High-spin cobalt(II) ions in square planar coordination: structures and magnetism of the oxysulfides Sr2CoO2Cu2S2 and Ba2CoO2Cu2S2 and their solid solution

The antiferromagnetic structures of the layered oxychalcogenides (Sr(1-x)Ba(x))(2)CoO(2)Cu(2)S(2) (0 ≤ x ≤ 1) have been determined by powder neutron diffraction. In these compounds Co(2+) is coordinated by four oxide ions in a square plane and two sulfide ions at the apexes of an extremely tetragonally elongated octahedron; the polyhedra share oxide vertexes. The magnetic reflections present in the diffraction patterns can in all cases be indexed using a √2a × √2a × c expansion of the nuclear cell, and nearest-neighbor Co(2+) moments couple antiferromagnetically within the CoO(2) planes. The ordered magnetic moment of Co(2+) in Sr(2)CoO(2)Cu(2)S(2) (x = 0) is 3.8(1) μ(B) at 5 K, consistent with high-spin Co(2+) ions carrying three unpaired electrons and with an additional significant unquenched orbital component. Exposure of this compound to moist air is shown to result in copper deficiency and a decrease in the size of the ordered moment to about 2.5 μ(B); there is a strong correlation between the size of the long-range ordered moment and the occupancy of the Cu site. Both the tetragonal elongation of the CoO(4)S(2) polyhedron and the ordered moment in (Sr(1-x)Ba(x))(2)CoO(2)Cu(2)S(2) increase with increasing Ba content, and in Ba(2)CoO(2)Cu(2)S(2), which has Co(2+) in an environment that is close to purely square planar, the ordered moment of 4.5(1) μ(B) at 5 K is over 0.7 μ(B) larger than that in Sr(2)CoO(2)Cu(2)S(2), so the unquenched orbital component in this case is even larger than that observed in octahedral Co(2+) systems such as CoO. The experimental observations of antiferromagnetic ground states and the changes in properties resulting from replacement of Sr by Ba are supported by ab initio calculations on Sr(2)CoO(2)Cu(2)S(2) and Ba(2)CoO(2)Cu(2)S(2). The large orbital moments in these systems apparently result from spin-orbit mixing of the unequally populated d(xz), d(yz), and d(z(2)) orbitals, which are reckoned to be almost degenerate when the CoO(4)S(2) polyhedron reaches its maximum elongation. The magnitudes of the ordered moments in high-spin Co(2+) oxide, oxychalcogenide, and oxyhalide systems are shown to correlate well with the tetragonal elongation of the coordination environment. The large orbital moments lead to an apparently magnetostrictive distortion of the crystal structures below the Nee?l temperature, with the symmetry lowered from tetragonal I4/mmm to orthorhombic Immm and the size of the distortion correlating well with the size of the long-range ordered moment for all compositions and for temperature-dependent data gathered on Ba(2)CoO(2)Cu(2)S(2).     

CoO(100)表面高分辩电子能损失谱与量子化学的从头算

ＣｏＯ（１００）表面高分辩电子能损失谱与量子化学的从头算石守衡（大连轻工业学院基础部物理化学教研室,大连,１１６０３４）关键词ＣｏＯ（１００）表面,高分辩电子能损失谱,从头算Ａ．Ｆｒｅｉｔａｇ等［１］用高辩电子能损失谱研究了ＮｉＯ（１００）表面的电子...     

The formation mechanism of a textured ceramic of thermoelectric [Ca2CoO3](0.62)[CoO2] on beta-Co(OH)2 templates through in situ topotactic conversion

We investigated the formation mechanism of thermoelectric [Ca(2)CoO(3)](0.62)[CoO(2)] (CCO) on beta-Co(OH)(2) templates with maintained orientations by identifying the intermediate phases and specifying the relationship between their crystallographic orientations. We mixed beta-Co(OH)(2) templates with the complementary reactant CaCO(3) and prepared a compact by tape casting, with the developed (001) plane of the templates aligned along the casting plane. High-temperature XRD of the compact revealed that beta-Co(OH)(2) decomposed into Co(3)O(4) by 873 K, and Co(3)O(4) reacted with CaO to form CCO by 1193 K via the formation of the newly detected intermediate phase beta-Na(x)()CoO(2)-type Ca(x)()CoO(2) at 913-973 K. Pole figure measurements and SEM and TEM observations revealed that the relationship between the crystallographic planes was (001) beta-Co(OH)(2)//{111} Co(3)O(4)//(001) Ca(x)()CoO(2)//(001) CCO. The crystal structures of the four materials possess the common CoO(2) layer (or similar), which is composed of edge-sharing CoO(6) octahedra, parallel to the planes. The cross-sectional HRTEM analysis of an incompletely reacted specimen showed transient lattice images from Ca(x)()CoO(2) into CCO, in which every other CoO(2) layer of Ca(x)()CoO(2) was preserved. Thus, it was demonstrated that a textured CCO ceramic is produced through a series of in situ topotactic conversion reactions with a preserved CoO(2) layer of its template.     

Ce-doped ZnO (Ce(x)Zn(1-x)O) becomes an efficient visible-light-sensitive photocatalyst by co-catalyst (Cu2+) grafting

We have fabricated an efficient visible-light-sensitive Cu(2+)-grafted Ce-doped ZnO photocatalyst (Cu(2+)-Ce(x)Zn(1-x)O) by adopting a metal ion doping and co-catalyst modification. Impurity states were formed below the conduction band (CB) edge in Ce(x)Zn(1-x)O, and these impurity states induce the visible-light absorption. Ce(x)Zn(1-x)O without a Cu(2+)-co-catalyst showed negligible visible-light activity due to the low reduction power of electrons in impurity levels. Surprisingly, Cu(2+)-modification over Ce(x)Zn(1-x)O drastically increased its visible-light activity. Excited electrons in impurity states can transfer to the Cu(2+)-ions on the surface and form Cu(2+)/Cu(+) redox couples, which cause the efficient oxygen reduction through a multi-electron reduction process. One of the striking features of the present study is that the metal doped semiconductors which were inactive due to their impurity states become efficient visible-light photocatalysts upon co-catalyst modification. The successful strategy used here for designing a highly active visible-light photocatalyst would provide numerous opportunities to develop an efficient metal-ion based visible-light photocatalyst.     

Transformation of proton-conducting Perovskite-type into fluorite-type fast oxide ion electrolytes using a CO2 capture technique and their electrical properties

Fast oxide ion conducting Ce 1- x M x O 2-delta (M = In, Sm; x = 0.1, 0.2) and Ce 0.8Sm 0.05Ca 0.15O 1.825 were prepared from the corresponding perovskite-like structured materials with nominal chemical composition of BaCe 1- x M x O 3-delta and BaCe 0.8Sm 0.05Ca 0.15O 2.825, respectively, by reacting with CO 2 at 800 degrees C for 12 h. Powder X-ray diffraction (PXRD) analysis showed the formation of fluorite-type CeO 2 and BaCO 3 just after reaction with CO 2. The amount of CO 2 gained per ceramic gram was found to be consistent with the Ba content. The CO 2 reacted samples were washed with dilute HCl and water, and the resultant solid product was characterized structurally and electrically employing various solid-state characterization methods, including PXRD, and alternating current (ac) impedance spectroscopy. The lattice constant of presently prepared Ce 1- x M x O 2-delta and Ce 0.8Sm 0.05Ca 0. 15O 1.825 by a CO 2 capture technique follows the expected ionic radii trend. For example, In-doped Ce 0.9In 0.1O 1.95 (In (3+) (VIII) = 0.92 A) sample showed a fluorite-type cell constant of 5.398(1) A, which is lower than the parent CeO 2 (5.411 A, Ce (4+) (VIII) = 0.97 A). Our attempt to prepare single-phase In-doped CeO 2 samples at 800, 1000, and 1500 degrees C using the ceramic method was unsuccessful. However, we were able to prepare single-phase Ce 0.9In 0.1O 1.95 and Ce 0.8In 0.2O 1.9 by the CO 2 capture method from the corresponding barium perovskites. The PXRD studies showed that the In-doped samples are thermodynamically unstable above 800 degrees C. The ac electrical conductivity studies using Pt electrodes showed the presence of bulk, grain-boundary, and electrode contributions over the investigated temperature range in the frequency range of 10 (-2)-10 (7) Hz. The bulk ionic conductivity and activation energy for the electrical conductivity of presently prepared Sm- and (Sm + Ca)-doped CeO 2 samples shows conductivities similar to those of materials prepared by the ceramic method reported in the literature. For instance, the conductivity of Ce 0.8Sm 0.2O 1.9 using the CO 2 capture technique was determined to be 4.1 x 10 (-3) S/cm, and the conductivity of the same sample prepared using the ceramic method was 3.9 x 10 (-3) S/cm at 500 degrees C. The apparent activation energy of the area-specific polarization resistance for the symmetric cell (Sm,Sr)CoO 3- x |Ce 0.8Sm 0.2O 1.9|(Sm,Sr)CoO 3- x was determined to be 1 eV in air.     

Isomorphic coordination polymers of cobalt(II), zinc(II) with a flexible ligand of cis,cis,cis-1,2,3,4-cyclopentanetetracarboxylic acid and their molecular alloys: crystal structures, thermal decomposition mechanisms and magnetic properties

Three new isomorphic coordination polymers of Co(2+), Zn(2+) ions with flexible multicarboxylic acid ligand of the cis,cis,cis-1,2,3,4-cyclopentanetetracarboxylic acid (H(4)L), [Co(4)L(2)(H(2)O)(8)]·3H(2)O (1), [Zn(4)L(2)(H(2)O)(8)]·3H(2)O (2) and [Co(0.8)Zn(3.2)L(2)(H(2)O)(8)]·3H(2)O (3), have been synthesized under hydrothermal conditions and by means of controlling the pH of the reaction mixtures (with an initial pH of 6.0 for 1, 4.0 for 2, and 5.0 for 3, respectively). In the crystal of 1, two crystallographically different Co(2+) ions (Co1 and Co2) form a negatively-charged coordination polymeric chain, which contains a centrosymmetric, linear, trinuclear Co(2+) cluster (Co(3)L(2)) subunit; another crystallographically independent Co(2+) ion (Co3) coordinated to six water molecules acts as a counter ions to link the neighboring coordination polymeric chains via intermolecular H-bond interactions. The Co(2+) ions in 1 were completely and partially replaced by Zn(2+) ions to give 2 and 3, respectively. Complex 3 shows a novel molecular alloy nature, due to the random distributions of the Co(2+) and Zn(2+) ions. Three isomorphic complexes exhibit distinct thermal decomposition mechanisms. The deprotonated cis,cis,cis-1,2,3,4-cyclopentanetetracarboxylic acid ligands decompose at 420-750 °C to give the residue CoO in 1, ZnO + C in 2 and CoO + ZnO in 3. Complex 1 shows a complicated magnetic behavior with co-existence of antiferromagnetic exchange interactions between neighboring Co(2+) ions as well as strong spin-orbital coupling interactions for each Co(2+) ion; complex 3 exhibits a magnetically isolated high-spin Co(2+) ion behavior with strong spin-orbital coupling interactions.     

Electron-transfer chemistry of Ru-linker-(heme)-modified myoglobin: rapid intraprotein reduction of a photogenerated porphyrin cation radical

We report the synthesis and characterization of RuC7, a complex in which a heme is covalently attached to a [Ru(bpy)(3)](2+) complex through a -(CH(2))(7)- linker. Insertion of RuC7 into horse heart apomyoglobin gives RuC7Mb, a Ru(heme)-protein conjugate in which [Ru(bpy)(3)](2+) emission is highly quenched. The rate of photoinduced electron transfer (ET) from the resting (Ru(2+)/Fe(3+)) to the transient (Ru(3+)/Fe(2+)) state of RuC7Mb is >10(8) s(-1); the back ET rate (to regenerate Ru(2+)/Fe(3+)) is 1.4 x 10(7) s(-1). Irreversible oxidative quenching by [Co(NH(3))(5)Cl](2+) generates Ru(3+)/Fe(3+): the Ru(3+) complex then oxidizes the porphyrin to a cation radical (P*+); in a subsequent step, P*+ oxidizes both Fe(3+) (to give Fe(IV)=O) and an amino acid residue. The rate of intramolecular reduction of P*+ is 9.8 x 10(3) s(-1); the rate of ferryl formation is 2.9 x 10(3) s(-1). Strong EPR signals attributable to tyrosine and tryptophan radicals were recorded after RuC7MbM(3+) (M = Fe, Mn) was flash-quenched/frozen.     

Ag/Yb掺杂对Ca_3Co_(3.9)Cu_(0.1)O_(9-δ)热电性能的影响

采用溶胶凝胶及冷压方法,通过在Ca_3Co_(3.9)Cu_(0.1)O_(9-δ)体系中引入不同量的Ag~+或Yb~(3+)离子来调控体系的热电性能,制备了可在300~880 K下稳定存在且热电性能优良的陶瓷材料Ca_(3-x)Ag_xCo_(3.9)Cu_(0.1)O_(9-δ)(x=0.1,0.15,0.2,0.3)和Ca_(3-y)Yb_yCo_(3.9)Cu_(0.1)O_(9-δ)(y=0.05,0.1,0.2,0.3).通过X射线衍射(XRD)和扫描电子显微镜(SEM)等测试手段对产物进行了表征,结果显示所制备的样品纯度较高,晶粒均匀,晶粒间较致密.适量的Ag~+,Yb~(3+)离子取代Ca~(2+)离子固溶到晶体中使制备的双掺杂材料晶胞体积发生了变化,但并未引起晶体对称结构的变化.电阻率和Seebeck系数的表征结果说明双掺杂优化了载流子的浓度,随着温度的升高电阻率不断减小,Seebeck系数不断增大.经过计算可知Seebeck系数的增大还有电子有效质量的贡献.热导率表征结果显示双掺杂体系的热导率随着温度的升高而减小,其中声子热导依然起主要作用,这与单掺杂体系的结果一致.随着温度的升高,双掺杂样品Ca_(2.7)Ag_(0.3)Co_(3.9)Cu_(0.1)O_(9-δ)在880 K下ZT值达到最大,为0.2.     

Copper-complex-linked polytungsto-bismuthate (-antimonite) chain containing sandwich Cu(II) ions partially modified with imidazole ligand

Two sandwich-type complexes Na9n(Cu(im)4(H2O)2)1.5n(Cu(im)4(H2O))n[{Cu(im)4}{Na(H2O)2}3{Cu3(im)2(H2O)}(XW9O33)2]2n .(xH2O)n (im=imidazole, X=Bi (1), Sb(2), x=42.5 (1), 40 (2)) have been synthesized and structurally characterized. Basic frameworks of 1 and 2 are built from sandwich-type [{Na(H2O) 2} 3{Cu3(im)2(H2O)}(XW9O33)2](9-) (X=Bi or Sb) anions and [Cu(im) 4](2+) cations. The Cu(2+) and Na(+) ions in the central belt are coordinated by alpha-[XW9O33](9-) units, im, and water molecules to form {CuO4(im)}, {CuO4(H2O)}, and {NaO4(H2O)2} groups in which Cu (2+) ions are partially modified with im ligands. These groups connect alternately forming a six-membered ring including six alpha-[XW9O 33](9-) units. Neighboring anions are further linked by [Cu(im) 4](2+) cations to display an unprecedented anionic chain, which is first observed in sandwich-type tungsto-bismuthate (-antimonite) system. Two kinds of isolated copper complexes and sodium ions are located as counterions, which cause three-dimensional packings of 1 and 2 to present interesting cage structures. The magnetic properties for 1 and 2 both indicate dominant antiferromagnetic interactions among trinuclear Cu(II) clusters.     

Ca2.9M0.1Co4O9 (M=Ag,La, Ba)复合氧化物体系的制备及电输运性能

采用柠檬酸溶胶-凝胶结合放电等离子烧结方法制备了p型Ca位掺杂的Ca2.9M0.1Co4O9(M=Ag, La, Ba)复合氧化物块体试样, 对其进行X 射线衍射(XRD)分析, 表明产物为单一物相, Ca位掺杂原子可以改变Ca2.9Co4O9多晶体的取向度, 掺杂试样取向度随着掺杂原子电负性的降低而提高|对其进行扫描电子显微镜(SEM)分析结果表明, 试样呈层状结构, 且层状结构随掺杂原子电负性降低而逐渐明显; 电性能分析结果表明, 测试温度范围内掺杂试样各温度点的电阻率随着掺杂原子电负性的降低而升高, 所有试样的载流子传输层未受影响, 导电机理未发生变化. 其中掺杂电负性最高的Ag原子的烧结体保持最低取向度的同时具有最低的电阻率, 在973 K时达6.87 mΩ·cm, 而掺杂电负性最低的Ba原子的烧结体具有高的取向度的同时具有较高的电阻率, 在973 K时达8.22 mΩ·cm.     

Synthesis and characterization of copper-, zinc-, manganese-, and cobalt-substituted dimeric heteropolyanions, [(alpha-XW9O33)2M3(H2O)3](n-) (n = 12, X =As(III), Sb(III), M = Cu(2+), Zn(2+); n = 10, X = Se(IV), Te(IV), M = Cu(2+) and [(alpha-AsW9O33)2WO(H2O)M2(H2O)2](10-) (M = Zn(2+), Mn(2+), Co(2+)

Interaction of the lacunary [alpha-XW9O33](9-) (X = As(III), Sb(III)) with Cu(2+) and Zn(2+) ions in neutral, aqueous medium leads to the formation of dimeric polyoxoanions, [(alpha-XW9O33)2M3(H2O)3](12-) (M = Cu(2+), Zn(2+); X = As(III), Sb(III)), in high yield. The selenium and tellurium analogues of the copper-containing heteropolyanions are also reported: [(alpha-XW9O33)2Cu3(H2O)3](10-) (X = Se(IV), Te(IV)). The polyanions consist of two [alpha-XW9O33] units joined by three equivalent Cu(2+) (X = As, Sb, Se, Te) or Zn(2+) (X = As, Sb) ions. All copper and zinc ions have one terminal water molecule resulting in square-pyramidal coordination geometry. Therefore, the title anions have idealized D3h symmetry. The space between the three transition metal ions is occupied by three sodium ions (M = Cu(2+), Zn(2+); X = As(III), Sb(III)) or potassium ions (M = Cu(2+); X = Se(IV), Te(IV)) leading to a central belt of six metal atoms alternating in position. Reaction of [alpha-AsW9O33](9-) with Zn(2+), Co(2+), and Mn(2+) ions in acidic medium (pH = 4-5) results in the same structural type but with a lower degree of transition-metal substitution, [(alpha-AsW9O33)2WO(H2O)M2(H2O)2](10-) (M = Zn(2+), Co(2+), Mn(2+)). All nine compounds are characterized by single-crystal X-ray diffraction, IR spectroscopy, and elemental analysis. The solution properties of [(alpha-XW9O33)2Zn3(H2O)3](12-) (X = As(III), Sb(III)) were also studied by 183W-NMR spectroscopy.     

Vibrational modes and structural characteristics of (Ba(0.3)Sr(0.7))[(Zn(x)Mg(1-x))(1/3)Nb(2/3)]O3 solid solutions

(Ba(0.3)Sr(0.7))[(Zn(x)Mg(1-x))(1/3)Nb(2/3)]O(3) (BSZMN) (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) solid solution ceramics were synthesized by the conventional solid-state sintering technique. Vibration spectra (Raman spectroscopy and Fourier transform far-infrared reflection spectroscopy, short for FTIR) and X-ray diffraction (XRD) were employed to evaluate the correlation between crystal structures and vibration modes of these solid solutions as a function of Mg(2+) ions replaced by Zn(2+) ions. It is verified that these ceramics present a phase transition, i.e., the crystal structure changes from hexagonal phase (P ?3m1, where x≤ 0.4) to the pseudocubic phase (I4/mcm, where x≥ 0.8) with increasing Zn(2+) content. The phase transition is a gradual process, the sample where x = 0.6 is of the transition phase, i.e., at x = 0.6, phase transition begins to appear from hexagonal phase to pseudocubic phase but is not complete. The phase transition is also verified by the FTIR spectra. Tilting of oxygen octahedra is the main reason for the phase transition. The phonon modes of the vibration spectra were assigned, the position and width were determined, and the correlation of phonon vibrations with the microstructure for the different atoms substituted in B'-site was found.     

Lightly doping Ca2+ in perovskite PrCoO3 for tailored spin states and electrical properties

A series of Pr(1-x)Ca(x)CoO(3) samples were prepared using a novel molten salt reaction that is convenient to obtain single phases avoiding aggregates compared to conventional solid state reactions. The formation reaction was monitored by X-ray diffraction combined with thermal analysis, and all samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and alternating current impedance. It is demonstrated that all Pr(1-x)Ca(x)CoO(3) samples crystallized in a pure orthorhombic perovskite structure. By increasing the doping level, the symmetry of the orthorhombic structure was enhanced, and is followed by an increase in the population of Co(3+) in the intermediate spin state. All samples exhibited typical semiconducting behavior, showing conductivities highly dependent on the Ca(2+) doping. The conduction for x = 0 shows a simple thermal activated process, which changed into a Mott's variable range hopping mechanism for x > 0. By increasing the Ca(2+) doping level, the relevant activation energy is decreased, while the density of the localized electronic state is increased.     

Synthesis and characterization of iron(III)-substituted, dimeric polyoxotungstates, [Fe(4)(H(2)O)(10)(beta-XW(9)O(33))(2)](n-) (n = 6, X = As(III), Sb(III); n = 4, X = Se(IV), Te(IV))

Interaction of the lacunary [alpha-XW(9)O(33)](9-) (X = As(III), Sb(III)) with Fe(3+) ions in acidic, aqueous medium leads to the formation of dimeric polyoxoanions, [Fe(4)(H(2)O)(10)(beta-XW(9)O(33))(2)](6-) (X = As(III), Sb(III)) in high yield. X-ray single-crystal analyses were carried out on Na(6)[Fe(4)(H(2)O)(10)(beta-AsW(9)O(33))(2)] x 32H(2)O, which crystallizes in the monoclinic system, space group C2/m, with a = 20.2493(18) A, b = 15.2678(13) A, c = 16.0689(14) A, beta = 95.766(2) degrees, and Z = 2; Na(6)[Fe(4)(H(2)O)(10)(beta-SbW(9)O(33))(2)] x 32H(2)O is isomorphous with a = 20.1542(18) A, b = 15.2204(13) A, c = 16.1469(14) A, and beta = 95.795(2) degrees. The selenium and tellurium analogues are also reported, [Fe(4)(H(2)O)(10)(beta-XW(9)O(33))(2)](4-) (X = Se(IV), Te(IV)). They are synthesized from sodium tungstate and a source of the heteroatom as precursors. X-ray single-crystal analysis was carried out on Cs(4)[Fe(4)(H(2)O)(10)(beta-SeW(9)O(33))(2)] x 21H(2)O, which crystallizes in the triclinic system, space group P macro 1, with a = 12.6648(10) A, b = 12.8247(10) A, c = 16.1588(13) A, alpha = 75.6540(10) degrees, beta = 87.9550(10) degrees, gamma = 64.3610(10) gamma, and Z = 1. All title polyanions consist of two (beta-XW(9)O(33)) units joined by a central pair and a peripheral pair of Fe(3+) ions leading to a structure with idealized C(2h) symmetry. It was also possible to synthesize the Cr(III) derivatives [Cr(4)(H(2)O)(10)(beta-XW(9)O(33))(2)](6-) (X = As(III), Sb(III)), the tungstoselenates(IV) [M(4)(H(2)O)(10)(beta-SeW(9)O(33))(2)]((16)(-)(4n)-) (M(n+) = Cr(3+), Mn(2+), Co(2+), Ni(2+), Zn(2+), Cd(2+), and Hg(2+)), and the tungstotellurates(IV) [M(4)(H(2)O)(10)(beta-TeW(9)O(33))(2)]((16-4n)-) (M(n+) = Cr(3+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), and Hg(2+)), as determined by FTIR. The electrochemical properties of the iron-containing species were also studied. Cyclic voltammetry and controlled potential coulometry aided in distinguishing between Fe(3+) and W(6+) waves. By variation of pH and scan rate, it was possible to observe the stepwise reduction of the Fe(3+) centers.     

纳米La0.8A’0.2Mn1-xCuxO3（A’=Ce and/or Sr）的制备、表征及其高效催化NO+CO的性能研究

采用柠檬酸-溶胶凝胶法制得钙钛矿型复合氧化物La0.8Ce0.2Mn1-xCuxO3(x=0.2,0.3,0.4),La0.8Sr0.2Mn0.6Cu0.4O3,La0.8Ce0.1Sr0.1Mn0.6 Cu0.4 O3,并采用X射线衍射(XRD)、扫描电镜(SEM)、比表面积(BET)、X射线光电子能谱(XPS)对其进行表征,测试了复合氧化物对CO+NO的催化活性。结果表明:La0.8Ce0.1Sr0.1Mn0.6Cu0.4O3催化活性最好,150℃时CO转化率91.8%,300℃时NO转化率100%;对于La0.8Ce0.2Mn1-xCuxO3(x=0.2,0.3,0.4),比表面积和颗粒的大小及分散度是影响催化活性的主要因素;对于La0.8Ce0.2Mn0.6Cu0.4O3,La0.8 Sr0.2 Mn0.6 Cu0.4 O3,La0.8 Ce0.1 Sr0.1 Mn0.6 Cu0.4 O3,催化剂的组成是影响催化活性的关键因素。     

Interconversion and Reactivity of Two Heterometallic Tin-Containing Cuboidal Clusters from [Mo(3)S(4)(H(2)O)(9)](4+): X-ray Structure of the Single Cube with an Mo(3)SnS(4) Core

The Mo(3)SnS(4)(6+) single cube is obtained by direct addition of Sn(2+) to [Mo(3)S(4)(H(2)O)(9)](4+). UV-vis spectra of the product (0.13 mM) in 2.00 M HClO(4), Hpts, and HCl indicate a marked affinity of the Sn for Cl(-), with formation of the more strongly yellow [Mo(3)(SnCl(3))S(4)(H(2)O)(9)](3+) complex complete in as little as 0.050 M Cl(-). The X-ray crystal structure of (Me(2)NH(2))(6)[Mo(3)(SnCl(3))S(4)(NCS)(9)].0.5H(2)O has been determined and gives Mo-Mo (mean 2.730 ?) and Mo-Sn (mean 3.732 ?) distances, with a difference close to 1 ?. The red-purple double cube cation [Mo(6)SnS(8)(H(2)O)(18)](8+) is obtained by reacting Sn metal with [Mo(3)S(4)(H(2)O)(9)](4+). The double cube is also obtained in approximately 50% yield by BH(4)(-) reduction of a 1:1 mixture of [Mo(3)SnS(4)(H(2)O)(10)](6+) and [Mo(3)S(4)(H(2)O)(9)](4+). Conversely two-electron oxidation of [Mo(6)SnS(8)(H(2)O)(18)](8+) with [Co(dipic)(2)](-) or [Fe(H(2)O(6)](3+) gives the single cube [Mo(3)SnS(4)(H(2)O)(12)](6+) and [Mo(3)S(4)(H(2)O)(9)](4+) (up to 70% yield), followed by further two-electron oxidation to [Mo(3)S(4)(H(2)O)(9)](4+) and Sn(IV). The kinetics of the first stages have been studied using the stopped-flow method and give rate laws first order in [Mo(6)SnS(8)(H(2)O)(18)](8+) and the Co(III) or Fe(III) oxidant. The oxidation with [Co(dipic)(2)](-) has no [H(+)] dependence, [H(+)] = 0.50-2.00 M. With Fe(III) as oxidant, reaction steps involving [Fe(H(2)O)(6)](3+) and [Fe(H(2)O)(5)OH](2+) are implicated. At 25 degrees C and I = 2.00 M (Li(pts)) k(Co) is 14.9 M(-)(1) s(-)(1) and k(a) for the reaction of [Fe(H(2)O)(6)](3+) is 0.68 M(-)(1) s(-)(1) (both outer-sphere reactions). Reaction of Cu(2+) with the double but not the single cube is observed, yielding [Mo(3)CuS(4)(H(2)O)(10)](5+). A redox-controlled mechanism involving intermediate formation of Cu(+) and [Mo(3)S(4)(H(2)O)(9)](4+) accounts for the changes observed.     

Rational enantioselective design of chiral heterobimetallic single-chain magnets: synthesis, crystal structures and magnetic properties of oxamato-bridged M(II)Cu(II) chains (M=Mn, Co)

A new series of neutral oxamato-bridged M(II)Cu(II) chiral chains of general formula [MCuL(x)(S)(m)(H(2)O)(n)]·aS·bH(2)O [L(1)=(M)-1,1'-binaphthalene-2,2'-bis(oxamate) with M=Mn (1a) and Co (1b); L(2)=(P)-1,1'-binaphthalene-2,2'-bis(oxamate) with M=Mn (2a) and Co (2b)] and the analogous racemic chains of formula [MCuL(3)(S)(m)(H(2)O)(n)]·aS·bH(2)O [L(3)=1,1'-binaphthalene-2,2'-bis(oxamate) with M=Mn (3a) and Co (3b)] have been prepared by reaction of the corresponding dianionic oxamatocopper(II) complex [Cu(L(x))](2-) with Mn(2+) or Co(2+) cations in either dimethylformamide (DMF) or dimethyl sulfoxide (DMSO). Solid circular dichroism (CD) spectra of the bimetallic chain compounds were recorded to establish their chiral and enantiomeric nature. They exhibit maximum positive and negative Cotton effects, each pair of enantiomeric chains being non-superimposable mirror images. The crystal structures of the Mn(II)Cu(II) (1a-3a) and the Co(II)Cu(II) (1b and 2b) chain compounds were solved by single-crystal X-ray diffraction methods. Our attempts to obtain X-ray quality crystals of 3b were unsuccessful. The values of the shortest interchain Mn···Mn and Co···Co distances are indicative of a good isolation of neighbouring chains in the crystal lattice, which is caused by the bulky aromatic ligand. Although all the Mn(II)Cu(II) and Co(II)Cu(II) chains exhibit ferrimagnetic behaviour (-J(MnCu)=18.9-26.6 cm(-1) and -J(CoCu)=19.5-32.5 cm(-1)), only the enantiopure Co(II)Cu(II) chains (1b and 2b) show slow magnetic relaxation at low temperatures (T(B)=0.6-1.8 K), which is a characteristic of single-chain magnets (SCMs) and is related to the magnetic anisotropy of the high-spin Co(II) ion. Analysis of the SCM behaviour of 1b and 2b, based on Glauber's theory for an Ising one-dimensional system, shows a thermally activated mechanism for the magnetic relaxation (Arrhenius law dependence). The energy barriers (E(a)) to reverse the magnetisation direction are 8.2 (1b) and 8.1cm(-1) (2b), whereas the pre-exponential factor (τ(0)) is 1.9×10(-8) (1b) and 6.0×10(-9) s (2b). Interestingly, the racemic Co(II)Cu(II) chain analogue, 3b, showed no evidence of SCM behaviour.     

Synthesis and characterization of self-assembled c-axis oriented Bi2Sr3Co2O(y) thin films by the sol-gel method

Bi(2)Sr(3)Co(2)O(y) thin films are prepared on SrTiO(3) (100), (110) and (111) single crystal substrates using the sol-gel method. All the thin films are c-axis oriented regardless of the orientation of the substrate suggesting self-assembled c-axis orientation, and X-ray photoelectron spectroscopy results give evidence of coexistence of Co(3+) and Co(2+) ions in the derived films. Transmission electronic microscopy observations reveal that all samples are c-axis oriented with no obvious differences for different samples, and the c-axis lattice constant is determined as ~15 ? suggesting the misfit structure. A phenomenological thermodynamic phase diagram for self-assembled c-axis orientation is established for misfit cobaltate-based films using chemical solution deposition. All samples behave like semiconductors due to the coexistence of Co(3+)/Co(2+) ions, and the resistivity at 350 K is ~47, 39 and 17 mΩ cm for the thin films on SrTiO(3) (100), (110) and (111), respectively, whereas the Seebeck coefficient at 300 K is 97, 89 and 77 μV K(-1). The successful attainment of Bi(2)Sr(3)Co(2)O(y) thin films with self-assembled c-axis orientation will provide an effective prototype for investigation of growth mechanisms in complex oxide thin films with a misfit structure.     

Cobalt(II)/nickel(II)-centered Keggin-type heteropolymolybdates: syntheses, crystal structures, magnetic and electrochemical properties

New Keggin-type cobalt(II)/nickel(II)-centered heteropolymolybdates, (C3H5N2)6[Co(II)Mo12O40]10H2O (1) and (NH4)3(C4H5N2O2)3[Ni(II)Mo12O40] (2), were isolated and characterized by IR, UV-vis, single-crystal X-ray diffraction, thermogravimetric, magnetic, as well as electrochemical analyses. The polyanion in the two compounds displays the well-known alpha-Keggin structure, which is composed of four Mo3O13 units formed by edge-sharing octahedra. Four Mo3O13 units connect each other by vertices, and the Co(2+) or Ni(2+) is located in the center. Magnetic measurements show that the central Co(2+) and Ni(2+) are in high spin states (with S = 3/2 and S = 1, respectively) exhibiting paramagnetic behaviors. Cyclic voltammetric experiments for 1 represent a quasi-reversible one-electron redox Co(3+)/Co(2+) couple and two four-electron reversible redox processes ascribed to Mo centers, while 2 only shows two four-electron redox processes attributed to Mo centers in pH = 0.5 H2SO4 solution.