Search results for "Cuprate"
showing 10 items of 28 documents
Photochemistry and Redox Chemistry of an Unsymmetrical Bimetallic Copper(I) Complex
2016
The bimetallic copper(I) complex Cu2L2 (cis-1) is formed with high diasteroselectivity from [Cu(NCCH3)4][BF4] and HL (4-tert-butyl phenyl(pyrrolato-2-yl-methylene)amine) in a kinetically controlled reaction. cis-1 features a rather short Cu···Cu distance of 2.4756(6) A and is weakly emissive at room temperature in solution. Oxidatively triggered disproportionation of cis-1 yields elemental copper and the mononuclear copper(II) complex CuL2 (trans-2). One-electron reduction of trans-2 gives cuprate [2]– with a bent bis(pyrrolato) coordinated copper(I) entity. The imine donor atoms of [2]– can insert an additional copper(I) ion giving exclusively the bimetallic complex cis-1 closing the oxida…
Bis(2-methylbenzimidazole-κN1)copper(I) dichlorocuprate(I)
2004
By using alternating-current electrochemical synthesis, crystals of the copper(I) ionic compound composed of [Cu(C8H8N2)2]+ and [CuCl2]− ions have been obtained and structurally investigated. Both crystallographically independent Cu atoms lie on centres of inversion and exhibit the less-common coordination number 2. A linear arrangement of the metal atoms includes two N atoms of the different organic moieties in the [Cu(2-methylbenzimidazole)2]+ cation and two Cl atoms in the case of the inorganic anion.
Ferromagnetic coupling through a carbonate bridge in the copper (II) chain [Cu(CO3)(4-apy)2] · H2O (4-apy = 4-aminopyridine)
1999
Abstract Atmospheric CO2 fixation by aqueous solutions containing copper(II) bromide and 4-aminopyridine (4-apy) yields the first carbonatobridged copper(II) chain of formula [Cu(CO3)(4-apy)2] · H2O that exhibits an intrachain ferromagnetic coupling.
Versatile supramolecular self-assembly : Part II. Network formation and magnetic behaviour of copper(ii) malonate anions in ammonium derivatives
2006
Five new metal–organic compounds of formula An[Cu(mal)2(H2O)m] (A being an amine cation and H2mal = malonic acid) have been structurally and magnetically characterized. The crystal structure of these compounds consists of an alternation of malonate-containing copper(II) anionic and amine cationic layers. Depending on the amine cation, the bis(malonate)cuprate(II) units can be connected to other units through carboxylate bridges resulting in anionic networks which exhibit different topologies: monomers (2 and 5), layers (3 and 4) and three-dimensional structures (1). Hydrogen bonding plays an important role in the self-assembling of metal–organic compounds and how the size of the amine catio…
The composite operator method route to the 2D Hubbard model and the cuprates
2018
In this review paper, we illustrate a possible route to obtain a reliable solution of the 2D Hubbard model and an explanation for some of the unconventional behaviours of underdoped high-$T_\text{c}$ cuprate superconductors within the framework of the composite operator method. The latter is described exhaustively in its fundamental philosophy, various ingredients and robust machinery to clarify the reasons behind its successful applications to many diverse strongly correlated systems, controversial phenomenologies and puzzling materials.
Single-particle properties of the Hubbard model in a novel three-pole approximation
2017
We study the 2D Hubbard model using the Composite Operator Method within a novel three-pole approximation. Motivated by the long-standing experimental puzzle of the single-particle properties of the underdoped cuprates, we include in the operatorial basis, together with the usual Hubbard operators, a field describing the electronic transitions dressed by the nearest-neighbor spin fluctuations, which play a crucial role in the unconventional behavior of the Fermi surface and of the electronic dispersion. Then, we adopt this approximation to study the single-particle properties in the strong coupling regime and find an unexpected behavior of the van Hove singularity that can be seen as a prec…
Discrete trinuclear copper(II) compounds as building blocks: the influence of the peripheral substituents on the magnetic coupling in oxamato-bridged…
2014
Two new trinuclear copper(ii) complexes without end-capping ligands, (Bu4N)2[Cu(dmso)2{Cu(dnopba)(dmso)}2] () and (Bu4N)2[Cu(dmso)2{Cu(dcopba)(dmso)}2] () [dnopba = 4,5-dinitro-ortho-phenylenebis(oxamate), dcopba = 4,5-dichloro-ortho-phenylenebis(oxamate), Bu4N(+) = tetra-n-butylammonium and dmso = dimethylsulfoxide], were synthesized and their structures were determined by single crystal X-ray diffraction. The crystal structures of and consist of two outer bis(oxamato)(dmso)cuprate(ii) units which act as bidentate ligands toward a trans-bis(dmso)copper(ii) inner entity leading to centrosymmetric tricopper(ii) complexes with copper-copper separations across the oxamate bridges of 5.1916(3) …
Homo‐ and Heteroleptic Hypersilylcuprates — Valuable Reagents for the Synthesis of Molecular Compounds with a Cu−Si Bond
2003
Unsolvated hypersilanides MHyp [Hyp = Si(SiMe3)(3)] of the heavier alkali metals (M-I = Na, K, Cs) react with copper tert-butoxide in toluene to yield crystalline heteroleptic cuprates [M-I(toluene)][tBuOCuHyp]. These cuprates proved to be valuable sources for pure hypersilylcopper and other cuprates bearing hypersilyl ligands such as the di(hypersilyl)cuprates M-I[CuHyp(2)]((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).
Versatile supramolecular self-assembly. Part I. Network formation and magnetic behaviour of the alkaline salts of the bis(malonate)cuprate(ii) anion
2006
Five malonate-containing copper(II) compounds of formula {[A(H2O)n]2 [Cu(mal)2(H2O)m]} [A = Li (1), Na (2), K (3), Rb (4) and Cs (5); H2mal = malonic acid] have been synthetized and characterized by X-ray diffraction. The structure of these compounds consists of bis(malonate)cuprate(II) anions and alkaline cations that are held together by means of carboxylate bridges and water molecules leading to 3D networks. A study of the self-assembling of the bis(malonate)cuprate(II) and the alkaline cations is carried out, the size of the alkaline metal ion playing an important role in the control of the resulting malonate-bridged copper(II) structure. A regular alternation of layers of anionic malon…
The Influence of Morphological Aspects in the Reaction Pathway and Superconductive Properties of Bi2223-Ca2CuO3 Ceramic Composites
1994
ABSTRACTA variation of the solid-state matrix technique has been developed as a procedure for the preparation of 2223 bismuth superconducting phases [(Bi,Pb)2Sr2Ca1-nCunO4+2n, n=3]. The adequate processing of samples of nominal compositions 2223+x 0021, obtained both by this procedure and by the polymer matrix method, has allowed the modification of the microstructure of the calcium copper excess, with no noticeable change in that of the 2223 grains. The study of the phase evolution in the processing of the samples has shown that the formation rate of the 2223 phase is faster when the particle size of the calcium cuprate is smaller. A dependence of the intergranular superconducting properti…