DFT Studies on Detonation Properties,Pyrolysis Mechanism,and Stability of the Nitro and Hydroxyl Derivatives of Benzene

Ninety‐one nitro and hydroxyl derivatives of benzene were studied at the B3LYP/6‐31G?? level of density functional theory. Detonation properties were calculated using the Kamlet‐Jacobs equation. Three candidates (pentanitrophenol, pentanitrobenzene, and hexanitrobenzene) were recommended as potential high energy density compounds for their perfect detonation performances and reasonable stability. The pyrolysis mechanism was studied by analyzing the bond dissociation energy (BDE) and the activation energy (E_a) of hydrogen transfer (H–T) reaction for those with adjacent nitro and hydroxyl groups. The results show that E_a is much lower than BDEs of all bonds, so when there are adjacent nitro and hydroxyl groups in a molecule, the stability of the compound will decrease and the pyrolysis will be initiated by the H–T process. Otherwise, the pyrolysis will start from the breaking of the weakest C–NO₂ bond, and only under such condition, the Mulliken population or BDE of the C–NO₂ bond can be used to assess the relative stability of the compound.     

Synthesis,characterization, and reactivity of palladium(II) complexes containing piperidoimidazolin‐2‐ylidene

A series of Pd–N‐heterocyclic carbene (Pd‐NHC) complexes with pyrazine ( 1 ) or pyridine ( 2 ) and NHC ( 3 ) were synthesized and characterized by elemental analysis and spectroscopic methods. In addition, the molecular structure of 3 was determined by X‐ray diffraction studies. The effects of these ligands on catalyst activation and the performance of complexes 1 , 2 , 3 were studied on Suzuki–Miyaura reactions of phenylboronic acid with aryl chlorides. Finally, we demonstrated that complex 1 is very adept at re‐forming the Kumada–Tamao–Corriu cross‐coupling reaction. Copyright © 2013 John Wiley & Sons, Ltd.     

Re‐Determination of the Crystal Structure of MIL‐91(Al)

The structure of one of the first permanently porous metal phosphonates, MIL‐91(Al) was re‐determined using high resolution synchrotron powder X‐ray diffraction data. The new model is in a lower symmetry space group, with no disordered ligands in the structure, whilst remaining otherwise consistent with the reported compound. New milder synthetic conditions were also developed.     

Synthesis and characterization of a novel terpolymer based on L‐lactide,glycolide, and trimethylene carbonate for specific medical applications

The bioresorbable new terpolymers of L ‐lactide, glycolide, and trimethylene carbonate were synthesized via ring‐opening polymerization reaction of the cyclic monomers using Stannous octoate as initiator. Glycolide and L ‐lactide were prepared from their parent acids and then purified by multiple re‐crystallization from ethyl acetate. The thermal and mechanical properties of this polymer were characterized by means of thermogravimetry, differential scanning calorimetry, stress–strain measurements, and dynamic mechanical analysis. The glass transition temperature of the terpolymers changed from 33 to 51°C with composition in a predictable manner. The rheological properties of copolymers and molecular weight of each copolymer were determined showing good processability for making fibers. Using a mini‐extruder, it was possible to produce some filaments. The filaments produced at 140°C had appropriate ductility. The in vitro measurements, specifying the biological properties were also carried out. The sample with monomer composition LLA:GA:TMC = 60:34:6 showed a slower degradation rate than the one with LLA:GA:TMC = 54:34:12. The low‐toxicity bioresorbable terpolymers with good rheological and in vitro properties are the promising new materials for biomedical applications specially a new suture formulation. Copyright © 2011 John Wiley & Sons, Ltd.     

Discovery,Total Synthesis and Key Structural Elements for the Immunosuppressive Activity of Cocosolide,a Symmetrical Glycosylated Macrolide Dimer from Marine Cyanobacteria

A new dimeric macrolide xylopyranoside, cocosolide ( 1 ), was isolated from the marine cyanobacterium preliminarily identified as Symploca sp. from Guam. The structure was determined by a combination of NMR spectroscopy, HRMS, X‐ray diffraction studies and Mosher's analysis of the base hydrolysis product. Its carbon skeleton closely resembles that of clavosolides A–D isolated from the sponge Myriastra clavosa, for which no bioactivity is known. We performed the first total synthesis of cocosolide ( 1 ) along with its [α,α]‐anomer ( 26 ) and macrocyclic core ( 28 ), thus leading to the confirmation of the structure of natural 1 . The convergent synthesis featured Wadsworth–Emmons cyclopropanation, Sakurai annulation, Yamaguchi macrocyclization/dimerization reaction, α‐selective glycosidation and β‐selective glycosidation. Compounds 1 and 26 potently inhibited IL‐2 production in both T‐cell receptor dependent and independent manners. Full activity requires the presence of the sugar moiety as well as the intact dimeric structure. Cocosolide also suppressed the proliferation of anti‐CD3‐stimulated T‐cells in a dose‐dependent manner.     

金属含量对Ni-Pd/H-Y上正癸烷加氢异构化反应活性和产物选择性的影响

在Y分子筛上浸渍0.1 wt% Pd和0.1–0.5 wt% Ni,用X射线衍射表征了该催化剂的结晶度,用透射电镜测得平均金属粒径.催化剂中Pd和Ni的化学态用X射线光电子能谱测定,其酸性则用氨-程序升温脱附进行了表征,发现一些酸位被Ni2+离子交换.采用程序升温还原表征了HY分子筛负载的Pd, Ni和Pd-Ni催化剂的还原性能.正癸烷加氢异构化反应在200–450 oC和1 atm条件下进行.结果发现,当0.1 wt% Pd/HY中Ni添加量增至0.3 wt%时,正癸烷转化率和异构化选择性增加.单支链和双支链异构体选择性的增加表明该反应遵循质子化环丙烷中间体机理. Ni添加量超过阈值导致活性和异构化选择性急剧下降.综上可见,双金属催化剂更有利于选择性生成双支链异构体,其辛烷值更高.     

Poly(3,5‐dichloroaniline) Doped with Different Sulfonic Acids

Poly(3,5‐dichloroaniline) was prepared by chemical oxidation in the presence of various sulfonic acids as doping agent, using potassium permanganate as oxidant. 1‐Naphtalene sulfonic acid, 2‐naphatalene sulphonic acid, 1,5‐naphtalene disulfonic acid, and p‐toluenesulfonic acid were the acids of choice. Infrared and UV‐Vis spectroscopy, utilized to characterize the polymers, revealed that the compounds exist in the emeraldine (conductive) oxidation state. The level of doping, conductivity, and morphology were determined as well. The presence of a sulfonic acid produces a morphological change, from granular to microtubule structures, which is responsible for the strong increase in the conductivity of the polymer.     

Synthesis,Photophysics, and Self‐Assembly of Furan‐Embedded Heteroarenes

A series of pyrene/phenanthrene‐fused furan derivatives ( 1 – 8 ) were synthesized by a simple condensation reaction between pyrene‐4,5‐diketone/phenanthrenequinone and substituted phenol/naphthol in the presence of trifluoromethanesulfonic acid in 1,2‐dichlorobenzene heated at reflux. The formed compounds can emit strong blue light in organic solvents. Additionally, the self‐assembly behaviors of two of the compounds ( 3 and 5 ) were studied through re‐precipitation method and the resulting nanostructures were characterized by UV/Vis, fluorescence spectra, and field‐emission scanning electron microscopy (FESEM). The findings showed that the shape and size of compounds 3 and 5 could be tuned by the ratio of THF and hexadecyl trimethyl ammonium bromide (CTAB) solution in water.     

Diazadithia[7]helicenes: Synthetic Exploration,Solid‐State Structure,and Properties

Diazadithia[7]helicenes were synthesized from the readily available building block ethyl 7‐chloro‐8‐formylthieno[3,2‐f]quinoline‐2‐carboxylate by a Wittig reaction–photocyclization strategy. The helicene core was functionalized by nucleophilic aromatic substitution with a variety of nucleophiles (e.g., O‐, N‐, and C‐centered) and palladium‐catalyzed reactions such as Suzuki coupling and Buchwald–Hartwig amination. Racemization studies confirmed that the enantiopure forms of these [7]helicenes are conformationally stable compared to their lower analogues. The solid‐state structures of the novel diazadithia[7]helicenes were determined by single‐crystal X‐ray diffraction. The crystal structures of these azathia[7]helicenes show columnar stacking in antiparallel fashion. The HOMO–LUMO gaps of the new compounds were determined on the basis of electrochemical and optical measurements.     

Thiol‐terminated polyisobutylene: Synthesis,characterization, and derivatization

Thiol‐terminated polyisobutylene (α,ω‐PIB‐SH) was synthesized from thiourea and α,ω‐bromine‐terminated PIB in a three‐step, one‐pot procedure, using a cosolvent system of 1:1 (v:v) heptane:dimethylformamide. The initial alkylisothiouronium salt was produced at 90 °C. Aqueous base hydrolysis at 110 °C resulted in thiolate chain ends, which were re‐acidified to form telechelic PIB‐SH. ¹H and ¹³C NMR confirmed thiol functionality and complete terminal halogen conversion. Thiol‐based “click” reactions were used to demonstrate PIB‐SH utility. Alkyne‐terminated PIB was synthesized by a phosphine‐catalyzed thiol‐ene Michael addition with propargyl acrylate. Reaction of this product with 6‐mercaptohexanol produced tetrahydroxy‐functional PIB by a sequential thiol‐ene/thiol‐yne procedure. ¹H NMR confirmed the structures of both products. PIB‐SH was reacted with isocyanates in the presence of base to produce polythiourethanes. A model reaction used phenyl isocyanate in THF with catalytic triethylamine. Similar conditions were used to produce PIB‐based thiourethanes with and without a small‐molecule chain extender. Increased molecular weights and thiol group conversion were observed with GPC and ¹H NMR, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Simple,Efficient, and Catalyst‐Free Synthesis of (2‐Amino‐4H‐1‐benzopyran‐4‐yl)phosphonates in Polyethylene Glycol

Several (2‐amino‐4H‐1‐benzopyran‐4‐yl)phosphonates were efficiently synthesized by employing a multicomponent protocol involving a salicylaldehyde, malononitrile or ethyl cyanoacetate, and a trialkyl phosphite in polyethylene glycol. The latter could be recovered and re‐used. No additional solvent or catalyst was required. To the best of our knowledge, this is the first report of the one‐pot preparation of (2‐amino‐4H‐1‐benzopyran‐4‐yl)phosphonic acid dimethyl esters.     

Synthesis,Properties, and Redox Behavior of 1,1,4,4‐Tetracyano‐2‐ferrocenyl‐1,3‐butadienes Connected by Aryl,Biaryl, and Teraryl Spacers

Aryl‐substituted 1,1,4,4‐tetracyano‐1,3‐butadienes (FcTCBDs) and bis(1,1,4,4‐tetracyanobutadiene)s (bis‐FcTCBDs), possessing a ferrocenyl group on each terminal, were prepared by the reaction of a variety of alkynes with tetracyanoethylene (TCNE) in a [2+2] cycloaddition reaction, followed by retro‐electrocyclization of the initially formed [2+2] cycloadducts (i.e., cyclobutene derivatives). The characteristic intramolecular charge transfer (ICT) between the donor (ferrocene) and acceptor (TCBD) moieties were investigated by using UV/Vis spectroscopy. The redox behaviors of FcTCBDs and bis‐FcTCBDs were examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their properties of multi‐electron transfer depending on the number of ferrocene and TCBD moieties. Moreover, significant color changes were observed by visible spectroscopy under the electrochemical reduction conditions.     

Zn助剂对铁基催化剂费托合成制低碳烯烃性能的影响

低碳烯烃(C2=–C4=)是十分重要的基础化工原料,目前主要采用热裂解或催化裂解石脑油、蜡油等工艺路线生产。近年来,针对全球范围的石油危机及我国富煤贫油这一基本的国情,以煤、天然气(页岩气)和生物质等丰厚的碳资源,经合成气制取低碳烯烃的工艺路线备受关注。其中,合成气经由甲醇或二甲醚间接制取烯烃技术(MTO/MTP)已经工业化;与之相比,费托合成直接生产低碳烯烃(FTO)工艺流程短、投资和操作费用低,具有良好的工业发展前景。目前,费托合成催化剂活性组分的研究主要集中于Fe, Co, Ni和Ru等元素,其中Fe基催化剂具有较高低碳烯烃选择性、较低甲烷选择性和制造廉价等优势,更适合于FTO反应。最近,人们大多聚焦于对负载型铁基催化剂的研究,但传统非负载型铁催化剂由于其制备简单、价格低廉,仍然具有巨大的开发前景。近来,我们组报道了采用微波水热法制备的Zr助剂改性Fe-Zr催化剂应用于CO加氢研究,提高了催化剂的活性,与传统Mn改性铁基催化剂相比, CO2选择性明显降低。目前,已有研究小组对Zn助剂提高铁基催化剂烯烃选择性进行报道,但反应过程中的严重积碳问题却少有研究。我们在Fe-Zr催化剂的基础上,进一步研究了Zn助剂在提高铁基催化剂低碳烯烃选择性、改善产物分布和降低反应过程积碳方面的作用。
　　我们分别采用微波水热法和浸渍法对铁基催化剂进行了Zn改性,并将其用于费托合成制取低碳烯烃反应。运用扫描电镜(SEM)、X射线衍射(XRD)、N2物理吸附(BET)、H2程序升温还原(H2-TPR)和X射线光电子能谱(XPS)技术手段对催化剂的物理和化学性质进行了表征。结果表明,两种方法改性后的铁基催化剂具有高低碳烯烃选择性和稳定性,重质烃(C5+)含量降低,且保持低CO2选择性。此外,采用两种方法Zn改性的铁基催化剂展现出了不同的特性。 XRD结果表明,反应前两种方法制备的样品α-Fe2O3物相晶粒大小均为15–18 nm,反应后浸渍法制备的样品对应物相(ZnFe2O4)晶粒大小约为25 nm、而微波水热法制备的样品约为20 nm,说明微波水热法改性的催化剂有效分散了Fe活性组分; H2-TPR结果显示,两种Zn助剂加入方法对催化剂Fe组分的还原行为有不同程度影响,体现了活性组分间不同的相互作用; XPS结果表明, Zn助剂改变了催化剂Fe活性位的化学性质,在微波水热法制得催化剂的表面Zn含量更低、分散度更高,而Zn助剂的加入对Zr组分没有明显影响。所有催化剂经200 h在线活性测试后,采用传统浸渍法制备的催化剂表面有大量积碳生成;而采用微波水热改性铁基催化剂积碳量明显减少,表现出更高的催化活性与稳定性。     

Interpretation on Band‐Broadening in Chromatography with Spatial Peak Profiles Obtained Using Whole‐Column Detection

Fifteen liquid chromatographic experiments were investigated using a whole‐column detection (WCD) system and a conventional post‐column UV/Vis detector. The peak widths obtained from chromatograms were found dependent on the retention factor; the larger the retention factor was the greater the peak width. However, the on‐column spatial peak widths were dependent on the locations where they were measured in the column. The peak widths monitored at 17 cm from the column inlet were found essentially the same no matter what their retention factors were. In addition, a linear relationship was found between the chromatographic peak width and the reciprocal of the average linear rate of the solute migration. The peak widths on chromatograms did not reflect how they appeared in the column; instead, the widths were determined by the solute speed passing the detector.     

Crystal and Molecular Structures of the Pentafluorosulfanyl Compounds,SF5X (X = ‐NC, ‐CN, ‐NCO, ‐NCS and ‐NCCl2) by X‐ray Diffraction at Low Temperature

A new method for the synthesis of the unstable pentafluorosulfanyl isocyanide from N‐(pentafluorosulfanyl)(dichloromethanimine) was developed, thereby allowing for the study of its spectroscopic data. The structure of pentafluorosulfanyl isocyanide was determined by X‐ray crystallography at 113 K. The molecule possesses an almost linear S‐N‐C arrangement and an unexpectedly long S‐N bond. In addition, the structures of pentafluorosulfanyl cyanide, pentafluorosulfanyl isocyanate, pentafluorosulfanyl isothiocyanate, and N‐(pentafluorosulfanyl)(dichloro)methanimine were determined by single crystal X‐ray crystallography at low temperatures.     

Synthesis,Characterization, and Anticancer Effect of Trifluoromethylated Aurone Derivatives

A series of trifluoromethylated aurone derivatives were synthesized, and the structure of 6‐hydroxy‐4‐trifluoromethylated aurone was determined by single crystal X‐ray analysis. Their anticancer activities against leucocythemia (HL‐60) and colorectal adenocarcinoma (HT‐29) were evaluated by the standard MTT method in vitro with 5‐fluorouracil as a positive contrast drug. The results showed that all the (Z)‐trifluoromethylated aurone derivatives had potential anticancer activities.     

Thermal and X‐ray analysis of polymorphic crystals,melting, and crystalline transformation in poly(butylene adipate)

Polymorphic crystals and complex multiple melting behavior in an aliphatic biodegradable polyester, poly(butylene adipate) (PBA), were thoroughly examined by wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). Further clarification on mechanisms of multiple melting peaks related to polymorphic crystal forms in PBA was attempted. More stable α‐form crystal is normally favored for crystallization from melt at higher temperatures (31–35 °C), or upon slow cooling from the melt; while the β‐form is the favored species for crystallization at low temperatures (25–28 °C). We further proved that PBA crystallization could also result in all α‐form even at low temperatures (25–28 °C) if it crystallized with the presence of prior α‐form nuclei. PBA packed with both crystal forms could display as many as four melting peaks (P1 ? P4, in ascending temperature order). However, PBA initially containing only the α‐crystal exhibited dual melting peaks of P1 and P3, which are attributed to dual lamellar distributions of the α‐crystal. By contrast, PBA initially containing only the β‐crystal could also exhibit dual melting peaks (P2 and P4) upon scanning. While P2 is clearly associated with melting of the initial β‐crystal, the fourth melting peak (P4), appearing rather broad, was determined to be associated with superimposed thermal events of crystal transformation from β‐ to α‐crystal and final re‐melting of the new re‐organized α‐crystal. Crystal transformation from one to the other or vice versa, lamellae thickening, annealing at molten state, and influence on crystal polymorphism in PBA were analyzed. Relationships and mechanisms of dual peaks for isolate α‐ or β‐crystals in PBA are discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1662–1672, 2005     

Preparation,Cellular Internalization,and Biocompatibility of Highly Fluorescent PMMA Nanoparticles

Methacrylate monomers were functionalized with a 4‐hydroxythiazole chromophore and copolymerized with methyl methacrylate via RAFT. Nanoparticles of 120 and 500 nm in size were prepared without using stabilizers/surfactants. For comparative studies, preparative ultracentrifugation was applied for the separation into small and large particle fractions. All suspensions were characterized by DLS, AUC, and SEM and tested regarding their stability during centrifugation and re‐suspension, autoclavation, and incubation in cell culture media. In vitro studies with mouse fibroblast cell line and differently sized NP showed a particle uptake into cells. Biocompatibility, non‐toxicity, and hemocompatibility were demonstrated using a XTT assay, a live/dead staining, and an erythrocyte aggregation and hemolysis assay.     

An Electrochemical Sensor Based on Nitrogen‐doped Carbon Nanofiber for Bisphenol A Determination

In this paper, bisphenol A was determined by electrochemical method at a nitrogen‐doped carbon nanofiber modified carbon paste electrode (NCNF/CPE) with high sensitivity and good selectivity. NCNF was obtained by a simple electrospinning followed by carbonization procedure, in which polyacrylonitrile (PAN) as precursor and nitrogen doping was realized by re‐utilizing the tail gas that produced in the thermal pretreatment process. Good reproducibility and high stability were obtained for BPA detection at NCNF modified CPE. Current response plotted with BPA concentration was linear in the range of 0.1–60 μM with LOD of 0.05 μM. The proposed electrochemical sensor was employed for BPA determination with satisfactory recoveries for real water samples, indicating the practical applicability of NCNF/CPE.     

Energetic Derivatives of 4, 4′,5, 5′‐Tetranitro‐2, 2′‐bisimidazole (TNBI)

4, 4′,5, 5′‐Tetranitro‐2, 2′‐bisimidazole (TNBI) was synthesized by nitration of bisimidazole (BI) and recrystallized from acetone to form a crystalline acetone adduct. Its ammonium salt ( 1 ) was obtained by the reaction with gaseous ammonia. In order to explore new explosives or propellants several energetic nitrogen‐rich 2:1 salts such as the hydroxylammonium ( 3 ), guanidinium ( 4 ), aminoguanidinium ( 5 ), diaminoguanidinium ( 6 ) and triaminoguanidinium 7 4, 4′,5, 5′‐tetranitro‐2, 2′‐bisimidazolate were prepared by facile metathesis reactions. In addition, methylated 1, 1′‐dimethyl‐4, 4′,5, 5′‐tetranitro‐2, 2′‐bisimidazole (Me₂TNBI, 8 ) was synthesized by the reaction of 2 and dimethyl sulfate. Metal salts of TNBI can also be easily synthesized by using the corresponding metal bases. This was proven by the synthesis of pyrotechnically relevant dipotassium 4, 4′,5, 5′‐tetranitro‐2, 2′‐bisimidazolate ( 2 ), which is a brilliant burning component e.g. in near‐infrared flares. All compounds were characterized by single crystal X‐ray diffraction, NMR and vibrational spectroscopy, elemental analysis and DSC. The sensitivities were determined by BAM methods (drophammer and friction tester). The heats of formation were calculated using CBS‐4M electronic enthalpies and the atomization method. With these values and mostly the X‐ray densities different detonation parameters were computed by the EXPLO5 computer code. Due to the great thermal stability and calculated energetic properties, especially guanidinium salt 4 could be served as a HNS replacement.