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991.
992.
Metal–Organic Frameworks Containing Missing‐Linker Defects Leading to High Hydroxide‐Ion Conductivity
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Dr. Carmen Montoro Prof. Dr. Pilar Ocón Dr. Félix Zamora Prof. Dr. Jorge A. R. Navarro 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(5):1646-1651
The ionic conductivity properties of the face‐centered cubic [Ni8(OH)4(H2O)2(BDP_X)6] (H2BDP_X=1,4‐bis(pyrazol‐4‐yl)benzene‐4‐X with X=H ( 1 ), OH ( 2 ), NH2 ( 3 )) metal–organic framework (MOF) systems as well as their post‐synthetically modified materials K[Ni8(OH)5(EtO)(BDP_X)5.5] ( 1@KOH , 3@KOH ) and K3[Ni8(OH)3(EtO)(BDP_O)5] ( 2@KOH ), which contain missing‐linker defects, have been studied by variable temperature AC impedance spectroscopy. It should be noted that these modified materials exhibit up to four orders of magnitude increase in conductivity ‐values in comparison to pristine 1 – 3 systems. As an example, the conductivity value of 5.86×10?9 S cm?1 (activation energy Ea of 0.60 eV) for 2 at 313 K and 22 % relative humidity (RH) increases up to 2.75×10?5 S cm?1 (Ea of 0.40 eV) for 2@KOH . Moreover, a further increase of conductivity values up to 1.16×10?2 S cm?1 and diminution of Ea down to 0.20 eV is achieved at 100 % RH for 2@KOH . The increased porosity, basicity and hydrophilicity of the 1@KOH – 3@KOH materials compared to the pristine 1 – 3 systems should explain the better performance of the KOH‐modified materials. 相似文献
993.
994.
β‐Hydrogen Elimination Reactions of Nickel and Palladium Methoxides Stabilised by PCP Pincer Ligands
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Dr. Luis M. Martínez‐Prieto Elena Ávila Dr. Pilar Palma Dr. Eleuterio Álvarez Prof. Dr. Juan Cámpora 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(27):9833-9849
Nickel and palladium methoxides [(iPrPCP)M‐OMe], which contain the iPrPCP pincer ligand, decompose upon heating to give products of different kinds. The palladium derivative cleanly gives the dimeric Pd0 complex [Pd(μ‐iPrPCHP)]2 (iPrPCHP=2,6‐bis(diisopropylphosphinomethyl)phenyl) and formaldehyde. In contrast, decomposition of [(iPrPCP)Ni‐OMe] affords polynuclear carbonyl phosphine complexes. Both decomposition processes are initiated by β‐hydrogen elimination (BHE), but the resulting [(iPrPCP)M‐H] hydrides undergo divergent reaction sequences that ultimately lead to the irreversible breakdown of the pincer units. Whereas the Pd hydride spontaneously experiences reductive C?H coupling, the decay of its Ni analogue is brought about by its reaction with formaldehyde released in the BHE step. Kinetic measurements showed that the BHE reaction is reversible and less favourable for Ni than for Pd for both kinetic and thermodynamic reasons. DFT calculations confirmed the main conclusions of the kinetic studies and provided further insight into the mechanisms of the decomposition reactions. 相似文献
995.
The concept of “flux” is proposed for quantitatively describing the manner in which the relative concentrations of three chain ends remain at a steady state in a terpolymerization. The flux is a measure of the net rate of transition from one chain end to another. If a terpolymerization remains at a steady state with respect to the relative concentrations of the three chain ends, then the flux must be either zero or some finite number which is independent of the choice of chain ends used to calculate it. It is a necessary and sufficient condition for Ham's concept of sequence reversibility to be true that the flux be zero. The flux calculated for many systems using reactivity ratio data is quite near zero. However, the calculations necessarily share the imprecision of reactivity ratio data. Ter-polymer sequence distribution data, if available, could be used in a proposed method of calculating flux. 相似文献
996.
Fausto N. Comba Fabiana Gutierrez Pilar Herrasti María D. Rubianes Gustavo A. Rivas 《Electroanalysis》2012,24(7):1541-1546
This work reports the effect of the incorporation of different proteins within carbon paste electrodes (CPE) modified with electrochemically synthesized magnetite nanoparticles (20 nm) on the electrochemical response towards hydrogen peroxide. Scanning electron microscopy images reveal that the proteins produce a more efficient dispersion of the nanoparticles within the composite. When CPE is modified with 5.0 % w/w magnetite and 5.0 % w/w albumin the sensitivity for hydrogen peroxide at ?0.100 V is enhanced 40 times and the charge transfer resistance significantly decreases. The increase in sensitivity and the decrease in Rct was dependent on the nature of the protein. 相似文献
997.
Pablo Martín‐Gago Dr. Marc Gomez‐Caminals Dr. Rosario Ramón Prof. Xavier Verdaguer Pau Martin‐Malpartida Eric Aragón Dr. Jimena Fernández‐Carneado Dr. Berta Ponsati Prof. Pilar López‐Ruiz Maria Alicia Cortes Prof. Begoña Colás Prof. Maria J. Macias Prof. Antoni Riera 《Angewandte Chemie (International ed. in English)》2012,51(8):1977-1977
998.
Highly Enantioselective Hydrogenation of N‐Aryl Imines Derived from Acetophenones by Using Ru–Pybox Complexes under Hydrogenation or Transfer Hydrogenation Conditions in Isopropanol
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Estefanía Menéndez‐Pedregal Dr. Mónica Vaquero Dr. Elena Lastra Prof. Pilar Gamasa Dr. Antonio Pizzano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):549-553
The asymmetric reduction of N‐aryl imines derived from acetophenones by using Ru complexes bearing both a pybox (2,6‐bis(oxazoline)pyridine) and a monodentate phosphite ligand has been described. The catalysts show good activity with a diverse range of substrates, and deliver the amine products in very high levels of enantioselectivity (up to 99 %) under both hydrogenation and transfer hydrogenation conditions in isopropanol. From deuteration studies, a very different labeling is observed under hydrogenation and transfer hydrogenation conditions, which demonstrates the different nature of the hydrogen source in both reactions. 相似文献
999.
1000.