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901.
A series of nine porphyrin analogues have been synthesized using the "3 + 1" variant on the MacDonald condensation. Tripyrrane-type systems with a centrally unsubstituted pyrrole, furan, or thiophene ring were prepared using conventional methods, and these were condensed with indene-1,3-dicarbaldehyde, 5-formylsalicylaldehyde, or 3-hydroxy-2,6-pyridinedicarbaldehyde in the presence of TFA to generate benzocarba-, oxybenzi-, and oxypyriporphyrins, respectively. The furan-containing analogues proved to be highly basic and could only be isolated as the corresponding hydrochloride salts. All nine analogue systems showed porphyrin-like UV-vis spectra with one or two Soret absorptions near 400 nm and a series of weaker bands at longer wavelengths. These systems also showed large diatropic ring currents by proton NMR spectroscopy that were comparable to true porphyrins. In the presence of trace amounts of TFA, benzocarbaporphyrin 12 formed a monocation, and in 50% TFA a C-protonated dication was generated. The 23-oxacarbaporphyrin 14 gave a monocation in chloroform, although the free base was generated in 5% Et(3)N-chloroform. In 50% TFA-CHCl(3), 14 afforded a mixture of mono- and diprotonated species. Thiacarbaporphyrin 15 also formed a monocation in the presence of TFA, but C-protonation was relatively disfavored for this system. Nonetheless, in the presence of TFA-d, 12, 14, and 15 all showed rapid exchange of the internal NH and CH protons. Carbaporphyrin 12 also showed slow exchange at the meso-positions, but this process was not observed for its heteroanalogues 14 and 15. Protonation studies were also conducted for oxybenziporphyrins and oxypyriporphyrins 16-21. Oxacarbaporphyrin 14 was shown to be a superior organometallic ligand and afforded good yields of the related nickel(II) and palladium(II) derivatives under mild conditions. A low yield of the platinum(II) complex could also be isolated. All three complexes retained their aromatic character, although the Pd(II) derivative appeared to possess a slightly larger diatropic ring current. The palladium(II) complex 27 was further characterized by X-ray crystallography. The macrocyclic core was shown to be highly planar where the dihedral angles of the component pyrrole, furan and indene rings relative to the mean [18]annulene plane were all =2.1 degrees. 相似文献
902.
Yue Shen Xiaohui Tang Yuwei Xu Haichao Liu Shitong Zhang Bing Yang Yuguang Ma 《中国化学快报》1990,30(11):1947-1950
Cyanophenyl as ancillary acceptor to modify donor-acceptor compound,plays an effective role in shifting the emission color to deep red and maintaining the luminescent efficiency. 相似文献
903.
用射央求地在硅单晶衬底上沉积出电导率高达60S/cm的a-SiHY合金薄膜。在20-300K,对于钇含量高的样品,其电导仍是热激活的。lgσ与1/T的关系曲线能够被拟合成斜率不同的两条直线,直线的斜率和两直线间拐点所地 温度依赖于膜中钇的含量。但对钇含量低的薄膜,电导对温度的依赖关系度为σ∝exp(-1/T^1/4)。结果表明,这些钇含量不同的样品在没的温度范围内具有不同的导电机制。 相似文献
904.
测定了Pt-Sn型催化剂浸渍状态下的Sn-119、Pt-195的多核核磁共振。当SnCl2/DCl溶液体系中加入H2PtCl6以后,出现了Sn(Ⅳ)和另外一种Sn(Ⅱ)的构型,Sn-119峰向高场位移,说明部分Sn(Ⅱ)被氧化成Sn(Ⅳ),H2PtCl6的量对这种氧化性影响较小。而H2PtCl6/D2O溶液体系中加入SnCl2以后部分Pt(Ⅳ)被还原成Pt(Ⅱ),随着SnCl2量的增加,Pt(Ⅱ) 相似文献
905.
聚双环戊二烯反应注射成型 总被引:3,自引:0,他引:3
本文介绍了国外有关聚双环戊二烯反应注射成型的研究进展,讨论了国内进行聚双环戊二烯反应注射成型开发研究的现实意义,并对这一领域的发展进行了展望 相似文献
906.
Electrospray ionization tandem mass spectrometric study of the aconitines in the roots of aconite 总被引:3,自引:0,他引:3
Fragmentation pathways of aconitine-type alkaloids were investigated by electrospray ionization/ion trap multistage tandem mass spectrometry. Low-energy collision-induced dissociation of protonated aconitines follows a dominant first step, the elimination of the C(8)-substituent as acetic acid or fatty acid in MS(2) spectra. Successive losses of 1-4 CH(3)OH molecules, 1-3 H(2)O, CO, benzoic acid, and CH(3) or C(2)H(5) (N-substituents) are all fragmentation pathways observed in MS(3) and MS(4) spectra. By applying knowledge of these fragmentation pathways to the aconitines in the ethanolic extract of aconite roots, all the known aconitines were detected and also 23 unknown aconitine-type alkaloids, in which the lipo-alkaloids containing residues of 15C, 17C and 19C saturated or unsaturated fatty acids were characterized. These odd-carbon-number fatty acid substituents have not been reported previously. 相似文献
907.
A high-quality polyene can be obtained by exensive dehydrochlorination of poly(vinyl chloride) (PVC) in aliquid/solid two-phase system. The liquid phase is a tetrahydrofuran solution of PVC containing a small amount ofpoly(ethylene glycol) with molar mass of 400 g as a phase transfer catalys. The solid phase is potassium hydroxide particles.The structure of the polyene is polyacetylene-like and has a long conjugated C=C sequence and a narrow dispersity ofpolyene sequences according to its FT-infrared and Raman spectra. The environmental stability of the polyene was alsostudied by IR, Raman spectra and elemental analysis. Experimental results demonstrated that the polyene was susceptible toair and could be changed into a material containing high concentrations of hydroxyl and carbonyl groups. The polyenesequences were shortened and its dispersity became broader due to the effect of dioxygen. 相似文献
908.
909.
Zhiming Liu Jiming Hao Lixin Fu Tianle Zhu Junhua Li Xiangyu Cui 《Reaction Kinetics and Catalysis Letters》2003,80(1):45-52
SnO2/Al2O3 catalyst prepared by sol-gel method showed higher activity than those prepared by impregnation method, and their activity
was significantly improved by pre-treatment in the reaction gas. The increased activity is closely related to the agglomeration
of SnO2 species and the re-exposure of Al2O3, which was previously covered by dispersed SnO2 species.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
910.
A new method based on hollow fiber-protected liquid-phase microextraction (LPME) was developed for the simultaneous determination
of atrazine, desethyl atrazine and desisopropyl atrazine in environmental water samples. In LPME, analytes were extracted
into 1-octanol immobilized in the micropores of a poly(vinylidene fluoride) porous hollow fiber membrane, and back extracted
into the acceptor (4 M HCl) filled in the lumen of the hollow fiber. After LPME, the analytes trapped in the acceptor were
analyzed with high-performance liquid chromatography after neutralization. The effect of extraction factors such as sample
pH, acceptor pH, salinity, extraction time, stirring rate, and humic acid were studied. Under the optimized conditions, the
limits of detection and relative standard deviations were respectively in the range of 0.5–1.0 μg L−1 and 3.9–4.7% (n = 5). The proposed method was applied to determine atrazine, desethyl atrazine and desisopropyl atrazine in wastewater and
groundwater samples. The three analytes were below the limits of detection, but good relative spiked recoveries over 90.1
± 5.9% at 5 μg L−1 spiked level were obtained. 相似文献