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  Subjects -> CHEMISTRY (Total: 849 journals)
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CHEMISTRY (598 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 8)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 32)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 17)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 23)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 227)
ACS Photonics     Full-text available via subscription   (Followers: 11)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 21)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription   (Followers: 1)
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 7)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 50)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 53)
Advances in Chemical Science     Open Access   (Followers: 13)
Advances in Chemistry     Open Access   (Followers: 14)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 9)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 15)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 19)
Advances in Nanoparticles     Open Access   (Followers: 14)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 19)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 67)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 26)
American Journal of Plant Physiology     Open Access   (Followers: 13)
American Mineralogist     Hybrid Journal   (Followers: 13)
Analyst     Full-text available via subscription   (Followers: 38)
Angewandte Chemie     Hybrid Journal   (Followers: 164)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 212)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 1)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 3)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 8)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 14)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 28)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 3)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 285)
Biochemistry Insights     Open Access   (Followers: 5)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 110)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 93)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 2)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 67)
Catalysis for Sustainable Energy     Open Access   (Followers: 6)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 7)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 12)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 70)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 23)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 19)
Chemical Reviews     Full-text available via subscription   (Followers: 174)
Chemical Science     Open Access   (Followers: 21)
Chemical Technology     Open Access   (Followers: 16)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemical Week     Full-text available via subscription   (Followers: 8)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 55)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 25)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 150)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 18)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 45)
Chemistry of Materials     Full-text available via subscription   (Followers: 243)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access  
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 2)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 9)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 24)
Chromatography Research International     Open Access   (Followers: 7)
Clay Minerals     Full-text available via subscription   (Followers: 9)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 8)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 3)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 2)
Copernican Letters     Open Access  
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 3)
CrystEngComm     Full-text available via subscription   (Followers: 11)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 56)
Dalton Transactions     Full-text available via subscription   (Followers: 19)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 12)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 4)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 4)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EJNMMI Radiopharmacy and Chemistry     Open Access  
Elements     Full-text available via subscription   (Followers: 2)
Environmental Chemistry     Hybrid Journal   (Followers: 9)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)

        1 2 3 | Last

Journal Cover Acta Chimica Sinica
  [SJR: 0.417]   [H-I: 29]   [1 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 0567-7351
   Published by Chinese Chemical Society Homepage  [2 journals]
  • Morita-Baylis-Hillman Reaction of α,β-Unsaturated Ketones with Allylic
           Alcohols by the Combination of Transition-Metal Catalysis and
           Organomediation
    • Authors: Ya-Qiong Li; Zhi-Zhen Huang
      Abstract: The MBH reaction of α,β-unsaturated carbonyl compounds with allylic halides or allylic esters has been reported. Compared with allylic halides and allylic esters, allylic alcohols are usually more easily prepared. However, to the best of our knowledge, there is no systematic results on the MBH reaction of α,β-unsaturated carbonyl compounds with allylic alcohols. Our experimental results demonstrated that by the catalysis of 10 mol% Pd(PPh3)4 and the mediation of 100 mol% P(n-Bu)3, various aryl vinyl ketones 1a-g were able to undergo the MBH reaction smoothly with allylic alcohol 2a in the mixed solvents of toluene/(CF3)2CHOH (V/V=35/1) at 60℃ under nitrogen, affording desired α-allylated products 3aa-ga in the yields of 57-80%. The MBH reaction is compatible with a series of functional groups on the benzene ring in 1a-g, such as fluoro, chloro, trifluoromethyl methyl, and methoxyl group. Naphthyl group instead of benzene group in aryl vinyl ketone 1h also led to α-coupling product 3ha in a good yield. Various 3-aryl allylic alcohols 2b-f were also able to undergo the MBH reaction smoothly with vinyl ketone 1b, affording the desired α-allylated products 3bb-bf in good yields with excellent regioselectivities and E-selectivities. 2-Methylprop-2-en-1-ol 2g, 1-phenylprop-2-en-1-ol 2h or 1,3-diphenylprop-2-en-1-ol 2i also performed the MBH reaction expediently with vinyl ketone 1b to give the correponding α-coupling product 3bg, 3bb,or 3bi. A plausible mechanism using (CF3)2CHOH to both form phosphonium salt 4 and activate allylic alcohols was also proposed. The MBH reaction has many advantages, such as easy availability of starting materials, good tolerance to many functional groups, excellent regioselectivities and E-stereoselectivities, and satifactory yields. Thus the MBH reaction of aryl vinyl ketones with allylic alcohols may have practical applications in organic synthesis or industry in the future.
      PubDate: 2016-12-20 00:00:00.0
       
  • Theoretical Investigations on the Structures and the Chemical Boding of
           NbMoS n -/0(n=3-7) Clusters
    • Authors: Wang Bin; Wang Jianfu, Zhang Xiaofei, Chen Wenjie, Zhang Yongfan, Huang Xin
      Abstract: Recently, transition metal sulfides (TMS) have played an important role in many catalytic reactions. In particular, they are widely used in the petrochemical industry, such as the hydrodesulfurization (HDS) and the hydrodenitrogenation (HDN) processes. In this work, density functional theory (DFT) and coupled cluster theory[CCSD(T)] calculations were used to study the niobium-mixed di-nuclear molybdenum sulfide clusters NbMoSn-/0 (n=3-7). In our calculations, their ground-state structures were determined and the effects of doping metal, adjusting the sulfur content (n) and changing the charge states of clusters were discussed on the geometries, electronic structures and chemical bonding of NbMoSn-/0(n=3-7). NbMoSn-/0 (n=3-7) clusters can be viewed as linking different sulfur ligands to the NbMoS2 four-membered rings. Among them, diverse poly-sulfur ligands, such as bridging S2, terminal S2 and terminal S3 groups, emerged in the sulfur-rich clusters. Generalized Koopmans' Theorem was employed to predict the vertical detachment energies (VDEs), and simulate the corresponding anionic photoelectron spectra (PES). The first VDEs (VDE1st) of NbMoSn-(n=3-6) increased gradually as a function of n, and then decreased suddenly when the sulfur content (n) reached 7. The VDE1st reached the maximum by 4.69 eV when the sulfur content equaled to 6. The driving forces (-ΔG) of the reduction reactions between NbMoSn-/0(n=3-7) and H2 were evaluated. The NbMoS7- anion with the terminal S22- group yielded the negative value of ΔG, which indicated that the reaction is thermodynamically favored even at the room temperature. We predicted that doping niobium into the molybdenum sulfides may improve the emergence of S2 group which may be helpful in producing the coordinatively unsaturated sites (CUS) under the H2/H2S atmosphere. Molecular orbital analyses are performed to improve our understanding on the structural evolution and the chemical bonding of NbMoSn-/0 (n=3-7) clusters.
      PubDate: 2016-12-20 00:00:00.0
       
  • Synthesis of Sn Nanoparticle/Graphene Nanosheet Hybrid Electrode Material
           with Three-Dimension Conducting Network for Magnesium Storage
    • Authors: Zhang Chang-Huan; Li Nian-Wu, Yao Hu-Rong, Liu Lin, Yin Ya-Xia, Guo Yu-Guo
      Abstract: Rechargeable magnesium (Mg) batteries have attracted research attention as one promising alternative for energy storage because of abundant raw materials. However, the strong electrostatic interaction between bivalent Mg-ions and host lattices often cause sluggish solid state diffusion of Mg-ion within the local crystal structure and consequently prevent reversible insertion/extraction of Mg-ion. Thus much more effort has been paid to develop suitable electrode materials with Mg-ion storage capability. This paper reports the synthesis of Sn nanoparticle/reduced-graphene-oxide nanosheet hybrid nanocomposite (Sn/rGO), by simple hydrothermal method and subsequent thermal treatment. Transmission electron microscopy (TEM) clearly shows that in the as-synthesized Sn/rGO powder Sn nanoparticles are well crystallized, and X-ray diffraction (XRD) pattern was consistent well with tetragonal Sn. Thermogravimetric analysis (TG) suggested that the mass percentage of Sn is ~82.3 wt.% in the Sn/rGO nanocomposite, very close to the design ratio of ~83.4 wt.%. As Mg-ion battery anode, the Sn/rGO electrode material exhibit a high initial discharge specific capacities (545.4 mA h g-1 at 15 mA g-1), good reversible ability and rate performance. The impressive electrochemical property could be attributed to the unique structure of Sn/rGO, in which the three-dimension (3D) conducting network of rGO can effectively prevent the aggregation of Sn nanoparticles and alleviate the serious volume variation of Sn during repeated discharging/charging process, as well as facilitate the fast access of electrons and Mg-ion to improve kinetics for Mg-ion insertion/extraction. Ex situ XRD and SEM characterization were performed to investigate the electrochemical evolution of Sn/rGO electrode at different discharging/charging states. It is found that upon magnesiation crystalline Mg2Sn appears and subsequently disappears during de-magesiation process, which indicates the good electrochemical activity of Sn nanoparticles in Sn/rGO hybrid nanocomposite for magnesium storage. Our result will open new avenue to develop high-efficient magnesium storage material for rechargeable Mg batteries.
      PubDate: 2016-12-20 00:00:00.0
       
  • A Comparison of Me2(CH2Cl)SiCN and Me3SiCN in Catalytic Enantioselective
           Cyanation of Aldehydes
    • Authors: Xu Ye; Xing-Ping Zeng, Jian Zhou
      Abstract: We report the comparative studies of Me2(CH2Cl)SiCN and Me3SiCN in the catalytic enantioselective cyanation reactions of aldehydes, which were catalyzed by the merger of 5 mol% Jacobsen's catalyst (salen)AlCl (R,R)-1 and 6 mol% ylide 2a, and are conducted at -50℃ using i-Pr2O as the solvent. This was based on our recent finding that (R,R)-1 could be effectively activated by ylide to form an enhanced chiral Lewis acid. Generally, the use of Me2(CH2Cl)SiCN as the cyanating reagent afforded obviously higher activity in the reaction of all the aldehydes we examined, along with by-and-large similar enantioselectivity. This further suggested that Me2(CH2Cl)SiCN might be useful cyanating reagent to develop reaction involving the use of less active substrates. Under the indicated condition, aromatic aldehydes worked well to give the desired adducts in up to 99% yield and 94% ee, but the reactions of vinyl aldehydes and aliphatic aldehydes were not successful. All the reactions were performed by the following general procedure. To a 4 mL vial were successively added complex (R,R)-1 (30.3 mg, 0.05 mmol), ylide 2a (22.6 mg, 0.06 mmol) and i-Pr2O (1.0 mL). The resulting solution was stirred at -50℃ for 0.5 h before the addition aldehydes (1.0 mmol) and the cyanating reagent, Me2(CH2Cl)SiCN or Me3SiCN, (2.0 mmol, 250 μL). After TLC analysis indicated the full consumption of the aldehydes, the reaction mixture was filtrated with a pad of silica gel and eluted with Et2O. The filtrate is concentrated under reduced pressure to give a crude residue for column chromatography purification. In contrast, when Me2(CH2Cl)SiCN is used, both cyanohydrins and its silyl ethers were obtained, so a further deprotection by p-TsOH is adopted to obtain free cyanohydrins as the only product.
      PubDate: 2016-12-20 00:00:00.0
       
  • Preparation and Electrochemical Properties of Honeycomb-like Pt-Ni-P/Ti
           Electrode for Methanol Oxidation
    • Authors: Tao Xiongxin; Li Li, Qi Xueqiang, Wei Zidong
      Abstract: A honeycomb-like metallic catalyst (Pt-Ni-P/Ti) supported on a Ti sheet was prepared by electrodeposition-displacement method. The Ni-P amorphous alloy was first electrodeposited on the Ti substrate, and then replaced by displacement of Ni in amorphous Ni-P with H2PtCl6. The morphology and methanol oxidation performance of the prepared catalyst were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), anodic linear sweep voltammetry (LSV), cyclic voltammetry (CV), and the anodic stripping of a pre-adsorbed CO monolayer. The SEM results show that the Pt-Ni-P nanoparticles obtained by displacement of Ni in amorphous Ni-P with H2PtCl6 had a honeycomb-like porous structure, while the Pt-Ni nanoparticles had a wheat-like structure. The formation of the honeycomb-like porous structure can be explained by the so-called "out-situ dissolution-deposition mechanism", in which the metallic Ni in Ni-P/Ti electrode preferentially dissolve to form pore structure and release electron. The released electrons can be captured by the PtCl62- ion adsorbed on the surface of Ni-P and reduced on the surface of Ni-P to form Pt shell, thereby forming a honeycomb-like pore structure. For the Pt-Ni/Ti electrode, the formation of wheat-like structure Pt-Ni nanoparticles can be explained by a so-called "in-situ dissolution-deposition mechanism", in which the Pt replacement reaction can only occur at the surface of Ni, and the replacement Pt monolayer can prevent the further chemical substitution of Pt on Ni, thereby forming a wheat-like structure. The electrochemical test results show that the methanol oxidation and CO oxidation onset potential on Pt-Ni-P/Ti electrode in alkaline solution is more negative than that on Pt-Ni/Ti electrode, indicating that P incorporation can significantly enhance the methanol oxidation activity and CO-tolerance. Moreover, the unique honeycomb-like porous structure is beneficial to the fast mass transportation during the catalytic reaction. The combination of compositionally and geometrically favorable factors provides a new avenue to design new electrocatalysts with excellent methanol oxidation activity and CO-tolerance.
      PubDate: 2016-12-20 00:00:00.0
       
  • Design and Preparation of Advanced Materials for Lithium-Air Batteries
    • Authors: Liu qing-chao; Ma shi-yu, Xu ji-jing, Li zhong-jun, Zhang xin-bo
      Abstract: Due to the ultrahigh theoretical energy density, lithium-air battery is proposed as the next generation electrochemical energy storage devices. The improvement of lithium-air battery's electrochemical performances and its application highly rely on highly efficient and stable electrodes. In this review, the development and design of air cathode, modification and protection of lithium anode and assembly of new type lithium-air batteries were summarized.
      PubDate: 2016-12-20 00:00:00.0
       
  • In-situ TEM study of the liquid-phase reaction of Ag nanowires
           with a sulfur solution
    • Authors: Rong Genlan; Zhang Xinyi, Xu Yan, Zhang Yuegang
      Abstract: Using transmission electron microscopy (TEM) to directly observe a dynamic chemical reaction process in liquid-phase environment is a big challenge because it is difficult to keep liquid reactants under vacuum. In this work, we reported a liquid-based cell that enables in-situ observation of a solution reaction process under TEM. The novel liquid cell design not only realizes the self-alignment of top/bottom windows, but also achieves an adjustable liquid layer thickness down to nanometer scale. The cell consists of top and bottom frames, both of which are fabricated from silicon wafers using conventional micro-fabrication techniques. The transparent observation windows are made of silicon nitride (SiNx) membranes. In a typical assembling process, an ethanol solution containing silver nanowires and an ethanol solution containing saturated sulfur were sequentially dropped into the liquid tank of the bottom-frame of a liquid cell by using 1 mL syringe. Then, the liquid tank was covered by the top-frame with a window direction of 90 degrees, and an epoxy was used to seal the edge between the top-frame and bottom-frame. Using this assembled liquid cell, we performed in-situ TEM observation of the chemical reaction between Ag nanowires and sulfur in ethanol solution. Additional ex-situ X-ray diffraction (XRD) and Raman spectroscopy were also performed to study the reaction intermediates and final products. Instead of a simple reaction process in which sulfur diffuses into Ag to form the final product of Ag2S, we found that the real reaction process involves the formation of a soluble intermediate phase (Ag2S4), which led to a partial dissolution of Ag nanowires in ethanol solution during reaction. These results well demonstrate that the in-situ TEM technique is a powerful tool to reveal the "real" chemical reaction mechanism. The experimental technique developed here could also be used to study a broad range of dynamic phenomena in liquid environment.
      PubDate: 2016-12-05 00:00:00.0
       
  • Hierarchical self-assembly of polyamide helical fibers
    • Authors: Huang Lei; Huang Tong, Bai Yongping, Zhou Yongfeng
      Abstract: Herein, we reported the synthesis and self-assembly of a novel temperature-responsive polyamide. The temperature-responsive polyamides (APA) was synthesized by forming-salts and solution-melt polycondensation based on the hexanedioic acid and temperature-responsive poly(propylene glycol) bis(2-aminopropyl ether). The polyamide structures of as-prepared polyamides were ascertained by fourier transform infrared spectroscopy (FT-IR) measurement. And the gel permeation chromatography (GPC) curve showed that the as-prepared temperature-responsive polyamide possessed a distribution with a number-average molecular weight of 17,800 Da and a polydispersity of 2.91. The micro differential scanning calorimetry (Micro-dsc) and UV results showed that the APA possessed a LCST of 33℃. Then a direct hydration method was used to induce the self-assembly of APA by putting polymers into deionized water with a concentration of 1.0 mg/mL at room temperature. On the other hand, we also prepared the other self-assemblies through the same direct hydration method while the temperature is at 60 oC, which is beyond the LCST of as-prepared APA. The transmission electron microscope (TEM) images ascertained that the as-prepared APA should self-assemble into normal fibers at room temperature (c=1.0 mg/mL). And the formation of these long fibers are attributed to the aggregation and fusion of the primary polyamide micelles. However, very interesting, when the temperature was increased to 60℃, the atomic force microscope (AFM) and TEM results showed that the original fibers have transformed into helical fibers with more than 5 μm length. And the average helix pitch was about 35 nm. This fascinating morphology transformation should be attributed to the solubility change of PPG segments in APA fibers. When the temperature was increased to 60℃ beyond the LCST of APA, the solubility of PPG segments would decrease, and the PPG segments would also collapse. And what's more, due to an alternating hydrophilic/hydrophobic structure of APA, and the PPG segments on the surface of the APA fibers should twist. Finally, the helical APA fibers have been obtained. The present work represents a new progress for macromolecular self-assembly.
      PubDate: 2016-12-05 00:00:00.0
       
  • Research Progress on the Phthalocyanine Based Targeting Photosensitizers
           in Photodynamic Therapy
    • Authors: Li Mingle; Peng Xiaojun
      Abstract: In recent years, photodynamic therapy (PDT) technology, as a noninvasive method of treating malignant tumors and age-related macular degeneration, which is different from the traditional cancer treatments, has drawn more and more attention of scientists. PDT treatment relies on the combination of photosensitizer, oxygen and light, when the photosensitizer is irradiated by special light, it can generate singlet oxygen, which is a cytotoxic agent can eradicate tumors via vasculature damage and cell damage, and sometimes the response of immune system. Due to its special advantages, i.e small traumatic, low toxicity, good compatibility, collaborative surgical treatment and repeatable treatment etc., PDT is widely used in many kinds of tumor treatments. Current practice of photodynamic therapy is limited to a few functionalized photosensitizers, for example porphyrins, however these compounds has several disadvantageous properties such as low absorption in the tissue transparency window (650-900 nm), prolonged skin photosensitivity, and slow clearance rate from body. This has inspired efforts to develop more effective PDT photosensitizers with improved photophysical characteristics and special targeting advantages. So in this review, the authors briefly outline the theories of PDT as well as the development process of photosensitizer, and summarize the characteristics of ideal photosensitizer. At present, the third generation photosensitizers mainly based on phthalocyanines have become a research highlight in PDT. However, how to improve the targeting of photosensitizer so as to achieve precise photodynamic efficiency is still an urgent problem to be solved. Therefore, this review mainly summarizes the recent research on phthalocyanine based targeting photosensitizers. In addition, the development of key research directions in the future has also been pointed out. According to the present researches, in the aspects of PDT, overcoming the limitation of cancer hypoxic microenvironment, developing Type Ⅰ independently from oxygen, and penetrating more deeply targeting photosensitizers possess enormous potential, and they may become a kind of photosensitizer with excellent performance in the field of photodynamic therapy.
      PubDate: 2016-12-05 00:00:00.0
       
  • Theoretical Study on Electronic Properties and Structural Evolution in
           Hf2O n -/0 (n=1-6) Clusters
    • Authors: Chen Shifang; Chen Wenjie, Wang Bin, Zhang Xiaobin, Huang Xin, Zhang Yongfan
      Abstract: Extensive density functional theoretical (DFT) and ab initio[CCSD(T)] calculations were combined to investigate the geometric and electronic structure of a series of dinuclear hafnium oxide clusters, Hf2On-/0 (n=1-6). DFT calculations were performed to search for the lowest energy structures for both the anionic clusters and the neutral counterparts. The search for the global minima was performed using analytical gradients with the Stuttgart relativistic small core potential and the valence basis sets augmented with two f-type and one g-type polarization functions for Hf and the aug-cc-pVTZ basis set for oxygen. The relative energies of the low-lying structures (within ~0.35 eV) were further evaluated via single-point calculations at the coupled cluster[CCSD(T)] level with the Hf/Stuttgart+2f1g/O/aug-cc-pVTZ basis sets at the B3LYP geometries. Generalized Koopmans' theorem (GKT) was applied to predict VDEs and simulate the anion photoelectron spectra (PES). The trends of structural evolution and the behavior of sequential oxidation of the Hf2On- (n=1-6) clusters were observed. For the anionic species, starting from the C2v triangular structure Hf2O-, the next O atom in the Hf2O2- cluster was again bridge-bonded, forming a rhombus structure. The third O atom occupied the terminal site. The fourth O atom favored the bridging site and the fifth O atom occupied the terminal site. In Hf2O6-, the additional O atom was bonded to a terminal site. Molecular orbital analyses were performed to elucidate the chemical bonding and the structural evolution in Hf2On- (n=1-4) clusters. Spin density analyses revealed oxygen radical, diradical, and superoxide characters in the oxygen-rich clusters, except for the singlet Hf2O5 cluster. We showed that Hf2O3 contains a localized Hf2+ site, which can readily react with O2 to form the Hf2O5 cluster. The Hf2O6- and Hf2O6 clusters, which can be viewed to be formed by the interaction of Hf2O4-/0 and O2, may be utilized as molecular models to understand dioxygen activation on Hf2O4- and Hf2O4 clusters.
      PubDate: 2016-12-05 00:00:00.0
       
  • Decarboxylative 1,6-Conjugate Addition of α-Keto Acids with para-Quinone
           Methides Enabled by Photoredox Catalysis
    • Authors: Wu Zijun; Wang Jian
      Abstract: α-Arylated and α,α'-diarylated carbonyls are an important class of building blocks and widely found in biologically active natural and unnatural molecules. The most popular approach to access α-arylated and α,α'-diarylated carbonyls involves transition-metal-catalyzed cross-coupling reactions and metal-free coupling reactions, which always request harsh conditions or high catalytic loading. Visible-light photoredox catalysis, a novel and green catalytic strategy, has recently received increasing attention from chemists and been widely applied to organic synthesis in the past years. Inspired by the recent process of the visible light photocatalytic generation and exploration of α-keto acids as the precursor for acyl radical in decarboxylative coupling reactions and 1,4-Michael addition reactions, we found that, however, expand their utilization in more complex systems, such as 1,6-conjugate addition with electron deficient olefins, remains underdeveloped, particularly due to the difficult to design the appropriate substrate, and the thermos-instability that the 1,6-acceptors incompatible with the harsh conditions often required for metal-catalyzed redox neutral decarboxylation. Here, we report a photoredox catalytic C-C bond formation reaction that enabled by visible-light. The versatility of this protocol has been portrayed by using a wide range of stable and easily accessible aromatic α-keto acids as well as p-QMs. This synthetic strategy also offers access to 24 kinds of different α-keto-α,α'-diarylated ketones in moderate to excellent yields under mild conditions. A representative procedure for the reaction is as follows:2-oxo-2-phenylacetic acid 1a (0.10 mmol), the p-QM (2,6-di-tert-butyl-4-(4-methoxybenzylidene)cyclohexa-2,5-dien-1-one) 2a (0.12 mmol), photocatalyst Ir[dF(CF3) PPy]2(dtbbpy) PF6(0.001 mmol) and K2HPO4(0.12 mmol) were dissolved in DCM (1 mL). Then, the resulting mixture was degassed and refilled with N2 via ‘freeze-pump-thaw’ procedure (3 times). After that, the solution was stirred at a distance of ~5 cm from a 36W blue LEDs at room temperature for about 12 h with TLC monitoring. Upon completion of the reaction, the crude product was purified by flash chromatography on silica gel (hexane/ethyl acetate) to give the desired product 3.
      PubDate: 2016-12-05 00:00:00.0
       
  • Application of Metal-Organic Frameworks in Chromatographic Separation
    • Authors: Li Xiaoxin; Shu Lun, Chen Sha
      Abstract: Metal-organic frameworks (MOFs) are synthesized via the self-assembling combination of inorganic metals or metal-oxo units (secondary building units, SBUs) with strong bonds to form a porous open crystalline framework. Because of their outstanding thermal stability, chemical stability and designability, MOFs are successfully applied in various fields, such as gas absorption, separation, purification, catalysis, as well as templates for various functional materials. MOFs are also used as columns materials for gas or liquid chromatography separation. In this paper, the studies about MOFs used as stationary phases in gas chromatography and high-performance liquid chromatography were reviewed according to the separated various analytes. We summarized the separation effects of different MOFs for different substances, especially focusing on the separation mechanism of MOFs. The key influence factors on the chromatographic separation, such as pore diameter, functional groups and unsaturated metal sites of MOFs, were expounded. Then, the challenges of MOFs as stationary phases in gas and high-performance liquid chromatography were discussed, which include the mechanism, chiral separation, the limited MOFs in chromatographic separation. The future research in this field is to be seen as expounding the clear separation mechanism, improving their stability and synthesizing the MOFs with special function.
      PubDate: 2016-12-05 00:00:00.0
       
  • Preparation of Three-dimensional Nitrogen-doped Carbon Nanoribbon and
           Application in Lithium/Sulfur Batteries
    • Authors: Li Wanfei; Ma Qian, Zheng Zhaozhao, Zhang Yuegang
      Abstract: Lithium/sulfur (Li-S) batteries have recently attracted intensive research interests due to their high theoretical specific energy of 2600 W h kg-1. However, the poor electronic conductivity of sulfur and the high solubility of polysulfides in organic electrolytes lead to poor cycling stability and rate capability. Herein, we report a three-dimensional (3D) nanocomposite network made from nitrogen-doped carbon nanoribbon (NCNB) and nitrogen-doped graphene (NG), which has a high electronic conductivity and can serve as a conductive matrix and a sulfur immobilizer for the sulfur cathode. The NCNB is prepared by thermal nitridation of a unique 3D phenolic resin (PHF) isolated from the polycondensation reaction of 1,4-hydroquinone and formaldehyde. The N content of NCNB-NG can reach as high as 9.7wt%. Although three types of N bonding geometries, including pyridinic N, pyrrolic N, and graphitic N, are identified in the NCNB-NG composites, we found the pyridinic N is dominant, which facilitates the trapping of intermediate lithium polysulfides. The sulfur was loaded on NCNB-NG by using a Na2S2O3 solution as sulfur source. The scanning electron microscope (SEM) images show that almost no large S particle can be observed in the as-prepared S@NCNB-NG nanocomposites, suggesting a uniform coating of S on the NCNB-NG networks. The transmission electron microscopic (TEM) images and the elemental mapping by Energy-Dispersive X-ray (EDX) analysis also show that nano-sized S particles are uniformly distributed on the NCNB-NG matrix. The as-obtained S@NCNB-NG cathode can deliver a high specific capacity of 1338 mA h g-1 at 0.05 C with about 80% S utilization. It also exhibits excellent rate capability and good cycle stability with a retained specific capacity of 556 mA h g-1 after 300th cycles. These performances are much higher than the control samples using the S@NCNB and the S@PHF nanocomposites as cathodes. The improved performance can be attributed to the unique microstructure and the improved electronic conductivity of the NCNB-NG matrix.
      PubDate: 2016-12-05 00:00:00.0
       
  • Visible Light Induced Cross-Coupling Hydrogen Evolution Reactions
    • Authors: Zhong Jian-Ji; Meng Qing-Yuan, Chen Bin, Tung Chen-Ho, Wu Li-Zhu
      Abstract: Taking advantages of the mild, clean and earth-abundant characters of visible light catalysis, we have invented a new reaction, namely cross-coupling hydrogen evolution (CCHE) reaction, for the construction of a series of C-C bond, C-X (heteroatom) bond, or X-X bond directly from two different C-H bonds, C-H and X-H bonds, or X-H and X-H bonds, respectively. In contrast to traditional strategies, this CCHE reaction avoids the use of any external oxidant and H2 is the sole product at ambient condition. In this contribution, we will highlight the development of CCHE reaction since the first report in 2013 to provide guidance for cleaner, safer, and more efficient, step-economic and atom-economic organic transformation.
      PubDate: 2016-11-24 00:00:00.0
       
  • Benzothiadiazole conjugated metal-organic framework for organic aerobic
           oxidation reactions under visible light
    • Authors: Zhang Wen-Qiang; Li Qiu-Yan, Yang Xinyu, Ma Zheng, Wang Huanhuan, Wang Xiao-Jun
      Abstract: In the past several years, visible light induced organic transformations via photoredox catalysis have attracted increasing attention from chemists, owing to their mild, environmentally benign and low cost characteristics. Photoredox catalysts including noble metal complexes as well as some organic dyes are often used to promote the transformations under visible light irradiation. However, most of the reactions were conducted in homogeneous system, which makes it difficult to recycle the catalysts for reuse. From a sustainable viewpoint, an ideal photocatalyst should be easily recoverable, reusable and free of precious metals. To this end, photoactive metal-organic frameworks (MOFs) demonstrate unique advantageous features working as novel heterogeneous photocatalytic systems, yet their utilization toward organic transformations promoted by visible light has been limited. Herein we designed and synthesized a benzothiadiazole functionalized TPDC ligand H21 (TPDC=terphenyl-4,4"-dicarboxylic acid). Briefly, a Suzuki reaction of 4,7-dibromo-2,1,3-benzothiadiazole with 4-(methoxycarbonyl)phenylboronic acid yielded methyl ester precursor, which was hydrolysed by KOH to get the ligand H21 in a high yield. Dimethyl-substituted TPDC H22, on account of its better solubility, was synthesized to replace the original TPDC for preparation of MOF UiO-68 framework. Due to the same length of the two ligands, the mix-and-match synthetic strategy was utilized to construct the benzothiadiazole functionalized UiO-68 topological framework (i.e. MOF UiO-68-S). UiO-68-S was synthesized by heating the mixture of ZrCl4 and a combination of ligands H21 and H22 (1:1 molar ratio) in N,N'-dimethylformamide (DMF) using HAc as an additive at 100℃ for 2 days. Powder X-ray diffraction (XRD) was employed to confirm its crystalline nature and isostructural with the parent UiO-68 framework. Nitrogen sorption experiment at 77 K revealed a typical type I reversible isotherm with Brunauer-Emmett-Teller (BET) surface area up to 1135 m2g-1, indicating its high porosity. Moreover, the MOF can serve as a highly active photocatalyst for visible light promoted aerobic oxidation reactions, including the selective oxygenation of sulfides and oxidative hydroxylation of arylboronic acids. In addition, UiO-68-S can be recycled at least 5 times without significant loss of catalytic activity and its framework is maintained following the catalytic reaction.
      PubDate: 2016-11-24 00:00:00.0
       
  • Pyrenyl Peripheral-Decorated Polyamidoamine Dendrimer for Fluorescent
           Temperature Detection in Aqueous Phase
    • Authors: Qin Tianyi; Zeng Yi, Chen Jinping, Yu Tianjun, Li Yi
      Abstract: A protonated polyamidoamine (PAMAM) dendrimer of generation 2 with pyrenyl attached to its periphery (G2 PAMAM-PyH) was designed and synthesized. G2 PAMAM-Py was synthesized by a condensation of the terminal amino group of the PAMAM dendrimer and the aldehyde group of 1-pyrenecarboxaldehyde followed by a reduction of Schiff base through "one pot" reaction. G2 PAMAM-Py was further protonated by adding HCl, giving the target product G2 PAMAM-PyH. The structure of G2 PAMAM-PyH was characterized by NMR, FTIR, and MS. The functionalization extent of the peripheral amino groups of PAMAM by pyrenyl is 100% according to the 1H NMR and UV-visible spectra. The amphiphilic G2 PAMAM-PyH is soluble in water with a critical aggregation concentration of 3.3 × 10-7 mol·dm-3. Absorption, dynamic light scattering (DLS), and transmission electronic microscopy (TEM) studies demonstrate that G2 PAMAM-PyH exists as vesicle with a bilayer membrane and an average hydrodynamic diameter of ca. 184 nm in aqueous phase. G2 PAMAM-PyH in aqueous phase exhibits dual fluorescence, pyrenyl monomer and excimer emission. The pyrenyl monomer fluorescence increases slightly and the pyrenyl excimer emission decreases monotonically upon temperature raising from 1 to 70℃. Meanwhile, the fluorescence color changes from green (low temperature) to blue (high temperature). The monomer emission enhancement is mainly attributed to less formation of excimer when rising temperature. The fluorescence intensity ratio of pyrenyl excimer to pyrenyl monomer (I495nm/I398nm) changes with varying temperature recoverably, and the relationship between I495nm/I398nm and temperature can be expressed as I495nm/I398nm=28.23-0.68t+3.21×10-3t2+1.83×10-5t3. The accuracy for the measurement of the temperature is better than 0.9℃ in the temperature range of 1~70℃, facilitating in situ gradient temperature measurement. The temperature gradient of aqueous phase in a glass tube is investigated by using G2 PAMAM-PyH, which is consistent with the detection result by using a thermocouple meter. This study provides a potential strategy for developing fluorescent temperature sensing system.
      PubDate: 2016-11-24 00:00:00.0
       
  • Review on advanced functional separators for lithium-sulfur batteries
    • Authors: Huang Jiaqi; Sun Yingzhi, Wang Yunfei, Zhang Qiang
      Abstract: As the demand to energy storage devices for portable electronics and electric vehicles increase, lithium-sulfur (Li-S) batteries have attracted much attention for its extremely high energy density. However, the low columbic efficiency, rapid fading capacity, and poor cycle performance of lithium anode hinders the demonstration of practical Li-S cells. The advanced functional separator/interlayer system have been proposed and verified to retard the shuttle of polysulfides and extend the cycling life of a Li-S cell. In this review, the progress of multifunctional separators/interlayers including permselective separator inhibiting polysulfide shuttles, separator with low interfacial resistance, and composite electrolyte stabilizing anode and retarding the formation of Li dendrites. New insights to challenge and opportunities of multifunctional separator/interlayer system are also prospected.
      PubDate: 2016-11-24 00:00:00.0
       
  • Novel Cu based Oxides with Tunnel Structure as Cathode for Sodium-ion
           Batteries
    • Authors: Liu Lilu; Qi Xingguo, Hu Yong-Sheng, Chen Liquan, Huang Xuejie
      Abstract: Lithium-ion batteries have dominated the electronic and portable device market, since its commercialization in 1990s. However, the cost gets boosted as the shortage and uneven distribution of lithium. Due to the advantage of cost compared with lithium-ion batteries, sodium-ion batteries are considered as the potential candidates for large scale energy storage systems. Cu based tunnel type materials were first synthesized through simple solid state reaction, with Na2CO3, CuO, Fe2O3, MnO2 and TiO2 as starting materials. These raw materials were weighed and grounded in an agate mortar, followed by heated treatment at 950℃ for 24h in air. The obtained samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical performance test. The XRD results demonstrate the tunnel structure was formed with space group pbam (the same with Na0.44MnO2) for each compound. SEM observation manifests that the distribution of particle size is from several hundred of nanometers to several micrometers. The specifically designed compound with Mn substitution (Na0.66Cu0.17Mn0.33Ti0.50O2) can deliver 90 mAh/g cycled between 1.5-4.1 V. Good cycling stability was verified for this compound, of which 90% of its capacity maintained after 50 cycles at 0.1C rate. Moreover, the rate capability is also good and 74% of its capacity remained when cycled at 1C. Charge transfer mechanism was studied by X-ray photoelectron spectroscopy (XPS), and the electroactivity of Cu3+/Cu2+ in this tunnel structure was proved. Moreover, we also performed in-situ XRD in order to examine the structure change during sodium extraction and intercalation. Only solid solution reaction took place during the test with shrifts of peaks or change of the peaks' intensity, however without the appearance of new peaks or disappearance of existed peaks. Here we report, for the first time, the electroactivity of Cu3+/Cu2+ in tunnel type structure. Our results provide new insights in designing tunnel type compound as cathode material for sodium-ion batteries.
      PubDate: 2016-11-24 00:00:00.0
       
  • Visible-Light-Driven Aromatization Hydrogen Evolution by Organic Dye and
           Ni Complex
    • Authors: Xiaoju Wang; Kui Dong, Qiang Liu
      Abstract: Pyridine derivatives play an important role in curing and controlling mites, bacteria, weed and so on. Pyrimidine derivatives exist in a number of bioactive natural products, and they have anti-allergy, anti-cancer, anti-inflammatory, insecticidal and some other properties. 3,4-disubstituted thiophenes not only are important units for the synthesis of natural products, but also serve as key components in some biologically active compounds and material chemistry. In modern society, we have the urgent demand for achieving our products at the expense of the lowest effect to the environment. Under this background, "atom-economy" reactions have been drawing great attention from many chemists and they have got many exciting improvements since then. So, we want to make our own contributions to this area and the following are some of our preliminary results.
      Our method was based on synergistic application of eosin Y with nickel(Ⅱ) complex and an external oxidant-free oxidative dehydrogenation aromatization has been developed. Hantzsch 1,4-dihydropyridines, 1,4-dihydropyrimidines, 2,5-dihydrothiophenes and 2,5-dihydropyrroles produced corresponding aromatic compounds in good to excellent yield under visible light irradiation at room temperature and H2 is generated as the only side product. We determined the hydrogen with GC-TCD using pure hydrogen as an external standard. It features very mild reaction conditions, high yields and excellent chemo-selectivity. In the previous reports, these transformations usually required higher temperatures and/or stronger oxidizing reagents, resulting in the generation of a large amount of by-products. In addition, the hydrogen evolution reactions were also compared with those of aerobic dehydrogenation. The results indicated that the dehydrogenation aromatizations of hantzsch 1,4-dihydropyridines and 1,4-dihydropyrimidine derivatives under the hydrogen evolution conditions proceeded in higher yields but very low conversions, while the reactions of 2,5-dihydrothiophenes and 2,5-dihydropyrroles gave higher conversions in the aerobic dehydrogenation conditions. So far, this is the first report using organic dye material combined with nickel(Ⅱ) complexes to achieve dihydrogen dehydrogenation aromatization of heterocyclic compounds.
      PubDate: 2016-11-24 00:00:00.0
       
  • Doping and Heterojuntional Cooperation of NaNbO3 by Fe and their
           Photocatalytic Properties for Degradation of Rhodamine B
    • Authors: CUI Su-Zhen; YANG Han-Pei, SUN Hui-Hua, NIE Kun, WU Jun-Ming
      Abstract: The perovskite-type NaNbO3 were prepared through a solvothermal process followed by calcinations at high temperature. The Fe3+-doping inside the NaNbO3 lattice and the heterojunctions between α-Fe2O3 and NaNbO3 were acquired synchronously in a similar process by treating NaNbO3 with ferric nitrates. The photocatalytic activity of catalysts was evaluated from the photodegradation of Rhodamine B (RhB) in aqueous solution under UV light irradiation and significant enhancement of degradation rate of aqueous RhB on modified NaNbO3 was observed, with the degradation ratio of RhB reached as high as 95% within 1 h, and the quasi-first-grade rate constant of the RhB degradation reaction over the modified NaNbO3 reached almost 7 times of the pristine one. Characterizations by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectrophotometry (DRS), Adsorption-desorption of N2 at low temperature (BET calculation), photoluminescence spectroscopy (PL), electron spin resonance spectroscopy (ESR) and photocurrent measurement were performed. The compositions and structures of the as-prepared catalysts were carefully identified. It is found that the optimal mass fraction of Fe in modified catalysts is 2.5%, with about 30% of it exists as Fe3+ inside the lattice of NaNbO3 and the remainder as α-Fe2O3 outside the NaNbO3. The results of characterizations or measurements suggest that the moderate Fe3+-doping improved the photocatalytic performance of NaNbO3 by the donor level of impurities, charge capturing and adsorption of dissolved oxygen. A fitting amount of α-Fe2O3 cooperates harmoniously with NaNbO3 in degradation of RhB by enhancing the light quantum efficiency through the migration and jumping of electrons or holes between α-Fe2O3 and NaNbO3. It is proposed that the modification promotes the excitation and suppresses the recombination of photogenerated charge carriers, considering an improved light adsorption indicated by DRS, a restrained recombination of holes and electrons revealed by PL spectra and a promoted charge transfer founded by photocurrent responses.
      PubDate: 2016-11-24 00:00:00.0
       
  • First-Principles Theory Investigation on Structural and Photoelectronic
           Properties of Perovskites: Trigonal versus Hexagonal HC(NH2)2PbI3
    • Authors: Zhao Zigang; Lu Xiaoqing, Li Ke, Wei Shuxian, Liu Xuefeng, Niu Kai, Guo Wenyue
      Abstract: Formamidinium lead halide perovskite FAPbI3 (FA=HC(NH2)2+) has drawn wide attention as efficient photoelectronic conversion material. First-principles calcualtions were performed by using the Vienna ab initio simulation package (VASP) based on density functional theory. The structure configuration, electronic property, absorption spectrum, and bonding energy were analyzed to elucidate the structural and photoelectronic properties of trigonal and hexagonal FAPbI3 perovskites. Results showed that the crystal deformation from trigonal to hexagonal crystal would distort the PbI3 framework, change the covalent/ionic Pb-I bonds, and eventually alter the semiconductor bandgaps. The trigonal and hexagonal FAPbI3 perovskites are both direct-bandgap semiconductors. The direct-bandgap nature of trigonal crystal locates at Z (0, 0, 0.5) symmetry point with the ideal bandgap of ~1.50 eV; the direct-bandgap nature of hexagonal crystal locates at Γ (0, 0, 0) symmetry point with the wide bandgap of ~2.50 eV. For the both crystals, the main contributions to VBM are I 5p orbitals with a little overlapping of Pb 6s orbitals, and the main components of CBM are Pb 6p orbitals. The FA cations do not directly participate into the electron transition process, just acting as charge donors to supply PbI3 framework with more than 0.7 e. There exists both covalent and ionic interactions between Pb and I ions. Compared with the hexagonal crystal, the trigonal FAPbI3 possesses smaller electron and hole effective masses. It exhibits dramatic red shifted absorption spectrum and a better absorption efficiency than hexagonal FAPbI3 and tetragonal MAPbI3 (MA=CH3NH3+) perovskites. Bonding energy analyses showed that the hexagonal FAPbI3 was more stable than the trigonal crystal, and interaction between FA and PbI3 framework was stronger than that between MA and PbI3 framework. Our results could provide theoretical guidence for the experimental design and synthesis of FAPbI3 perovskite solar cells.
      PubDate: 2016-10-20 00:00:00.0
       
  • Azo-bridged New Diiron Carbonyl Complex: Synthesis of
           Fe2(NR)2(CO)6-x(PR3)x and the Derivatives
    • Authors: Li Ran; Xu Wenyuan, Zhao Jinqin, Yu Xin, Wang Wenguang, Tung Chen-Ho
      Abstract: Heating the toluene solution of 4,4-dimethyl-4,5-dihydro-3H-pyrazole (N2C5H10) and Fe3(CO)12 at reflux for 1 h produces diiron hexacarbonyls Fe2(N2C5H10)(CO)6 (1, vCO(CH2Cl2):2069, 2022, 1986 cm-1). Compound 1 exhibits 34 e- configuration, in which (N2C5H10)2- coordinates to diiron (FeIFeI) centers featuring a butterfly structure. To a solution of 1 in toluene was added one equiv of decarbonyl agent Me3NO in MeCN, and the mixture was stirred at room temperature for 20 min. Then, one equiv of monophosphine was added. After 3 h, the solvent was removed and the residue was extracted into 5 mL CH2Cl2. The product Fe2(N2C5H10)(CO)5(PR3) (PR3=PPh3, 2a; PCy3, 2b) was obtained as brown crystals by allowing a pentane layer to diffuse into the CH2Cl2 solution at -20℃. 31P NMR spectra exhibit a singlet at δ 67 for 2a and δ 70 for 2b in CH2Cl2, respectively. In IR spectra, the vCO bands for 2a were displayed at 2032, 1968, 1952, 1907 cm-1, which are compared to 2024, 1959, 1937, 1893 cm-1 for 2b. Photolysis the toluene solution of 1 in the presence of chelating diphosphine ligands such as dppe (dppe=1,2-C2H4(PPh2)2) and dppbz (dppbz=1,2-C6H4(PPh2)2) affords diiron diphosphine carbonyl compounds. For dppe, the product was Fe2(N2C5H10)(CO)4(μ-dppe) (3a, 31P NMR (CD2Cl2):δ 95, FT-IR (CH2Cl2, vCO):1984, 1940, 1925 and 1900 cm-1), in which dppe is bridging the two iron centers. For more rigid diphosphine ligand dppbz, X-ray crystallographic analysis reveals the structure of Fe2(N2C5H10)(μ-CO)(CO)4(dppbz) (3b, 31P NMR (CD2Cl2):δ 93). In 3b, (N2C5H10)2- coordinates to diiron centers in a planar mode, and dppbz chelates at one Fe site by the replacement of one CO ligand. Compound 3b features a Fe-CO-Fe rotated structure with a bridging CO ligand between the two Fe centers. The vCO bands for 3b were displayed at 1990, 1947, 1919, 1895 cm-1. With such a rotated structure, compound 3b provides a new approach for synthetic models of Hred state of[FeFe]-H2ase. The CCDC number for 1, 2a, 2b, 3a and 3b are 1494954, 1494955, 1494956, 1494966 and 1494957. All the compounds were well characterized by NMR, IR spectroscopy and elemental analysis.
      PubDate: 2016-10-20 00:00:00.0
       
  • Advances in Ru (II)-based Photoactivated Chemotherapy Agents
    • Authors: Zhou Qianxiong; Wang Xuesong
      Abstract: Many Ru (Ⅱ) complexes can undergo photoinduced ligand dissociation in aqueous solutions,and the formed aqua Ru (Ⅱ) species may bind to DNA covalently.This property has been applied to develop novel photoactivated chemotherapy (PACT) agents for cancer treatment in recent years.By finely tuning ligand structures and coordination configurations,PACT may realize highly selective and on-demand release of active species in cancer tissues,leading to an improved efficacy and diminished side effects.In this review,the progress in Ru (Ⅱ)-based PACT agents was fully discussed and a perspective for their future development was included.
      PubDate: 2016-10-10 00:00:00.0
       
  • Germanium Nanotube as the Catalyst for Oxygen Reduction
           Reaction:Performance and Mechanism
    • Authors: Chen Xin; Yan Huijuna, Xia Dingguo
      Abstract: One of the major technical barriers to the commercialization of proton exchange membrane fuel cells is the high cost of Pt-based oxygen reduction reaction (ORR) electrocatalysts.In this paper,the ORR catalytic performance and the possible mechanism on (5,5) germanium nanotube (GeNT) were studied by density functional theory methods using DZP basis set.The results indicate that the ORR on the GeNT may undergo three mechanisms including O2 dissociation,OOH dissociation and H2O2 dissociation.For any of the above mechanism,the whole process could easily take place on the GeNT with a complete 4e- ORR pathway.The adsorption properties of the ORR intermediates,especially for O and OH,are also very important for evaluating the catalytic performance.The calculated adsorption energies of the above species are respectively -4.33 and -2.21 eV,much close to those on the Pt.Furthermore,the adsorption energy of H2O on the GeNT is only -0.05 eV,much weaker than the O2 binding,indicating the catalytic cycle of ORR could repeat most easily on the GeNT.Therefore,both the reaction energies of the ORR steps and the adsorption energies of ORR intermediates show that the current GeNT model has the catalytic performance similar to that of precious Pt catalyst.Furthermore,the solvent effect was also studied by using three-water-molecule clusters as the real solvent.The obtained results indicate that the solvent effect could affect the geometrical structure of some adsorbed ORR intermediates,such as atomic O.This would lead to the decrease of the heat loss during the O2 dissociation mechanism.The decreased heat loss would accelerate the following electron transfer steps,due to the fact that an effective electrocatalyst must make the energy loss as small as possible for non-electron-transfer step,in which case the cathode electrocatalyst would deliver all the Gibbs energy of the ORR as electrical work.With solvation,the heat loss is slightly increased from *O2 to *OOH,and decreased from *OOH to *OH in the H2O2 dissociation mechanism,which are also more favorable for ORR.
      PubDate: 2016-10-10 00:00:00.0
       
  • Visible-Light Photoredox Catalytic α-Cyanation Reactions of
           Tertiary Amines
    • Authors: Zhou Quan-Quana; Liu Dana, Xiao Wen-Jinga, Lu Liang-Qiu
      Abstract: Visible-light photoredox catalysis,a novel and green catalytic strategy,has recently received increasing attention from chemists and been widely applied to organic synthesis in the past years.This catalytic strategy enables the generation of various reactive species under mild conditions without stoichiometric activation reagents and shows its significance for sustainable chemistry.α-Amino nitriles are highly versatile intermediates having extensive applications in organic synthesis and biological transformation.The oxidation of tertiary amines using stoichiometric oxidants followed by the nucleophilic addition reaction of the iminium intermediate by cyanide ion (CN-) represents a direct approach for their synthesis.However,the use of stoichiometric oxidants and the production of huge amounts of hazardous waste (i.e.,CN-) is undesirable from environmental viewpoints.Here,we report a photoredox catalytic α-cyanation reaction of tertiary amines using cyanobenziodoxol as a stable and safe cyanide source.This protocol is favored for mild conditions,the avoidance of extra oxidant and highly toxic cyano anion,good functional tolerance as well as safe and simple operations.By doing so,a variety of α-amino nitriles are afforded in good to excellent yields.A sunlight-driven reaction and a gram-scale reaction further demonstrate the utility of this methodology.In addition,we also succeed to apply the same strategy to the decarboxylative cyanation of carboxylic acids,affording the nitriles in moderate yields.A possible mechanism was proposed on the basis of known literature and our previous reports.The representative procedure for the α-cyanation reaction of tertiary amines is as following:N-phenyl piperidine 1a (0.48 mmol),cyanobenziodoxol 2a (0.40 mmol),photocatalyst Ir[dF(CF3)PPy]2(dtbbpy)PF6(0.008 mmol) and CsHCO3(0.60 mmol) were dissolved in DCM (8 mL).Then,the resulting mixture was degassed via ‘freeze-pump-thaw’ procedure (3 times).After that,the solution was stirred at a distance of ~5 cm from a 7W blue LEDs (450-460 nm) at room temperature for 16 h.Upon completion,the crude product was purified by flash chromatography on silica gel (petroleum ether/ethyl acetate 30:1~10:1) directly to give the desired product.The procedure for the decarboxylative cyanation of carboxylic acids is similar.
      PubDate: 2016-10-10 00:00:00.0
       
  • Pt Tube-in-Tube Arrays as High-Performance Electrocatalysts for Direct
           Methanol Fuel Cell
    • Authors: Qi Li; Han Xu, Ye-Xiang Tong, Gao-Ren Li
      Abstract: The Pt tube-in-tube arrays (TTAs) were designed and synthesized by ZnO template-assisted electrodeposition.As a robust integrated 3D electrocatalyst with high utilization rate and fast transport of electroactive species,the Pt TTAs exhibit a high electrochemically active surface area (ECSA) of 64.9 m2/gPt.Compared with Pt NTAs and commercial Pt/C catalyst,the Pt TTAs exhibit much improved electrocatalytic activity and durability for methanol oxidation.In addition,the Pt TTAs as electrocatalysts exhibit superior CO poisoning tolerance.This work shows the significant progress of Pt-based electrocatalysts with high-performance for direct methanol fuel cells.
      PubDate: 2016-10-10 00:00:00.0
       
  • Resumption of the Discharged Li-AgVO3 Primary Batteries for Rechargeable
           Li-O2 Batteries
    • Authors: Ran Li; Yanying Lu, Kaixiang Lei, Fujun Li, Fangyi Cheng, Jun Chen
      Abstract: Recycling use is one of the energy and resource saving strategies to dispose depleted batteries,especially primary lithium batteries that employ electrode materials based on expensive and low-abundance elements.In this study,we report in detail the recycling use of discharged Li-AgVO3 primary battery for rechargeable Li-O2 battery.We demonstrate that the discharged Li-AgVO3 cell,in which metallic silver nanoparticles in-situ generated in the vanadium oxide nanowires cathode efficiently catalyze the oxygen reduction/evolution reactions (ORR/OER),can be resumed as rechargeable Li-O2 cells when they are exposed at O2 atmosphere.By controlling the discharge depths,we obtained different cathodes that were composed of vanadium oxide nanowires and silver nanoparticles.As the electrode was discharged to a lower voltage,more silver nanoparticles with larger particle size were distributed on the surface of vanadium oxides,as a result of the sequential reduction of Ag+ to Ag0 and V5+ to V4+.Specifically,the average size of formed Ag nanoparticles was 15 nm and 70 nm at ceased discharge voltage of 2.9 V and 2.0 V,respectively,while the formation of V4+ was observed at discharge voltage lower than 2.3 V.Electrochemical tests indicated that the Li-O2 cells assembled with the AgVO3 cathode discharged to 2.3 V (AgVO3-2.3) exhibited the highest specific capacity (9000 mAh gcarbon-1),the lowest overpotentials and robust cycling performance (up to 95 cycles at the current density of 300 mA gcarbon-1).The remarkable electrochemical performance of the Li-O2 battery with the AgVO3-2.3 cathode is attributed to the optimization of amount,size and distribution of generated silver nanoparticles that contribute to high electronic conductivity and abundant active sites for the ORR/OER.A combined analysis of electrochemical impedance spectroscopy,X-ray diffraction,and X-ray photoelectron spectroscopy confirmed that the AgVO3-2.3 cathode enables the reversible formation and decomposition of Li2O2 with lower charge transfer resistance on discharge and charge.The results presented here would provide new insight into the promising recycling application of depleted primary Li-AgVO3 batteries in rechargeable high-capacity Li-O2 batteries.
      PubDate: 2016-10-10 00:00:00.0
       
  • Synthesis and Electrochemical Performance of Lithium Rich Cathode
           
    • Authors: Chun Yanga; Zhengliang Gong, Wengao Zhao, Yong Yang
      Abstract: Lithium rich material xLi3NbO4·(1-x)LiMnO2(0 < x < 1) was successfully synthesized by solid state method.Stoichiometric amounts of Li2CO3,Mn2O3 and Nb2O5 were mixed by ball milling,and the mixture was calcinated at 900℃ for 5 hours under Ar atmosphere.X-ray diffraction (XRD) results indicate that the samples with 0.25 < x < 0.67 can be indexed as a cubic structure with Fm-3m space group.Electrochemical results show that the samples of x=0.25 and 0.43 have better electrochemical performance,both delivering 216 mAhg-1 in the initial cycle between 2-4.8V.Although voltage decay is an intrinsic drawback of lithium excess materials,the sample of x=0.43 decays slower.We speculate that Li3NbO4 helps stabilizing the crystal structure.Ex-situ XPS and XAS studies show that the charging process can be divided into two stages.In the first stage,below 4.3V,Mn3+ is oxidized to Mn4+,in the second stage,O2- is oxidized.The reversible oxidation of O2- is the origin of the achievement of large reversible capacity.Co3+ doped material 0.43Li3NbO4·0.57 LiMn1-yCoyO2(y=0.25;0.5) was also synthesized by the same procedure.The structure of the doped material maintains the cubic structure with smaller lattice constant and the variation of lattice constant is in proportion to the amount of Co3+.Galvanostatic charge and discharge tests show that 0.43Li3NbO4·0.57LiMn0.75Co0.25O2 also delivers a large capacity of 215 mAhg-1 in the first cycle between 2-4.8V,but the voltage plateau in the charging process decreased from 4.3V to 4.1V,it can be attributed to the weak dissociation energy of Mn-O bond and the overlap of Co3+/4+3d and O2- 2p energy band.The electrochemical impedance spectroscopy results show that a moderate amount of Co3+ doped into the material decreases the charge transfer resistance.After doped with Co3+,the rate capability is improved.
      PubDate: 2016-10-10 00:00:00.0
       
  • Halogen-Bond-Promoted Radical Isocyanide Insertion of o-Diisocyanoarenes
           with Perfluoroalkyl Bromides under Visible Light Irradiation
    • Authors: Sun Xiaoyang; Wang Wenmin, Ma Jing, Yu Shouyun
      Abstract: A halogen-bond-promoted double radical isocyanide insertion of o-diisocyanoarenes with perfluoroalkyl bromides is reported, in which perfluoroalkyl bromides as halogen bond donors and organic bases as halogen bond acceptors. Fluoroalkyl radicals can be generated by a visible-light-induced single electron transfer (SET) process. Fluoroalkyl radicals are trapped by o-diisocyanoarenes to give 2-fluoroalkylated quinoxaline derivatives. These reactions could be carried out under mild conditions with good chemical yields and broad substrate scope. A broad range of fluoroalkyl bromides with different functionalities could undergo this reaction to give the corresponding quinoxaline derivatives in good yields. A variety of o-diisocyanides could be fluoroalkylated to give quinoxalines under our established conditions. The radical nature of this reaction was confirmed by electron paramagnetic resonance (EPR) experiments using tert-butyl-α-phenylnitrone (PBN) as a spin trap. When PBN was introduced into the reaction mixture, a spectrum signal attributed to the spin adduct C8F17-PBN appeared as a triplet of doublets. Without light and amine, almost no signal was observed. These phenomena strongly suggested that the perfluoroalkyl radical was the key intermediate and the generation of the intermediate heavily relied on the presence of light and amine. A series of deuteration experiments were performed and these results suggested that both the amine and solvent could serve as the hydrogen source and solvent was the major source.
      PubDate: 2016-09-27 00:00:00.0
       
  • Visible Light Promoted Benzylic Csp3-H Bond Activation and
           Functionalization
    • Authors: Pei Pengkuna; Zhang Fana, Yi Honga, Lei Aiwen
      Abstract: In recent years, visible-light-promoted photoredox catalytic activation of organic molecules has been flourishing vigorously. This kind of methodology usually takes advantage of transition-metal complexes and organic dyes as photosensitizers, which can directly react with organic substrates through a single-electron-transfer (SET) progress under visible light irradiation. It's operable to construct C-X(X=C, N, O…) bond via the radical or radical ion generated during the SET process. On the basis of different key intermediates, this highlight gives a brief summary on the recent development of visible light promoted benzylic Csp3-H activation and functionalization.
      PubDate: 2016-09-27 00:00:00.0
       
  • Visible Light Mediated Photocatalytic Aerobic Dehydrogenation: A General
           and Direct Approach to Access 2,3-Dihydro-4-Pyridones and 4-Quinolones
    • Authors: Tianju Shao; Zhiyong Jiang
      Abstract: A visible-light-induced photocatalytic aerobic dehydrogenation of 4-piperidones and 2,3-dihydro-4-quinolones has been developed. By utilizing DPZ as the photocatalyst, the dehydrogenation could provide 2,3-dihydro-4-pyridones and 4-quinolones with satisfactory results (up to 75% yield). The current methodology presents a direct, sustainable and highly atom-economic approach to access these valuable N-containing heterocycles.
      PubDate: 2016-09-27 00:00:00.0
       
  • Visible Light Photocatalytic N-Radical-based Intramolecular Hydroamination
           of Benzamides
    • Authors: Yu Xiao-Ye; Zhou Fan, Chen Jia-Rong, Xiao Wen-Jing
      Abstract: The 3,4-dihydroisoquinolinones are a privileged class of heterocyclic motifs and widely found in numerous biologically active compounds. Thus, the development of more efficient and practical methods for their synthesis is highly desirable. Traditional methods are typically focused on transition-metal catalyzed C-H functionalization. Inspired by the recent process of the visible light photocatalytic generation and exploration of N-radials in organic synthesis, our group in 2014 developed a visible light-induced photocatalytic strategy for direct conversion of the N-H bonds of β,γ-unsaturated hydrazones into N-centred radicals for the first time, and used them in intramolecular radical hydroamination, enabling efficient synthesis of 4,5-dihydropyrazole derivatives. By employing suitable additives or changing reaction parameters, we also successfully achieved highly regioselective 6-endo N-radical cyclisation and oxyamination reactions based on N-centred radicals, providing the valuable 1,6-dihydropyradazines, pyrazolines, and pyridazines in good yields. In the hope of extending such N-radical-mediated heterocycle synthesis further, we reported a transition-metal free and visible light photocatalytic N-radical-based intramolecular hydroamination of benzamides. The reaction provides a practical and efficient approach to various biologically important 3,4-dihydroisoquinolinones with generally high yields. Importantly, the continuous flow reaction could significantly shorten the reaction time and still give rise to satisfactory yield. The sunlight irradiation reaction and gram-scale reaction also highlighted the potential synthetic utility of this method. A general procedure for the reaction is as follows: Eosin Y Na (6.21 mg, 0.009 mmol), NaOH (14.4 mg, 0.36 mmol), amide 1 (0.3 mmol) were dissolved in MeOH (6.0 mL), then, the resulting mixture was degassed via a ‘freeze-pump-thaw’ procedure (3 times). After that, the resulting mixture was stirred at a distance of ~5 cm from 3 W blue LEDs (450-460 nm) at room temperature until the starting amides were consumed as monitored by TLC analysis. After concentration in vacuo, the reaction residue was purified by flash chromatography on silica gel (petroleum ether/ethyl acetate 5:1~2:1) directly to give the desired product.
      PubDate: 2016-09-27 00:00:00.0
       
  • Photo-induced Catalytic Asymmetric Free Radical Reactions
    • Authors: Wang Dehong; Zhang Long, Luo Sanzhong
      Abstract: Enantioselective control of free radical reactions has eluded organic chemists for decades. Echoed with the renaissance of photo-induced processes, or so called photocatalysis or photoredox catalysis in organic synthesis, photo-induced organic radical chemistry has regained its prominence in developing catalytic asymmetric radical reaction. The generally mild conditions inherited with photochemistry, particularly visible light photo-processes, have allowed for controllable generation of free radicals as well as the subsequent bond formations. The past five years have witnessed dramatic advances in exploring photo-induced catalytic asymmetric free radical reactions, and enormous potentials along this line are envisaged. This perspective gives a brief summary on the important advances in this field. Accordingly, the major advances are classified based on different radical species including α-amino/oxyl radicals, radicals generated from enones and its analogues, benzyl radicals, α-carbonyl radicals, polyhalogenated alkyl radicals and nitrogen radicals. Brief discussion of mechanism is presented whenever relevant.
      PubDate: 2016-09-18 00:00:00.0
       
  • Radical Fluoroalkylation of Aryl Alkenes with Fluorinated Sulfones by
           Visible-Light Photoredox Catalysis
    • Authors: Rong Jian; Ni Chuanfa, Wang Yunze, Kuang Cuiwen, Gu Yucheng, Hu Jinbo
      Abstract: The incorporation of fluorine atoms or fluorinated moieties into organic molecules can often lead to significant changes of their physical, chemical, or biological properties. Consequently, fluorinated organic molecules are widely used in areas of pharmaceuticals, agrochemicals and materials. Traditional approaches for the incorporation of fluorinated moieties into organic molecules include nucleophilic, electrophilic, and radical pathways. Among them, radical fluoroalkylations under visible-light photoredox catalysis have attracted much attention because of the mild reaction conditions and broad functional-group tolerance. In our previous work, the radical fluoroalkylation of isocyanides with fluorinated sulfones as the fluoroalkyl radical precursors via Rf-SO2Ar bond cleavage has been achieved under visible-light photoredox catalysis (Rong, J. et al. Angew. Chem., Int. Ed. 2016, 55, 2743). Herein, as a logical extension of our previous research, we report the radical fluoroalkylation of aryl alkenes with fluorinated sulfones as the practical fluoroalkyl radical precursors under visible-light photoredox catalysis. Various fluoroalkyl radicals, including trifluoromethyl (CF3), difluoromethyl (HCF2), 1,1-difluoroethyl (CH3CF2) and (phenyl)difluoromethyl (PhCF2) radicals, can be incorporated into styrene derivatives via this method, delivering the oxyfluoroalkylation products in 46–93% yields. Typical procedures for this reaction are given as follows: to a Schlenk tube were added 2-vinylnaphthalene (1a) (0.20 mmol, 30.8 mg, 1.0 equiv), trifluoromethyl 2-benzo[d]thiazolyl sulfone (2b) (0.24 mmol, 64.1 mg, 1.2 equiv), fac-Ir(ppy)3 (2.7 mg, 0.004 mmol, 2 mol %), H2O (0.5 mL), and acetone (4.5 mL) sequentially. The resulting mixture was degassed with a freeze-pump-thaw procedure (3 times) and irradiated by a 6 W blue LED for 12 h. After the reaction completed, the mixture was extracted with Et2O and dried over anhydrous MgSO4. The organic solvent was removed under reduced pressure and the residue was purified by column chromatography on silica gel by using a 10:1 mixture of petroleum ether/EtOAc as an eluent to provide the hydroxytrifluoromethylation product 3a (31.2 mg, 65% yield).
      PubDate: 2016-09-18 00:00:00.0
       
  • Visible light promoted carbodifluoroalkylation of homopropargylic alcohols
           via concomitant 1,4-aryl migration
    • Authors: Zhou Nengneng; Xu Pan, Li Weipeng, Cheng Yixiang, Zhu Chengjian
      Abstract: Fluorinated compounds have gained much attention because of their unique electronegativity, metabolic stability, and bioavailability, and thus, the synthesis of organofluorine compounds has found wide applications in pharmaceuticals, agrochemicals, and materials science. Among them, the incorporation of a difluoromethyl group (CF2) into organic compounds is of great concern in medicinal chemistry owing to its isosterism with the hydroxyl group. Therefore, the development of new difluoroalkylation methods has attracted great interest in synthetic organic chemistry. Visible light-driven photocatalysis as an eco-friendly and powerful theme has been widely utilized into organic synthesis. In particular, free radical fluorination is emerging as a powerful tool for C–F bond formation, especially under the catalysis of visible light. Recent progress on the visible light-promoted directing difluoroalkylation using ethyl bromodifluoroacetate provided an efficient approach to the target. Herein, we report a contribution towards visible light induced carbodifluoroalkylation of homopropargylic alcohols with the use of ethyl bromodifluoroacetate as a source of difluorinated moieties. This strategy provides a facile way to access functional-difluorinated alkenes through a tandem radical difluoroalkylation and 1,4-aryl migration process. A representative procedure for this reaction is as following: An oven-dried Schlenk tube (10 mL) was equipped with a magnetic stir bar, homopropargylic alcohols (0.2 mmol), fac-Ir(ppy)3 (0.02 equiv, 0.004 mmol), 2-bromo-2,2-difluoroacetate (2.5 equiv, 0.5 mmol), Na2HPO4 (2 equiv, 0.4 mmol). The flask was evacuated and backfilled with Ar for 3 times. 0.5 ml dry DMA and 0.5 ml dry DCE was added with syringe under Ar. The tube was placed at a distance (app.5 cm) from 33w fluorescent light bulb, and the resulting solution was stirred at ambient temperature under visible-light irradiation. After the reaction was finished, the mixture was then diluted with MTBE (2×20 mL) and water. The combined organic layers were dried over sodium sulfate and the solvent concentrated in vacuo and the residue was purified by chromatography on silica gel to afford the corresponding products.
      PubDate: 2016-09-18 00:00:00.0
       
  • Visible-Light Induced Trifluoromethylation of Internal Olefinic C-H Bonds
           through Photoredox Catalysis
    • Authors: Baoquan Gou; Chao Yang, Lei Zhang, Wu jiong Xia
      Abstract: An approach for direct trifluoromethylation of internal olefins of α-oxoketene dithioacetals has been achieved by using Ru(bpy)3Cl2 as photocatalyst and Togni's reagent as trifluoromethylating agent under irradiation with visible light. Under a nitrogen atmosphere, a mixture of a-oxoketene dithioacetal (0.1 mmol), Togni reagent (0.15 mmol), Ru(bpy)3Cl2 (0.005 mmol), and Na2CO3 (0.3 mmol) in DMSO (1 mL) was stirred at room temperature for 72 h under 5 W Blue LEDS, which led to the trifluoromethylated products in 40%-90% yield. This protocol provides an efficient and easy access to prepare trifluoromethylated dithionalkyl α-oxoketene acetals under mild conditions, and is highlighted by its operational simplicity and avoiding using toxic reagent. Furthermore, the gram-scale reaction of 1a suggested the potential application of this protocol in organic synthesis.
      PubDate: 2016-08-24 00:00:00.0
       
  • Advance and Prospect of Functional Materials for Sodium Ion Batteries
    • Authors: Xiang Xingde; Lu Yanying, Chen Jun
      Abstract: Sodium ion batteries (SIBs) as a new chemical power source have recently attracted a great attention for large-scale energy storage owing to the abundance and low cost of sodium resources. In order to achieve advanced SIBs with high specific energy, long cycling lifetime and fast charge/discharge ability, efforts have been devoted to developing advanced electrode materials with large specific capacity, robust cycling stability and good rate capability, as well as functional electrolytes with high ion-conductivity and wide electrochemical window. Promising cathode materials include high-capacity layered oxides, high-potential fluorophosphates and long-lifetime phosphates. Available anode materials consist of highly stable Ti-based layered oxides and carbon materials, high-capacity elemental metals/non-metals and low-cost metal-based compounds. Effective electrolytes involve ester-based electrolytes and ether-based electrolytes. This review summarizes the recent advance of electrode materials and electrolytes for SIBs, mainly focusing on their electrochemical properties, exsiting challenges and resolution strategies.
      PubDate: 2016-08-10 00:00:00.0
       
  • Visible-Light Photoredox Catalysis: Direct Arylation of Electron-Deficient
           Heterocycles and Arenes with Aryl Diazonium Salts
    • Authors: Xuan Zuo; Wenliang Wu, Weiping Su
      Abstract: Visible-light-mediated Ru(bpy)3(PF6)2 catalyzed arylation of electron-deficient heteroarenes with aryl diazonium salts has been achieved under mild conditions, and a series of benzene derivatives can also be arylated under similar reaction conditions in moderate to good yields.
      PubDate: 2015-08-18 00:00:00.0
       
  • Synthesis and reactivity of cobalt pincer complexes formed by
           carbon-hydrogen bond activation
    • Authors: Hua Zhao; Hongjian Sun, Lin Wang, Xiaoyan Li
      Abstract: By treating diphosphinito [PCP]-pincer ligand, (Ph2P(ortho-C6H4))2CH2 (1) with CoMe(PMe3)4 or CoMe3(PMe3)3 the same Csp3-H bond activation product [PCP]Co(I)(PMe3) (2) was obtained at room temperature. Treatment of 2 with C6Cl6, EtBr or nBuBr and CH3I gave rise to the single electron oxidation addition products [PCP]Co(II)X(PMe3) (X = Cl (3); Br (4) and I (5)). The molecular structures of 2-6 were confirmed by X-ray diffraction analysis.
      PubDate: 2015-05-13 00:00:00.0
       
  • Synthesis and Photovoltaic Properties of Narrow Band-Gap Polymer Based on
           Octyl Substituted Triphenylamine
    • Authors: Chen Guiting; Xu Jin, Zhang Bin, Yang Wei
      Abstract: Polymer solar cells (PSCs), as one of the most promising sustainable energy sources which are potentially alternative to inorganic-based solar cells, have attracted much attention due to their unique characteristics in light weight, flexibility, solution processing, and low-cost manufacturing by roll-to-roll technique. In PSCs, the excellent polymer donors are usually narrow band-gap conjugated polymers, which are always constructed as donor-acceptor (D-A) architecture. In this work, a new kind of alternating copolymer POTPADTBT based on triphenylamine (TPA) derivative and 2,1,3-benzothiadiazole (BT) moiety was synthesized by Suzuki polycondensation and characterized in thermal, optical, electrochemical and photovoltaic properties detailedly. This polymer shown interesting properties such as excellent thermal stability and good solubility in common organic solvents. From Uv-vis absorption spectra, POTPADTBT displayed two absorption peaks at 376 and 519 nm, corresponding to the π-π* transition between polymer main chains and the intramolecular charge transfer (ICT) interaction between TPA and BT moieties, respectively. On the other side, the absorption peaks in film were located at 386 and 547 nm, which was red-shifted by 30 nm than those in solution. This result indicated intermolecular π-π stacking interaction existed in POTPADTBT film. The hole mobility of neat POTPADTBT film was 1.1×10-4 cm2·V-1·s-1 by characterized from space charge limited current (SCLC) method. The bulk-heterojunction (BHJ) solar cells were fabricated by using POTPADTBT as donor and PC61BM or PC71BM as acceptor under the device structure of ITO/PEDOT: PSS/polymer: PCBM(1:2, wt/wt)/(poly[(9,9-dioctyl-2,7-fluorene)-alt-(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)]) (PFN)/Al. The device based on ITO/PEDOT: PSS/polymer: PC71BM(1:2, w/w)(80 nm)/PFN(5 nm)/Al gave the best photovoltaic performance with the open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF) and power conversion efficiency (PCE) of 0.85 V, 5.61 mA·cm-2, 46% and 2.52%, respectively. According to the photovoltaic properties, the devices with PC71BM as acceptor shown better performance than those with PC61BM, which displayed broader absorption in visible region resulting in higher Jsc. On the other hand, the devices by utilizing PFN as cathode interfacial layer exhibited higher Voc than those without PFN interlayer. This is possibly because PFN layer can protect active layer when cathode evaporation and exist the built-in electric field between active layer and cathode.
      PubDate: 2014-10-10 00:00:00.0
       
 
 
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