Graph-Theory Derived Models for the Skeletal Chemical Bonding in Organometallic Metal Carbonyl Clusters

Ideas derived from topology and graph theory can be used to model the skeletal chemical bonding in metal carbonyl clusters as well as boranes and carboranes. In such molecules delocalized skeletal bonding occurs when there is a mismatch between the number of internal orbitals provided by a vertex atom and the number of polyhedral edges meeting at that vertex. Such global delocalization in deltahedral metal clusters may be regarded as a three-dimensional analogue of the aromaticity in planar polygonal molecules such as benzene. Elementary graph-theoretical considerations provide a basis for the 2n+2 skeletal electrons normally observed in n vertex delocalized deltahedral metal clusters lacking tetrahedral chambers. Electron-rich n-vertex metal clusters have more than 2n + 2 skeletal electrons and form polyhedra having at least one face with at least 4 edges. Electron-poor n-vertex metal clusters have less than 2n + 2 skeletal electrons and form deltahedra having at least one tetrahedral chamber. Ideas derived from group theory and graph theory can be used to analyze molecular orbital energy parameters for the most symmetrical deltahedral borane anions B_nH_n²⁻ (particularly n = 6 and 12) computed using either semiempirical extended Hückel methods or ab initio methods based on Gaussian orbitals. Some of the fundamental aspects of the graph-theory derived models for skeletal bonding in delocalized deltahedral metal clusters are closely related to the tensor surface harmonic theory of Stone.     

Metal Phosphates as a New Class of Supports for Gold Nanocatalysts

Oxides and carbon are commonly used as supports for gold nanoparticles, but metal salts are barely considered as suitable supports. Our group recently communicated that gold nanoparticles supported on nanosized LaPO₄ (6–8 nm) are active for CO oxidation (Yan et al., Angew Chem Int Ed 45:3614, 2006). In the current work, we systematically developed an array of Au/M–P–O catalysts and tested them for catalytic activity and stability. It was found that 200 °C-pretreated Au/M–P–O (M = Ca, Fe, Co, Y, La, Pr, Nd, Sm, Eu, Ho, Er) show high CO conversions below 50 °C, and 500 °C-pretreated Au/M–P–O (M = Ca, Y, La, Pr, Nd, Sm, Eu, Ho, Er) show high CO conversions below 100 °C. These samples were characterized by ICP-OES, BET, XRD, TEM, SEM, and H₂-TPR. The stability of selected catalysts was studied as a function of time on stream. This work furnishes a new catalyst system for further fundamental and applied research.     

Microwave Discharge of O2 and CO2 as a Synthetic Tool for Oxidations of Unsaturated Compounds Adsorbed on Solid Supports

Cis and trans stilbene, styrene, 1-decene and 6-dodecene adsorbed on silica gel were reacted with oxygen atoms produced by microwave discharge of O₂ and CO₂. At 0°C these compounds gave mainly epoxides and carbonyl compounds as in neat liquid reactions. Below — 60°C ozonolysis products were formed; cis and trans stilbene and styrene gave benzaldehyde while 1-decene and 6-dodecene resulted mainly in ozonides.     

石墨烯的制备及其负载金属催化剂的研究进展

石墨烯是一种新型的碳纳米材料,具有优异的物理和电学性能,已成为物理和半导体电子研究领域的国际前沿和热点之一。概括了几种制备石墨烯的方法,评述了其作为载体负载金属催化剂如Pd、Pt和Ir的研究进展。指出了石墨烯作为金属催化剂载体的发展趋势。     

Metal and Metal Oxide Nanoparticle as a Novel Antibiotic Carrier for the Direct Delivery of Antibiotics

In addition to the benefits, increasing the constant need for antibiotics has resulted in the development of antibiotic bacterial resistance over time. Antibiotic tolerance mainly evolves in these bacteria through efflux pumps and biofilms. Leading to its modern and profitable uses, emerging nanotechnology is a significant field of research that is considered as the most important scientific breakthrough in recent years. Metal nanoparticles as nanocarriers are currently attracting a lot of interest from scientists, because of their wide range of applications and higher compatibility with bioactive components. As a consequence of their ability to inhibit the growth of bacteria, nanoparticles have been shown to have significant antibacterial, antifungal, antiviral, and antiparasitic efficacy in the battle against antibiotic resistance in microorganisms. As a result, this study covers bacterial tolerance to antibiotics, the antibacterial properties of various metal nanoparticles, their mechanisms, and the use of various metal and metal oxide nanoparticles as novel antibiotic carriers for direct antibiotic delivery.     

Studies on the Phototransformations of Perylene Adsorbed on Non-Activated Silica Gel and Alumina as Models of Atmospheric Particulate Matter

Studies have been performed on the photochemical transformations of perylene adsorbed on non-activated silica gel of different pore sizes and alumina used as models of atmospheric particulate matter. Fluorescence, diffuse reflectance and EPR techniques have been used to study the effect of coadsorbed gases (O₂ and Ar), H₂O, time of storage in the dark, and loading on the photodegradation rates and on the formation of intermediate products. Oxygen quenches significantly the fluorescence and accelerates the photodegradation rate, suggesting the participation of O₂ reactive species in the degradation reactions. The formation of photoproducts emitting and absorbing at longer wavelengths than the original compound is observed. It is suggested that oxygen participates in the destruction pathways since in an argon atmosphere these bands do not appear. Adsorbed H₂O induces the formation of absorbing and emitting complexes with perylene or of aggregates of it formed by its displacement from the adsorption sites. New emitting intermediate products are observed in the presence of H₂O. The pore sizes and the loading influence the rate of product formation. The EPR spectra of irradiated samples confirm the presence of the radical cation and the photoionization of Per into Per⁺ on the silica gel.     

An Overview on the Performance of 1,2,3-Triazole Derivatives as Corrosion Inhibitors for Metal Surfaces

This review accounts for the most recent and significant research results from the literature on the design and synthesis of 1,2,3-triazole compounds and their usefulness as molecular well-defined corrosion inhibitors for steels, copper, iron, aluminum, and their alloys in several aggressive media. Of particular interest are the 1,4-disubstituted 1,2,3-triazole derivatives prepared in a regioselective manner under copper-catalyzed azide-alkyne cycloaddition (CuAAC) click reactions. They are easily and straightforwardly prepared compounds, non-toxic, environmentally friendly, and stable products to the hydrolysis under acidic conditions. Moreover, they have shown a good efficiency as corrosion inhibitors for metals and their alloys in different acidic media. The inhibition efficiencies (IEs) are evaluated from electrochemical impedance spectroscopy (EIS) parameters with different concentrations and environmental conditions. Mechanistic aspects of the 1,2,3-triazoles mediated corrosion inhibition in metals and metal alloy materials are also overviewed.     

二-(三苯基膦)铵盐在合成及表征过渡金属羰基簇合物中的应用

过渡金属羰基簇合物常具有新颖的几何构型和多样化的成键方式。它们不仅扩展了配位化学的研究范畴和深度 ,更在工业催化〔1〕和分子材料〔2〕领域显示出重要的科学意义和广泛的应用前景〔3〕。而如何合成出具有新奇结构的过渡金属羰基簇合物便成为不少化学工作者所感兴趣的研究方向。本文通过实例阐述了二 - (三苯基膦 )铵盐 (简称PPN)在过渡金属羰合物合成及表征等方面中的应用。1　用PPN合成的过渡金属羰基簇合物PPN常被用于制备含填隙、半填隙配原子的过渡金属羰基簇合物。合成此类化合物大体有两种方法 :一是用过渡金属二元羰合物与…     

不同载体和金属助剂负载Pt催化剂对丙烷催化氧化活性研究

制备了不同载体、不同金属助剂及不同贵金属Pt含量的蜂窝催化氧化催化剂,并评价了催化剂催化氧化含丙烷有机废气的活性:通过表面结构表征和活性评价实验,发现r-氧化铝作为载体时催化剂活性比分子筛和二氧化钛好;随着Pt含量的增加,催化剂的活性先升高后降低,Pt质量分数为0.2%时催化剂的活性最高;分别制备Pt/MO_x/Al_2O_3(M为铜、锰、钨、铈、锆、镧中的一种),在催化剂表面发现Pt聚集的颗粒,CeO_x的加入可改善贵金属的分布,Pt/CeO_x/Al_2O_3活性最佳,在400℃条件下,丙烷转化率达到95%以上,此时CeO_x的质量分数为1.0%。     

Oxidation of Hardwood Kraft-Lignin to Phenolic Derivatives. Nitrobenzene and Copper Oxide as Oxidants

A hardwood kraft lignin (obtained by precipitating an industrial black liquor with a solution of calcium salt in alcohol) was oxidized in alkaline medium to obtain phenolic compounds (syringaldehyde, vanillin, syringic acid and vanillic acid). Nitrobenzene and copper (II) oxide were the oxidants employed. Influence of temperature, reaction time and oxidant concentration on yield and product distribution were studied. The results show that nitrobenzene is a more effective oxidant (15–18 % of aldehydes on kraft lignin) than copper (II) oxide (7–8 %). Product distribution showed the highest aldehyde selectivity for nitrobenzene, due to the presence of two additional oxidation products in the copper oxide oxidations. In the oxidation to aldehydes, the alcohol-calcium precipitated kraft lignin is a better raw material than other precipitated kraft lignin.     

DTC类重金属捕集剂研究的进展

二硫代氨基甲酸盐(dithiocarbamate，DTC)衍生物对重金属有极强的螯合能力，在环境治理中主要有螯合剂和螯合树脂两种利用形式。前者主要用于成分复杂污染物中重金属离子的去除；后者主要用于环境分析中金属的分离与预富集。今后进一步研究方向应为：根据物质结构与性能的关系，开发更加稳定、高效、低毒的产品，并加强其应用工艺的研究开发。     

氧化铁及含氧化铁药品重金属检查方法的建立

目的:采用新型比色法建立氧化铁及含氧化铁药品重金属检查法。方法:采用过量盐酸与Fe~(3+)生成HFeCl_6~(2-)络合物,继而通过二甲基异丁基甲酮的萃取而特定去除溶液中的Fe~(3+),避免其干扰的比色法测定氧化铁及含氧化铁药品重金属含量。结果:改良比色法可有效检查氧化铁及含氧化铁药品重金属含量,结果可靠,回收率良好。结论:所建方法简单可行,适用范围广,不使用昂贵仪器,且安全风险更小。     

超级电容器RuO_2及其金属氧化物复合电极材料的研究现状

本文综述了超级电容器RuO_2电极材料及其TiO_2、SnO_2、Co_3O_4、MnO_2及NiO_2等过渡族金属氧化物复合电极材料的研究进展,结果表明仅从制备方法上提高RuO_2电极材料的综合性能存在局限性,难以获得到高比电容、低成本的电极材料。采用过渡族金属氧化物掺杂RuO_2基电极材料,在性能与成本上获得了一定的进展,但是还没有真正达到降低成本与改善性能的双重作用。同时寻求性能较为优良、成本低廉的电极材料仍将成为当今超级电容器电极材料的研究热点。     

金属催化剂选择性催化氧化甘油及其衍生物的研究

阐述了甘油氧化的路径,利用Pd、Pt和Au等金属催化剂,选择性催化氧化甘油及其衍生物制备甘油酸、1,3-二羟基丙酮、羟基丙酮酸、丙醇二酸和丙酮二酸等一系列重要化学品的研究,此方法选择性高,反应温和,对环境友好,前景广阔。     

偕胺肟基聚丙烯腈螯合纤维中金属离子含量与其力学性能关系的研究

以聚丙烯腈(PAN)为原料纤维,与羟胺溶液反应,制得偕胺肟纤维(AOCF)。以偕胺肟纤维与金属离子Cu(Ⅱ)、Co(Ⅱ)、Hg(Ⅱ)、Zn(Ⅱ)、Cd(Ⅱ)反应生成一系列的金属螯合纤维(M-AOCF),测定了各M-AOCF的单纤强力。结果显示:制得的金属螯合纤维,随着金属离子含量的增加,纤维断裂强度逐渐降低;且当含量较低时,纤维断裂强度大于原AOCF;当含量超过一定值时,断裂强度小于原AOCF。     

羰基金属对甲醇催化剂的毒害及其净化剂的研究进展

论述了羰基金属的形成、来源及其对催化剂的危害,综述了羰基镍、羰基铁的分析方法、脱除方法以及存在的问题,论述了目前国内外羰基金属净化剂的研究进展情况。