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981.
Yeong‐Tarng Shieh Gin‐Lung Liu Yawo‐Kuo Twu Tzong‐Liu Wang Chien‐Hsin Yang 《Journal of Polymer Science.Polymer Physics》2010,48(2):145-152
Effects of carbon nanotubes (CNT) on the dynamic mechanical property, thermal property, and crystal structure of poly(L ‐lactic acid) (PLLA) were investigated. Dynamic mechanical analysis (DMA) found that CNT via grafting modification with PLLA (CNT‐g‐PLLA) could result in effective reinforcing effects. Tan δ of DMA found that CNT‐g‐PLLA was compatible with the PLLA matrix, giving a single Tg of the composite with a higher CNT‐g‐PLLA loading giving a higher Tg of the composite. Wide angle X‐ray diffraction (WAXD) data demonstrated that CNT could assist the disorder‐to‐order (α′‐to‐α) transition in PLLA crystals but did not lead to a more compact chain packing of the crystal lattice in PLLA composites than in pure PLLA. The equilibrium melting temperature (T) obtained from Hoffman‐Weeks plots were found to increase with increasing CNT‐g‐PLLA content. Small angle X‐ray scattering data revealed that thicknesses of crystal layer and amorphous layer of PLLA both decreased with increasing CNT contents. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 145–152, 2010 相似文献
982.
Luo Mei Sun Jie Zhou Shi-Ming Yin Hao Hu Ke-Liang 《Research on Chemical Intermediates》2010,36(9):1049-1054
Two opposite configuration (R/S) of chiral complexes (C8H11N)2·CuCl2 were obtained from the reaction of chiral d(+)/l(−)-α-ethylphenyl amine with copper chloride (II) in dry ethanol. The crystal structures of 1a and 1b were characterized by
IR, elemental analysis and X-ray crystallography. 相似文献
983.
K. B. Sophy Dr. Jer‐Lai Kuo Prof. Dr. Xue‐Wei Liu Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(2):588-594
We carried out a principle study on the reaction mechanism of rhodium‐catalyzed intramolecular aziridination and aziridine ring opening at a sugar template. A sulfamate ester group was introduced at different positions of glycal to act as a nitrene source and, moreover, to allow the study of the relative reactivity of the nitrene transfer from different sites of the glycal molecule. The structural optimization of each intermediate along the reaction pathway was extensively done by using BPW91 functional. The crucial step in the reaction is the Rh‐catalyzed nitrene transfer to the double bond of the glycal. We found that the reaction could proceed in a stepwise manner, whereby the N atom initially induced a single‐bond formation with C1 on the triplet surface or in a single step through intersystem crossing (ISC) of the triplet excited state of the rhodium–nitrene transition state to the singlet ground state of the aziridine complexes. The relative reactivity for the conversion of the nitrene species to the aziridine obtained from the computed potential energy surface (PES) agrees well with the reaction time gained from experimental observation. The aziridine ring opening is a spontaneous process because the energy barrier for the formation of the transition state is very small and disappears in the solution calculations. The regio‐ and stereoselectivity of the reaction product is controlled by the electronic property of the anomeric carbon as well as the facial preference for the nitrene insertion, and the nucleophilic addition. 相似文献
984.
Yuen MY Kui SC Low KH Kwok CC Chui SS Ma CW Zhu N Che CM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(47):14131-14141
A series of platinum(II) complexes bearing tridentate cyclometalated C^N^N (C^N^N=6-phenyl-2,2'-bipyridine and π-extended R-C^N^N=3-[6'-(naphthalen-2'-yl)pyridin-2'-yl]isoquinoline) ligands with fluorene units have been synthesised and their photophysical properties have been studied. The fluorene units are incorporated into the cyclometalated ligands by a Suzuki coupling reaction. An increase in the π-conjugation of the cyclometalated ligands confers favourable photophysical properties compared to the 6-phenyl-2,2'-bipyridine analogues. The fluorene-based platinum(II) complexes display vibronic-structured emission bands with λ(max)=558-601 nm, and high emission quantum yields up to 0.76 in degassed dichloromethane. Their emissions are tentatively assigned to excited states with mixed (3)IL/(3)MLCT parentage (IL=intraligand, MLCT=metal-to-ligand charge transfer). The crystal structures of these platinum(II) complexes reveal extensive Pt(II)···π and/or π-π interactions. The fluorene-based platinum(II) complexes are soluble in organic solvents, have high thermal stability with decomposition temperature >350 °C, and can be thermally vacuum-sublimed or solution-processed as phosphorescent dopants for the fabrication of organic light-emitting diodes (OLEDs). A monochromic OLED with 3d as dopant (2 wt%) fabricated by vacuum deposition gave a current efficiency of 14.7 cd A(-1) and maximum brightness of 27000 cd m(-2). A high current efficiency (9.2 cd A(-1)) has been achieved in a solution-processed OLED using complex 3f (5 wt%) doped in a PVK (poly(9-vinylcarbazole)) host. 相似文献
985.
Shoushuang Huang Jianmei Huang Jian Yang Prof. Jun‐Jun Peng Qingbo Zhang Dr. Feng Peng Prof. Hongjuan Wang Dr. Hao Yu Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(20):5920-5926
Heterodimer nanostructures have attracted extensive attention, owing to an increasing degree of complexity, functionality, and then importance. So far, all the reported ones are built from solid nanoparticles. Herein, nearly monodisperse heterodimer nanostructures are constructed by hollow PbSx and solid Au domains simultaneously through a mild reaction between PbS nanocrystals and the gold species in the presence of dodecylamine. Control experiments clearly reveal the underlying formation mechanism of the hollow PbSx–solid Au heterodimers. The AuIII species in the solution, lead to the etching of PbS nanocrystals and the AuI species facilitate the control of the number of gold domains per nanoparticle. Dodecylamine molecules not only work as a stabilizer in the reaction, but also act as a reducing agent that could greatly affect the morphology of the product. The optical properties of the heterodimers are investigated based on UV/Vis absorption spectroscopy and Raman spectroscopy. This novel heterodimer nanostructure pushes the development of complex nanocrystal‐based architectures forward, and also provides many opportunities for potential applications. 相似文献
986.
Ming‐Zhong Wang Cong‐Ying Zhou Man‐Kin Wong Dr. Chi‐Ming Che Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(19):5723-5735
Ruthenium porphyrins (particularly [Ru(2,6‐Cl2tpp)CO]; tpp=tetraphenylporphinato) and RuCl3 can act as oxidation and/or Lewis acid catalysts for direct C‐3 alkylation of indoles, giving the desired products in high yields (up to 82 % based on 60–95 % substrate conversions). These ruthenium compounds catalyze oxidative coupling reactions of a wide variety of anilines and indoles bearing electron‐withdrawing or electron‐donating substituents with high regioselectivity when using tBuOOH as an oxidant, resulting in the alkylation of N‐arylindoles to 3‐{[(N‐aryl‐N‐alkyl)amino]methyl}indoles (yield: up to 82 %, conversion: up to 95 %) and the alkylation of N‐alkyl or N‐H indoles to 3‐[p‐(dialkylamino)benzyl]indoles (yield: up to 73 %, conversion: up to 92 %). A tentative reaction mechanism involving two pathways is proposed: an iminium ion intermediate may be generated by oxidation of an sp3 C? H bond of the alkylated aniline by an oxoruthenium species; this iminium ion could then either be trapped by an N‐arylindole (pathway A) or converted to formaldehyde, allowing a subsequent three‐component coupling reaction of the in situ generated formaldehyde with an N‐alkylindole and an aniline in the presence of a Lewis acid catalyst (pathway B). The results of deuterium‐labeling experiments are consistent with the alkylation of N‐alkylindoles via pathway B. The relative reaction rates of [Ru(2,6‐Cl2tpp)CO]‐catalyzed oxidative coupling reactions of 4‐X‐substituted N,N‐dimethylanilines with N‐phenylindole (using tBuOOH as oxidant), determined through competition experiments, correlate linearly with the substituent constants σ (R2=0.989), giving a ρ value of ?1.09. This ρ value and the magnitudes of the intra‐ and intermolecular deuterium isotope effects (kH/kD) suggest that electron transfer most likely occurs during the initial stage of the oxidation of 4‐X‐substituted N,N‐dimethylanilines. Ruthenium‐catalyzed three‐component reaction of N‐alkyl/N‐H indoles, paraformaldehyde, and anilines gave 3‐[p‐(dialkylamino)benzyl]indoles in up to 82 % yield (conversion: up to 95 %). 相似文献
987.
Hui Ming Ge Dr. Wen Hao Yang Yan Shen Dr. Nan Jiang Dr. Zhi Kai Guo Qiong Luo Qiang Xu Prof. Jing Ma Prof. Ren Xiang Tan Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(21):6338-6345
Two novel resveratrol aneuploids, hopeachinols A ( 1 ) and B ( 2 ), as well as a potent immunosuppressive polyphenol diptoindonesin G ( 3 ) were characterized from the ethanol extract of Hopea chinensis stem barks. The structure of the polyphenols was accommodated by comprehensive spectroscopic analysis with the absolute stereochemistry determined by the CD approach coupled with theoretical ECD spectra computer‐generated through the Gaussian 03 program. The distinct structure and biological profile of 3 recommended it as a starting molecule for the relevant drug discovery. 相似文献
988.
X. H. Lu X. Che L. Shi J. F. Han Z. X. Lian Y. Q. Li 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(13):2320-2324
The mechanism of the sulfur extraction reaction between singlet silylene carbine and its derivatives and thiirane has been
investigated with density functional theory (DFT), including geometry optimization and vibrational analysis for the involved
stationary points on the potential energy surface. The energies of the different conformations are calculated by B3LYP/6-311G(d, p) method. From the potential energy profile, it can be predicted that the reaction pathway of this kind consists in two steps:
(1) the two reactants firstly form an intermediate through a barrier-free exothermic reaction; (2) the intermediate then isomerizes
to a product via a transition state. This kind of reactions has similar mechanism: when the silylene carbene and its derivatives
[X2Si=C: (X = H, F, Cl, CH3)] and thiirane approach each other, the shift of 3p lone electron pair of S in thiirane to the 2p unoccupied orbital of C in X2Si=C: gives a p → p donor-acceptor bond, thereby leading to the formation of intermediate (INT). As the p → p donor-acceptor bond continues to strengthen (that is the C-S bond continues to shorten), the intermediate (INT) generates
product (P + C2H4) via transition state (TS). It is the substituent electronegativity that mainly affect the extraction reactions. When the
substituent electronegativity is greater, the energy barrier is lower, and the reaction rate is greater. 相似文献
989.
Ching-Hua Kuo Chia-Wen Lee I-Lin Tsai Y. Jane Tseng Jaw-Jou Kang Fu-Chuo Peng 《Talanta》2010,80(5):1672-161
Aristolochic acids (AAs) are a mixture of structural-related compounds, in which aristolochic acid I (AA I) and aristolochic acid II (AA II) are reported to be correlated with Aristolochic acid nephropathy (AAN). In this work, a rapid and sensitive ultra-high-pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed to determine AA I and AA II in herbal products and biological fluids. By using gradient elution with a mobile phase composed of a mixture of 10 mM ammonium formate buffer (pH 3.0) and acetonitrile, AAs could be determined within 10 min. Under optimum UHPLC-MS/MS conditions, the limit of detections was 0.14 and 0.26 ng mL−1 for AA I and AA II, respectively. Run-to-run repeatability and intermediate precision of peak area for AA I and AA II were less than 5.74% relative standard deviation (RSD). Accuracy was tested by spiking 10, 100 and 1000 ng mL−1 in rat serum and the recoveries were within 76.5-92.9%. Matrix effects were within 78.8-127.7%. The developed method was successfully applied to determine AA I and AA II in several herbal products and to investigate their pharmacokinetic behavior in female Wister rats. The result shows that the developed UHPLC-MS/MS method is efficient, sensitive, and accurate for the determination of AA I and AA II in herbal products and biological samples. 相似文献
990.
Yang Yu Hao Gao Yi Dai Ying Wang He‐Ru Chen Xin‐Sheng Yao 《Helvetica chimica acta》2010,93(4):763-771
Eight new monoterpenoids, jasminoside J ( 1 ), jasminoside K ( 2 ), 6′‐O‐trans‐sinapoyljasminoside B ( 3 ), 6′‐O‐trans‐sinapoyljasminoside L ( 4 ), jasminosides M–P ( 5 – 8 ), together with three known analogues, jasminoside C ( 9 ), jasminol E ( 10 ), and sacranoside B ( 11 ), were isolated from the fruit of Gardenia jasminoides Ellis (Rubiaceae). Their structures were elucidated by spectral and chemical methods. 相似文献