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731.
Company A Gómez L Mas-Ballesté R Korendovych IV Ribas X Poater A Parella T Fontrodona X Benet-Buchholz J Solà M Que L Rybak-Akimova EV Costas M 《Inorganic chemistry》2007,46(12):4997-5012
A new family of dicopper(I) complexes [CuI2RL](X)2 (R=H, 1X, R=tBu, 2X and R=NO2, 3X, X=CF3SO3, ClO4, SbF6, or BArF, BArF=[B{3,5-(CF3)2C6H3}4]-), where RL is a Schiff-base ligand containing two tridentate binding sites linked by a xylyl spacer, has been prepared and characterized, and its reaction with O2 has been studied. The complexes were designed with the aim of reproducing structural aspects of the active site of type 3 dicopper proteins; they contain two three-coordinate copper sites and a rather flexible podand ligand backbone. The solid-state structures of 1ClO4, 2CF3SO3, 2ClO4, and 3BArF.CH3CN have been established by single-crystal X-ray diffraction analysis. 1ClO4 adopts a polymeric structure in the solid state while 2CF3SO3, 2ClO4, and 3BArF.CH3CN are monomeric. The complexes have been studied in solution by means of 1H and 19F NMR spectroscopy, which put forward the presence of dynamic processes. 1-3BArF and 1-3CF3SO3 in acetone react rapidly with O2 to generate metaestable [CuIII2(mu-O)2(RL)]2+ 1-3(O2) and [CuIII2(mu-O)2(CF3SO3)(RL)]+ 1-3(O2)(CF3SO3) species, respectively, that have been characterized by UV-vis spectroscopy and resonance Raman analysis. Instead, reaction of 1-3BArF with O2 in CH2Cl2 results in intermolecular O2 binding. DFT methods have been used to study the chemical identities and structural parameters of the O2 adducts, and the relative stability of the CuIII2(mu-O)2 form with respect to the CuII2(mu-eta2:eta2-O2) isomer. The reaction of 1X, X = CF3SO3 and BArF, with O2 in acetone has been studied by stopped-flow UV-vis exhibiting an unexpected very fast reaction rate (k=3.82(4)x10(3) M-1 s-1, DeltaH=4.9+/-0.5 kJ.mol-1, DeltaS=-148+/-5 J.K-1.mol-1), nearly 3 orders of magnitude faster than in the parent [CuI2(m-XYLMeAN)]2+. Thermal decomposition of 1-3(O2) does not result in aromatic hydroxylation. The mechanism and kinetics of O2 binding to 1X (X=CF3SO3 and BArF) are discussed and compared with those associated with selected examples of reported models of O2-processing copper proteins. A synergistic role of the copper ions in O2 binding and activation is clearly established from this analysis. 相似文献
732.
733.
Shan X Rohde JU Koehntop KD Zhou Y Bukowski MR Costas M Fujisawa K Que L 《Inorganic chemistry》2007,46(20):8410-8417
The reactions of iron(II) complexes [Fe(T(pt-Bu,i-Pr))(OH)] (1a, Tp(t-Bu,i-Pr) = hydrotris(3-tert-butyl-5-isopropyl-1-pyrazolyl)borate), [Fe(6-Me2BPMCN)(OTf)2] (1b, 6-Me2BPMCN = N,N'-bis((2-methylpyridin-6-yl)methyl)-N,N'-dimethyl-trans-1,2-diaminocyclohexane), and [Fe(L8Py2)(OTf)](OTf) (1c, L8Py2 = 1,5-bis(pyridin-2-ylmethyl)-1,5-diazacyclooctane) with tert-BuOOH give rise to high-spin FeIII-OOR complexes. X-ray absorption spectra (XAS) of these high-spin species show characteristic features, distinct from those of low-spin Fe-OOR complexes (Rohde, J.-U.; et al. J. Am. Chem. Soc. 2004, 126, 16750-16761). These include (1) an intense 1s --> 3d preedge feature, with an area around 20 units, (2) an edge energy, ranging from 7122 to 7126 eV, that is affected by the coordination environment, and (3) a 1.86-1.96 A Fe-OOR bond, compared to the 1.78 A Fe-OOR bond in low-spin complexes. These unique features likely arise from a flexible first coordination sphere in those complexes. The difference in Fe-OOR bond length may rationalize differences in reactivity between low-spin and high-spin FeIII-OOR species. 相似文献
734.
735.
We analyze the radiative pion decay π+→e+νeγ within nonlocal chiral quark models that include wave function renormalization. In this framework we calculate the vector and axial-vector form factors FV and FA at q2=0 — where q2 is the e+νe squared invariant mass — and the slope a of FV(q2) at q2→0. The calculations are carried out considering different nonlocal form factors, in particular those taken from lattice QCD evaluations, showing a reasonable agreement with the corresponding experimental data. The comparison of our results with those obtained in the (local) NJL model and the relation of FV and a with the form factor in π0→γ?γ decays are discussed. 相似文献
736.
In the framework of two-sided assignment markets, we first consider that, with several markets available, the players may
choose where to trade. It is shown that the corresponding game, represented by the maximum of a finite set of assignment games,
may not be balanced. Some conditions for balancedness are provided and, in that case, properties of the core are analyzed.
Secondly, we consider that players may trade simultaneously in more than one market and then add up the profits. The corresponding
game, represented by the sum of a finite set of assignment games, is balanced. Moreover, under some conditions, the sum of
the cores of two assignment games coincides with the core of the sum game. 相似文献
737.
Miquel Grau-Sánchez José Luis D?´az-Barrero 《Applied mathematics and computation》2011,217(12):5366-5376
In this paper some families of zero-finding iterative methods for nonlinear equations are presented. The key idea to derive them is to solve an initial value problem applying Runge-Kutta techniques. More explicitly, these methods are used to solve the problem that consists in a differential equation in what appears the inverse function of the one which zero will be computed and the condition given by the value attained by it at the initial approximation. Carrying out this procedure several families of different orders of local convergence are obtained. Furthermore, the efficiency of these families are computed and two new families using like-Newton’s methods that improve the most efficient one are also given. 相似文献
738.
Laia Ferrer-Martí Rafael Pastor G. Miquel Capó Enrique Velo 《Journal of Global Optimization》2011,50(1):127-143
Electrification systems based on the use of renewable energy sources are suitable for providing electricity to isolated communities
autonomously. Specifically, electrification by wind power is one of the technological options that have been used recently
in projects implemented in the Andean highlands of Peru. To date, these projects have tended to install individual microwind
turbines at each demand point. Alternatively, we propose a solution that considers both individual generators and microgrids.
We develop a mathematical model that gives the location and size or type of the wind turbines and the design of the microgrids,
taking into account the demand of the consumption points and the wind potential. The criterion is the minimization of the
initial investment cost required to meet the demand. The model is validated by application to a real case in the northern
highlands of Peru. Results show that microgrids are used despite the village dispersion, and the solutions significantly reduce
the initial investment costs. 相似文献
739.
Casitas A Ioannidis N Mitrikas G Costas M Ribas X 《Dalton transactions (Cambridge, England : 2003)》2011,40(35):8796-8799
Well-defined aryl-Cu(III) species undergo rapid reductive elimination upon reaction with phenolates (PhO(-)), to form aryl-OPh cross-coupling products. Kinetic studies show that the reaction follows a different mechanistic pathway compared to the reaction with phenols. The pH active cyclized pincer-like ligand undergoes an initial amine deprotonation that triggers a faster reactivity at room temperature. A mechanistic proposal for the enhanced reactivity and the role of EPR-detected Cu(II) species will be discussed in detail. 相似文献
740.
Noguera P Posthuma-Trumpie GA van Tuil M van der Wal FJ de Boer A Moers AP van Amerongen A 《Analytical and bioanalytical chemistry》2011,399(2):831-838
The use of carbon nanoparticles is shown for the detection and identification of different Shiga toxin-producing Escherichia coli virulence factors (vt1, vt2, eae and ehxA) and a 16S control (specific for E. coli) based on the use of lateral flow strips (nucleic acid lateral flow immunoassay, NALFIA). Prior to the detection with NALFIA,
a rapid amplification method with tagged primers was applied. In the evaluation of the optimised NALFIA strips, no cross-reactivity
was found for any of the antibodies used. The limit of detection was higher than for quantitative PCR (q-PCR), in most cases
between 104 and 105 colony forming units/mL or 0.1–0.9 ng/μL DNA. NALFIA strips were applied to 48 isolates from cattle faeces, and results were
compared to those achieved by q-PCR. E. coli virulence factors identified by NALFIA were in very good agreement with those observed in q-PCR, showing in most cases sensitivity
and specificity values of 1.0 and an almost perfect agreement between both methods (kappa coefficient larger than 0.9). The
results demonstrate that the screening method developed is reliable, cost-effective and user-friendly, and that the procedure
is fast as the total time required is <1 h, which includes amplification. 相似文献