六方硼碳氮化合物的溶剂热合成与表征

采用溶剂热合成方法,以无水乙腈、叠氮化钠和四氟硼酸钠为原料,以苯为溶剂,在温度为400℃条件下,成功合成出了硼碳氮(BCN)三元化合物.利用X射线粉末衍射(XRD)、Fourier变换红外光谱(FTIR)、透射电子显微镜(TEM)、选区电子衍射(SAED)、X射线能谱(EDS)和电子能量损失谱(EELS)对合成产物进行了表征.XRD和SAED分析表明,合成产物为六方相,晶格常数为a=0.2678nm,c=0.6639nm;TEM结果表明,合成产物中存在纳米棒和四方柱状块体BCN;EELS和EDS分析表明,产物由B,C,N三种元素组成,化学式为B0.23C0.60N0.17;FTIR分析表明样品中存在C—N,B—C和B—N键,表明B,C,N三元素之间达到了原子级化合.     

Solvothermal syntheses of high-nuclearity vanadium(III) clusters

Superheating alcohol solutions of simple trimetallic vanadium(III) precursors gives the octa- and decametallic vanadium(III) clusters [V(8)(OEt)(8)(OH)(4)(O(2)CPh)(12)] (1) and [V(10)(OMe)(20)(O(2)CMe)(10)] (2). Cluster 2 is the largest vanadium(III) cluster synthesised to date. Thus solvothermal synthetic techniques are an excellent route to high-nuclearity vanadium(III) clusters. Both 1 and 2 consist of a planar or near-planar array of V(III) ions. The metal ions in 1 are bridged by either a micro(2)-hydroxide and two micro(2)-benzoate groups or two micro(2)-ethoxides and a micro(2)-benzoate groups, the two bridging arrangements alternating around the ring. In 2 each pair of neighbouring metal ions is bridged by two micro(2)-methoxides and a micro(2)-acetate, and this molecule is the V(III) analogue of Lippard's famous "ferric wheel". Preliminary magnetic susceptibility studies show the exchange coupling in both complexes to be antiferromagnetic in nature, with the coupling stronger in 1 than in 2.     

Fabrication of Ordered Macroporous CdS and ZnS by Colloidal Crystal Template

Ordered macroporous semiconductors CdS and ZnS with regular arrays of spherical pores have been fabricated by poly (styrene-acrylic) (PSA) colloidal crystal template. It was found that the exact three-dimensional (3D) structure of the template had been imprinted in the final material.     

From an Impurity to the Pure Compound – an Electron Microscopy Study

The power of electron microscopy techniques for the determination of structure and composition of marginal byproducts is demonstrated for rare earth metal cluster compounds. Small amounts of the new phase Gd₄GaI₆ in samples with the nominal composition Gd₇GaI₁₂ could only be identified by a combined approach of EDX, electron diffraction and HRTEM. The structure of Gd₄GaI₆ can be assigned to the Y₄BBr₆‐type containing chains of Gd₆ octahedra which are centered by Ga atoms. The results of the electron microscopy study initiated the synthesis of homogeneous samples of the new compound Gd₄GaI₆ by applying the correct ratio of the starting materials.     

Heterometallic Clusters [CuSn3S9]5− and [Cu6Sn6S20]10−: Solvothermal Synthesis and Characterization of 4f–3d Thiostannates

Two types of 4f–3d thiostannates with general formula [Hen]₂[Ln(en)₄(CuSn₃S₉)] ? 0.5 en ( Ln1 ; Ln=La, 1 ; Ce, 2 ) and [Hen]₄[Ln(en)₄]₂[Cu₆Sn₆S₂₀] ? 3 en ( Ln2 ; Ln=Nd, 3 ; Gd, 4 ; Er, 5 ) were prepared by reactions of Ln₂O₃, Cu, Sn, and S in ethylenediamine (en) under solvothermal conditions between 160 and 190 °C. However, reactions performed in the range from 120 to 140 °C resulted in crystallization of [Sn₂S₆]^4? compounds and CuS powder. In 1 and 2 , three SnS₄ tetrahedra and one CuS₃ triangle are joined by sharing sulfur atoms to form a novel [CuSn₃S₉]^5? cluster that coordinates to the Ln³⁺ ion of [Ln(en)₄]³⁺ (Ln=La, Ce) as a monodentate ligand. The [CuSn₃S₉]^5? unit is the first thio‐based heterometallic adamantane‐like cluster coordinating to a lanthanide center. In 3 – 5 , six SnS₄ tetrahedra and six CuS₃ triangles are connected by sharing common sulfur atoms to form the ternary [Cu₆Sn₆S₂₀]^10? cluster, in which a Cu₆ core is enclosed by two Sn₃S₁₀ fragments. The topological structure of the novel Cu₆ core can be regarded as two Cu₄ tetrahedra joined by a common edge. The Ln³⁺ ions in Ln1 and Ln2 are in nine‐ and eightfold coordination, respectively, which leads to the formation of the [CuSn₃S₉]^5? and [Cu₆Sn₆S₂₀]^10? clusters under identical synthetic conditions. The syntheses of Ln1 and Ln2 show the influence of the lanthanide contraction on the quaternary Ln/Cu/Sn/S system in ethylenediamine. Compounds 1 – 5 exhibit bandgaps in the range of 2.09–2.48 eV depending on the two different types of clusters in the compounds. Compounds 1 , 3 , and 4 lost their organic components in the temperature range of 110–350 °C by multistep processes.     

A combination of lacunary polyoxometalates and high-nuclear transition-metal clusters under hydrothermal conditions. Part II: From double cluster, dimer, and tetramer to three-dimensional frameworks

The hydrothermal reactions of trivacant Keggin A-alpha-XW(9)O(34) polyoxoanions (X=P(V)/Si(IV)) with transition-metal ions (Ni(II)/Cu(II)/Fe(II)) in the presence of amines result in eight novel high-nuclear transition-metal-substituted polyoxotungstates [{Ni(7)(mu(3)-OH)(3)O(2)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))][{Ni(6)(mu(3)-OH)(3)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))][Ni(dap)(2)(H(2)O)(2)]4.5 H(2)O (1), [Cu(dap)(H(2)O)(3)](2)[{Cu(8)(dap)(4)(H(2)O)(2)}(B-alpha-SiW(9)O(34))(2)]6 H(2)O (2), (enH(2))(3)H(15)[{Fe(II) (1.5)Fe(III) (12)(mu(3)-OH)(12)(mu(4)-PO(4))(4)}(B-alpha-PW(9)O(34))(4)]ca.130 H(2)O (3), [{Cu(6)(mu(3)-OH)(3)(en)(3) (H(2)O)(3)}(B-alpha-PW(9)O(34))]7 H(2)O (4), [{Ni(6)(mu(3)-OH)(3)(en)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))]7 H(2)O (5), [{Ni(6)(mu(3)-OH)(3)(en)(2)(H(2)O)(8)}(B-alpha-PW(9)O(34))]7 H(2)O (6), [{Ni(6)(mu(3)-OH)(3)(dap)(2)(H(2)O)(8)}(B-alpha-PW(9)O(34))] 7 H(2)O (7), and [{Ni(6)(mu(3)-OH)(3)(en)(3)(H(2)O)(6)}(B-alpha-SiW(9)O(34))][Ni(0.5)(en)] 3.5 H(2)O (8) (en=ethylenediamine, dap=1,2-diaminopropane). These compounds have been structurally characterized by elemental analyses, IR spectra, diffuse reflectance spectra, thermogravimatric analysis, and X-ray crystallography. The double-cluster complex of phosphotungstate 1 simultaneously contains hepta- and hexa-Ni(II)-substituted trivacant Keggin units [{Ni(7)(mu(3)-OH)(3)O(2)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))](2-) and [{Ni(6)(mu(3)-OH)(3)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))]. The dimeric silicotungstate 2 is built up from two trivacant Keggin [B-alpha-SiW(9)O(34)](10-) fragments linked by an octa-Cu(II) cluster. The main skeleton of 3 is a tetrameric cluster constructed from four tri-Fe(III)-substituted [Fe(III) (3)(mu(3)-OH)(3)(B-alpha-PW(9) O(34))](3-) Keggin units linked by a central Fe(II) (4)O(4) cubane core and four mu(4)-PO(4) bridges. Complex 4 is an unprecedented three-dimensional extended architecture with hexagonal channels built by hexa-Cu(II) clusters and trivacant Keggin [B-alpha-PW(9)O(34)](9-) fragments. The common feature of 5-8 is that they contain a B-alpha-isomeric trivacant Keggin fragment capped by a hexa-Ni(II) cluster, very similar to the hexa-Ni(II)-substituted trivacant Keggin unit in 1. Magnetic measurements illustrate that 1, 2, and 5 have ferromagnetic couplings within the magnetic metal centers, whereas 3 and 4 reveal the antiferromagnetic exchange interactions within the magnetic metal centers. Moreover, the magnetic behavior of 4 and 5 have been theoretically simulated by the MAGPACK magnetic program package.     

Imaging of Self‐Assembled Structures: Interpretation of TEM and Cryo‐TEM Images

The investigation of solution‐borne nanostructures by transmission electron microscopy (TEM) is a frequently used analytical method in materials chemistry. In many cases, the preparation of the TEM sample involves drying and staining steps, and the collection of images leads to the interaction of the specimen with the electron beam. Both aspects call for cautious interpretation of the resulting electron micrographs. Alternatively, a near‐native solvated state can be preserved by cryogenic vitrification and subsequent imaging by low‐dose cryogenic TEM. In this Minireview, we provide a critical analysis of sample preparation, and more importantly, of the acquisition and interpretation of electron micrographs. This overview should provide a framework for the application of (cryo)‐TEM as a powerful and reliable tool for the analysis of colloidal and self‐assembled structures with nanoscopic dimensions.     

Structure and properties of iron oxide clusters: From Fe6 to Fe6O20 and from Fe7 to Fe7O24

Geometrical and electronic structures of the neutral and singly negatively charged Fe₆O_n and Fe₇O_m clusters in the range of 1 ≤ n ≤ 20 and 1 ≤ m ≤ 24, respectively, are computed using density functional theory with the generalized gradient approximation. The largest clusters in the two series, Fe₆O₂₀ and Fe₇O₂₄, can be described as Fe(FeO₄)₅ and Fe(FeO₄)₆ or alternatively as [FeO₅](FeO₃)₅ and [FeO₆](FeO₃)₆, respectively. The Fe₆O₂₀ and Fe₇O₂₄ clusters possess adiabatic electron affinities (EA_ad) of 5.64 eV and 5.80 eV and can be attributed to the class of hyperhalogens since FeO₄ is an unique closed‐shell superhalogen with the EA_ad of 3.9 eV. The spin character of the lowest total energy states in both series changes from ferromagnetic to ferrimagnetic or antiferromagnetic when the first Fe? O? Fe bridge is formed. Oxidation decreases substantially the polarizability per atom of the initial bare clusters; namely, from 5.98 ų of Fe₆ to 2.47 ų of Fe₆O₂₀ and from 5.67 ų of Fe₇ to 2.38 ų of Fe₇O₂₄. The results of our computations pertaining to the binding energies of O, Fe, O₂, and FeO in the Fe₇O_m series provide an explanation for the experimentally observed abundance of the iron oxide nanoparticles with stoichiometric compositions. © 2016 Wiley Periodicals, Inc.     

Grafting and thermal stripping of organo-bimetallic clusters on AU surfaces: toward controlled CO/RU aggregates

The controlled stoichiometry of heterometallic carbonyl clusters make them attractive precursors for the stabilization of bare metal alloy clusters for magnetic applications. The mixed-metal molecular cluster [RuCo3(H)(CO)12] has been functionalized with the phosphane-thiol ligand Ph2PCH2CH2SH to allow subsequent anchoring on a gold surface. The resulting tetrahedral cluster [RuCo3(H)(CO)11(Ph2PCH2CH2SH)] (1) has been characterized by X-ray diffraction and the P-monodentate ligand is axially bound to a cobalt center and trans to the ruthenium cap. This synthesis also yielded the product of oxidative coupling, in which two SH groups were coupled intermolecularly to give a disulfide ligand that links two tetrahedral cluster units in [{RuCo3(H)(CO)11(Ph2PCH2CH2S)}2] (2). This cluster has also been characterized by X-ray diffractions studies. After deposition of 1 on a Au(111) surface by self-assembly, the carbonyl ligands were stripped off by thermal annealing in ultra-high vacuum (UHV) to form a metallic species. X-ray photoelectron spectroscopic measurements performed as a function of the annealing temperature show that the cobalt and ruthenium centers converge towards metallic character and that the stoichiometry of the alloy is retained during the annealing process. Preliminary X-ray absorption spectroscopy (XAS) synchrotron experiments indicate that clusters 1 and 2 behave similarly, which is consistent with the retention of their tetrahedral units on the gold surface after transformation of the thiol function or breaking of the disulfide bond to form Au--S bonds, respectively, has occurred.     

四维扫描透射电子显微镜技术：从材料微观结构到物性分析

扫描透射电子显微镜(Scanning transmission electron microscopy,STEM)目前已经达到了原子级分辨率,并且由于其具有灵活的多通道成像能力以及强大的与谱学分析相结合的特点,因此在材料科学、生命科学等领域展现出强大的微尺度表征能力。但传统STEM的探测器受单像素积分式探测机制的限制,使其只能收集特定角度的散射电子,这导致不仅丢失了散射电子的角分辨信息,还降低了入射电子的剂量效率,因此迫切需要发展全新成像技术来实现高通量、高电子剂量效率成像。近年来,电子探测技术和分区或像素化探测器的研发联合计算机运算、存储能力的大幅提高,推动了四维扫描透射电子显微镜技术(Four-dimensional scanning transmission electron microscopy,4D-STEM)的蓬勃发展,并为最大化、最高效挖掘散射电子信息带来希望。在采集4D-STEM数据时,会聚电子束在样品平面上进行二维扫描,与此同时使用一块具有高帧速、高动态范围以及高信噪比的像素化阵列式探测器在远场收集二维的衍射数据。因为这些衍射数据是角度解析的,所以既可以用来进行常规的...