巯基保护的中空金纳米球

基于全统一模型和密度泛函理论(DFT)计算,我们提出了具有高对称性和稳定性的巯基保护的中空金纳米球Au₆₀(SR)₂₀的原子结构。Au₆₀(SR)₂₀由一个二十面体Au₅₀富勒烯中空笼子(由20个四面体Au₄融合构成)和10个[―RS―Au―SR―]订书针结构组成,并遵循“分离和保护”规则。DFT计算表明,这种空心Au₆₀(SR)₂₀纳米球具有大的带隙(1.3 eV)以及在笼中心的核独立化学位移(NICS)为负值(−5),表明其高度的化学稳定性。此外,四面体Au₄单元中心的NICS值远大于空心笼中心的NICS值,表明Au₆₀(SR)₂₀的总体稳定性可能来自每个四面体Au₄单元的局部稳定性。正的谐波振动频率说明Au₆₀(SR)₂₀纳米球至少是势能表面的局部最小值。另外,我们还通过融合四面体Au₄层设计了双层中空金纳米球,表明调整中空金纳米球壳层厚度是可行的。最后,我们还介绍了更大的中空金纳米球Au₁₈₀(SR)₆₀的设计。这项工作提供了可控设计中空金纳米球的新策略。     

Crystalline O,O′-di-sec-butyl and O,O′-diethyl dithiophosphate platinum(II) complexes: Synthesis, C and P CP/MAS NMR, single crystal X-ray diffraction studies and thermal behaviour

Crystalline bis(O,O′-di-sec-butyldithiophosphato)platinum(II) was prepared and studied by means of ¹³C, ³¹P CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. The unit cell of the platinum(II) compound is comprised of one centrosymmetric mononuclear molecule [Pt{S₂P(O-sec-C₄H₉)₂}₂], in which the dithiophosphate groups display structural equivalence in both ³¹P NMR and XRD data. A pair of the dithiophosphate ligands exhibit the same S,S′-bidentate chelating structural function and form two planar four-membered chelate rings, [PtS₂P], in this molecule. The planar configuration of the [PtS₄] chromophore in structure 1 is governed by the dsp²-hybrid state of platinum(II). The structural states of the dithiophosphate groups in two different samples of complex 1 (one crystallised from ethanol and the other one precipitated from an aqueous solution) are all characterised by almost rhombic ³¹P chemical shift tensors. The observed essential dispersion of the ³¹P NMR chemical shift is caused by a coexistence of six optical isomers of molecule 1. The thermal behaviour of this compound was studied by means of simultaneous thermal analysis (a combination of TG and DSC) under an argon atmosphere. The thermal behaviour shows that the mass of 1 is lost in three steps, involving successive thermal decompositions of the organic and inorganic parts of this compound with platinum(II) dithio-meta-phosphate and reduced metallic platinum as the intermediate and the final products, respectively.     

Rapid detection of Rosa laevigata polysaccharide content by near-infrared spectroscopy

We have investigated surface-enhanced Raman spectroscopy (SERS) spectrum of Omethoate (O,O-dimethyl-S-methylcarbamoylmethylthiophosphate). It is found significant signals in the ordinary Raman spectrum for solid-state Omethoate as well as strong vibrational signals absorbed on the silver sol surface which is prepared by γ-irradiation technique at a very low concentration. Effects of pH and anions (Cl-, Br-, I-) on the adsorption orientation are investigated as well. Two different adsorption mechanisms are deduced, depending on the experimental conditions. The sulfur atom or the sulfur and two oxygen atoms are adsorbed onto the silver sol surface. Among halide ions, Br- and I- are more strongly adsorbed onto the silver sol surface. As a result, the adsorption of Omethoate is less effective due to their steric hindrance.     

Parametric signal fitting by gaussian peak adjustment: A new multivariate curve resolution method for non-bilinear voltammetric measurements

A new methodology based on the fitting of signals to parametric functions is proposed for the multivariate curve resolution (MCR) analysis of overlapping and peak-shaped voltammetric signals which progressively get broader or narrower and move along the potential axis, thus causing a dramatic loss of linearity. The method is based on the least squares fitting of gaussian functions at both sides of the peaks by using adjustable parameters for the peak height, position and symmetry. It consists of several home-made programs written in Matlab environment, which are freely available as supplementary material of the present work. The application to the systems Zn(II)–oxalate, and to the phytochelatin PC₅ in a wide pH range provides excellent results as compared to these of more conventional linear methods, which raises good expectations about future application to electrochemical and even non-electrochemical data.     

Solvent and Temperature Dependence of 59Co NMR Chemical Shifts of Tris(acetylacetonato)cobaIt(III) and Tris(dipivaloylmethanato)cobalt(III)

Cobalt-59 NMR chemical shifts of Co(acac)₃, and Co(dpm)₃ (acac^– = acetylacetonate ion and dpm^– = dipivaloylmethanate ion) in 14 organic solvents, C₆H₁₄, C₆H₆, CH₂Cl₂, CHCl₃, CCl₄, CH₃CN, CH₃OH, C₂H₅OH, CH₃CH(OH)CH₃, (C₂H₅)₂O, (CH₃)₂CO, (CH₃)₂SO, (CH₃)₂NCHO and C₆H₅NO₂, were measured at five temperatures ranging from 289 to 329 K. The observed chemical shift (_obs) was linearly correlated to the maximum absorption wavelength in the visible spectra (_max) corresponding to the d-d electronic transition energy between the ground ¹A_1g and excited ¹T_1g states. The _obs-_max relation was explained by the ligand field theory. The temperature coefficients of _obs, of each complex showed a negative correlation with _obs. The _obs, of Co(acac)₃ decreased with the increasing electrophilic ability of the solvent (Mayer's acceptor number), whereas no tendency was observed in the case of Co(dpm)₃.     

核磁共振在对映体纯度测定中的应用

综述了核磁共振技术对映体纯度测定中的应用，它包括三个方面：（１）手性衍生剂法；（２）手性镧系位移试剂法；（３）手性溶剂法，对三种方法的测定机理和特点也做了讨论，全文共６５篇参考文献。     

NiTi过渡金属团簇的结构和芳香性的理论研究

在B3PW91/6-311+G(d)计算水平上, 计算并讨论了Ni₄Ti₂, [Ni₄Ti₂]²⁺, [Ni₄Ti₂]^2-与Ni₄Ti₄, [Ni₄Ti₄]²⁺, [Ni₄Ti₄]^2-团簇的几何结构和芳香性. 在构型优化过程中得到了Ni₄Ti₂(D_4h), [Ni₄Ti₂]²⁺(D_4h), [Ni₄Ti₂]^2-(D_4h)和Ni₄Ti₄(D_2h)4个稳定构型, 发现当引入上下2个Ti原子后, Ni₄环成为了平面正方形构型. 核无关化学位移(NICS)计算结果表明, Ni₄Ti₂(D_4h)与Ni₄Ti₄(D_2h)的NICS值为正, 而[Ni₄Ti₂]²⁺(D_4h)和[Ni₄Ti₂]^2-(D_4h)的NICS值为负, 且[Ni₄Ti₂]^2-(D_4h)的NICS值更负. 同时还发现, 由s与d轨道参与形成的反磁性环流是引起[Ni₄Ti₂]²⁺(D_4h)和[Ni₄Ti₂]^2-(D_4h)具有较大芳香性的主要原因; 其中Ti原子主要提供d_z²与s轨道, 而Ni原子主要利用其d_z²与d_x²-y²轨道形成正方形环, 它们之间构成了球状的d轨道环流, 且[Ni₄Ti₂]²⁺(D_4h)和[Ni₄Ti₂]^2-(D_4h)中还有非常明显的π轨道环流.     

Effect of different ratios of wheat to corn flour in the diet on the development and isotopic composition (δ13C, δ15N) of the red flour beetle Tribolium castaneum

The back-calculation of the diet is a common application of stable isotopes in animal ecology. The method is based on a predictable relation between the isotopic signature of the diet and the animal’s tissues. Frequently, the assumption of a constant difference in isotopic signatures (trophic shift) is made. Carbon isotopic ratios of C₃ and C₄ plants differ by approximately 10 ‰, making wheat (C₃-plant) and corn (C₄-plant) ideal materials for isotopic studies in nutritional ecology and especially for testing the back-calculation method. In this experiment, red flour beetles, Tribolium castaneum, were reared on wheat flour, corn flour and three different mixtures thereof, either in pure flour or with the addition of yeast inoculum or yeast grains. Development of T. castaneum on these experimental diets was monitored, and isotopic signatures of carbon and nitrogen in emerging adults were analysed. The values of trophic shift of C and N isotopes for wheat and corn flour were different, and the values for the mixtures did not correspond to those expected from a linear mixing model. The latter can be taken as an indication that the tiny larvae of T. castaneum may be capable of differentiating between particles of wheat and corn flour, making this animal model unsuitable for testing the back-calculation method.