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551.
Olexyj M. Huta Ihor O. Patsaj Antoni Konitz Joanna Meszko Jerzy Baejowski 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(5):o295-o297
The title compound, C15H11N2+·HN2O6?, crystallizes in the monoclinic space group C2/c with four molecules in the unit cell. The planar 9‐cyano‐10‐methylacridinium cations lie on crystallographic twofold axes and are arranged in layers, almost perpendicular to the ac plane, in such a way that neighbouring molecules are positioned in a `head‐to‐tail' manner. These cations and the hydrogen dinitrate anions are linked through C—H?O interactions involving four of the six O atoms of the anion and the H atoms attached to the C atoms of the acridine moiety in ring positions 2 and 4. The H atom of the hydrogen dinitrate anion appears to be located on the centre of inversion relating two of the four O atoms engaged in the above‐mentioned C—H?O interactions. In this way, columns of either anions or cations running along the c axis are held in place by the network of C—H?O interactions, forming a relatively compact crystal lattice. 相似文献
552.
Mairata i Payeras A Ho RY Fujita M Que L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(20):4944-4953
The reaction of [FeII(tpa)(OTf)2] (tpa=tris(2-pyridylmethyl)amine) and its related 5-Me3-tpa complex with hydrogen peroxide affords spectroscopically distinct iron(III)-peroxo intermediates in CH3CN and acetone. The reaction in acetonitrile at -40 degrees C results in the formation of the previously reported Fe(III)-OOH intermediate, the end-on hydroperoxo coordination mode of which is established in this paper by detailed resonance Raman isotope-labeling experiments. On the other hand, the reaction in acetone below -40 degrees C leads to the observation of a different peroxo intermediate identified by resonance Raman spectroscopy to be an FeIII-OOC (CH3)2OH species; this represents the first example of an intermediate derived from the adduct of H2O2 and acetone. The peroxoacetone intermediate decays more rapidly than the corresponding FeIII-OOH species and converts to an FeIV=O species by O-O bond homolysis. This decay process is analogous to that observed for [FeIII(tpa)(OOtBu)]2+ and in fact exhibits a comparable enthalpy of activation of 54(3) kJ mol(-1). Thus, with respect to their physical properties at low temperature, the peroxoacetone intermediate resembles [FeIII(tpa)(OOtBu)]2+ more than the corresponding FeIII-OOH species. At room temperature, however, the behavior of the Fe(tpa)/H2O2 combination in acetone in catalytic hydrocarbon oxidations differs significantly from that of the Fe(tpa)/tBuOOH combination and more closely matches that of the Fe(tpa)/H2O2 combination in CH3CN. Like the latter, the Fe(tpa)/H2O2 combination in acetone catalyzes the hydroxylation of cis-1,2-dimethylcyclohexane to its tertiary alcohol with high stereoselectivity and carries out the epoxidation and cis-dihydroxylation of olefins. These results demonstrate the subtle complexity of the Fe(tpa)/H2O2 reaction surface. 相似文献
553.
Sens C Rodríguez M Romero I Llobet A Parella T Sullivan BP Benet-Buchholz J 《Inorganic chemistry》2003,42(6):2040-2048
Two isomeric Ru(II) complexes containing the dinucleating Hbpp (3,5-bis(2-pyridyl)pyrazole) ligand together with Cl and dmso ligands have been prepared and their structural, spectroscopic, electrochemical, photochemical, and catalytic properties studied. The crystal structures of trans,cis-[Ru(II)Cl(2)(Hbpp)(dmso)(2)], 2a, and cis(out),cis-[Ru(II)Cl(2)(Hbpp)(dmso)(2)], 2b, have been solved by means of single-crystal X-ray diffraction analysis showing a distorted octahedral geometry for the metal center where the dmso ligands coordinate through their S atom. 1D and 2D NMR spectroscopy corroborates a similar structure in solution for both isomers. Exposure of either 2a or 2b in acetonitrile solution under UV light produces a substitution of one dmso ligand by a solvent molecule generating the same product namely, cis(out)-[Ru(II)Cl(2)(Hbpp)(MeCN)(dmso)], 4. While the 1 e(-) oxidation of 2b or cis(out),cis-[Ru(II)Cl(2)(bpp)(dmso)(2)](+), 3b, generates a stable product, the same process for 2a or trans,cis-[Ru(II)Cl(2)(bpp)(dmso)(2)](+), 3a, produces the interesting linkage isomerization phenomenon where the dmso ligand switches its bond from Ru-S to Ru-O (K(III)(O)(-->)(S) = 0.25 +/- 0.025, k(III)(O)(-->)(S) = 0.017 s(-1), and k(III)(S)(-->)(O) = 0.065 s(-1); K(II)(O)(-->)(S) = 6.45 x 10(9), k(II)(O)(-->)(S) = 0.132 s(-1), k(II)(S)(-->)(O) = 2.1 x 10(-11) s(-1)). Finally complex 3a presents a relatively high activity as hydrogen transfer catalyst, with regard to its ability to transform acetophenone into 2-phenylethyl alcohol using 2-propanol as the source of hydrogen atoms. 相似文献
554.
For quantitative application of paramagnetic shifts observed in the NMR spectra of many organic molecules upon addition of rare earth chelates, the geometry of interaction between these molecules and the “shift reagent” must be known. The authors describe and evaluate a set of computer programs useful for routine analysis of data obtained by an NMR lanthanideinduced shift technique, namely for positioning of the lanthanide ion in reference to the substrate, and for automatic interpretation of the shifted spectra. 相似文献
555.
Few-Body Systems—News Section
New books 相似文献556.
H-measures, as originally introduced by Luc Tartar and Patrick Gérard, are suited to hyperbolic problems. However, they turned out not to be well adjusted to the study of parabolic equations. A variant of H-measures is proposed, which is much better adapted to such kind of problems. We present the new parabolic scaling and the main ingredients for the proof of existence of the new variant. Some applications to the Schrödinger equation and vibrating plate equation are shown, together with an outlook to possible applications in other problems. 相似文献
557.
Ulrike M Kr?mer Nuria Rojo Rebecca Schüle Toni Cunillera Ludger Sch?ls Josep Marco-Pallarés David Cucurell Estela Camara Antoni Rodriguez-Fornells Thomas F Münte 《BMC neuroscience》2009,10(1):150-11
Background
Dopamine is believed to be a key neurotransmitter in the development of attention-deficit/hyperactivity disorder (ADHD). Several recent studies point to an association of the dopamine D4 receptor (DRD4) gene and this condition. More specifically, the 7 repeat variant of a variable number of tandem repeats (VNTR) polymorphism in exon III of this gene is suggested to bear a higher risk for ADHD. In the present study, we investigated the role of this polymorphism in the modulation of neurophysiological correlates of response inhibition (Go/Nogo task) in a healthy, high-functioning sample. 相似文献558.
559.
Antoni Guillamon Marco Sabatini 《Journal of Mathematical Analysis and Applications》2007,331(2):986-1000
In this paper we present a new method to study limit cycles' hyperbolicity. The main tool is the function ν=([V,W]∧V)/(V∧W), where V is the vector field under investigation and W a transversal one. Our approach gives a high degree of freedom for choosing operators to study the stability. It is related to the divergence test, but provides more information on the system's dynamics. We extend some previous results on hyperbolicity and apply our results to get limit cycles' uniqueness. Liénard systems and conservative + dissipative systems are considered among the applications. 相似文献
560.
Michal Araszkiewicz Antoni Koziol Anita Lupinska Michal Lupinski 《Transport in Porous Media》2007,66(1-2):173-186
Fluidization is an efficient way to dry granular materials. Incorporating microwave heating into the fluidization makes the
overall drying process shorter, and the quality of the final products can be improved. However, in order to understand the
mechanisms of water removal, an exact knowledge of changes inside the dried material is necessary. The temperature and moisture
distribution pattern within the heated material should be identified and analyzed. Unfortunately, the microwave environment
makes the measurements very difficult. This paper gives new information on the temperature distribution inside small particles
of various shapes dried with microwaves. The tests were carried out in a laboratory-scale, fluid-bed dryer equipped with a
microwave source. Five different shapes were examined: sphere, cylinder, half-cylinder, rectangular prism, and prism with
triangle base. All particles tested were suspended in an air stream and heated with microwaves. The internal temperature distribution
has been analyzed in each case. The rate of drying is also presented and discussed for every case tested. 相似文献