Facile synthesis of a melt-spinnable polyborazine from asymmetric alkylaminoborazine

<正>A novel asymmetric alkylaminoborazine monomer,2-propylamino-4,6-bis(methylamino)borazine,was synthesized for the first time,and directly polymerized to give a melt-spinnable polyborazine(PBN).This asymmetric alkylaminoborazine was synthesized by an aminolysis reaction of 2,4,6-trichloroborazine(TCB) with different amines under mild conditions.This route turns out to be much cheaper and simpler than the conventional routes.The chemical composition,structure,molecular weights and ceramic yield were investigated by EA,FTIR,NMR,GPC and TG analysis.The PBN exhibits suitable rheological property for melt-spinning, which suggests that it is a potential precursor for BN fibers.     

Two new homoisoflavanones from Polygonatum odoratum (Mill.) Druce

<正>Two new homoisoflavanones were isolated from the rhizomes of Polygonatum odoratum(Mill.) Druce and their structures were elucidated as(3R)-5,7-dihydroxy-8-methoxy-3-(4-methoxybenzyl)-6-methylchrom-an-4-one(1) and(3R)-5,7,8-trihydroxy-3-(4- hydroxybenzyl)-6-methylchroman-4-one(2),on the basis of spectral analysis.     

Synthesis and Cytotoxicity of Novel Diaryl Ureas Containing 2-Amino-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidinyl Group

<正>A series of 2-amino-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidinyl substituted diaryl urea derivatives was designed and synthesized.Their in vitro cytotoxicities against two cancer cell lines(Bel-7402 and A549) were evaluated by standard MTT assay.Six of tested compounds 6,8,10,17,21 and 22 exhibited more potent cytotoxicity superior to sorafenib.The structure activity relationship(SAR) study indicates that 2-amino-5,6,7,8-tetrahydropyrido- [4,3-d]pyrimidinyl group was an option for cytotoxic potency.     

Pyrolysis-GC/MS of Menthyl Esters of N-Benzoxycarbonyl Amino Acid

With the aid of a Pyrolysis-GC/TOF MS technique,the pyrolysis behaviour of two menthyl esters of N-benzoxycarbonyl amino acid was investigated.A clear pattern emerges involving the cleavage of the bond linking the menthyl ring to the carboxy group,followed by further degradation of the fragments.The major pyroproducts were p-menth-1-ene pyrolysed at a higher temperature or p-menth-2-ene pyrolysed at a lower temperature,and va-rious derivatives of cyclohexene pyrolyzed from the menthyl ring.In addition,some ...     

O-季铵化-N-壳聚糖Schiff碱的合成及表征

对壳聚糖氨基和羟基进行化学改性,合成了水溶性双功能化壳聚糖衍生物O-季铵化-N-壳聚糖Schiff碱(O-HTCCS);用红外光谱表征了产物的结构;确定了O-HTCCS的最佳合成条件,并测定了其溶解性能.结果表明,合成O-HTCCS的最佳条件为:壳聚糖Schiff碱/缩水甘油三甲基氯化铵(GTMAc)摩尔比为1∶5;反应时间24 h;反应温度70℃.在最佳条件下合成O-HTCCS的产率为78.5%,季铵化度为89.7%.与此同时,O-HTCCS的水溶性随季铵化度的增大而提高,季铵化度达到70%以上能溶于水;且其在有机溶剂中的溶解性优于壳聚糖.     

Effects of carbon nanotubes on dynamic mechanical property,thermal property,and crystal structure of poly(L‐lactic acid)

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 T_g of the composite with a higher CNT‐g‐PLLA loading giving a higher T_g 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     

The crystal structures of chiral (<Emphasis Type="Italic">R</Emphasis>/<Emphasis Type="Italic">S</Emphasis>) (C<Subscript>8</Subscript>H<Subscript>11</Subscript>N)<Subscript>2</Subscript>·CuCl<Subscript>2</Subscript>

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.     

Mechanistic Insights into the Substrate‐Controlled Stereochemistry of Glycals in One‐Pot Rhodium‐Catalyzed Aziridination and Aziridine Ring Opening

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.     

Synthesis, photophysical and electrophosphorescent properties of fluorene-based platinum(II) complexes

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.     

Chemical Synthesis,Structure Characterization,and Optical Properties of Hollow PbSx–Solid Au Heterodimer Nanostructures

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 PbS_x 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 PbS_x–solid Au heterodimers. The Au^III species in the solution, lead to the etching of PbS nanocrystals and the Au^I 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.