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PubMed2003

Century-known copper salt Cu(OAc)(OMe) proven to be a unique magnetic lattice composed of tetranuclear copper(II) species with a rare binding mode of the acetate anion.

The structure, spectroscopy, and magnetism of a century-old copper salt, Cu(OAc)(OMe), is reported. The crystal structure contains two independent Cu(II) ions, which are both five-coordinated and which are bridged by methoxo and acetate anions to form an infinite 2D network. Thereby the methoxo groups connect Cu1 and Cu2 with their symmetry-generated counterparts Cu1(i) and Cu2(i), respectively, resulting in Cu.Cu distances of 2.9803(10) and 2.9874(10) A. Cu1 and Cu2 themselves are bridged via the carboxylate groups of two acetates leading to a Cu1.Cu2 distance of 2.9473(7) A. The tetranuclear units thus generated are cross-linked via acetate oxygens to form a 2D sheet structure. One of the two independent acetate ligands has a rare binding mode, whereby it acts as a tetradentate syn-anti, syn-anti bridging ligand. The temperature dependence of the magnetic susceptibility was assigned to be dominated by the very strong antiferromagnetic exchange coupling via bis(mu-methoxo) bridges (J(1) = -409(1) cm(-)(1)).

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PubMed2005

Reaction of copper(II) with ferrocene and 1,1'-dimethylferrocene in aqueous acetonitrile: the copper(II/I) self-exchange rate.

The kinetics of the reactions of copper(II) with ferrocene (Fc) and 1,1'-dimethylferrocene (Dmfc) have been studied at 25 degrees C in aqueous acetonitrile (AN) containing 50-97.5 vol % AN. With increasing % AN, the rate constant increases along with the driving-force for the reaction. The results are analyzed in terms of Marcus theory to estimate the Cu(II/I) electron self-exchange rate constant (k11) for the system. Over the solvent range studied, the calculated k11)changes from 1.1 x 10(-9) to 17 x 10(-9) M(-1) s(-1), with an average value of 5 x 10(-9). In addition, the structures of the trifluoromethanesulfonate salts of [Cu(AN)4]+, [Cu(OH2)2(AN)2]2+, and [Cu(AN)4]2+ are reported. It is found that the Cu-NCCH3 bond-length difference between the Cu(I) and Cu(II) oxidation states is only approximately 0.02 A.

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PubMed1996

Spectroelectrochemical Studies of Copper(I) Complexes with Binaphthyridine and Biquinoline Ligands. Crystal Structure Determination of Bis(6,7-dihydrodipyrido[2,3-b:3',2'-j][1,10]phenanthroline)copper(I) Tetrafluoroborate.

The electrochemical and spectral properties of some copper(I) polypyridyl complexes based on 6,7-dihydrodibenzo[b,j][1,10]phenanthroline, dmbiq, and 6,7-dihydrodipyrido[2,3-b:3',2'-j][1,10]phenanthroline, dmbinap, are reported. These complexes are [Cu(dmbiq)(2)](+), 1; [Cu(dmbiq)(PPh(3))(2)](+), 2; [Cu(dmbinap)(2)](+), 3; and [Cu(dmbinap)(PPh(3))(2)](+), 4. 3 and 4 may be reduced to form ligand-based radical anion species. The resonance Raman spectra of 3(*)()(-)() and 4(*)()(-)() are almost identical and correspond closely to the spectrum of dmbinap(*)()(-)() and the reported spectra of complexes containing 2,2'-biquinoline radical anion moieties. Reduction processes for 1 and 2 are irreversible. For 1 the electronic spectral changes arising from reduction suggest demetallation of the complex. The structure of [Cu(C(18)H(12)N(4))(2)][BF(4)].CH(2)Cl(2) (3[BF(4)].CH(2)Cl(2)) was determined by single-crystal X-ray diffraction. It crystallized in the monoclinic space group P2(1)/c with cell dimensions a = 14.059(7) Å, b = 15.058(6) Å, c = 16.834(9) Å, beta = 111.56(5) degrees, Z = 4, rho(calcd) = 1.611 g/cm(3), and R(F(o)) = 0.0497.

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PubMed1996

Perturbation of the Electronic Structure of a Copper(II) ion by a Cu(I)Cl Moiety in a Class I Mixed Valence Copper Complex, Cu(II)(Me(5)dien)Cl(2)(Cu(I)Cl).

A new mixed valence copper complex Cu(II)(Me(5)dien)Cl(2)(Cu(I)Cl) (2) was obtained from the reaction of CuCl with Cu(II)(Me(5)dien)Cl(2) (1) in acetonitrile. The structures of 1 and 2 have been determined by single-crystal X-ray diffraction analyses. Compound 1 crystallizes in the monoclinic space group P2(1)/n with a = 8.374(5) Å, b = 17.155(3) Å, c = 23.806(5) Å, beta = 94.40(4) degrees, Z = 8, and V = 3398(1) Å(3) while compound 2 crystallizes in orthorhombic space group Pbcn with a = 14.71(1) Å, b = 16.06(2) Å, c = 13.38(1) Å, Z = 8, and V = 3159(5) Å. The Cu(II)(Me(5)dien)Cl(2) unit in both compounds has a similar distorted square-pyramidal geometry. The Cu(I)Cl moiety in 2 is attached to the Cu(II) unit via two bridging chlorine atoms and has a distorted trigonal planar geometry. UV-vis and EPR spectroscopic studies and molecular orbital calculations established the presence of significant perturbation of the Cu(I)Cl unit to the electronic structure of the Cu(II) ion in compound 2.

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PubMed1997

Copper Sites in Copper-Exchanged ZSM-5 for CO Activation and Methanol Synthesis: XPS and FTIR Studies.

Cu-ZSM-5 samples with various Cu(+)/Cu(2+) ratios have been successfully prepared in three different methods and studied by XPS and FTIR. Cu(+) ions are found, by XPS, to mainly exist in the samples prepared by solution ion exchange and microwave solid-state reaction exchange. On the basis of the chemical shift of the Al 2p core level to a higher binding energy [Al(species II)], with the atomic ratio of Cu(+)/Al(species II) being approximately one, and the vanishing of the IR band at 3640 cm(-)(1) due to copper exchange, it is suggested that Cu(+) ions locate in the open channels of the ZSM-5 framework and bind to mixed (Si- and Al-) bridged oxide ion. From the ZSM-5 pore structure consideration, as well as from the observed decrease in the IR intensity ratio of bands 550/450 cm(-)(1) with enhanced Cu(2+) loading, it is also suggested that Cu(2+) ions are a predominant Cu species in solid-state reaction exchanged Cu-ZSM-5 samples and exist as a CuO cluster in small cages as well as in open channels. The IR bands at 907 and 964 cm(-)(1) are identified as zeolite asymmetric internal vibration perturbed by exchanged Cu(2+) and Cu(+) ions, respectively. Cu ions in Cu-ZSM-5 samples can be reduced to Cu(0) by CO adsorption at room temperature. The IR bands at 2128, 2158, and 2176 cm(-)(1) are observable and ascribed to the CO adsorbed on Cu(0), Cu(+), and Cu(2+) sites, respectively. Methanol formation from syngas over Cu-ZSM-5 is observed at 250 degrees C and 2 MPa.

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PubMed2004

Discrete bridging and terminal copper carbenes in copper-catalyzed cyclopropanation.

The Cu(I) beta-diketiminate [Me2NN]Cu(eta2-ethylene) (2) catalyzes the cyclopropanation of styrene with N2CPh2 to give 1,1,2-triphenylcyclopropane in 67% yield. Addition of N2CPh2 to 2 equiv of 2 allows for the isolation of the dicopper carbene [[Me2NN]Cu]2(mu-CPh2) (3) in which the diphenylcarbene moiety is symmetrically bound between two [Me2NN]Cu fragments (Cu-C = 1.922(4) and 1.930(4) A) with a Cu-Cu separation of 2.4635(7) A. In toluene-d8 solution, 3 reversibly dissociates a [Me2NN]Cu fragment to give [Me2NN]Cu(toluene) and the terminal carbene [Me2NN]Cu=CPh2. Dicopper carbene 3 reacts with 3 equiv of styrene to give 1,1,2-triphenylcyclopropane and 2 equiv of [Me2NN]Cu(eta2-styrene) within minutes. DFT studies with simplified ligands indicate a stronger Cu-C pi-back-bonding interaction from two Cu(I) centers to the carbene acceptor orbital in a dicopper carbene than that present in a monocopper carbene. Nonetheless, the terminal carbene [Me3NN]Cu=CPh2 (8) that possesses a p-methyl group on each beta-diketiminato N-aryl ring may be isolated and exhibits a shortened Cu-C distance of 1.834(3) A. The stoichiometric cyclopropanation of styrene by 8 in 1,4-dioxane is first-order in both copper carbene 8 and styrene with activation parameters DeltaH = 10.4(3) kcal/mol and DeltaS = -32.3(9) cal/mol.K. In 1,4-dioxane, 8 decomposes to Ph2C=CPh2 via first-order kinetics with activation parameters DeltaH = 21(1) kcal/mol and DeltaS = -8(3) cal/mol.K. Arene solutions of thermally sensitive terminal carbene 8 decompose to [Me3NN]Cu(arene), which reacts with 8 still present in solution to give the more thermally stable [[Me3NN]Cu]2(mu-CPh2).

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PubMed2002

Copper(I) tert-butoxide-promoted 1,4 C sp 2-to-O silyl migration: generation of vinyl copper equivalents and their stereospecific cross-coupling with allylic, aryl, and vinylic halides.

Successive treatment of the (Z)-gamma-trimethylsilyl allylic alcohols with copper(I) tert-butoxide and allylic halides followed by the tetrabutylammonium fluoride-assisted hydrolysis produced the allylation products, 2,5-alkadien-1-ols, with complete retention of configuration. Similar treatment of the organometallic intermediates with aryl and vinylic halides in the presence of palladium(0) catalyst gave the corresponding cross-coupling products in good yields. The stereoselective preparation of the starting materials is also described.

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PubMed2005

Copper hydroxide nanoneedle and nanotube arrays fabricated by anodization of copper.

Cu(OH)2 nanoneedle and nanotube arrays were electrochemically synthesized by anodization of a copper foil in an aqueous solution of KOH. The nanoneedles and nanotubes were constructed from nanosheets of Cu(OH)2. Controlling the electrochemical conditions can qualitatively modulate the lengths, amounts, and shapes of Cu(OH)2 nanostructures. The composition of as-prepared Cu(OH)2 nanostructures has been confirmed by X-ray diffraction and select-area electron diffraction. The influences of the KOH concentration of the aqueous electrolyte, the reaction temperature, and current density on the morphology of Cu(OH)2 nanostructures were investigated, and the formation mechanism of the nanostructures is discussed. Furthermore, Cu(OH)2 nanoneedles can be successfully transformed to CuO nanoneedles with little morphology change by heating. This work developed a simple, clean, and effective route for fabrication of large area Cu(OH)2 or CuO nanostructured films.

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PubMed2006

Double half-cubane copper(II) complexes available from copper(II) 1,1,1,5,5,5-hexafluoropentane-2,4-dionate dissolved in formamides.

Tetranuclear copper(II) complexes were obtained after simply dissolving [Cu(hfac)2] in formamide-methanol mixed solvents (Hhfac=1,1,1,5,5,5-hexafluoropentane-2,4-dione). X-Ray diffraction studies revealed that they possessed a tetranuclear double half-cubane core sandwiched with two trianionic ligands from 2,4,6-tris(trifluoromethyl)tetrahydropyran-2,4,6-triol (H3ttpt). Complexes [Cu4(ttpt)2(hfac)2(dmf)2.5], [Cu4(ttpt)2(tfa)2(def)4], and [Cu4(ttpt)2(hfac)2(H2O)4](fa) were prepared from N,N-dimethylformamide(dmf)-MeOH, N,N-diethylformamide (def)-MeOH, and formamide(fa)-MeOH (Htfa=trifluoroacetic acid), respectively. A possible mechanism is proposed where a templated aldol-type reaction takes place between hfac and 1,1,1-trifluoroacetonate. Magnetic measurements revealed the presence of antiferromagnetic interaction in the Cu4O6 core.

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PubMed2004

(4,4,12,12-Tetramethyl-5,8,11-triazapenta-2,14-dione 2-oxime 14-oximato-kappa(5)N)copper(II) perchlorate: a copper(II) compound with a pentadentate triamine-oxime-oximate ligand.

The title compound, [Cu(C(16)H(34)N(5)O(2))]ClO(4), has discrete square-pyramidal (triamine-oxime-oximato)copper(II) cations and perchlorate anions. The cations have very approximate mirror symmetry, with the oxime [Cu-N = 2.066 (2) A], oximate [Cu-N = 2.087 (2) A] and amine N atoms [Cu-N = 2.138 (2) and 2.095 (2) A] in the tetrahedrally twisted basal plane, and the 'central' amine N atom coordinated axially [Cu-N = 2.183 (2) A]. The oxime and oximate groups are linked by an O-H.O hydrogen bond, forming a pseudo-cyclic pentadentate ligand, with an O.O distance of 2.395 (3) A.

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PubMed2005

Transition metal complexes with pyrazole-based ligands. XXII. Part XXI: Mészáros Szécsényi, Leovac, Kovacs, Pokol & Jaćimović (2005). Di-mu-thiocyanato-bis[(3,5-dimethyl-1H-pyrazole-1-carboxamidine-kappa2N,N')(thiocyanato-kappaN)copper(II)] and a redetermination of bis(3,5-dimethyl-1H-pyrazole-1-carboxamidine-kappa2N,N')bis(nitrato-kappaO)copper(II).

The title Cu(II) complex, [Cu2(NCS)4(C6H10N4)2], represents the first crystal structure of a polynuclear transition metal complex with the 3,5-dimethyl-1H-pyrazole-1-carboxamidine ligand (HL). It is compared with previously reported crystal structures of metal complexes with the same HL ligand. The molecule contains an eight-membered binuclear Cu2(NCS)2 ring, which is centrosymmetric and in a chair conformation. The Cu atom has a distorted square-pyramidal geometry with a very elongated Cu-S bond of 2.993 (2) A. The crystal structure redetermination of the bis(3,5-dimethyl-1H-pyrazole-1-carboxamidine-kappa(2)N,N')bis(nitrato-kappaO)copper(II)complex, [Cu(NO3)2(C6H10N4)2], and analysis of its hydrogen bonds confirm the significance of the NO3 groups in the formation of a three-dimensional hydrogen-bonding network. Both complexes are centrosymmetric, the inversion centre being located at the mid-point of the Cu...Cu line in (I) and the Cu atom being located at the inversion centre in (II).

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PubMed1996

Direct visualization of copper-metallothionein in LEC rat kidneys: application of autofluorescence signal of copper-thiolate cluster.

We report on the histochemistry of copper-metallothionein (Cu-MT) in the kidneys of Long Evans Cinnamon (LEC) rats. We used the visualization principle of histochemistry based on the autofluorescence emission from the fluorophore of Cu(+)-thiolate clusters in proteins. Intense autofluorescence signals were observed with a ring at the outer stripe of the outer medulla. Orange fluorescence signals were observed in the nuclei and cytoplasm of proximal straight tubular (PST) cells of segment 3 (S3) at the outer stripe of the outer medulla, and yellow-orange signals were detected in lysosome-like organelles in the proximal convoluted tubule (PCT) cells of segments 1 and 2 (S1 and S2) adjacent to the glomeruli in the cortex. These fluorescent materials were identified as Cu-MT because both signals were quenched by withdrawing Cu+ or by blocking cysteine residues, the distributions of cysteine residues and immunoreactive MT showed identical patterns to the localization of the fluorescence signals, and the fluorescent proteins containing Cu were eluted at the same Kd value of purified Cu-MT by gel filtration chromatography. However, a high level of MT mRNA was detected only in the outer stripe of the outer medulla where the orange fluorescence signals were detected, but not in the cortex. This difference in localization between the protein and the mRNA suggested that synthesis of renal MT occurs do novo in the outer stripe of the outer medulla. The yellow-orange fluorescent Cu-MT located in the lysosomal organelles at S1 and S2 of the PCT cells in the cortex could be Cu-MT of nonrenal origin, i.e., Cu-MT transported from other organs.

Animals↗
PubMed1994

Copper(II)[2,3-butanedionebis(N4-methylthiosemicarbazone)], a stable superoxide dismutase-like copper complex with high membrane penetrability.

To obtain a superoxide dismutase (SOD)-like drug that could readily cross the cell membrane, we investigated the SOD-like activity, intracellular uptake, and stability of several Cu(II)Bisthiosemicarbazones (Cu(II)BTS). Among these Cu(II)BTS chelates, Cu(II)[2,3-Butanedionebis(N4-methylthiosemicarbazone)] (Cu(II)BMTS) was the most effective SOD-like compound with activity similar to activity reported for various previously reported SOD-like Cu complexes. Biodistribution studies in mice indicated that Cu(II)BMTS rapidly distributed to all tissues and readily crossed cell membranes as well as the blood-brain barrier with high distributions to the brain and the heart. Moreover, Cu(II)BMTS was stable in mouse brain homogenate and mouse blood. These results suggest that Cu(II)BMTS has the potential to be used as a SOD-like drug capable of reaching intracellular superoxide generating sites.

Animals↗