The NMR spectra of porphyrins 20—proton and 13C characterization of porphyrin atropisomers

The preparation, isolation and characterization by proton and ¹³C NMR of the four possible atropisomers of meso-tetra(2-methoxy-1-naphthyl)porphyrin is described. Chemical shift differences due to atropisomerization effects are observed in the porphyrin and naphthyl rings. Comparison of the naphthyl chemical shifts with those of the model compound 1-isopropenyl-2-methoxynaphthalene allows the shifts due to the porphyrin ring current to be isolated. The observed Δδ values of the naphthyl protons agree well with those calculated from the previously described porphyrin ring current model, and allow both the angle of tilt of the naphthyl ring and the dihedral angle of the 2-methoxy substituent to be estimated. In contrast, the Δδ values for the naphthyl carbons bear no relationship to the calculated ring current shifts. Calculations of the total ring current contribution (porphyrin plus naphthyl rings) at the different naphthyl rings of the unsymmetric type III isomer show that at least part of the observed atropisomerism effects are due to the long-range current shifts of the naphthyl rings. The results also provide a clear demonstration of the identity of the porphyrin ring current in the free base and porphyrin dication.     

A colorimetric and fluorometric fluoride sensor based on a BODIPY-phenol conjugate

A boradiazaindacenes (BODIPY)-phenol conjugate,1,can act as a colorimetric and fluorometric sensor for sensitive and se-lective measurement of F-over AcO-and H2PO-4 in CH3CN. Sensor 1 gives response to F-in a 1:1 ratio via the deprotonation of the phenolic OH proton,which results in color change from pale yellow to light green and quenching of bright green fluo-rescence.     

A mechanophysical phase transition provides a dramatic example of colour polymorphism: the tribochromism of a substituted tri(methylene)tetrahydrofuran-2-one

Background

Derivatives of fulgides have been shown to have interesting photochromic properties. We have synthesised a number of such derivatives and have found, in some cases, that crystals can be made to change colour on crushing, a phenomenon we have termed “tribochromism”. We have studied a number of derivatives by X-ray crystallography, to see if the colour is linked to molecular structure or crystal packing, or both, and our structural results have been supported by calculation of molecular and lattice energies.

Results

A number of 5-dicyanomethylene-4-diphenylmethylene-3-disubstitutedmethylene-tetrahydrofuran-2-one compounds have been prepared and structurally characterised. The compounds are obtained as yellow or dark red crystals, or, in one case, both. In two cases where yellow crystals were obtained, we found that crushing the crystals gave a deep red powder. Structure determinations, including those of the one compound which gave both coloured forms, depending on crystallisation conditions, showed that the yellow crystals contained molecules in which the structure comprised a folded conformation at the diphenylmethylene site, whilst the red crystals contained molecules in a twisted conformation at this site. Lattice energy and molecular conformation energies were calculated for all molecules, and showed that the conformational energy of the molecule in structure IIIa (yellow) is marginally higher, and the conformation thus less stable, than that of the molecule in structure IIIb (red). However, the van der Waals energy for crystal structure IIIa, is slightly stronger than that of structure IIIb – which may be viewed as a hint of a metastable packing preference for IIIa, overcome by the contribution of a more stabilising Coulomb energy to the overall more favourable lattice energy of structure IIIb.

Conclusions

Our studies have shown that the crystal colour is correlated with one of two molecular conformations which are different in energy, but that the less stable conformation can be stabilised by its host crystal lattice.

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Graphical abstract Graphical representation of the structural and colour change in the tribochromic compound (III).

     

Temperature dependence of optical and structural properties of ferroelectric B3.15Nd0.85Ti3O12 thin film derived by sol–gel process

We report the annealing temperature dependence of optical properties in ferroelectric B_3.15Nd_0.85Ti₃O₁₂ (BNdT) thin film for the first time. BNdT thin films are prepared by a sol–gel/spin coating method. Structural properties of BNdT thin films upon different thickness and annealing temperatures are characterized using the X-ray diffraction, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The BNdT thin film annealed at 650 °C exhibits a well defined perovskite crystalline structure with high c-axis orientation, which leads to a saturated polarization–electric field (PE) hysteresis with a remanent polarization of 2P _r = 39.6 μC/cm² and coercive field of 85 kV/cm at 5 V. Little fatigue degradation (<5%) is demonstrated upon 1 × 10¹⁰ switching cycles indicating a good fatigue endurance. Additionally, a superior optical transparency T(λ) of >80% is observed for wavelengths from 250 to 2,000 nm. Fundamental optical parameters of BNdT material such as refractive index n, extinction coefficient k, and band gap energy E _g are extracted from an ellipsometry measurement. Microstructure and annealing temperature dependence of T(λ), n, k, and E _g variation are also investigated and explained in detail.     

Production of high-quality agarwood in Aquilaria sinensis trees via whole-tree agarwood-induction technology

We used whole-tree agarwood-induction technology to produce agarwood from Aquilaria sinensis trees within 20 months,and evaluated the quality of this agarwood.The results showed its characteristics were similar to those of high-grade wild agarwood in terms of texture,chemical constituents,essential oil content,and ethanol-soluble extract content,with the lattermost quality far surpassing the requirement of traditional Chinese medicine agarwood,as indicated in Chinese Pharmacopoeia 2010.To the best of our knowledge,this is first study to show that high-quality agarwood can be produced in whole A.sinensis trees via a chemically induced technology.     

螺旋波激发甲烷等离子体光谱诊断

利用螺旋波激发等离子体化学气相沉积(LPP-CVD)技术,以甲烷和氦气为反应气体产生等离子体.通过采集到甲烷的可见光到紫外发射光谱,对甲烷等离子体进行原位诊断,发现存在CH、Ha及Hβ等碎片粒子的光辐射,同时,分析了不同入射功率、气压下CH粒子以及Hβ、Hγ的相对强度变化情况.结果表明:CH粒子的相对强度随着射频功率是先增大而后减小,随工作气压的增大而逐渐减小;随气压及功率的增加,Hβ、Hγ相对强度变化的总体趋势都是先增加而后减小的.     

Minor antifungal aromatic glycosides from the roots of Gentiana rigescens （Gentianaceae）

Two new phenolic glycosides,2,3-dihydroxybenzoic acid methyl ester 3-O-β-D-glucopyranosyl-(1-6)-β-D-glucopyranoside(1) and 2,5-dihydroxylbenzofuran 5-O-β-D-xylopyranosyl-(1-6)-O-β-D-glucopyranoside(2),were isolated as the minor chemical constituents from the roots of Gentiana rigescens,along with 15 known compounds.Their structures were elucidated by detailed spectroscopic analysis,including 1D,2D NMR and chemical method.All of these compounds were isolated for the first time from the title plant.Moreove...     

应用ICP—MS测定KCl肥料中重金属元素含量

肥料是重金属的重要污染源之一,重金属可以通过作物直接进入人类食物链对人体产生危害,研究肥料中重金属含量对于农产品安全溯源意义重大。文章选用北京市场上销售的进口KCl肥料作为实验材料,全面分析了其中的10种重金属元素含量,分别为,Cr0.00,Ni65.54,Cu238.85,As190.60,Cd0.98,Sn14.98,Sb2.97,Hg10.04,Tl1.28,Pb97.42ng·g-1。上述结果表明,KCl肥料中重金属含量普遍比较低,特别是Cr没有检测到,其余四中主要重金属(As,Cd,Hg,Pb)的含量除了As(190.60ng·g-1)以外,也都在100ng·g-1以下,不会对土壤环境造成重大污染,含量最高的重金属是Cu,为238.85ng·g-1。由此看来,KCl肥料与磷肥相比重金属含量较低,对农产品是相对安全的。