Remote substituent effects on homolytic Fe?C bond energies of p‐G‐C6H4CH2Fe(CO)2(η5‐C5H5) and p‐G‐C6H4(H)(CN)CFe(CO)2(η5‐C5H5) studied by Hartree–Fock and density functional theory methods

In general, both stoichiometric and catalytic reactions of organometallic complexes involve breaking and forming metal–ligand bonds. Therefore, an evaluation of the thermodynamics of such reactions requires the knowledge of metal–ligand bond energies (BDEs). The homolytic Fe? C bond dissociation energies [i.e., ΔH_homo(Fe? C)s] of 12 para‐substituted benzyldicarbonyl(η⁵‐cyclopentadienyl)iron, p‐G‐C₆H₄CH₂Fp [1,G = NO₂, CN, COMe, CO₂Me, CF₃, Br, Cl, F, H, Me, MeO, NMe₂; Fp = (η⁵‐C₅H₅)(CO)₂Fe] and 12 para‐substituted α‐cyanobenzyldicarbonyl (η⁵‐cyclopentadienyl)iron, p‐G‐PANFp [2,PAN = C₆H₄CH(CN)] were studied using Hartree–Fock (HF) and density functional theory (DFT) methods with large basis sets. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of ΔH_homo(Fe? C)s. The B3LYP method satisfactorily predicts the α and remote substituent effects on ΔH_homo(Fe? C)s [ΔΔH_homo(Fe? C)s]. The fair correlations [r = 0.97 (g, 1), 0.99(g, 2)] of ΔΔH_homo(Fe? C)s of series 1 and 2 with the substituent σ constants imply that the para substituent effects on ΔH_homo(Fe? C)s originate mainly from polar effects, but those on radical stability originate from both spin delocalization and polar effects. The molecule stabilization effects (MEs) causes that not only the magnitude of ΔΔH_homo(Fe? C)s(1) varies significantly but also the direction changes from S‐pattern to O‐pattern. ΔΔH_homo(Fe? C)s(2) were found to conform to the Capto‐dative Principle. The detailed knowledge of the factors that determine the Fp? C bond strengths would greatly aid in understanding reactivity patterns in many processes. Copyright © 2010 John Wiley & Sons, Ltd.     

Structure comparison between Th2Zn17-type and TbCu7-type Sm–Fe intermetallic compounds and their nitrides by means of 57Fe-Mössbauer spectroscopy

Samarium–iron intermetallic compounds were prepared by a melt spinning method with low and high wheel speeds, which resulted in a Th₂Zn₁₇-type and a TbCu₇-type structure, respectively. Structure comparison between these types was investigated for Sm–Fe intermetallic compounds and their nitrides by ⁵⁷Fe-Mössbauer spectroscopy.     

Sonochemical synthesis of a new nano-sized cerium(III) supramolecular compound; Precursor for nanoceria

Using a sonochemical method, nanoparticles of a new Ce(III) supramolecular compound, (NAMH⁺)₂[Ce₄(pydc)₆(pydcH)₂(H₂O)₈]·8H₂O (1), (H₂pydc = 2,6-pyridinedicarboxylic acid, NAM = nicotinamide), have been synthesized. Compound 1 was characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), FT-IR spectroscopy and elemental analyses, and its structure was determined by X-ray crystallography. It has been revealed that its structure consists of tetra-nuclear building units that extend to a 3D supramolecular network via non-covalent interactions mainly hydrogen bonding. The thermal stability of complex 1 both for its crystals and nanostructures has been studied by the thermal gravimetric (TG) method and compared with each other. The role of ultrasound irradiation power and the concentration of initial reactants on the size and morphology of the nano-structured complex 1, has been investigated. Ceria nanoparticles were obtained upon the calcination of complex 1 at 800 °C under atmospheric air. Furthermore, the fluorescent properties of complex 1 at room temperature were studied.     

Effects of preheating on diaspore: Modifications in colour centres, structure and light emission

The thermal properties and thermal stability of diaspore-corundum (AlOOH-Al₂O₃), from Goian (Pontevedra, Spain) were studied by means of differential thermal analysis (DTA), thermogravimetry (TG), high temperature X-ray diffraction (HTXRD) and thermally stimulated luminescence (TL) techniques. The samples were annealed to link the combined effect of (i) dehydroxylation, (ii) oxidation-reduction of chromophores (Mn 0.5%, Fe₂O₃ 0.12%, TiO₂ 0.021% and Cr 80 ppm) determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and (iii) phase transitions whilst sample heating (i.e. α-AlOOH→α′-Al₂P₃→α-Al₂O₃). The blue colour of diaspore, attributed to the Ti⁴⁺-Fe²⁺ intervalence-charge-transfer mechanism, turns to white (circa 500 °C) in good agreement with the DTA endothermic peak (dehydroxylation). The coexistence of α-AlOOH and α′-Al₂P₃ phases has been detected by in situ HTXRD and could be correlated to the thermoluminescence tests performed on preheated aliquots (up to 500 °C).     

Tb2AlFe16-xMnx化合物的结构、磁性及正电子湮没谱研究

通过X射线衍射、磁测量及正电子湮没谱等手段研究了Tb₂AlFe_16-xMn_x（x=1—8）化合物的结构和磁性.X射线衍射研究结果表明Tb₂AlFe_16-xMn_x化合物具有六角相的Th₂Ni₁₇型结构.室温下的正电子湮没实验研究表明,Mn对Fe的替代导致化合物中的铁磁相互作用减弱,并且化合物中存在着较强烈的磁弹耦合效应.磁测量研究结果表明,Mn的替代导致Tb₂AlFe_16-xMn_x化合物的居里温度及自发磁化强度急剧下降. 关键词： 2AlFe_16-xMn_x化合物')" href="#">Tb₂AlFe_16-xMn_x化合物 磁弹耦合效应 居里温度     

柴油机进气道喷射甲醇的排放与经济性研究

在一台增压中冷的电控单体泵柴油机上采用柴油/甲醇组合燃烧（DMCC）方式进行排放特性与经济性试验研究。结果表明:采用DMCC方式能够大量减少NO_x排放,同时CO₂排放也有所降低。可以通过在排气管上加装氧化催化转换器（DOC）很好地清除掉DMCC方式增加的HC和CO排放,其催化效率在90%以上,比原机排放低很多,DMCC方式的甲醛排放比原机高,DOC对其催化率达98%,接近超低排放。DMCC模式外特性的热效率提高了7.607%,且存在一个最佳燃料匹配区间。     

Electrochemically induced oxidative cyclization of 2,3‐dihydroxypyridine. Synthesis of a novel highly oxygenated heterocyclic compound

Electrochemical oxidation of 2,3‐dihydroxypyridine in aqueous phosphate buffer solution at a glassy carbon electrode has been studied using cyclic voltammetry and controlled potential coulometry. The results indicate that oxidation of 2,3‐dihydroxypyridine on glassy carbon electrode shows an irreversible feature in aqueous solution. This data indicates that the electrochemically generated pyridindione is unstable and via an oxidative conversion pathway converts to a novel highly oxygenated heterocyclic compound. By means of the obtained electrochemical data, an efficient, one‐pot method for the synthesis of this heterocyclic compound based on the oxidative cyclization of 2,3‐dihydroxypyridine under green conditions, and in a good yield and purity is described. Copyright © 2011 John Wiley & Sons, Ltd.     

如何通过测量复摆的周期计算转动惯量

本文给出一种简约可行的方法,用来计算不规则物体绕任意轴转动时的转动惯量,同时,亦可定出质心轴位置.本文讨论的内容对教学有意义.     

Effect of ion beam irradiation on palladium (II) acetyl acetonate dispersed in polymer matrix

Composites, containing different concentrations of palladium (II) acetylacetonate in polymethyl methacrylate (PMMA) matrix were prepared by vigorous mixing. PMMA was prepared by solution polymerization technique. The composites were irradiated with a 120 MeV Ni¹⁰⁺ beam at two different fluences of 1×10¹¹ and 5×10¹² ions/cm² to study ion-induced effects on their dielectric, structural properties and surface morphology. AC electrical properties of these samples were studied in the frequency range 100 Hz to 10 MHz. The dielectric permittivity/loss shows frequency dependent behavior and it obeys the universal law of dielectric (i.e. ?α f ^n?1) for pristine and irradiated samples at high frequency. The crystalline size and crystallinity of the composites were studied by X-ray diffraction analysis. Decrease in peak intensity after irradiation signifies the amorphization which is also responsible for decrease in T _g as obtained by means of differential scanning calorimetry measurement. Fourier transform infrared spectra also support this result. Surface roughness increases upon irradiation as observed from scanning electron microscopy.     

TCs-Fe(Ⅲ)体系离子液体气浮浮选荧光光谱法分离/富集四环素类抗生素残留的研究

将离子液体应用于气浮溶剂浮选,建立了一种分离/富集四环素类(tetracyclines, TCs)抗生素的新方法——离子液体气浮溶剂浮选。最优化浮选条件为：以1-己基-3-甲基咪唑六氟磷酸盐([Hmim]PF₆)和乙酸乙酯(EA)的混合溶剂(φ=1/0.9)为浮选剂,以Fe(Ⅲ)为捕集剂,pH值为7.6,气体流速为40 mL·min-1,浮选时间为50 min。富集TCs-Fe(Ⅲ)配合物的[Hmim]PF₆-EA相用荧光光谱法直接测定,其线性回归方程为F=246.5c+4.32(c: μg·10 mL-1),相关系数r=0.999 1。实测了鱼塘表面水体和沉积物中四环素类抗生素的含量,加标回收率达到94.2%～100.4%,RSD＜3.2%(n=5)。红外光谱分析显示TCs-Fe(Ⅲ)配合物没有和离子液体发生反应,离子液体在气浮溶剂浮选中只起到溶剂作用。该方法适合于环境水样中痕量四环素类抗生素的分离/富集及分析。