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1.
Bento I Martins LO Gato Lopes G Arménia Carrondo M Lindley PF 《Dalton transactions (Cambridge, England : 2003)》2005,(21):3507-3513
The multi-copper oxidases oxidise substrate molecules by accepting electrons at a mononuclear copper centre and transferring them to a trinuclear centre. Dioxygen binds to the trinuclear centre and, following the transfer of four electrons, is reduced to two molecules of water. The precise mechanism of this reduction has been unclear, but recent X-ray structural studies using the CotA endospore coat protein from Bacillus subtilis have given further insights into the principal stages. It is proposed that the mechanism involves binding of the dioxygen into the trinuclear centre so that it is sited approximately symmetrically between the two type 3 copper ions with one oxygen atom close to the type 2 copper ion. Further stages involve the formation of a peroxide intermediate and following the splitting of this intermediate, the migration of the hydroxide moieties towards the solvent exit channel. The migration steps are likely to involve a movement of the type 2 copper ion and its environment. Details of a putative mechanism are described herein based both on structures already reported in the literature and on structures of the CotA protein in the oxidised and reduced states and with the addition of peroxide and the inhibitor, azide. 相似文献
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Marcelo R. L. Oliveira José E. J. C. Graúdo Nivaldo L. Speziali Vito M. De Bellis 《Structural chemistry》1999,10(1):41-45
Potassium N-4-methylphenylsulfonyldithiocarbimate, K2(4-CH3C6H4SO2N=CS2), reacted with nickel(II) chloride hexahydrate and tetrabutylammonium bromide to form the bis(N-4-methylphenylsulfonyldithiocarbimate)nickelate(II) tetrabutylammonium salt (Bu4N)2[Ni(4-CH3C6H4S2C=NSO2)2]. The elemental analyses, IR and UV-Vis data obtained were consistent with the formation of a
diamagnetic planar complex. The 1H NMR and the 13C NMR spectra showed the expected signals for the dithiocarbimate moiety and the tetrabutylammonium cation. The single-crystal structure analysis showed that this substance crystallizes in the triclinic
space group with a = 10.474(3) Å, b = 10.767(3) Å, c = 13.657(3) Å and = 81.54(2)°, = 80.44(2)°, = 67.63(2)°, V = 1398.5(8) Å3, and Z = 2. The nickel atom is coordinated to four sulfur atoms. 相似文献
3.
A simple and sensitive method for the determination of cysteine is reported based on fluorescence quenching and recovery of L-tyrosine. At pH 10, copper(II) reacted with L-tyrosine to form a 1:1 complex that resulted in the quenching of L-tyrosine. However, the quenched fluorescence of L-tyrosine was recovered upon adding cysteine due to the strong affinity between these components. Under the optimized conditions, the recovered fluorescence was linearly proportional to the concentration of cysteine from 6.5?×?10?7 to 4?×?10?5?mol?L?1 with a detection limit of 7.32?×?10?8?mol?L?1, demonstrating high sensitivity for the determination of cysteine. The mechanisms of fluorescence quenching and recovery were characterized and the method was used to determine cysteine in a pharmaceutical product with satisfactory results. 相似文献
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Müchler L Zhang H Chadov S Yan B Casper F Kübler J Zhang SC Felser C 《Angewandte Chemie (International ed. in English)》2012,51(29):7221-7225
Heavy stuff: Topological insulators are formed of heavy atoms and host special surface or edge states. The electronic structure is characterized by a Dirac cone within a bulk band gap (see picture) that is generated by strong spin-orbit coupling. A chemist's perspective in terms of bonds, bands, symmetry, and nuclear charge is provided. 相似文献
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《Journal of Coordination Chemistry》2012,65(5):587-593
The rate constant for the basic hydrolysis of benzonitrile (PhCN) to benzamide (PhCONH2) in the [RuII(tpy)(bpy)] moiety (tpy = 2,2' : 6',2"-terpyridine, bpy = 2,2'-bipyridine) (kOH = 3.7 2 10-2 M-1s-1) is 5 2 103 times higher than that of the free ligand and two times higher than that corresponding to the analogous acetonitrile complex. This effect is unusual for a transition metal in the (II) oxidation state, and can be attributed to the π-electron acceptor properties of both the polypyridyl ligands and the phenyl group. Since amides, being poor π-acceptor ligands, are rapidly released from the coordination sphere of ruthenium(II), the final product of this process is the [Ru(tpy)(bpy)(OH)]+ complex. The activation parameters for this nitrile hydrolysis have been determined and compare reasonably well with other values for similar reactions. 相似文献
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E. A. Kataev G. V. Lavrov V. V. Roznyatovskii V. N. Khrustalev 《Journal of Structural Chemistry》2007,48(5):977-980
The interaction of a Pd(II) salt with macrocyclic ligand 1 containing thiophene-2,5-carboxamide and bipyrrole fragments is studied. It is demonstrated that only mono-palladium complex 2 is formed in the reaction of PdCl2(CH3CN)2 with ligand 1. Complex 2 was isolated as crystalline compound 2b additionally involving also triethylammonium acetate and solvent molecules. According to single crystal XRD data, the crystals of complex 2b have the composition of [C50H45N6O4PdS]?[C6H16N]+· 1/4(C5H12)·CH2Cl2, triclinic, space group \(P\bar 1\), a = 14.9608(5) Å, b = 17.5574(6) Å, c = 22.5893(8) Å, α = 75.218(5)°, β = 74.086(5)°, γ = 81.244(5)°, V = 5495.7(4) Å3, Z = 4 (two independent formula units), d calc = 1.375 g/cm3, μ = 0.526 mm?1. The central atom of palladium(II) is coordinated with amide, imine, pyrrole nitrogen atoms, and the oxygen atom of triethylammonium acetate. 相似文献
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The way to find the optimum packing of quasicrystal-constituting clusters is discussed based on the projected-cell approach. We illustrate why the quasiperiodic arrangement of partially overlapping clusters with decagonal or icosahedral symmetry is the most efficient one, by relating it to the packing of unit cells in hypercubic lattices. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(9):2347-2351
In metal‐mediated O2 activation, nickel(II) compounds hardly play a role, but recently it has been shown that enzymes can use nickel(II) for O2 activation. Now a low‐coordinate Lewis acidic nickel(II) complex has been synthesized that reacts with O2 to give a nickel(II) organoperoxide, as proposed for the enzymatic system. Its formation was studied further by UV/Vis absorption spectroscopy, leading to the observation of a short‐lived intermediate that proved to be reactive in both oxygen atom transfer and hydrogen abstraction reactions, while the peroxide efficiently transfers O atoms. Both for the enzyme and for the functional model, the key to O2 activation is proposed to represent a concomitant electron shift from the substrate/co‐ligand. 相似文献
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Yousoon Lee Forrest T. Sloane Dr. Geneviève Blondin Dr. Khalil A. Abboud Dr. Ricardo García‐Serres Prof. Dr. Leslie J. Murray 《Angewandte Chemie (International ed. in English)》2015,54(5):1499-1503
Reaction of a trinuclear iron(II) complex, Fe3Br3 L ( 1 ), with KC8 under N2 leads to dinitrogen activation products ( 2 ) from which Fe3(NH)3 L ( 2‐1 ; L is a cyclophane bridged by three β‐diketiminate arms) was characterized by X‐ray crystallography. 1H NMR spectra of the protonolysis product of 2 synthesized under 14N2 and 15N2 confirm atmospheric N2 reduction, and ammonia is detected by the indophenol assay (yield ~30 %). IR and Mössbauer spectroscopy, and elemental analysis on 2 and 2‐1 as well as the tri(amido)triiron(II) 3 and tri(methoxo)triiron 4 congeners support our assignment of the reduction product as containing protonated N‐atom bridges. 相似文献
15.
Bin DONG Ke Zhi WANG* Lin Pei JIN Li Hua GAO Department of Chemistry Beijing Normal University Beijing College of Chemistry Chemical Engineering Beijing Technology Business University Beijing 《中国化学快报》2003,14(2)
There has been explosive interest in the synthesis and applications of novel Ru(II) polypyridyl complexes with respect to molecular sensors1,2, switches3, and sensitizers of Gr鋞zel solar cells based on nanocrystalline TiO24. Here we report a novel Ru(II) complex, which can serve as pH-induced remarkable off-on-off luminescent switch. Scheme 1 The acid-base equilibria of the complex UV-vis absorption and emission spectroscopic pH titration experiments of the Ru complex wit… 相似文献
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Dr. Alexander A. Pavlov Dmitry Y. Aleshin Svetlana A. Savkina Alexander S. Belov Dr. Nikolay N. Efimov Dr. Joscha Nehrkorn Dr. Mykhaylo Ozerov Prof. Dr. Yan Z. Voloshin Prof. Dr. Yulia V. Nelyubina Prof. Dr. Valentin V. Novikov 《Chemphyschem》2019,20(8):1001-1005
Herein, we report a new trigonal prismatic cobalt(II) complex that behaves as a single molecule magnet. The obtained zero-field splitting, which is also directly accessed by THz-EPR spectroscopy (−102.5 cm−1), results in a large magnetization reversal barrier U of 205 cm−1. Its effective value, however, is much lower (101 cm−1), even though there is practically no contribution from quantum tunneling to magnetization relaxation. 相似文献
17.
During the past six decades, most discoveries in chemistry had structural aspects. Our brief overview selected some of the
most conspicuous cases that were recognized by Nobel Prizes. They include studies of the chemical bond and stereochemical
aspects, new methodologies of structure determination, and the structure of new materials. 相似文献
18.
Dmitriy S. Yambulatov Stanislav A. Nikolaevskii Mikhail A. Kiskin Kirill V. Kholin Mikhail N. Khrizanforov Yulia G. Budnikova Konstantin A. Babeshkin Nikolay N. Efimov Alexander S. Goloveshkin Vladimir K. Imshennik Yurii V. Maksimov Evgeny M. Kadilenko Nina P. Gritsan Igor L. Eremenko 《Molecules (Basel, Switzerland)》2021,26(10)
The reaction of the redox active 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-BIAN) and iron(II) iodide in acetonitrile led to a new complex [(dpp-BIAN)FeIII2] (1). Molecular structure of 1 was determined by the single crystal X-ray diffraction analysis. The spin state of the iron cation in complex 1 at room temperature and the magnetic behavior of 1 in the temperature range of 2–300 K were studied using Mossbauer spectroscopy and magnetic susceptibility measurements, respectively. The neutral character of dpp-BIAN in 1 was confirmed by IR and UV spectroscopy. The electrochemistry of 1 was studied in solution and solid state using cyclic voltammetry. The generation of the radical anion form of the dpp-BIAN ligand upon reduction of 1 in a CH2Cl2 solution was monitored by EPR spectroscopy. 相似文献
19.
We investigate the dynamical mean-field theory (DMFT) from a quantum chemical perspective. Dynamical mean-field theory offers a formalism to extend quantum chemical methods for finite systems to infinite periodic problems within a local correlation approximation. In addition, quantum chemical techniques can be used to construct new ab initio Hamiltonians and impurity solvers for DMFT. Here, we explore some ways in which these things may be achieved. First, we present an informal overview of dynamical mean-field theory to connect to quantum chemical language. Next, we describe an implementation of dynamical mean-field theory where we start from an ab initio Hartree-Fock Hamiltonian that avoids double counting issues present in many applications of DMFT. We then explore the use of the configuration interaction hierarchy in DMFT as an approximate solver for the impurity problem. We also investigate some numerical issues of convergence within DMFT. Our studies are carried out in the context of the cubic hydrogen model, a simple but challenging test for correlation methods. Finally, we finish with some conclusions for future directions. 相似文献