Study on the effects of fluorine and oxygen deficiency on YBa2Cu307 byab initio method

The calculations of clusters modeling the fluorine-doping and oxygen deficiency of YBa₂Cu₃0₇ have been performed by the method of all-electronab initio Hartree-Fock with self-consistent crystal field. Results show that in CuO planes electric charge significantly increases, the chemical valence of Cu decreases and the covalent bonding of Cu-O greatly weakens owing to oxygen deficiency, while the effect of F restores the local electronic structure of YBa₂Cu₃O₇. The reported opinion that F occupied the oxygen vacancy in Cu-O chains seems disputable according to the calculated bonding characteristics Project supported by the National Natural Science Foundation of China.     

高温超导体的Cu-O键型和氧上的部分电荷

多数钙钛矿型化合物是离子型绝缘体，而高温超导化合物则有金属电性，它们是以什么键型为主？对此等人[1]认为用共价或金属成键图像描述高温超导体在化学上更合理，Nepela等人[2]指出超导体临界温度（Tc）随阴离子平均电负性与阳离子平均电负性之差增大而升高．这意味着离子性较强的超导体有较高的人．杨频等问运用晶型键参数方法估算结果表明高温超导体属干部分离子性与部分共价性键．以上不同的结果都是基丁理论处理或估算得到的·本文试图在实验上通过比较不同成键特征的铜化合物的x光电子能潜（＊P8）来估计对高温超导性起重要作用的C…     

Co掺杂的YBa2Cu2O6+δ的氧非计量和氧渗透性能研究

研究钴离子部分取代铜离子对YBa2Cu3O6+δ的氧非计量值δ和氧渗透率的影响.对于钴替代的样品,氧非计量的绝对值变大,且其数值不再随温度和氧分压的变化发生显著变化.YBa2Cu2CoO6+δ样品在中、高温具有可观的氧渗透率.对于厚度为1.2 mm的致密YBa2Cu2CoO6+δ样品,在850℃时,只要在样品两端施加较小的氧分压差(PO2=21.2 kPa、 PO2=101 Pa),其氧渗透率即可达57 μmol/cm2 s, 明显高于YBa2Cu3O6+δ的氧渗透率(31 μmol/cm2 s).YBa2Cu2CoO6+δ的高氧渗透率在结构上可被归结为位于晶胞基面上的氧离子和氧空位的均匀分布.     

CO在YBa2Cu3Ox薄膜上吸附与加氢的研究

ＹＢａ２Ｃｕ３Ｏｘ（ｘ＝６－７）薄膜被合成在ＹＳＺ基底上，用ＦＴＩＲ，ＸＰＳ，ＸＲＤ等手段原位研究ＣＯ在薄膜上的吸附及加氢行为。ＣＯ吸附在Ｃｕ位置上，与ＹＢＣＯ体相中的Ｏ作用，生成表面ＣＯ２或－ＣＯＯ基团，导致ＹＢＣＯ中生产氧空位，使ＹＢＣＯ发生昌型转变，Ｃｕ＾２＋被还原为Ｃｕ＾＋或Ｃｕ＾０．ＹＢＣＯ中的氧空位有利于ＣＯ、ＣＯ２及Ｈ２的吸附。ＣＯ、ＣＯ２在ＹＢＣＯ膜上的加氢产物为ＣＨ３ＯＨ、ＣＨ３     

SURFACE STUDIES ON A YBa_2Cu_3O_(6～7) CATALYST FOR CO HYDROGENATION TO METHANOL

研究了ＹＢａ２Ｃｕ３Ｏ６～７超导催化剂上ＣＯ加氢反应，反应主要产物是甲醇和二甲醚。利用原位ＦＴＩＲ、ＸＰＳ和ＸＲＤ技术对催化剂进行了表征。原位ＦＴＩＲ结果表明，反应中间物可能为醛基、甲氧基和甲酸根。ＣＯ吸附到ＹＢａ２Ｃｕ３Ｏ６～７上与晶格氧发生反应生成ＣＯ２，ＹＢａ２Ｃｕ３Ｏ６～７产生氧空位并由Ｏｒｔｈｏｒｈｏｍｂｉｃ相转变为Ｔｅｔｒａｇｏｎａｌ相。     

导电高分子膜包覆YBa2Cu3O7超导体抗环境作用的研究

通过电化学途径和化学途径在ＹＢａ＿２Ｃｕ＿３Ｏ＿７超导体表面制备了导电高分子聚吡咯膜，用以保护超导体不受环境作用的影响，实验结果发现电化学过程能破坏ＹＢａ＿２Ｃｕ＿Ｏ＿７的超导性，而采用化学法制备的聚吡咯和聚氯乙烯混和材料包覆在ＹＢａ＿２Ｃｕ＿３Ｏ＿７表面后，超导体不仅保持原有超导性，而且有很好的保护超导体免遭环境中酸和水作用的能力。     

Comments on the nature of the bonding in oxygenated dinuclear copper enzyme models

The nature of the bonding in model complexes of di-copper metalloenzymes has been analyzed by means of the electronic localization function (ELF) and by the quantum theory of atoms in molecules (QTAIM). The constrained space orbital variations (CSOV) approach has also been used. Density functional theory (DFT) and CASSCF calculations have been carried out on several models of tyrosinase such as the sole Cu2O22+ central core, the Cu2O2(NH3)62+ complex and the Cu2O2(Imidazol)62+ complex. The influence on the central Cu(2)O(2) moiety of both levels of calculation and ligand environment have been discussed. The distinct bonding modes have been characterized for the two major known structures: [Cu(2)(mu-eta(2): eta(2)-O(2))](2+) and [Cu(2)(mu-O(2))](2+). Particular attention has been given to the analysis of the O-O and Cu-O bonds and the nature of the bonding modes has also been analyzed in terms of mesomeric structures. The ELF topological approach shows a significant conservation of the topology between the DFT and CASSCF approaches. Particularly, three-center Cu-O-Cu bonds are observed when the ligands are attached to the central core. At the DFT level, the importance of self interaction effects are emphasized. Although, the DFT approach does not appear to be suitable for the computation of the electronic structure of the isolated Cu(2)O(2) central core, competitive self interaction mechanisms lead to an imperfect but acceptable model when using imidazol ligands. Our results confirm to a certain extent the observations of [M.F. Rode, H.J. Werner, Theoretical Chemistry Accounts 4-5 (2005) 247.] who found a qualitative agreement between B3LYP and localized MRCI calculations when dealing with the Cu(2)O(2) central core with six ammonia ligands.     

New organically templated copper(I) sulfites: the role of sulfite anion as both soft and hard ligand

Two new organically templated layered copper(I) sulfites, namely, {H2pip}{Cu3(CN)3(SO3)} (1) and {H2pip}{NaCu2(SO3)2Br(H2O)}.2H2O (2) (pip = piperazine), have been synthesized by hydrothermal reactions of copper(I) cyanide or copper(I) bromide with NaHSO3 and piperazine. Both compounds exhibit a layered structure. The 2D layer of {Cu3(CN)3(SO3)}2- in 1 is composed of 1D chains of copper(I) cyanide interconnected by sulfite anions via both Cu-S and Cu-O bonds, whereas the 2D layer of {NaCu2(SO3)2Br}2- in 2 is formed by 1D chains of copper(I) bromide and 1D sodium(I) aqua chains that are interconnected by sulfite anions via Na-O, Cu-S, and Cu-O bonds. Chemical bonding in 1 and 2 has been also investigated by theoretical calculations based on DFT methods.     

Cu,Zn-SOD酶模型配合物催化O2-歧化作用的研究

为了解Cu,Zn-SOD酶中Cu周围环境对催化O_2~-歧化作用活性的影响,本文用NBT法测定了Cu,Zn-SOD酶及一系列咪唑桥异核模型配合物催化O_2~-歧化作用的活性,并用ESR方法鉴测了其中一个配合物与O_2~-作用的中间过程。结果表明,具有平面四方构型或轴向有弱配位H_2O或ClO_4~-基团的四方锥构型的Cu~(2+)配合物具有较高活性,说明配合物催化歧化O_2~-过程中,Cu~(2+)可能首先以轴向与O_2~-配位,形成Cu~(2+)-O_2~-中间化合物,紧接着Cu~(2+)被还原成Cu~+。     

Synthesis and Crystal Structure of Bis（barbiturato） triwater Complex of Copper（Ⅱ）

1 INTRODUCTION A variety of transition metal complexes with barbiturates have been prepared owing to their important roles in clinical detection and identi- fication of drug[1～5]. They have the general formula of M(Ⅱ)(barb)2L2, where M is a transition metal (Co, Cr, Zn, Cu etc), barb the anion of a substituted barbituratic acid and L an organic base, usually pyridine. In these complexes, the donor atom in the barbiturate anion is a deprotonated nitrogen atom and, the coordination …     

Synthesis and Crystal Structure of a Copper(II) Complex with α-Hydroxylated Acid, [Cu(C_(14)H_8O_3)(C_5H_(13)NO)(H_2O)].0.5H_2O

1 INTRODUCTION There has been considerable interest of copper(II) -hydroxylate complexes in the structural chemistry and biochemistry. There are two structural types in copper(II) -hydroxylate com- plexes: mononuclear[1~6] and dinuclear structure[7~9]. The present work is a part of our study on the copper complexes of -hydroxylated acid and reports the synthesis and structure of a mononuclear copper(II) complex with 9-hydroxy- fluorene-9-carboxylato acid, [Cu(C14H8O3)(C5H13- NO)(H…     

The solution structure of [Cu(aq)]2+ and its implications for rack-induced bonding in blue copper protein active sites

The structure of [Cu(aq)]2+ has been investigated by using full multiple-scattering theoretical (MXAN) analysis of the copper K-edge X-ray absorption (XAS) spectrum and density functional theory (DFT) to test both ideal Td and square-planar four-coordinate, five-coordinate square-pyramidal, and six-coordinate octahedral [Cu(aq)]2+ models. The best fit was an elongated five-coordinate square pyramid with four Cu-O(eq) bonds (2 x 1.98 +/- 0.03 A and 2 x 1.95 +/- 0.03 A) and a long Cu-O(ax) bond (2.35 +/- 0.05 A). The four equatorial ligands were D2d-distorted from the mean equatorial plane by +/-(17 +/- 4) degrees, so that the overall symmetry of [Cu(H2O)5]2+ is C2v. The four-coordinate MXAN fit was nearly as good, but the water ligands (4 x 1.96 +/- 0.02 A) migrated +/-(13 +/- 4) degrees from the mean equatorial plane, making the [Cu(H2O)4]2+ model again D2d-distorted. Spectroscopically calibrated DFT calculations were carried out on the C2v elongate square-pyramidal and D2d-distorted four-coordinate MXAN copper models, providing comparative electronic structures of the experimentally observed geometries. These calculations showed 0.85e spin on Cu(II) and 0.03e electron spin on each of the four equatorial water oxygens. All covalent bonding was restricted to the equatorial plane. In the square-pyramidal model, the electrostatic Cu-O(ax) bond was worth only 96.8 kJ mol(-1), compared to 304.6 kJ mol(-1) for each Cu-O(eq) bond. Both MXAN and DFT showed the potential well of the axial bond to be broad and flat, allowing large low-energy excursions. The irregular geometry and D2d-distorted equatorial ligand set sustained by unconstrained [Cu(H2O)5]2+ warrants caution in drawing conclusions regarding structural preferences from small molecule crystal structures and raises questions about the site-structural basis of the rack-induced bonding hypothesis of blue copper proteins. Further, previously neglected protein folding thermodynamic consequences of the rack-bonding hypothesis indicate an experimental disconfirmation.     

Influence of vanadium doping on the behavior of YBa_2Cu_3O_7-y

YBa2Cu3-xVxO7-y(x=0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) superconductors have been prepared. X-ray diffraction shows that the system remains orthorhombic for all compositions studied, but for x > 0.4 V2O5 was detected as an impurity phase. Substitution of V5+ for Cu2+ occurs in the Cu(2) sites on the Cu(2)-O planes. The introduction of the high valence element, vanadium, produces the extra free-electrons. These electrons recombine with the positive carrier of the system. It makes depression of the mobility and the Hall number of YBa2Cu3-xVxO7-v and also results in a depression of TC.     

Theoretical investigation of adsorption of molecular oxygen on small copper clusters

Adsorption of molecular oxygen on Cu(N) (N = 2-10) clusters is investigated using density functional theory under the generalized gradient approximation of Perdew-Burke-Ernzerhof. An extensive structure search is performed to identify low-energy conformations of Cu(N)O(2) complexes. Optimal adsorption sites are assigned for low-energy isomers of the clusters. Among these are some new arrangements unidentified heretofore. Distinct size dependences are noted for the ground state Cu(N)O(2) complexes in stability, adsorption energy, Cu-O(2) bond strength, and other characteristic quantities. Cu(N)O(2) with odd-N tend to have larger adsorption energies than their even-N neighbors, with the exception of Cu(6)O(2), which has a relatively large adsorption energy resulting from the adsorption-induced 2D-to-3D structural transition in Cu(6). The energetically preferred spin-multiplicity of all the odd-N Cu(N)O(2) complexes is doublet; it is triplet for N = 2 and 4 and singlet for N = 6, 8, and 10.     

A new binuclear germanium(IV) and copper(II) complex with 1,3-diamino-2-propanoltetraacetic acid: Crystal and molecular structure of [(H2O)(OH)Ge(μ-Hpdta)Cu(H2O)] · 3H2O

A heteronuclear germanium(IV) and copper(II) complex with 1,3-diamino-2-propanoltetraacetic acid (H₅Hpdta) has been synthesized for the first time. The compound has been characterized by elemental analysis, X-ray diffraction, thermogravimetry, and IR spectroscopy. The structure of the complex [(H₂O)(OH)Ge(μ-Hpdta)Cu(H₂O)] · 3H₂O (I) has been determined by single-crystal X-ray diffraction. The crystals of I are monoclinic, a = 1 5.327(4) Å, b = 11.626(3) Å, c =21.058(3) Å, β = 96.35(2)°, V = 3729.2(2) ų, Z = 8, space group C2/c, R1 = 0.0551 on 3090 reflections with I > 2σ(I). The structural units of the crystal of I are binuclear complex molecules [(H₂O)(OH)Ge(μ-Hpdta)Cu(H₂O)] and crystal water molecules. The germanium and copper atoms are linked by the bridging oxygen atom of the deprotonated isopropanol group of the Hpdta^5? ligand (Ge-O, 1.843(3) Å; Cu-O, 2.221(3) Å). The coordination spheres of the Ge and Cu atoms contain each one nitrogen atom (Ge-N, 2.090(4) Å; Cu-N, 2.000(4) Å) and two carboxyl oxygen atoms from four acetate arms of the heptadentate Hpdta^5? ligand (av. Ge-O, 1.909(3) Å; Cu-O, 1.948(3) Å). The coordination polyhedron of the Ge atom is completed to a distorted octahedron by the oxygen atoms of the terminal hydroxy group (Ge-O, 1.786(3) Å) and a water molecule (Ge-O, 1.904(3)Å). The coordination polyhedron of the copper atom is completed to a prolate tetragonal pyramid (4 + 1) by the oxygen atom of a water molecule in the equatorial position (Cu-O, 1.955(4) Å) and the bridging O(11) atom (Hpdta^5?) in the apical position. Binuclear molecules are linked pairwise in a head-to-head manner via double Cu-O(2) bridges to form the centrosymmetric tetranuclear supramolecule {[(H₂O)(OH)Ge(μ-Hpdta)Cu(H₂O)]}₂. The coordination of the Cu atom is completed by the weak Cu-O(2A) contact (3.303 Å) to an asymmetrically elongated tetragonal bipyramid (4 + 1 +1). In the crystal, the complex molecules and crystal water molecules are combined by a system of hydrogen bonds into a three-dimensional framework.     

La-Ba-Cu复合氧化物在催化消除NO反应中催化性能的研究

合成了具有钙钛石结构的复合氧化物YBa₂Cu₃O₇、LaBa₂Cu₃O₇、LaBaCu₂O₅、La₂BaCu₃O₇和La₄BaCu₅O₁₂.考察了它们对NO分解和NO+CO反应的催化性能.结合化学分析、XRD、TPD和TPR对催化剂的表征结果,探讨了该系列复合氧化物对NO分解和NO+CO反应的催化机理.     

Unusually large magnetic anisotropy in a CuO-based semiconductor Cu5V2O10

A CuO-based material Cu(5)V(2)O(10) was successfully grown in a closed crucible using Sr(OH)(2)·8H(2)O as flux. The structure of Cu(5)V(2)O(10) can be viewed as being composed of two types of zigzag Cu-O chains running along the b- and c-axes, which shows a two-dimensional crosslike framework with 12-column square tunnels along the a-axis. Magnetic measurements show that Cu(5)V(2)O(10) exhibits unexpected large magnetic anisotropy, which is the first time magnetic anisotropy energy of ～10(7) erg/cm(3) in the CuO-based materials has been observed. The origins of large anisotropy are suggested to arise from strong anisotropic exchanges due to the particular bonding geometry and the Jahn-Teller distortion of Cu(2+) ions. Further, the band structure investigated by the GGA+U method suggests that Cu(5)V(2)O(10) is a semiconductor.     

Variable-temperature, variable-field magnetic circular dichroism studies of tris-hydroxy- and mu3-oxo-bridged trinuclear Cu(II) complexes: evaluation of proposed structures of the native intermediate of the multicopper oxidases

Multicopper oxidases catalyze the 4e- reduction of O2 to H2O. Reaction of the fully reduced enzyme with O2 produces the native intermediate (NI) that consists of four oxidized Cu centers, three of which form a trinuclear cluster site, all bridged by the product of full O2 reduction. The most characteristic feature of NI is the intense magnetic circular dichroism pseudo-A feature (a pair of temperature-dependent C-terms with opposite signs) associated with O --> Cu(II) ligand-to-metal charge transfer (LMCT) that derives from the strong Cu-O bonds in the trinuclear site. In this study, the two most plausible Cu-O structures of the trinuclear site, the tris-mu2-hydroxy-bridged and the mu3-oxo-bridged structures, are evaluated through spectroscopic and electronic structure studies on relevant model complexes, TrisOH and mu3O. It is found that the two components of a pseudo-A-term for TrisOH are associated with LMCT to the same Cu that are coupled by a metal-centered excited-state spin-orbit coupling (SOC), whereas for mu3O they are associated with LMCT to different Cu centers that are coupled by oxo-centered excited state SOC. Based on this analysis of the two candidate models, only the mu3-oxo-bridged structure is consistent with the spectroscopic properties of NI. The Cu-O sigma-bonds in the mu3-oxo-bridged structure would provide the thermodynamic driving force for the 4e- reduction of O2 and would allow the facile electron transfer to all Cu centers in the trinuclear cluster that is consistent with its involvement in the catalytic cycle.     

HYDROGENATION OF CO_2 OVER A YBa_2Cu_3O_(6～7) CATALYST

研究了ＹＢａＣｕ３Ｏ６～７超导催化剂上ＣＯ２的加氢制醇反应。考察了温度、压力和空速等条件对催化剂反应性能的影响。反应的主要产物是甲醇、ＣＯ和少量甲醚。利用ＸＰＳ、ＸＲＤ和ＡＦＭ等技术对催化剂的结构、铜的存在状态和反应活性位进行表征发现，在反应过程中，ＹＢａ２Ｃｕ３Ｏ６～７由ｏｒｔｈｏｍｂｉｃ相转变为ｔｅｔｒａｇｏｎａｌ相。反应活性位可能是Ｃｕ（Ｉ）物种。反应后催化剂颗粒的分散程度明显提高     

Crystal and molecular structure of [N,N-bis(2-carbamoylethyl)aminoacetato](imidazole)copper(II) perchlorate monohydrate, [Cu(Bcegly)(Im)](ClO4) · H2O

The [Cu(Bcegly)(Im)](ClO₄) · H₂O aminocarboxylate, where HBcegly is N,N-bis(2-carbamoyl-ethyl)aminoacetic acid and Im is imidazole, is studied by X-ray diffraction. The polyhedron of the Cu atom is an asymmetrically elongated tetragonal bipyramid (4 + 1 + 1), whose equatorial plane is composed of two oxygen atoms (average Cu-O, 1.952 ?) and a nitrogen atom (Cu-N, 2.031 ?) of the Bcegly^? ligand and the nitrogen atom of the Im ligand (Cu-N, 1.970 ?) and the axial positions are occupied by oxygen atoms of the Bceglyligand (Cu-O, 2.357 ?) and the perchlorate ion (Cu-O, 2.830 ?). The Bcegly^? ligand fulfils the tetradentate chelate function closing three metallocycles, namely, two six-membered CuNC₃O cycles and one five-membered CuNC₂O cycle. Complex cations, ClO ₄ ^? anions, and crystallization water molecules are connected by an extended system of hydrogen bonds.