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Insertion Mechanism (insertion + mechanism)
Selected AbstractsStudy of the Insertion/Deinsertion Mechanism of Sodium into Na0.44MnO2.CHEMINFORM, Issue 28 2007F. Sauvage Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Combined First-Principle Calculations and Experimental Study on Multi-Component Olivine Cathode for Lithium Rechargeable BatteriesADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Hyeokjo Gwon Abstract The electrochemical properties and phase stability of the multi-component olivine compound LiMn1/3Fe1/3Co1/3PO4 are studied experimentally and with first-principles calculation. The formation of a solid solution between LiMnPO4, LiFePO4, and LiCoPO4 at this composition is confirmed by XRD patterns and the calculated energy. The experimental and first-principle results indicate that there are three distinct regions in the electrochemical profile at quasi-open-circuit potentials of ,3.5,V, ,4.1,V, and ,4.7,V, which are attributed to Fe3+/Fe2+, Mn3+/Mn2+, and Co3+/Co2+ redox couples, respectively. However, exceptionally large polarization is observed only for the region near 4.1,V of Mn3+/Mn2+ redox couples, implying an intrinsic charge transfer problem. An ex situ XRD study reveals that the reversible one-phase reaction of Li extraction/insertion mechanism prevails, unexpectedly, for all lithium compositions of LixMn1/3Fe1/3Co1/3PO4 (0,,,x,,,1) at room temperature. This is the first demonstration that the well-ordered, non-nanocrystalline (less than 1% Li,M disorder and a few hundred nanometer size particle) olivine electrode can be operated solely in a one-phase mode. [source] Interaction of FeO+ cation with benzene, aniline, and 3-methylaniline: DFT study of oxygen insertion mechanismINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 11 2008Karolina Kwapien Abstract The reaction pathways and energetics for oxygen insertion into CH bond in benzene, aniline, and 3-methylaniline by FeO+ in the gas phase were investigated by means of the DFT methodology with the B3LYP exchange-correlation functional and 6-311G** basis set. The main aim of this work was to elucidate the influence of substituents in phenyl ring on stationary points along the energy profile on sextet and quartet surfaces for the reaction of FeO+ with substituted benzenes. The studies show that the amino and methyl groups change the energetics of oxygen insertion by lowering the energy profile along the reaction pathway. The substituents studied in this work facilitate the insertion of oxygen into the aromatic CH bond by stabilizing the intermediate sigma complex (,-complex), the amino group being by far more effective. On the other hand, both functional groups increase the activation energy of the rate-determining step in the gas phase, so that they have unfavorable influence on the kinetics. The comparison of the energy diagrams for the sextet and quartet spin states indicates the dominance of the low-spin reactivity in oxygen insertion into aromatic CH bond. Aniline and 3-methylaniline oxidation occurs via electrophilic addition while the conversion of benzene to phenol by FeO+ is mediated by a ,-complex with mixed radical and cationic character. Present results are also discussed in the context of oxyferryl group reactivity. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Fluorenyl based syndiotactic specific metallocene catalysts structural features, origin of syndiospecificityMACROMOLECULAR SYMPOSIA, Issue 1 2004Abbas Razavi Abstract The stereochemistry of propylene insertion/propagation reactions with a variety of Cs symmetric fluorenyl- containing single site catalysts is discussed. Our recent results indicate that independent of the chemical composition of the ancillary ligand fragments, or nature of the transition metal, active sites with local Cs symmetry and enantiotopic coordination positions behave syndioselectively in the general context of chain migratory insertion mechanism. Perfect bilateral symmetry neither exists nor is required in these processes. In this context the mechanism of syndiospecific polymerization is revisited by taking into account the structural characteristics and catalytic behavior of the original metallocene based (,5 -C5H4 -CMe2 -,5 -C13H8) MCl2/ MAO; M = Zr (1), Hf (2) catalyst systems and new syndiotactic specific systems including (,5 -C5H4 -CPh2-,5-3,6-di-tBut-C13H6)ZrCl2 (3), ,1,,5 -(,Me2Si)(3,6-di-tBut-Flu)(t-ButN)MCl2/ MAO; M =Ti (4), Zr (5) and ,1,,5 -(,Me2Si)(2,7-di-tBut-Flu)(t-ButN)MCl2/ MAO; M = Ti (6), Zr (7). [source] Ring-opening polymerization of ,-caprolactone by a new yttrium complex: Y[2,2,-ethylidene-bis(4,6-di- tert -butylphenoxy)]2(ethylene glycol dimethyl ether)Na(ethylene glycol dimethyl ether)3POLYMER INTERNATIONAL, Issue 4 2010Guangming Wu Abstract The main aims of the work reported here were to synthesize and characterize a new 2,2,-ethylidene-bis(4,6-di- tert -butylphenol) (EDBPH2)-based bimetal yttrium complex, Y(EDBP)2(DME)Na(DME)3 (1c; where DME is ethylene glycol dimethyl ether), which was employed as an efficient initiator for the ring-opening polymerization of ,-caprolactone (,-CL). From single-crystal X-ray diffraction, the solid structure of this new bimetal initiator was well established. Experimental results show that 1c initiates the ring-opening polymerization of ,-CL to afford poly(,-CL) with a narrow molecular weight distribution (Mw/Mn = 1.09,1.36, 65 °C). Based on an in situ NMR study, a plausible coordination,insertion mechanism is then proposed. The bimetal complex 1c can be used as an initiator for the ring-opening polymerization of ,-CL with some living characteristics. A study of the mechanism reveals that DME displacement in 1c by ,-CL is involved in the initiation process and the propagation may proceed through three pathways by NaO insertion or YO insertion. Copyright © 2009 Society of Chemical Industry [source] Mechanistic Exploration of the Intramolecular Hydroalkoxylation of Allenyl Alcohols Mediated by Organolanthanide Complexes: A DFT StudyCHEMISTRY - A EUROPEAN JOURNAL, Issue 17 2010Sven Tobisch Dr. An efficient route toward functionalised cyclic ethers: Computational mechanistic analysis indicates an operative LnO ,-bond insertion mechanism with a turnover-limiting cyclisation for the intramolecular hydroalkoxylation of allenyl alcohols (see scheme). [source] Steerable catheters in minimally invasive vascular surgeryTHE INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERY, Issue 4 2009Yili Fu Abstract Background Remote-controlled catheter navigation systems have recently been introduced into minimally invasive vascular surgery and some of them have already been applied in clinical practice. Steerable catheters with improved manoeuvrability play an important role in these innovations for conventional catheterization. Methods This review details the development of various steerable catheters, both in use clinically and under investigation. Comprehensive comparison and analysis in several key aspects are followed to reveal both the advantages and limitations of these catheters, as well as the requirements for relevant techniques. Results Steerable catheters are able to select direction in the distal end, and superior to conventional counterparts in many aspects. Differences between magnetic and active catheters mainly lie in function, safety, configuration of operating room and cost. They have similar requirements for miniaturization and slave insertion mechanisms. Conclusions Steerable catheters are rapidly evolving and still require technological refinements to extend current capabilities. Copyright © 2009 John Wiley & Sons, Ltd. [source] Ring-opening polymerization of D,L -lactide by rare earth 2,6-dimethylaryloxidePOLYMER INTERNATIONAL, Issue 8 2004Lifang Zhang Abstract Ring-opening polymerization of D,L -lactide (LA) has been successfully carried out by using rare earth 2,6-dimethylaryloxide (Ln(ODMP)3) as single component catalyst or initiator for the first time. The effects of different rare earth elements, solvents, monomers and catalyst concentration as well as polymerization temperature and time on the polymerization were investigated. The results show that La(ODMP)3 exhibits higher activity to prepare poly(D,L -lactide) (PLA) with a viscosity molecular weight of 4.5 × 104 g mol,1 and the conversion of 97 % at 100 °C in 45 min. The catalytic activity of Ln(ODMP)3 has following sequence: La > Nd > Sm > Gd > Er > Y. A kinetic study has indicated that the polymerization is first order with respect to both monomer and catalyst concentration. The apparent activation energy of the polymerization of LA with La(ODMP)3 is 69.6 kJ mol,1. The analyses of polymer ends indicate that the LA polymerization proceeds according to ,coordination,insertion' mechanism with selective cleavage of the acyl,oxygen bond of the monomer. Copyright © 2004 Society of Chemical Industry [source] | |||||||||||||