合成的影响和纳米薄层ZSM-5分子筛的形成过程. 结果表明: 分子筛硅铝比越高, 结构导向剂用量越大, 所需的晶化时间越短; 晶化温度越高, 晶化时间越短; 且不同硅铝比纳米薄层ZSM-5分子筛的形貌规整度、比表面积和介孔/微孔孔容比例随着硅铝比而变化.     

低密度、块状氧化铝气凝胶制备

研究了工艺参数对氧化铝溶胶及气凝胶的影响。结果表明,稳定的氧化铝溶胶优化制备工艺为：仲丁醇铝为前驱体,水解温度60 ℃,仲丁醇铝、乙醇、水的物质的量之比为1∶(8～16)∶1.2;螯合剂乙酰乙酸乙酯能有效控制仲丁醇铝水解缩聚速率,提高溶胶的稳定性;块状氧化铝气凝胶主要成份为多晶勃姆石相,比表面积为447 m²·g^-1,其强度和密度随乙醇量的增加而降低,密度最低为0.040 g·cm^-3。氧化铝气凝胶微观结构由许多片叶状颗粒堆积形成,经1 200 ℃热处理后仍保持原有的微观形貌,比表面积为73 m²·g^-1。     

透明PANI/ATO杂化导电薄膜的制备与表征

以聚苯胺和掺锑的氧化锡作为主要原料、采用溶胶-凝胶法制备了新型有机-无机杂化的透明导电薄膜，薄膜的可见光透过率为80%以上、电导率达到1~10 S·cm^-1。着重研究了制备过程中热处理温度、引入水量以及浸涂液浓度对薄膜的结构、可见光透过率和电导率的影响。确定了薄膜的最佳工艺条件为： 热处理温度为300 ℃、引入水量为R_w = 12、浸涂液的浓度为114 g·L^-1。浸涂液的粘度可在长达25 d的时间内保持稳定。     

钇铝石榴石(YAG)透明陶瓷的研究进展EI北大核心CSCD

钇铝石榴石(Y_(3)Al_(5)O_(12))透明陶瓷具有机械强度高、物化性质稳定,特别是覆盖紫外、可见及红外光透过等优异性能,在固体激光器、导弹穹顶、红外窗口及透明装甲领域有着广泛的应用。本文系统总结了YAG透明陶瓷的制备工艺,包括粉体合成、坯体成型、陶瓷烧结及烧结助剂的选用,对比了不同工艺路线制备YAG透明陶瓷的性能、规格、成本等;就不同稀土离子掺杂对YAG基透明陶瓷性能的影响规律进行了全面阐述;最后通过对现有问题的总结,展望了钇铝石榴石(YAG)透明陶瓷未来的发展趋势。     

超级铝热剂Al/CuO前驱体的制备、表征、热分解机理及非等温分解反应动力学

以硝酸铜、无水乙醇、1,2-环氧丙烷和纳米铝粉为原料, 在超声振荡条件下, 采用溶胶-凝胶法制备了纳米复合含能材料——超级铝热剂Al/CuO的前驱体. 利用热重-差示扫描量热-傅里叶变换红外-质谱(TG- DSC-FTIR-MS)联用技术, 研究了纳米Al/CuO溶胶-凝胶前驱体的热行为和分解过程及机理. 利用不同升温速率下的TG-DTG分析, 研究了纳米超级铝热剂Al/CuO的溶胶-凝胶前驱体的热分解反应机理, 采用了6种动力学分析方法进行动力学参数计算, 得到前驱体分解反应的表观活化能、反应级数、频率因子等动力学参数, 纳米Al/CuO前驱体分解反应的动力学方程为: dα/dt=10^14.0×4α^3/4exp(-2.0×10⁴/T).     

钇(Ⅲ)的二特戊酰基甲烷螯合物的合成、表征及热稳定性和升华性能研究

合成了钇(Ⅲ)的二特戊酰基甲烷螯合物(简称Y(DPM)₃)，并以红外光谱、核磁共振谱及X-射线物相分析进行了表征和鉴定。研究了这种β-二酮类螯合物的升华性能。结果表明，其升华速率与温度呈指数关系，与载气流量呈线性关系；通过测定蒸气压与温度之间的关系，求得130℃～164℃温度范围内的升华焓和升华熵，分别为135 kJ·mol^-1和265 J·mol^-1·K^-1。实验研究表明，该螯合物具有良好的挥发性和热稳     

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.     

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.     

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.     

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.