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?离子水解过程 ,Al?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 MAS NMR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。     

叠氮二乙基铝合成及其相关反应的研究

在芳烃溶剂中用氯化二乙基铝和叠氮化钠反应合成了叠氮化二乙基铝(DEAA),其产率高达87%,比文献值高出17%。在正己烷中没有合成出DEAA,在含30%四氢呋喃(THF)的正己烷中合成出DEAA·THF配合物。在芳烃溶剂中,随着苯环上甲基数目的增加,DEAA的收率增加。测定了氯化二乙基铝、氯化二乙基铝的正己烷溶液、氯化二乙基铝的甲苯溶液的 ²⁷Al NMR谱。由 ²⁷Al NMR谱数 据确定了氯化二乙基铝在甲苯中解离平衡式,计算了氯化二乙基铝在甲苯中解离平衡的热力学数据。用DEAA与苯甲酸甲酯直接合成了苯甲酰叠氮,并表征了其结构。这是一个新反应,至今无文献报导。用实验证明了在正己烷溶液中,用氯化二乙基铝、叠氮化钠与苯甲酸甲酯合成苯甲酰叠氮,没有经过氯化二乙基铝和叠氮化钠反应生成中间体DEAA的这一步。依据实验事实建立了上述三种反应的反应机理。     

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.     

μ-氧-双[meso-四(对烷氧基苯基)卟啉合铝(III)]的合成、表征和液晶性能研究

合成了一系列未见文献报道的μ-氧-双[meso-四(对烷氧基苯基)卟啉合铝(Ⅲ)]配合物. 用UV-vis, ¹H NMR, IR, MS和元素分析对各个化合物的结构进行了表征和确认, 发现在该系列配合物中两个卟啉分子通过Al—O—Al键形成二聚体. 用差示扫描量热仪(DSC)和偏光显微镜(PM)研究了其液晶性, 发现其中九个配合物具有液晶性, 多为升温单变液晶, 有一至两个中介相, 有确定的相转变温度、热焓和相变区间. 考察了取代基、金属离子和配合物的空间结构对液晶性能的影响.     

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.     

三个新的海绵Spongia suriganensis神经酰胺

报道从中国南海硇洲岛产海绵Spongia suriganensis的乙醇浸提物中分离得到3个新的同系列神经酰胺2-N-(1,3,4-三羟基-17-甲基)十八烷基-2'-羟基-18-甲基二十碳酰胺(1), 2-N-(1,3,4-三羟基-17-甲基)十八烷基-2'-羟基-19-甲基二十一碳酰胺(2)和2-N-(1,3,4-三羟基-17-甲基)十八烷基-2'-羟基-20-甲基二十二碳酰胺(3), 其结构经过MS, IR, ¹H NMR, ¹³C NMR (DEPT), HMQC及HMBC等现代光谱手段和水解化学方法来确定.     

铝离子对α-酮戊二酸的催化脱羧作用

为了研究铝(Ⅲ)与生命体中重要的有机分子α-酮戊二酸的作用机制,我们采用了电位滴定、核磁共振、拉曼光谱和分子力学计算对酸性溶液中的反应体系的配位作用和互变异构进行了分析, 并采用电喷雾质谱以及固体和溶液核磁共振谱表征了浓溶液反应体系中的沉淀,来说明铝(Ⅲ)对α-酮戊二酸的催化脱羧反应过程。得到如下实验结论:(1)配位作用:铝(Ⅲ)与α-酮戊二酸在酸性溶液中配位形成1∶1[AlLH²⁺,AlL⁺,AlLH_-1]和1∶2[AlL₂]-,AlL₂]H_-2]^3-]的单核形态以及2∶1[Al₂]L⁴⁺]的双核形态。(2)互变异构:在酸性溶液中Al³⁺通过配位作用促进α-酮戊二酸烯醇化,生成易于脱羧的β、γ-不饱和酸的结构。(3)催化脱羧:由于铝(Ⅲ)的电子沉降作用,使β、γ-不饱和酸更易脱羧,如果是1∶2的形态,则脱羧生成沉淀。     

CXN天然沸石的研究 V. 结构超稳化

以离子交换结合控制焙烧的方法分别制得结构超稳化高硅H-STI-I和H-STI-II沸石. EDX, ²⁹Si MAS NMR, ²⁷Al MAS NMR, FT-IR等表征证明, 其骨架硅铝原子比分别为4.43和10.62. 分段程序升温焙烧后的沸石样品经粉末XRD表征表明, 其结构热稳定性达到1000 ℃以上. 结构稳定化沸石呈现反映微孔特性的I型吸附等温线, 吸附孔道完美、开放. 经历过酸处理的H-STI-II沸石, 结构缺陷增多, 其热稳定性、比表面积及孔容积略低于H-STI-I.     

氟硅酸铵改性纳米HZSM-5分子筛催化甲醇制丙烯

在静态条件下, 采用不同浓度的氟硅酸铵溶液对纳米ZSM-5分子筛进行了改性处理. 利用粉末X射线衍射(XRD)、²⁷Al 魔角旋转固体核磁共振(²⁷Al MAS NMR)、X射线荧光光谱(XRF)、X射线光电子能谱(XPS)、N₂ 吸附、透射电镜(TEM)、NH₃程序升温脱附(NH₃-TPD)、吡啶吸附红外光谱(Py-IR)等技术对改性前后纳米ZSM-5分子筛的骨架结构、织构性质、酸性质进行了表征. 并在常压、反应温度为450℃、甲醇质量空速(WHSV)为1 h^-1的条件下, 研究了改性前后纳米HZSM- 的甲醇制丙烯(MTP)催化性能. 结果表明, 合适浓度的氟硅酸铵处 理能够选择性地脱除纳米ZSM-5 分子筛的外表面铝, 从而使得HZSM-5 的酸密度降低, 比表面积和孔容增大, MTP催化性能显著提高. 氟硅酸铵改性后纳米HZSM-5 的丙烯选择性和丙烯/乙烯(P/E)质量比分别由原来的 28.8%和2.6提高到45.1%和8.0, 催化剂寿命增加了近2倍.     

中空介孔硅铝球形分子筛的制备及催化裂解性能

利用沸石前驱体溶液和介孔硅球(MSS)为原料, 通过水热法成功制备了具有中强酸性介孔壳的中空介孔硅铝球形分子筛(HMAS)。利用透射电镜(TEM)、扫描电镜(SEM)、X射线衍射(XRD)、N₂-吸脱附、²⁷Al核磁共振(²⁷Al NMR)及NH₃程序升温脱附(NH₃-TPD)对材料的结构和性能进行了表征。研究结果表明, 在MSS的中空过程中伴随有物质再分配和介孔结构的逐渐演变。MSS介孔孔道中的十六烷基三甲基溴化铵(CTAB)分子, 一方面保护MSS免遭强碱性沸石前驱体溶液的溶蚀, 另一方面作为形成HMAS介孔壳层的模板剂。在此CTAB分子的作用下, 沸石前驱体结构单元被引入到HMAS的介孔球壳上。所得材料具有介孔结构和中强酸性, 在催化裂解1, 3, 5-三异丙苯反应中表现出优异的催化性能。     

Analytical methods to determine Po and Pb in marine samples

This paper describes the methods of sampling, preconcentration, chemical separation and final count of ²¹⁰Po and ²¹⁰Pb present in different marine matrices to determine their background levels in a marine ecosystem. Complex, time consuming and selective radioanalytical methods have been used to prepare final clear sources for alpha spectrometry and beta count; in fact, gamma spectrometry, a method direct and non destructive, cannot be taken into account because the ²¹⁰Pb activity is very low which does not allow to carry out sufficiently accurate measurements and ²¹⁰Po is not a gamma emitter but it emits only alpha particle at 5.40 MeV. The results of ²¹⁰Po and ²¹⁰Pb activity concentrations obtained in different marine samples collected in the first two campaigns are still very few to discuss about the ²¹⁰Po and ²¹⁰Pb behavior in marine environment.     

Possibilities of multinuclear NMR in the chemistry of heteroorganic compounds

Results of multinuclear NMR studies of some heteroorganic compounds have been presented.According to a report at the conference «Current problems of organometallic chemistry» (May 8–13,1994, Moscow).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 614–616, April, 1994.     

Radiological characterization of drinking waters in Central Italy

Due to the importance of water in human life, its quality must be strictly controlled; for this purpose, simple and reliable analytical methods must be available. In this study, a monitoring of radioactivity content was performed in tap waters collected in a region of Central Italy to check the compliance with recent European and Italian regulations. Gross alpha and beta activities, ²³⁸U, ²³⁴U, ²²⁶Ra, ²²²Rn, and ³H concentrations were measured. Gross alpha and beta activities were determined by standard ISO 9696 and ISO 9697; for ²²⁶Ra, ²²²Rn and ³H determination, liquid scintillation was used. ²³⁸U and ²³⁴U concentrations were determined by alpha spectrometry after separation from the matrix by extraction chromatography and electroplating. The results revealed that the tritium concentration was always lower than 6.75 Bq l^− 1. The concentrations (mBq l^− 1) of ²²⁶Ra, ²²²Rn, ²³⁸U, and ²³⁴U ranged from < 1.70 to 15.31, from 0.69 to 20.3, from 0.65 to 48.77, and from 0.78 to 51.50, respectively.²³⁴U/²³⁸U ratios were higher than 1 in most cases. The results obtained revealed that, in most samples, gross alpha and gross beta were lower than the parameter value indicated in the international regulations. An attempt was also made to find a correlation between these results and the chemical parameters of waters.     

Rotational molecular motion and solvation of Na+ and Cs+ in water-dimethylacetamide. A nuclear magnetic relaxation study

Nuclear magnetic relaxation by intra- and intermolecular quadrupoleelectric field gradient interaction has been used for the study of the systems DMA-water-NaI and DMA-water-CsI at 25°C.¹⁴N relaxation of DMA and²H relaxation of D₂O measured over the complete mixture range reveal the behavior of the rotational molecular motion of the two solvent components. For both solvent components a marked maximum of the reorientational correlation time has been found, reflecting hydrophobic effects and strong DMA-water interaction. The quadrupolar relaxation rates of²³Na⁺ and¹³³Cs⁺ in pure DMA were evaluated giving an indication that the electric solvent dipoles in the solvation shell are not located on positions of cubic symmetry. A quantitative study of preferential solvation of the cations in the mixed solvent has been performed by using the H₂O-D₂O isotope effect on²³Na⁺ and¹³³Cs⁺ relaxation. For both cations an obviously typical change in the selectivity occurs. In the range l>x _{H2 O}>0.7 we find weak preferential hydration, but in the range 0.7>xH ₂ O>0 strong preferential solvation by DMA is reflected.     

A multinuclear NMR study in the solid state and in solution of thallium(I) tris-(pyrazol-1-yl)borates (thallium scorpionates)

The ¹H, ¹³C and ¹⁵N NMR spectroscopic properties of six thallium tris-(pyrazol-1-yl)borates, including a tetrakis derivative, were determined. The results in solution were necessary to understand those, more complicated, in the solid state. A collection of ²⁰⁵Tl-¹⁵N and ²⁰⁵Tl-¹³C couplings was measured in the latter state. Among those, a very large coupling constant (between 194 and 282 Hz) has been measured on the carbon at the position 4 of the pyrazole ring in several compounds and particularly for the cyclobutyl derivative [Tl(Tp^Cbu)]. It has been assigned to a direct interaction of the 4-C-H ? Tl type and related to the X-ray structures, when available.     

A N NMR study of tautomerism in dimethyl dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate

Dimethyl dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate can exist either in 1,2- or 1,4-dihydro tautomeric forms. The ¹⁵N NMR spectra of dimethyl dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate were measured at the ¹⁵N natural abundance level as well as in ¹⁵N doubly labelled selectively and in ¹⁵N completely labelled compounds (20% ¹⁵N). The J(¹⁵N,¹⁵N) value was determined in ¹⁵N completely labelled compounds (20% ¹⁵N) using 1D ¹⁵N INADEQUATE and was found to be 12.2 ± 0.2 Hz in deuteriochloroform, acetonitrile-d₃, DMSO-d₆ and CD₃OH. Very similar ¹⁵N chemical shifts and ¹J(¹⁵N,¹H) values were also observed in all the solvents. This indicates that compound 1 exists completely in the 1,4-dihydro tautomeric form (i.e., as dimethyl 1,4-dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate) in all the solvents tested.     

Nuclear magnetic resonance of donor atoms as a tool for determination of the structure of platinum metal complexes in solutions

Data on the NMR spectroscopy of C, N, O, Si, P, and Sn donor atoms of platinum metal complexes in solutions are surveyed. The chemical shift of a donor atom mainly depends on the ligand in the trans-position (due to the trans-effect). The chemical shift of a donor atom on a particular coordinate of the complex (coordinate shift, CSh) is an attribute of this coordinate and can be used to identify such a coordinate in platinum metal complexes and to determine the structures of complexes. Based on the known data, CSh diagrams were composed for ¹H, ¹³C, ¹⁴N, ¹⁷O, ¹⁹F, ³¹P, and ¹¹⁹Sn. Examples of using the CShs for determining the structures of platinum metal complexes in solutions are presented.     

Radiochemical characterization of spring waters in Balaton Upland, Hungary, estimation of radiation dose to members of public

Hungary is rich in spring waters. A survey studying the naturally occurring alpha emitter radionuclides in 30 frequently visited and regularly consumed spring waters was conducted out in the Balaton Upland region of Hungary.²²⁶Ra, ²²⁴Ra, ²³⁴U, ²³⁸U and ²¹⁰Po activity concentrations were determined by using alpha spectrometry after separation from matrix elements. Average concentration (mBq L^{− 1}) of ²²⁶Ra, ²²⁴Ra, ²³⁴U, ²³⁸U and ²¹⁰Po in the spring waters is varied from 2.1 to 601, from < 1.1 to 65.4, from 3.9 to 741.9, from < 0.44 to 274.3 and from 2 to 15.2 respectively. In most cases radioactive disequilibrium was observed between uranium and radium isotopes. The doses for the analyzed samples of spring water are in the range 3.59–166.73 μSv y^{− 1} with an average 18.2 μSv y^{− 1} .This is well below the 100 μSv y^{− 1} reference level of the committed effective dose recommended by WHO. Only one water sample had a dose higher than 100 μSv y^{− 1}, mainly due to the contribution from radium (²²⁶Ra, ²²⁴Ra) and ²¹⁰Po isotopes. This study provides important information for consumers and authorities about their internal radiological exposure risk from spring water intake.     

CO LMR spectrum of14N16O and its analysis with spectra of14N17O and14N18O

LMR spectra for v=1←0 transitions of¹⁴N¹⁶O in X²II_{1/2, 3/2} states were observed at 5.6 μm and 5.4 μm of CO laser. Introducing the advanced isotopic molecular constant scaling function to Hund’s case (a) diatomic structure model, these spectra were analyzed and fitted together with all reliable previous spectral data of¹⁴N¹⁶O as well as¹⁴N¹⁷O and¹⁴N¹⁸O. A full set of precise molecular parameters and their vibrational dependencies have been determined with much higher precision (1–2 orders for most parameters). Many of them have been obtained for the first time. Using isotopic scaling function, the molecular constants of¹⁴N¹⁷O and¹⁴N¹⁸O were deduced.     

The fractionation and determination procedures for the speciation of Pb and Po in soil samples

A method for speciation and determination of ²¹⁰Pb and ²¹⁰Po in soil samples was developed. The speciation was carried out by fractionating the soil samples into five fractions which are water soluble or exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and bound to residue. After mineralisation, 10% solution of each fraction was used to spontaneously deposit polonium on a silver disk at 85-90 °C and pH 1.5, and ²¹⁰Po was measured by α-spectrometry; the remain solution was used to separate lead by anion-exchange resin and purified by precipitation as PbS and PbSO₄, and ²¹⁰Pb was determined by a low background β-counter. The IAEA-327 reference material (soil) was studied for ²¹⁰Pb and ²¹⁰Po speciation. The results show that: (1) the average yields are 88.7 ± 6.4% for ²¹⁰Pb and 93.8 ± 8.2% for ²¹⁰Po; (2) if compared to the total ²¹⁰Pb activity in the sample, ²¹⁰Pb fractions are 0.95% in exchangeable form, 10.6% bound to carbonates, 14.3% bound to Fe-Mn oxides, 7.0% bound to organic matter and 67.2% bound to residue or acid soluble, and the corresponding values for ²¹⁰Po are 0.17%, 0.97%, 21.0%, 0.47% and 77.4%, respectively; and (3) the obtained ²¹⁰Pb concentration is in good agreement with the recommended value given by the IAEA.