一例混合配体构筑的钴(Ⅱ)一维配位聚合物的合成、晶体结构与磁性质

基于萘膦酸羧酸酯配体和氯化钴在水热条件下自组装得到配位聚合物[Co(5-pncee)(4,4′-bpy)(H₂O)₃(5-pnceeH₂)]·2H₂O(1)(5-pncee H₂=5-phosphono -naphthalene-1-carboxylic acid ethyl ester, 4,4′-bpy=4,4′-bipyridinyl)。采用单晶衍射(X-Ray)、元素分析(EA)、红外光谱(FT-IR)、粉末衍射(PXRD)、热重分析(TG-DTG)对配位聚合物进行晶体结构和热稳定性表征。晶体结构分析表明:该配位聚合物结晶于三斜晶系,P1空间群,a=0.824 06(6) nm,b=1.014 48(9) nm,c=1.151 44(8) nm。配位聚合物呈线性链状结构。相邻的链由中等强度的氢键连接,形成超分子层,层间被膦酸配体的有机基团所填充。通过研究配位聚合物1的磁性质,表明Co(II)离子存在自旋轨道耦合和/或Co(II)离子之间存在反铁磁相互作用。     

吡嗪基联吡啶锌配位聚合物的结构及发光性质

以2,6-双(2-吡嗪基)-4,4'-联吡啶为配体,对苯二甲酸为辅助配体,水热条件下合成了锌配位聚合物[Zn(dpb)(p-bdc)]n·0.5n(dpb),并用元素分析、红外光谱、X射线单晶衍射对此配位聚合物进行了测试分析.单晶结构解析表明,它是通过对苯二甲酸桥连锌离子形成一维链结构的配位聚合物.此外,对配体及配位聚合物的荧光进行了研究.     

Bi26-x-yMxNyO40(M,N=Fe,Co, Gd)软铋矿薄膜的制备和强磁光效应

磁光材料是现代光通信产业中不可或缺的关键功能材料。为了实现光通信器件的小型化,高质量磁光薄膜材料受到关注。软铋矿型Bi₂₅FeO₄₀具有高对称性的立方晶体结构,单位体积所含铋离子浓度高,理论上应具有较强的磁光效应,但却因为磁性偏弱、制备困难等缺点而限制了其应用。本文采用射频磁控溅射法,在掺钇二氧化锆(YSZ)基底上沉积获得具有立方相软铋矿型结构的Bi_26-x-yM_xN_yO₄₀ (M, N=Fe, Co, Gd)磁光薄膜,并对其形貌、磁性、透过率、磁圆二色信号等进行表征。结果表明,薄膜均较为平整,厚度约为190 nm,在近红外区的透过率约为60%~70%。薄膜的磁性随着掺杂离子含量的提高逐渐增强。Bi_13.6Gd_2.7Co_4.0Fe_5.7O₄₀/YSZ薄膜具有强磁光效应,在716 nm处的磁圆二色光谱信号高达到1 710 deg/cm,有望应用于集成光隔离器等光通信器件中。     

两例Ni(Ⅱ)/Cu(Ⅱ)配位聚合物的合成、晶体结构及热稳定性研究

在溶剂热的条件下,合成了两例金属-有机配位聚合物:{[Ni(H2O)2(1,3-BIP)2]·TFBDC}n(1)和{[Cu3(H2O)4(1,3-BIP)6]·(BTC)2·(H2O)15}n(2)(1,3-BIP为1,3-二(咪唑)丙烷,H2TFBDC为2,3,5,6-四氟对苯二甲酸和H3BTC为1,3,5-均苯三酸),并利用红外光谱、元素分析和X-射线单晶衍射等技术手段对其结构进行了表征.X-射线单晶衍射结果表明配位聚合物1呈现一维环形链构型,并通过分子间氢键作用进一步连接形成三维超分子网络结构.配位聚合物2呈现出(4,4)拓扑的二维层状结构.此外,研究了两例配位聚合物的热稳定性能.     

二维锰(Ⅱ)配位聚合物[Mn2(bppc)4(H2O)]n·2nH2O的合成、晶体结构及热稳定性研究

以2,6-双(2-吡嗪基)吡啶-4-对苯甲酸和MnCl2为原料,在水热条件下合成了二维锰(Ⅱ)配位聚合物[Mn2(bppc)4(H2O)]n·2nH2O,并用元素分析、红外光谱、X射线单晶衍射对此配位聚合物进行了表征,测定结果表明,晶体属于单斜晶系,P2(1)/c空间群,晶胞参数为:a=10.3918(9) nm, b=24.519(2) nm ,c=7.0140(6) nm,α=90°,β=105.0890(10)°,γ=90°.此配位聚合物中MnII之间通过配体中吡嗪环上的氮和羧基氧的桥连形成一维链状结构,一维链再通过羧基基团上的氧的进一步桥连形成二维结构.另外,热重分析表明,此配位聚合物具有较好的热力学稳定性.     

吡嗪席夫碱银配位聚合物的晶体结构、发光性质和抗菌活性

利用2-乙酰基吡嗪和异烟肼在无水乙醇中反应得到席夫碱化合物N-[(1-吡嗪基)-1-亚甲基]异烟酰肼(L)。以L和硝酸银为原料,通过扩散法合成了配位聚合物{[Ag₃L₂(NO₃)₂]CH₃CN}_n,并通过X-射线单晶衍射、元素分析、红外光谱、荧光光谱对其进行结构解析和性质表征。单晶衍射分析结果表明,该配位聚合物属单斜晶系,P2₁/c空间群,晶胞参数为a=0.611 70(10) nm,b=1.347 08(3) nm,c=2.018 69(4) nm,V=1.661 06(6) nm³,Z=2,Mr=970.19,Dc=1.940 g/cm³,配体分子以银离子为连接点形成二维网状结构。荧光光谱分析表明配体和配位聚合物均有较好的发光性能,且配位聚合物荧光强度优于配体。抗菌活性表明,配位聚合物对白色葡萄球菌、藤黄八叠球菌及枯草芽孢杆菌有较好的特异性,具有良好的医药应用前景。     

ZnO基稀磁半导体材料的最新研究进展

ZnO基稀磁半导体是目前最有应用前景的自旋电子器件候选材料之一.室温铁磁性材料的可控制备及其磁性起源是目前自旋电子学急待解决的两个基本问题.本文围绕这两个问题对目前国内外关于ZnO基稀磁半导体材料的实验和理论最新研究进行了综述.     

CdGd2(WO4)4单晶的结构与磁性研究

采用提拉法生长尺寸为φ12mm×50mm的钨酸钆镉单晶,名义组分为CdGd2(WO4)4,研究表明该晶体具有白钨矿结构,属于四方晶系,晶格常数为a=b=0.5203nm,c=1.1359nm.样品的磁性测量质量比磁化强度与温度σ-T曲线,以及室温下磁化曲线σ-H,都表明晶体具有朗之万顺磁性,但又具有磁各向异性,室温下的x//=3.5018×10-3,χ⊥=3.4403×10-2;电子自旋共振实验也显示出各向异性的特征.a-b平面的两个最近邻Gd3+离子间电子自旋耦合作用较强,沿晶体c轴方向Gd3+离子间电子自旋耦合作用较弱,晶体的磁各向异性体现了晶体的结构特征.     

1,3-间苯咪唑及间苯二甲酸根一维镍(Ⅱ)配位聚合物的合成、晶体结构及性质

以间苯咪唑(1,3-bib)和间苯二甲酸(H2MPA)为配体,采用水热法合成了1个一维镍(Ⅱ)配位聚合物[Ni(1,3-bib) (MPA)·2H2O]n(1).并对该配位聚合物进行了元素分析、红外光谱、固体紫外、热重(TGA)和Ⅹ-射线粉末衍射(PXRD)等表征,并用Ⅹ-射线单晶衍射法测定了它的单晶结构.该配位聚合物属于正交晶系,Pnma空间群,为一维结构.室温下固体紫外测试结果显示,配位聚合物具有强的紫外吸收.     

1,2,3-三唑二羧酸镉(II)配位聚合物的合成、晶体结构与性质

利用低温水热法合成了两个新的镉配位聚合物:[Cd(L1)(H2O)2]n(1)和[Cd(L2)(H2O)]n(2)(H2L1=1-羧甲基-4-(2-羧甲氧基苯基)-2H-1,2,3-三唑,H2L2=2-羧甲基-4-(2-羧甲氧基苯基)-2H-1,2,3-三唑,利用X-射线单晶衍射、红外光谱、核磁共振(1H NMR)、元素分析、X-射线粉末衍射和热重分析对配体和配位聚合物进行了表征.晶体结构分析表明配位聚合物1和2为二维结构;两种完全去质子化的配体以μ4为配位模式分别与镉离子形成二维配位聚合物,配位聚合物1呈现双节点(4,4)连接的{44·62}拓扑结构,配位聚合物2则呈现{43·63}拓扑结构.同时,在室温下研究了配体和配位聚合物的固体荧光性质.     

实用化Bi系超导带材的制备工艺研究进展

超导材料具备优异的电学和磁学性能,具有很大的发展前景。目前应用最多的是NbTi和Nb₃Sn两种低温超导材料,但是其需要在4.2 K超低温下(液氦制冷)使用,成本高昂。Bi-2223的临界超导温度高达110 K,液氮制冷就可以使用,展现出良好的实用价值。Bi-2223是一种层状结构的化合物,常被制备成带材,使层面方向平行于带材表面,以发挥其最佳超导性能。但是将其实用化过程中还存在着Bi-2223相纯度不高、致密度不够、晶粒连接性不佳、抗拉伸强度和延伸率不足等问题。为了能够实用化,必须兼顾电学性能、机械性能、制冷技术等因素。本文综述了实用化Bi系超导带材的制备工艺与研究进展,分别对Bi-2223前驱粉制备工艺、Bi-2223带材的制备工艺及研究进展、Bi-2223超导带材实用化进展等进行介绍,为其制备工艺和实用化的进一步深入研究提供参考。     

Structure of simple and complex noble gas fluorides

The structural parameters of simple and complex fluorides of noble gases in different aggregate states have been analyzed. The data on their molecular and crystal structure are reported. The structural features of simple, coordination, polymer, and clathrate-like compounds of krypton and xenon fluorides are considered     

吡啶-2,6-二甲酸铅配位聚合物的绿色合成与表征

以吡啶-2,6-二甲酸(H₂pda)和乙酸铅为原料,用室温固相法合成配位聚合物[Pb(μ-pda)]_n (1),用元素分析、X射线粉末衍射和单晶衍射、红外光谱对聚合物1的组成和结构进行了表征,并研究其热稳定性和荧光性能。单晶结构显示,1属于单斜晶系,P2₁/n空间群,晶胞参数为a=0.980 84(11) nm,b=0.554 73(7) nm,c=1.433 62(16)nm,β=105.093(3)°。1的分子结构由2个Pb²⁺和2个pda^2-构成,含2个[Pb(μ-pda)]单元,每个Pb²⁺与来自pda^2-的6个氧原子和1个氮原子配位,形成了七配位的单帽三角棱柱构型。热稳定性研究表明,1在氮气气氛中的热分解反应包括配位聚合物骨架的坍塌和配体的氧化分解,热解残余物为PbO。荧光性能测试结果表明,该配位聚合物具有荧光性,其荧光可能来自配体内部的π^*→π电荷跃迁。     

Structure and dynamics of oxide melts and glasses: A view from multinuclear and high temperature NMR

From a presentation of the various nuclear magnetic resonance (NMR) experiments that allows to characterize the local structure and dynamics of oxide glasses and melts, we show that it becomes possible to evidence not only the details of the coordination state of the constituting atoms but also the nature of polyatomic molecular motifs extending over several chemical bonds.     

Orientation of Guest Molecules and Formation of Mesoporous Silica Induced by Layered Silicate-Organic Interactions

Previous work has suggested that the molecular ordering in some main-chain thermotropic polymers is biaxial nematic. In one, a 60/40 copolyester of p-hydroxybenzoic acid and ethylene terephthalate residues, there is evidence for a temperature range where molecular rotation about the local chain axes occurs without an accompanying loss of overall chain segment alignment. The present paper reports a theoretical and experimental investigation of whether a magnetic field, applied to the polymer when held at such temperatures, can favour the formation of optical monodomains which are large enough to give an unambiguous uniaxial or biaxial interference figure.     

Rare earth based bulk metallic glasses

Recently, the rare earth based bulk metallic glasses (REBMGs) have attracted increasing interest due to their unique properties and potential applications as functional glassy materials. These REBMGs display many fascinating properties such as heavy fermion behavior, thermoplastic properties near room temperature, excellent magnetocaloric effect, hard magnetism, and polyamorphism, all of which are of interest not only for basic research but also for metallurgy and technology. These characteristics and properties are ascribed to the unique electronic, magnetic and atomic structures of the REBMGs. In this review paper, the fabrication, glass-forming ability, polyamorphism, elastic, thermal, and physical properties are summarized and discussed. Owing to the unique electronic structure of rare earth elements, the electric and magnetic properties of the REBMGs are especially addressed. The works have implications for seeking novel metallic glasses with controllable properties and for understanding the nature of glass formation. The development of REBMGs as functional materials might promote and extend the commercial applications of metallic glasses.     

混合碱媒介法制备磁性铁酸钴纳米粉体

采用混合碱媒介法制备铁酸钴磁性纳米粉体,探索了制备工艺,利用X射线衍射仪、透射电镜、振动样品磁强计对样品的结构和磁性能进行了研究.结果表明:以硝酸盐或醋酸盐为原料用混合碱法可制得粒度均匀、粒径范围在10～50 nm的铁酸钴纳米粉,所制备的样品具有粒径小、粒度均匀、分散性较好的特点,中等饱和磁化强度、高矫顽力,是性能优良的磁性材料.     

Magnetothermal investigation of crystallization of Ni–P amorphous alloys

A new magnetic phase analysis method is presented and its application to a certain class of amorphous alloys is thoroughly discussed. Special attention is paid to the size of clusters with strong magnetic properties that form the separating phase. This magnetothermal (MT) method reveals the formation or disappearance of a phase with strong magnetic properties, and in certain cases it can give valuable information, even in the temperature range where the sample is paramagnetic. The accuracy and applicability of the MT method are discussed. Combining this method with differential scanning calorimetry (DSC), the transformations in melt-quenched (MQ) and electrolessly deposited (ED) amorphous Ni–P alloys with hypoeutectic and close to eutectic composition are investigated under the condition of a constant heating rate. Up to four stages of Ni precipitation in the alloys are revealed, depending on the phosphorous content and the method of sample preparation.