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1.
Simonet Torres Guillermo Ferraudi Maria Jesus Aguirre Mauricio Isaacs Betty Matsuhiro Nancy P. Chandía Leonora Mendoza 《Helvetica chimica acta》2011,94(2):293-300
In contrast to the UV‐photoinduced ligand photoionization of the flavonoid complexes of FeIII, redox reactions initiated in ligand‐to‐metal charge‐transfer excited states were observed on irradiation of the quercetin ( 1 ) and rutin ( 2 ) complexes of CuII. Solutions of complexes with stoichiometries [CuIIL2] (L=quercetin, rutin) and [CuII2Ln] (n=1, L=quercetin; n=3, L=rutin) were flash‐irradiated at 351 nm. Transient spectra observed in these experiments showed the formation of radical ligands corresponding to the one‐electron oxidation of L and the reduction of CuII to CuI. The radical ligands remained coordinated to the CuI centers, and the substitution reactions replacing them by solvent occurred with lifetimes τ<350 ns. These are lifetimes shorter than the known lifetimes (τ>1 ms) of the quercetin and rutin radical's decay. 相似文献
2.
The title compound, {[Cu(NH3)4][Cu(CN)3]2}n, features a CuI–CuII mixed‐valence CuCN framework based on {[Cu2(CN)3]−}n anionic layers and [Cu(NH3)4]2+ cations. The asymmetric unit contains two different CuI ions and one CuII ion which lies on a centre of inversion. Each CuI ion is coordinated to three cyanide ligands with a distorted trigonal–planar geometry, while the CuII ion is ligated by four ammine ligands, with a distorted square‐planar coordination geometry. The interlinkage between CuI ions and cyanide bridges produces a honeycomb‐like {[Cu2(CN)3]−}n anionic layer containing 18‐membered planar [Cu(CN)]6 metallocycles. A [Cu(NH3)4]2+ cation fills each metallocyclic cavity within pairs of exactly superimposed {[Cu2(CN)3]−}n anionic layers, but there are no cations between the layers of adjacent pairs, which are offset. Pairs of N—H...N hydrogen‐bonding interactions link the N—H groups of the ammine ligands to the N atoms of cyanide ligands. 相似文献
3.
JosA. Campo Mercedes Cano JosV. Heras M.Cristina Lagunas Josefina Perles Elena Pinilla M.Rosario Torres 《Helvetica chimica acta》2002,85(4):1079-1095
We report the synthesis, characterization, and crystal structures of new ligands of the pyridinylpyrazole type, i.e., 3,5‐bis(4‐butoxyphenyl)‐1‐(pyridin‐2‐yl)‐1H‐pyrazole ( L 1 ) and 3,5‐bis(4‐phenoxyphenyl)‐1‐(pyridin‐2‐yl)‐1H‐pyrazole ( L 2 ) (Scheme 1), and the study of their coordination behavior towards CuI and CuII. The versatility of this type of ligand, which can give access to different coordination spheres about the metal center, depending on the nature of the copper starting material used in the preparation of the complexes (Scheme 2), is illustrated. Thus, pseudo‐tetrahedral CuI as well as six‐coordinated tetragonal and distorted tetragonal pyramidal CuII derivatives were obtained for [Cu(L)2]PF6, [Cu(Cl)2(L)2] (L= L 1 , L 2 ), and [Cu(Cl)( L 1 )2]PF6, respectively. We also present a crystallographic support of a distorted octahedral cis‐bis(tetrafluoroborato‐κF)copper(II) compound found for [Cu(BF4)2( L 1 )2] ( 3 ). 相似文献
4.
Combined EXAFS and DFT Structure Calculations Provide Structural Insights into the 1:1 Multi‐Histidine Complexes of CuII,CuI, and ZnII with the Tandem Octarepeats of the Mammalian Prion Protein
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Dr. M. Jake Pushie Kurt H. Nienaber Dr. Alex McDonald Prof. Dr. Glenn L. Millhauser Prof. Dr. Graham N. George 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(31):9770-9783
The metal‐coordinating properties of the prion protein (PrP) have been the subject of intense focus and debate since the first reports of its interaction with copper just before the turn of the century. The picture of metal coordination to PrP has been improved and refined over the past decade, but structural details of the various metal coordination modes have not been fully elucidated in some cases. In the present study, we have employed X‐ray absorption near‐edge spectroscopy as well as extended X‐ray absorption fine structure (EXAFS) spectroscopy to structurally characterize the dominant 1:1 coordination modes for CuII, CuI, and ZnII with an N‐terminal fragment of PrP. The PrP fragment corresponds to four tandem repeats representative of the mammalian octarepeat domain, designated as OR4, which is also the most studied PrP fragment for metal interactions, making our findings applicable to a large body of previous work. Density functional theory (DFT) calculations have provided additional structural and thermodynamic data, and candidate structures have been used to inform EXAFS data analysis. The optimized geometries from DFT calculations have been used to identify potential coordination complexes for multi‐histidine coordination of CuII, CuI, and ZnII in an aqueous medium, modelled using 4‐methylimidazole to represent the histidine side chain. Through a combination of in silico coordination chemistry as well as rigorous EXAFS curve‐fitting, using full multiple scattering on candidate structures derived from DFT calculations, we have characterized the predominant coordination modes for the 1:1 complexes of CuII, CuI, and ZnII with the OR4 peptide at pH 7.4 at atomic resolution, which are best represented as square‐planar [CuII(His)4]2+, digonal [CuI(His)2]+, and tetrahedral [ZnII(His)3(OH2)]2+, respectively. 相似文献
5.
Ming‐Lin Guo Feng‐Qin Wang 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(12):m379-m383
The coordination mode of the dimethylmalonate ligand in the two title CuII complexes, {[Cu(C5H3O4)(H2O)]·H2O}n, (I), and [Cu(C5H3O4)(H2O)]n, (II), is the same, with chelated six‐membered, bis‐monodentate and bridging bonding modes. However, the coordination environment of the CuII atoms, the connectivity of their metal–organic frameworks and their hydrogen‐bonding interactions are different. Complex (I) has a perfect square‐pyramidal CuII environment with the aqua ligand in the apical position, and only one type of square grid consisting of CuII atoms linked via carboxylate bridges to three dimethylmalonate ligands, with weak hydrogen‐bond interactions within and between its two‐dimensional layers. Complex (II) has a coordination geometry that is closer to square pyramidal than trigonal bipyramidal for its CuII atoms with the aqua ligand now in the basal plane. Its two‐dimensional layer structure comprises two alternating grids, which involve two and four different dimethylmalonate anions, respectively. There are strong hydrogen bonds only within its layers. 相似文献
6.
Ryo Sekiya Kazumasa Hosoya Shin‐ichi Nishikiori 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(5):i32-i34
The title compound, poly[diamminehexa‐μ‐cyano‐dicopper(I)copper(II)mercury(II)], [Cu3Hg(CN)6(NH3)2]n, has a novel threefold‐interpenetrating structure of three‐dimensional frameworks. This three‐dimensional framework consists of two‐dimensional network Cu3(CN)4(NH3)2 complexes and rod‐like Hg(CN)2 complexes. The two‐dimensional network complex contains trigonal–planar CuI (site symmetry m) and octahedral CuII (site symmetry 2/m) in a 2:1 ratio. Two types of cyanide group form bridges between three coordination sites of CuI and two equatorial sites of CuII to form a two‐dimensional structure with large hexagonal windows. One type of CN− group is disordered across a center of inversion, while the other resides on the mirror plane. Two NH3 molecules (site symmetry 2) are located in the hexagonal windows and coordinate to the remaining equatorial sites of CuII. Both N atoms of the rod‐like Hg(CN)2 group (Hg site symmetry 2/m and CN− site symmetry m) coordinate to the axial sites of CuII. This linkage completes the three‐dimensional framework and penetrates two hexagonal windows of two two‐dimensional network complexes to form the threefold‐interpenetrating structure. 相似文献
7.
Synthesis,Spectral, Thermal Studies of Co(II), Ni(II), Cu(II) and Zn(II)‐arginato Complexes. Crystal Structure of Monoaquabis(arginato‐κO,κN)copper(II). [Cu(arg)2(H2O)].NaNO3
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Dursun Ali Köse Emre Toprak Emre Avcı Gülçin Alp Avcı Onur Şahin Orhan Büyükgüngör 《中国化学会会志》2014,61(8):881-890
Transition metal complexes of arginine (using Co(II), Ni(II), Cu(II) and Zn(II) cations separately) were synthesized and characterized by FTIR, TG/DTA‐DrTG, UV‐Vis spectroscopy and elemental analysis methods. Cu(II)‐Arg complex crystals was found suitable for x‐ray diffraction studies. It was contained, one mole CuII and Na+ ions, two arginate ligands, one coordinated aqua ligand and one solvent NO3? group in the asymmetric unit. The principle coordination sites of metal atom have been occupied by two N atoms of arginate ligands, two carboxylate O atoms, while the apical site was occupied by one O atom for CuII cation and two O atoms for CoII, NiII, ZnII atoms of aqua ligands. Although CuII ion adopts a square pyramidal geometry of the structure. CoII, NiII, ZnII cations have octahedral due to coordination number of these metals. Neighbouring chains were linked together to form a three‐dimensional network via hydrogen‐bonding between coordinated water molecule, amino atoms and O atoms of the bridging carboxylate groups. CuII complex was crystallized in the monoclinic space group P21, a = 8.4407(5) Å, b = 12.0976(5) Å, c = 10.2448(6) Å, V = 1041.03(10) Å3, Z = 2. Structures of the other metal complexes were similar to CuII complex, because of their spectroscopic studies have in agreement with each other. Copper complex has shown DNA like helix chain structure. Lastly, anti‐bacterial, anti‐microbial and anti‐fungal biological activities of complexes were investigated. 相似文献
8.
Samia Benmansour Fatima Setifi Smaïl Triki Franck Thétiot Jean Sala-Pala Carlos J. Gómez-García Enrique Colacio 《Polyhedron》2009
Reactions of CuCl2 with different CN complexes in presence of a neutral ancillary ligand lead to two novel mixed-valence Cu complexes [CuII(bpy)CuI(CN)3]n, 1 (bpy = 2,2′-bipyridine) and {[CuII(tn)2][CuI4(CN)6]}n2 (tn = 1,3-diaminopropane). For compound 1, the asymmetric unit involves two Cu ions Cu1 and Cu2 (CuI and CuII centres, respectively) which strongly differ in their environments. The Cu1 ion presents a CuC4 pseudo-tetrahedral geometry, while the Cu2 ion presents a CuN5 slightly distorted square-pyramidal geometry. The extended structure of 1 is generated by three cyano ligands which differ in their coordination modes. One CN group has a μ3 coordination mode and bridges two CuI and one CuII ion, while the two other CN groups act as μ2 bridges leading to a sophisticated 3-D structure. As for 1, the asymmetric unit of 2 involves three crystallographically different Cu ions (Cu1A and Cu1B, presumably CuI centres, and Cu2 presumably CuII centres). The Cu2 ion presents centrosymmetric CuN4 coordination environments involving four nitrogen atoms from two bidentate tn ligands; while the Cu1A and Cu1B ions are three coordinated to cyano groups. The structure can be described as formed by 18-membered “[CuI(CN)]6” planar metallocycles that are connected to their six neighbors to generate 2-D sheets; these sheets stack forming infinite hexagonal channels in which the [Cu(tn)2]2+ units are located. Magnetic measurements show an unexpected weak ferromagnetic coupling (θ = 0.239(1) K) of the CuII ions through the long and “a priori diamagnetic” –NC–CuI–CN– bridges in compound 1 and an essentially paramagnetic behavior in compound 2. 相似文献
9.
Yang Liu Stefan G. Resch Iris Klawitter George E. Cutsail Serhiy Demeshko Sebastian Dechert Fritz E. Kühn Serena DeBeer Franc Meyer 《Angewandte Chemie (International ed. in English)》2020,59(14):5696-5705
A neutral hybrid macrocycle with two trans‐positioned N‐heterocyclic carbenes (NHCs) and two pyridine donors hosts copper in three oxidation states (+I–+III) in a series of structurally characterized complexes ( 1 – 3 ). Redox interconversion of [LCu]+/2+/3+ is electrochemically (quasi)reversible and occurs at moderate potentials (E1/2=?0.45 V and +0.82 V (vs. Fc/Fc+)). A linear CNHC‐Cu‐CNHC arrangement and hemilability of the two pyridine donors allows the ligand to adapt to the different stereoelectronic and coordination requirements of CuI versus CuII/CuIII. Analytical methods such as NMR, UV/Vis, IR, electron paramagnetic resonance, and Cu Kβ high‐energy‐resolution fluorescence detection X‐ray absorption spectroscopies, as well as DFT calculations, give insight into the geometric and electronic structures of the complexes. The XAS signatures of 1 – 3 are textbook examples for CuI, CuII, and CuIII species. Facile 2‐electron interconversion combined with the exposure of two basic pyridine N sites in the reduced CuI form suggest that [LCu]+/2+/3+ may operate in catalysis via coupled 2 e?/2 H+ transfer. 相似文献
10.
Li-Yang Zhang Li-Ping Lu Si-Si Feng 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(8):652-657
Coordination polymers are a thriving class of functional solid‐state materials and there have been noticeable efforts and progress toward designing periodic functional structures with desired geometrical attributes and chemical properties for targeted applications. Self‐assembly of metal ions and organic ligands is one of the most efficient and widely utilized methods for the construction of CPs under hydro(solvo)thermal conditions. 2‐(Pyridin‐3‐yl)‐1H‐imidazole‐4,5‐dicarboxylate (HPIDC2−) has been proven to be an excellent multidentate ligand due to its multiple deprotonation and coordination modes. Crystals of poly[aquabis[μ3‐5‐carboxy‐2‐(pyridin‐3‐yl)‐1H‐imidazole‐4‐carboxylato‐κ5N1,O5:N3,O4:N2]copper(II)dicopper(I)], [CuIICuI2(C10H5N3O4)2(H2O)]n, (I), were obtained from 2‐(pyridin‐3‐yl)‐1H‐imidazole‐4,5‐dicarboxylic acid (H3PIDC) and copper(II) chloride under hydrothermal conditions. The asymmetric unit consists of one independent CuII ion, two CuI ions, two HPIDC2− ligands and one coordinated water molecule. The CuII centre displays a square‐pyramidal geometry (CuN2O3), with two N,O‐chelating HPIDC2− ligands occupying the basal plane in a trans geometry and one O atom from a coordinated water molecule in the axial position. The CuI atoms adopt three‐coordinated Y‐shaped coordinations. In each [CuN2O] unit, deprotonated HPIDC2− acts as an N,O‐chelating ligand, and a symmetry‐equivalent HPIDC2− ligand acts as an N‐atom donor via the pyridine group. The HPIDC2− ligands in the polymer serve as T‐shaped 3‐connectors and adopt a μ3‐κ2N,O:κ2N′,O′:κN′′‐coordination mode, linking one CuII and two CuI cations. The Cu cations are arranged in one‐dimensional –Cu1–Cu2–Cu3– chains along the [001] direction. Further crosslinking of these chains by HPIDC2− ligands along the b axis in a –Cu2–HPIDC2−–Cu3–HPIDC2−–Cu1– sequence results in a two‐dimensional polymer in the (100) plane. The resulting (2,3)‐connected net has a (123)2(12)3 topology. Powder X‐ray diffraction confirmed the phase purity for (I), and susceptibilty measurements indicated a very weak ferromagnetic behaviour. A thermogravimetric analysis shows the loss of the apical aqua ligand before decomposition of the title compound. 相似文献
11.
Zakieh Yousefi Hossein Eshtiagh‐Hosseini Alireza Salimi Janet Soleimannejad 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(5):386-393
In the title compound, [Cu(C7H3N2O4)(C4H5N2)(H2O)], (I), pyridine‐2,6‐dicarboxylate (pydc2−), 2‐aminopyrimidine and aqua ligands coordinate the CuII centre through two N atoms, two carboxylate O atoms and one water O atom, respectively, to give a nominally distorted square‐pyramidal coordination geometry, a common arrangement for copper complexes containing the pydc2− ligand. Because of the presence of Cu...Xbridged contacts (X = N or O) between adjacent molecules in the crystal structures of (I) and three analogous previously reported compounds, and the corresponding uncertainty about the effective coordination number of the CuII centre, density functional theory (DFT) calculations were used to elucidate the degree of covalency in these contacts. The calculated Wiberg and Mayer bond‐order indices reveal that the Cu...O contact can be considered as a coordination bond, whereas the amine group forming a Cu...N contact is not an effective participant in the coordination environment. 相似文献
12.
Dr. Charlène Esmieu Guillaume Ferrand Dr. Valentina Borghesani Dr. Christelle Hureau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(5):1777-1786
In vitro Cu(Aβ1–x)-induced ROS production has been extensively studied. Conversely, the ability of N-truncated isoforms of Aβ to alter the Cu-induced ROS production has been overlooked, even though they are main constituents of amyloid plaques found in the human brain. N-Truncated peptides at the positions 4 and 11 (Aβ4–x and Aβ11–x) contain an amino-terminal copper and nickel (ATCUN) binding motif (H2N-Xxx-Zzz-His) that confer them different coordination sites and higher affinities for CuII compared to the Aβ1–x peptide. It has further been proposed that the role of Aβ4–x peptide is to quench CuII toxicity in the brain. However, the role of CuI coordination has not been investigated to date. In contrast to CuII, CuI coordination is expected to be the same for N-truncated and N-intact peptides. Herein, we report in-depth characterizations and ROS production studies of Cu (CuI and CuII) complexes of the Aβ4–16 and Aβ11–16 N-truncated peptides. Our findings show that the N-truncated peptides do produce ROS when CuI is present in the medium, albeit to a lesser extent than the unmodified counterpart. In addition, when used as competitor ligands (i.e., in the presence of Aβ1–16), the N-truncated peptides are not able to fully preclude Cu(Aβ1–16)-induced ROS production. 相似文献
13.
Ranjan Patra Israel Goldberg 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(4):344-347
5‐[(Imidazol‐1‐yl)methyl]benzene‐1,3‐dicarboxylic acid (H2L) was synthesized and the dimethylformamide‐ and dimethylacetamide‐solvated structures of its adducts with CuII, namely catena‐poly[[copper(II)‐bis[μ‐3‐carboxy‐5‐[(imidazol‐1‐yl)methyl]benzoato]] dimethylformamide disolvate], {[Cu(C12H9N2O4)2]·2C3H7NO}n, (I), and catena‐poly[[copper(II)‐bis[μ‐3‐carboxy‐5‐[(imidazol‐1‐yl)methyl]benzoato]] dimethylacetamide disolvate], {[Cu(C12H9N2O4)2]·2C4H9NO}n, (II), the formation of which are associated with mono‐deprotonation of H2L. The two structures are isomorphous and isometric. They consist of one‐dimensional coordination polymers of the organic ligand with CuII in a 2:1 ratio, [Cu(μ‐HL)2]n, crystallizing as the dimethylformamide (DMF) or dimethylacetamide (DMA) disolvates. The CuII cations are characterized by a coordination number of six, being located on centres of crystallographic inversion. In the polymeric chains, each CuII cation is linked to four neighbouring HL− ligands, and the organic ligand is coordinated via Cu—O and Cu—N bonds to two CuII cations. In the corresponding crystal structures of (I) and (II), the coordination chains, aligned parallel to the c axis, are further interlinked by strong hydrogen bonds between the noncoordinated carboxy groups in one array and the coordinated carboxylate groups of neighbouring chains. Molecules of DMF and DMA (disordered) are accommodated at the interface between adjacent polymeric assemblies. This report provides the first structural evidence for the formation of coordination polymers with H2Lvia multiple metal–ligand bonds through both carboxylate and imidazole groups. 相似文献
14.
Xia Chen Hong‐Feng Chen Gang Xue Hong‐Yu Chen Wen‐Tao Yu Qi Fang 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(4):m166-m168
The title complexes, [M(C5O5)(C12H8N2)2], with M = CoII, NiII and CuII, all lie across twofold rotation axes, around which two 1,10‐phenanthroline ligands are arranged in a chiral propeller manner. The CoII and NiII complexes are isostructural, with octahedral coordination geometry, while the local geometry of the CuII complex is severely distorted from octahedral. 相似文献
15.
Enhancement of TbIII–CuII Single‐Molecule Magnet Performance through Structural Modification
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María José Heras Ojea Dr. Victoria A. Milway Dr. Gunasekaran Velmurugan Dr. Lynne H. Thomas Dr. Simon J. Coles Dr. Claire Wilson Dr. Wolfgang Wernsdorfer Prof. Gopalan Rajaraman Dr. Mark Murrie 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(36):12839-12848
We report a series of 3d–4f complexes {Ln2Cu3(H3L)2Xn} (X=OAc?, Ln=Gd, Tb or X=NO3?, Ln=Gd, Tb, Dy, Ho, Er) using the 2,2′‐(propane‐1,3‐diyldiimino)bis[2‐(hydroxylmethyl)propane‐1,3‐diol] (H6L) pro‐ligand. All complexes, except that in which Ln=Gd, show slow magnetic relaxation in zero applied dc field. A remarkable improvement of the energy barrier to reorientation of the magnetisation in the {Tb2Cu3(H3L)2Xn} complexes is seen by changing the auxiliary ligands (X=OAc? for NO3?). This leads to the largest reported relaxation barrier in zero applied dc field for a Tb/Cu‐based single‐molecule magnet. Ab initio CASSCF calculations performed on mononuclear TbIII models are employed to understand the increase in energy barrier and the calculations suggest that the difference stems from a change in the TbIII coordination environment (C4v versus Cs). 相似文献
16.
T. V. Magdesieva A. V. Dolganov P. M. Polestchuk A. V. Yakimanskii M. Ya. Goikhman I. V. Podeshvo V. V. Kudryavtsev 《Russian Chemical Bulletin》2007,56(7):1380-1389
Structural reorganization of polyamide (PA) and low-molecular-weight CuI and CuII complexes with biquinolyl (biQ) ligands during their mutual redox transformations in solution was studied using the electrochemical
methods (cyclic voltammetry and preparative electrolysis) and quantum chemical DFT calculations. The influence of electronic
factors and geometry distortions in the complexes on the ionization energy on going from CuI to CuII was evaluated in comparison. The catalytically active form of the [CuI(PA)L2]BF4 complex can be synthesized in situ from the stable tetrahedral complex [CuI(PA)2]BF4 by the series of successive redox transitions CuI → CuII → CuI accompanied by the loss of one biQ-containing macroligand.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1331–1340, July, 2007. 相似文献
17.
Chun‐Sen Liu Ze Chang Jun‐Jie Wang 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(12):m589-m591
In the title coordination polymer, [Cu(C11H7O2)(OH)(H2O)]n, the CuII center is five‐coordinated by two O atoms from two different naphthalene‐1‐carboxylate (L) ligands, one O atom from one coordinated water molecule and two O atoms from two hydroxide anions. L ligands and hydroxide anions jointly bridge adjacent CuII centers to generate a one‐dimensional chain along the b‐axis direction. The results reveal that the steric bulk of the naphthalene ring system in L may play an important role in the formation of the title complex. 相似文献
18.
Christopher Paolucci Anuj A. Verma Shane A. Bates Vincent F. Kispersky Jeffrey T. Miller Rajamani Gounder W. Nicholas Delgass Fabio H. Ribeiro William F. Schneider 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(44):12022-12027
Operando X‐ray absorption experiments and density functional theory (DFT) calculations are reported that elucidate the role of copper redox chemistry in the selective catalytic reduction (SCR) of NO over Cu‐exchanged SSZ‐13. Catalysts prepared to contain only isolated, exchanged CuII ions evidence both CuII and CuI ions under standard SCR conditions at 473 K. Reactant cutoff experiments show that NO and NH3 together are necessary for CuII reduction to CuI. DFT calculations show that NO‐assisted NH3 dissociation is both energetically favorable and accounts for the observed CuII reduction. The calculations predict in situ generation of Brønsted sites proximal to CuI upon reduction, which we quantify in separate titration experiments. Both NO and O2 are necessary for oxidation of CuI to CuII, which DFT suggests to occur by a NO2 intermediate. Reaction of Cu‐bound NO2 with proximal NH4+ completes the catalytic cycle. N2 is produced in both reduction and oxidation half‐cycles. 相似文献
19.
Copper(II) and Sodium(I) Complexes based on 3,7‐Diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane‐5‐oxide: Synthesis,Characterization, and Catalytic Activity
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《化学:亚洲杂志》2018,13(19):2868-2880
The reaction of 3,7‐diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane (DAPTA) with metal salts of CuII or NaI/NiII under mild conditions led to the oxidized phosphane derivative 3,7‐diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane‐5‐oxide (DAPTA=O) and to the first examples of metal complexes based on the DAPTA=O ligand, that is, [CuII(μ‐CH3COO)2(κO‐DAPTA=O)]2 ( 1 ) and [Na(1κOO′;2κO‐DAPTA=O)(MeOH)]2(BPh4)2 ( 2 ). The catalytic activity of 1 was tested in the Henry reaction and for the aerobic 2,2,6,6‐tetramethylpiperidin‐1‐oxyl (TEMPO)‐mediated oxidation of benzyl alcohol. Compound 1 was also evaluated as a model system for the catechol oxidase enzyme by using 3,5‐di‐tert‐butylcatechol as the substrate. The kinetic data fitted the Michaelis–Menten equation and enabled the obtainment of a rate constant for the catalytic reaction; this rate constant is among the highest obtained for this substrate with the use of dinuclear CuII complexes. DFT calculations discarded a bridging mode binding type of the substrate and suggested a mixed‐valence CuII/CuI complex intermediate, in which the spin electron density is mostly concentrated at one of the Cu atoms and at the organic ligand. 相似文献
20.
Angelica M. Vecchio-Sadus 《Transition Metal Chemistry》1995,20(1):46-55
Summary The single-step electrochemical synthesis of neutral transition metal complexes of imidazole, pyrazole and their derivatives has been achieved at ambient temperature. The metal was oxidized in an Me2CO solution of the diazole to yield complexes of the general formula: [M(Iz)2] (where M = Co, Ni, Cu, Zn; Iz = imidazolate); [M(MeIz)2] (where M = Co, Ni, Cu, Zn; MeIz = 4-methylimidazolate); [M(PriIz)2] (where M = Co, Ni, Cu, Zn; PriIz = 2-isopropylimidazolate); [M(pyIz)n] (where M = CoIII, CuII, ZnII; pyIz = 2-(2-pyridyl)imidazolate); [M(Pz)n] (where M = CoIII, NiII, CuII, ZnII; Pz = pyrazolate); [M(ClPz)n] and [M(IPz)n] (where M = CoIII, NiII, CuII, ZnII; ClPz = 4-chloropyrazolate; IPz = 4-iodopyrazolate); [M(Me2Pz)n] (where M = CoII, CuI, ZnII; Me2Pz = 3,5-dimethylpyrazolate) and [M(BrMe2Pz)n] (where M = CoII, NiII, CuI, ZnII; BrMe2Pz = 3,5-dimethyl-4-bromopyrazolate). Vibrational spectra verified the presence of the anionic diazole and electronic spectra confirmed the stereochemistry about the metal centre. Variable temperature (360-90 K) magnetic measurements of the cobalt and copper chelates revealed strong antiferromagnetic interaction between the metal ions in the lattice. Data for the copper complexes were fitted to a Heisenberg (S=
) model for an infinite one-dimensional linear chain, yielding best fit values of J=–62––65cm–1 andg = 2.02–2.18. Data for the cobalt complexes were fitted to an Ising (S=
) model with J=–4.62––11.7cm–1 andg = 2.06–2.49. 相似文献