基于柔性羧酸配体和含氮辅助配体的金属有机配位聚合物的合成、结构及表征

本文通过水热合成的方法制备得到了一个新型的二维金属有机配位聚合物[Co2(L1)(4,4’-bipy)(3H2O).2H2O]n (1), (H4L1 = 3,3'-(1,4-苯二氧基)二邻苯二甲酸; 4,4’-bipy = 4,4’-联吡啶),并对其结构进行了系统的表征。研究表明3,3'-(1,4-苯二氧基)二邻苯二甲酸配体中的羧酸采用μ1-η1-η0和μ1-η1-η1两种桥联的方式跟两个钴离子配位形成十四圆环,形成的十四圆环被3,3'-(1,4-苯二氧基)二邻苯二甲酸配体连接进一步形成之字形的一维链状结构。最终,辅助配体4,4’-联吡啶将这些一维链状结构连接起来形成二维的(44)-sql网状拓扑结构。在本文中,我们还一步研究了这个配位聚合物的红外光谱以及热稳定性。     

二维配位聚合物[Cu(μ-Ⅰ)(μ-4,4-bipy)]n的溶液合成与晶体结构

碘化亚铜和4,4'-二联吡啶在溶液中反应的二种方法可制备出标题化合物的2个不同红色晶体,结构表征出两种晶体分别是单斜C2/c(1)和四方I41/acd(2)空间群.在[Cu(μ-Ⅰ)(μ-4,4-bipy)]n结构中,铜原子是处于与2个碘原子和2个相互扭曲4,4'-二联吡啶中的氮原子的扭曲四面体配位环境中,2个[Cu(μ-Ⅰ)]2单元和2个桥式4,4'-二联吡啶配体形成1个[Cu2(μ-Ⅰ)2(μ-4,4-bipy)]2直角单元,4个直角单元经4个4,4'-二联吡啶侧式桥联而形成1个大的八角环,并由此与直角单元相互垂直而形成1个二维框架结构.     

钴配合物[Co_2(H_2O)_8(C_(10)H_8N_2)_2]·(HO_3PCH_2CH_2SO_3)(SO_4)(H_2O)_4的合成与晶体结构研究

用硫酸钴、4,4'-联吡啶和2-磺酸基乙基膦酸合成了一个新颖的钴化合物:[Co_2(H_2O)_8(C_(10)H_8N_2)_2]·(HO_3PCH_2CH_2SO_3)(SO_4)(H_2O)_4,并对其进行了红外.元素分析、热重测试,通过单晶衍射仪测定了其晶体结构.结果表明,配合物属单斜晶系C2/c空间群,分子式为C_(22)H_(45)Co_2N_4O_(22)PS_2,分子量为930.57,晶胞参数为a=19.8456(18),b=11.2957(10),c=34.719(3)(A),β=106.095(3)°,晶胞体积为7477.9(12)(A)~3,Z=8,Dc=1.653 g/cm~3,F(000)=3856,μ=1.131 mm~(-1),最终残差因子R_1=0.0726,wR_2= 0.1719(相对于5612个I>2σ(I)的可观测衍射点).在这个化合物中,二齿配体4,4'-联吡啶把Co(II)桥连成[Co(4,4'-bipy)]~(2+)链.化合物中的[Co(4,4'-bipy)]~(2+)链有三个不同的朝向.2-磺酸基乙基膦酸没有参与配位而是做为一个有机模板剂填充在[Co(4,4'-bipy)]~(2+)链形成的空隙中.     

以5-叠氮间苯二甲酸为有机酸配体的配位聚合物的合成与表征

以5-叠氮间苯二甲酸(H2aip)为有机酸配体,选择3种不同的含氮辅配体,在溶剂热条件下合成了4个配位聚合物:Co(aip)(py)3(1),Co(aip)(4,4'-bipy)(2),Mn(aip)(4,4'-bipy)(3)和Mn(aip)(dptz)(4)[py=吡啶,4,4'-bipy=4,4'-联吡啶,dptz=3,6-二(4-吡啶基)-1,2,4,5-四嗪],通过X射线单晶衍射确定了化合物的晶体结构,并通过元素分析、红外光谱、热重和粉末X射线衍射对化合物进行了表征.结构分析表明,化合物1属单斜晶系,C2/c空间群,具有一维链状结构;化合物2和3结构相同,均属单斜晶系,C2/m空间群,具有二维层状结构,化合物4属三斜晶系,P1空间群,具有二维层状结构.变温磁化率测试结果表明,所得4个化合物中均存在弱反铁磁作用.     

二茂铁功能化的两例镉金属有机框架材料的合成、结构和表征※

含有二茂铁单元的1,1'-二茂铁二羧酸(H₂FcDCA)是构筑具有氧化还原活性的金属有机框架(MOFs)的理想配体, 然而由于其不可控的配位模式和扭转角, 目前基于H₂FcDCA的配合物的合成仍然具有挑战性. 本工作中, 利用H₂FcDCA与Cd²⁺反应合成了2个新颖的MOFs. 化合物1中, 镉中心被FcDCA和4,4'-联吡啶(bpy)桥连形成二维层. 在该体系中引入草酸则实现了三维框架的构筑(化合物2). 和1不同, 2中具有双核Cd₂单元, 该单元通过bpy和草酸连接形成具有金刚石型拓扑的框架, FcDCA同时作为功能单元和孔分割配体. 这2个化合物都表现出可见光吸收、光电流响应和典型的二茂铁氧化还原特性, 这些特性使其在光电催化方面具有潜在的应用前景.     

一种三维四元酸铜配合物的合成、结构及其性质（英文）

通过水热法合成了一种具有三维孔状结构的金属有机框架物{[Cu(BPTC)0.5·(bpy)]·H2O}∞(BPTC=3,3′,4,4′-苯甲酮-四甲酸和bpy=4,4′-联吡啶).运用元素分析、红外光谱、X射线单晶衍射以及X射线粉末衍射等对其进行了结构表征,利用热重分析评价了其热稳定性.X射线单晶衍射分析表明标题配合物通过一维右手螺旋链联接成为二维层状结构,进而经由4,4′-联吡啶联接成为三维孔状结构.当该孔状结构中包容的水分子被移除后,该金属有机框架物依然保持三维孔状结构.此外,实验还研究了标题配合物的磁学和固态荧光性质.     

两个3-氧乙酸基苯丙烯酸构筑的Cd(Ⅱ)配合物的合成、晶体结构和荧光性质(英文)

用水热法合成得到2个Cd(Ⅱ)配合物,[Cd(L)(4,4′-bipy)0.5(H2O)2]n(1)和[Cd(L)(bpp)(H2O)]n·2nH2O(2)(L=3-氧乙酸基苯丙烯酸,4,4′-bipy=4,4′-联吡啶,bpp=1,3-二吡啶基丙烷),并测定了他们的晶体结构。结构分析表明,在配合物1中,L配体连接Cd(Ⅱ)中心形成一维[CdL]n链,4,4′-联吡啶配体进一步桥联形成二维层状结构;配合物2是一个二重穿插的二维层状结构。此外,对配合物的荧光性能测试表明,它们在绿光区域有荧光发射。     

混合配体构筑的Zn(Ⅱ)金属有机骨架化合物的合成、结构与荧光性质

在水热条件下,利用锌离子与2种有机配体合成出1个结构新颖的金属有机骨架化合物[Zn2(BPDC)(IN)2](H2BPDC=4,4'-联苯二羧酸;HIN=异烟酸),并通过单晶X射线衍射、红外光谱、热重分析和荧光光谱等对该化合物进行了表征.结果表明,该化合物结构中Zn离子与BPDC的羧基形成双核金属次级结构单元[Zn2(—CO2)2(IN)2],相邻次级结构单元通过IN配离子连接形成[Zn2(—CO2)2(IN)2]∞二维层面,相邻的二维层通过BPDC相互连接形成具有三重互穿的简单格子拓扑结构.该化合物表现出良好的荧光性质.     

辅助配体导向合成两个锌金属配位聚合物:结构,稳定性和荧光性质（英文）

以二苯-4,4′-二羧酸和六水硝酸锌为原料,在相同反应条件下,通过改变不同的辅助配体(2,2′-二甲基-4,4′-联吡啶和三乙烯二胺),合成出2个金属有机配位聚合物:{[Zn(DBA)(dmbpy)_(0.5)]·2H_2O}_n(1)和[Zn_2(DBA)_2(dabco)]_n(2)(H_2DBA=二苯-4,4′-二羧酸,dmbpy=2,2′-二甲基-4,4′-联吡啶,dabco=三乙烯二胺)。通过元素分析、红外光谱、差热分析、X射线粉末衍射和X射线单晶衍射等手段对配合物进行了结构表征。结果显示,化合物1为二维(4,4)网络结构,2个二维结构在平行方向上通过互锁进一步形成2D→2D的互锁网络结构。化合物2为一维带状结构。热稳定性表明化合物1能够稳定到370℃;而化合物2稳定性差。荧光分析表明常温固态下配合物1和2均发射蓝色荧光,荧光寿命分别为231.4 ns和2.33 ns。     

混合配体构筑的Zn(Ⅱ)金属有机骨架化合物的合成、 结构与荧光性质

在水热条件下, 利用锌离子与2种有机配体合成出1个结构新颖的金属有机骨架化合物[Zn₂(BPDC)(IN)₂](H₂BPDC=4,4'-联苯二羧酸; HIN=异烟酸), 并通过单晶X射线衍射、 红外光谱、 热重分析和荧光光谱等对该化合物进行了表征. 结果表明, 该化合物结构中Zn离子与BPDC的羧基形成双核金属次级结构单元[Zn₂(—CO₂)₂(IN)₂], 相邻次级结构单元通过IN配离子连接形成[Zn₂(—CO₂)₂(IN)₂]_∞二维层面, 相邻的二维层通过BPDC相互连接形成具有三重互穿的简单格子拓扑结构. 该化合物表现出良好的荧光性质.     

浓度及冷冻鄄解冻处理对CuCl2水溶液中Cu2+区域结构的影响

应用扩展X射线吸收精细结构(EXAFS)光谱研究了CuCl2水溶液中Cu2+的区域环境结构, 通过测定CuCl2水溶液在不同浓度条件下及冷冻-解冻(FT)处理前后Cu K边EXAFS 吸收谱, 研究了浓度及冷冻-解冻处理对Cu2+第一配位层结构的影响. EXAFS实验结果表明, CuCl2水溶液中Cu2+第一配位层距离中心原子Cu最近邻原子为O原子, 配位数介于3.0-4.3之间, Cu—O键长在0.192-0.198 nm 之间, 这种结构与Cu2+的Jahn-Teller效应有关. 不同浓度的CuCl2水溶液中Cu2+的区域环境结构有很大不同, 随着CuCl2水溶液浓度的升高, Cu2+第一配位层配位数减小, Cu—O键伸长. 结构参数拟合结果证实冷冻-解冻处理对Cu2+的区域环境结构有影响, CuCl2溶液经冷冻-解冻处理后, Cu2+第一配位层配位数变大, 热无序度增加.     

浓度及冷冻-解冻处理对CuCl_2水溶液中Cu~(2+)区域结构的影响

应用扩展X射线吸收精细结构(EXAFS)光谱研究了CuCl2水溶液中Cu2+的区域环境结构,通过测定CuCl2水溶液在不同浓度条件下及冷冻-解冻(FT)处理前后CuK边EXAFS吸收谱,研究了浓度及冷冻-解冻处理对Cu2+第一配位层结构的影响.EXAFS实验结果表明,CuCl2水溶液中Cu2+第一配位层距离中心原子Cu最近邻原子为O原子,配位数介于3.0-4.3之间,Cu—O键长在0.192-0.198nm之间,这种结构与Cu2+的Jahn-Teller效应有关.不同浓度的CuCl2水溶液中Cu2+的区域环境结构有很大不同,随着CuCl2水溶液浓度的升高,Cu2+第一配位层配位数减小,Cu—O键伸长.结构参数拟合结果证实冷冻-解冻处理对Cu2+的区域环境结构有影响,CuCl2溶液经冷冻-解冻处理后,Cu2+第一配位层配位数变大,热无序度增加.     

Hydrated structures and dehydration processes of lanthanoid(III) chloranilates studied by EXAFS

The local structures of lanthanoid(III) chloranilate complexes of Pr(III), Nd(III), Tb(III) and Er(III) have been studied by EXAFS (extended X-ray absorption fine structure). Hydrated structures of the lanthanoid(III) ions in these complexes have been investigated with respect to their coordination numbers and interatomic distances. Six or four water molecules coordinate to the lanthanoid(III) ion of Pr(III) or Nd(III), respectively, just after preparation of the complexes. The temperature dependence of the first coordinated structures has been studied in order to reveal the behavior of the coordinated water molecules in dehydration process. The coordination number around the central lanthanoid(III) ion decreases stepwise as temperature increases, depending on the type of central lanthanoid(III) ion present. The interatomic distance between the central lanthanoid(III) ion and oxygen atoms in the first shell decreases, accompanying the decrease of the coordination numbers. A parameter representing proportion shows the reduction of interatomic distance as one coordinated water molecule removes from the central ion, depending on the type of lanthanoid(III) ions.     

离聚体的结构表征 Ⅲ.EXAFS法测定含氟的铜离聚体的精细结构

本文报道了用先进的EXAFS及ESR等方法研究了羧酸型含氟的铜(Ⅱ)离聚体离子微区的内部精细结构,结果表明,铜离聚体的离子微区主要由羧酸根桥键的双核配位结构单元及平面四方形的配位结构单元等聚集而成。在双核配位结构单元中第一层为Cu~(2+)—O配位,配位数为4,配位键键长为1.96A,第二配位层为Gu~(2+)—Cu~(2+)配位,Cu~(2+)—Gu~(2+)间距为2.64A。平面四方形的配位结构单元Cu~(2+)—O的配位数为4,配位键键长为1.96A。共聚物中羧基含量对离聚体的基本配位结构单元和离子微区的精细结构影响较小,但对微区大小有影响。     

X-Ray Absorption and Diffraction Studies of Pr3+, Tb3+ and Er3+-Activated Silica Gels

Rare-earth (Pr³⁺, Tb³⁺, Er³⁺) doped silica xerogels were studied by x-ray absorption spectroscopy and x-ray diffraction. A change of the local environment around rare-earth ions upon xerogel densification at 900–950°C and co-doping with aluminum ions was determined from the rare-earths L₃-edge EXAFS signals. The densification process induces a decrease of the coordination number and a compression and deformation of the first coordination shell, composed of oxygen atoms. The second coordination shell, composed of silicon and/or aluminum ions, also experiences some modification, which is attributed mainly to a shortening of the shell radius. No evidence of clustering of rare-earth ions upon densification was observed. X-ray diffraction data on Tb-doped gels confirm the EXAFS results.     

Hydration of lanthanoid(III) ions in aqueous solution and crystalline hydrates studied by EXAFS spectroscopy and crystallography: the myth of the "gadolinium break"

The structures of the hydrated lanthanoid(III) ions including lanthanum(III) have been characterized in aqueous solution and in the solid trifluoromethanesulfonate salts by extended X-ray absorption fine structure (EXAFS) spectroscopy. At ambient temperature the water oxygen atoms appear as a tricapped trigonal prism around the lanthanoid(III) ions in the solid nonaaqualanthanoid(III) trifluoromethanesulfonates. Water deficiency in the capping positions for the smallest ions starts at Ho and increases with increasing atomic number in the [Ln(H(2)O)(9-x)](CF(3)SO(3))(3) compounds with x=0.8 at Lu. The crystal structures of [Ho(H(2)O)(8.91)](CF(3)SO(3))(3) and [Lu(H(2)O)(8.2)](CF(3)SO(3))(3) were re-determined by X-ray crystallography at room temperature, and the latter also at 100 K after a phase-transition at about 190 K. The very similar Ln K- and L(3)-edge EXAFS spectra of each solid compound and its aqueous solution indicate indistinguishable structures of the hydrated lanthanoid(III) ions in aqueous solution and in the hydrated trifluoromethanesulfonate salt. The mean Ln--O bond lengths obtained from the EXAFS spectra for the largest ions, La-Nd, agree with estimates from the tabulated ionic radii for ninefold coordination but become shorter than expected starting at samarium. The deviation increases gradually with increasing atomic number, reaches the mean Ln-O bond length expected for eightfold coordination at Ho, and increases further for the smallest lanthanoid(III) ions, Er-Lu, which have an increasing water deficit. The low-temperature crystal structure of [Lu(H(2)O)(8.2)](CF(3)SO(3))(3) shows one strongly bound capping water molecule (Lu-O 2.395(4) A) and two more distant capping sites corresponding to Lu-O at 2.56(1) A, with occupancy factors of 0.58(1) and 0.59(1). There is no indication of a sudden change in hydration number, as proposed in the "gadolinium break" hypothesis.     

Nature of metal binding sites in Cu(II) complexes with histidine and related N-coordinating ligands, as studied by EXAFS

Knowledge of the complexes formed by N-coordinating ligands and Cu(II) ions is of relevance in understanding the interactions of this ion with biomolecules. Within this framework, we investigated Cu(II) complexation with mono- and polydentate ligands, such as ammonia, ethylenediamine (en), and phthalocyanine (Pc). The obtained Cu-N coordination distances were 2.02 A for [Cu(NH(3))(4)](2+), 2.01 A for [Cu(en)(2)](2+), and 1.95 A for CuPc. The shorter bond distance found for CuPc is attributed to the macrocyclic effect. In addition to the structure of the first shell, information on higher coordination shells of the chelate ligands could be extracted by EXAFS, thus allowing discrimination among the different coordination modes. This was possible due to the geometry of the complexes, where the absorbing Cu atoms are coplanar with the four N atoms forming the first coordination shell of the complex. For this reason multiple scattering contributions become relevant, thus allowing determination of higher shells. This knowledge has been used to gain information about the structure of the 1:2 complexes formed by Cu(II) ions with the amino acids histidine and glycine, both showing a high affinity for Cu(II) ions. The in-solution structure of these complexes, particularly that with histidine, is not clear yet, probably due to the various possible coordination modes. In this case the square-planar arrangements glycine-histamine and histamine-histamine as well as tetrahedral coordination modes have been considered. The obtained first-shell Cu-N coordination distance for this complex is 1.99 A. The results of the higher shells EXAFS analysis point to the fact that the predominant coordination mode is the so-called histamine-histamine one in which both histidine molecules coordinate Cu(II) cations through N atoms from the amino group and from the imidazole ring.     

Hydration of the calcium ion. An EXAFS, large-angle x-ray scattering, and molecular dynamics simulation study.

The structure of the hydrated calcium(II) ion in aqueous solution has been studied by means of extended X-ray absorption fine structure spectroscopy (EXAFS), large-angle X-ray scattering (LAXS), and molecular dynamics (MD) methods. The EXAFS data displayed a broad and asymmetric distribution of the Ca-O bond distances with the centroid at 2.46(2) A. LAXS studies on four aqueous calcium halide solutions (1.5-2 mol dm(-)(3)) gave a mean Ca-O bond distance of 2.46(1) A. This is consistent with a hydration number of 8 determined from correlations between mean distances and coordination numbers from crystal structures. The LAXS studies showed a second coordination sphere with a mean Ca.O(II) distance of 4.58(5) A, and for the hydrated halide ions the distances Cl.O 3.25(1) A, Br.O 3.36(1) A, and I.O 3.61(1) A were obtained. Molecular dynamics simulations of CaCl(2)(aq) were performed using three different Ca(2+)-OH(2) pair potentials. The potential from the GROMOS program gave results in agreement with experiments, i.e., a coordination number of 8 and an average Ca-O distance of 2.46 A, and was used for further comparisons. Theoretical EXAFS oscillations were computed for individual MD snapshots and showed very large variations, though the simulated average spectrum from 2000 snapshots gave satisfactory agreement with the experimental EXAFS spectra. The effect of thermal motions of the coordinated atoms is inherent in the MD simulation method. Thermal disorder parameters evaluated from simulated spatial atom distribution functions of the oxygen atoms coordinated to the calcium ion were in close agreement with those from the current LAXS and EXAFS analyses. The combined results are consistent with a root-mean-square displacement from the mean Ca-O distance of 0.09(2) A in aqueous solution at 300 K.     

γ-Mo2N和分子筛负载的钼氮化物的结构表征

采用程序升温氮化的方法制备了分子筛负载的钼氮化物催化剂,并用EXAFS方法研究了 氮化前后Mo原子的局域配位情况.氮化前负载MoO3样品的径向结构函数中有三个峰,其中前两 个峰对应着最近的Mo-O配位壳层,但是第一个峰与第二个峰的比例比晶体MoO3中的比例大很 多,表明分子筛负载的MoO3具有更紧密的结构.氮化以后,Mo2N样品的径向结构函数中有三个 峰,对应于一个Mo-N和两个Mo-Mo配位壳层,与面心立方模型符合得很好.根据XRD和EXAFS谱 的计算表明,Mo2N中的N原子使Mo-Mo键拉长并削弱.分子筛负载的Mo2N样品具有与非负载Mo2 N样品近似相同的径向结构函数,只是对应于Mo-N壳层的峰较弱,表明负载的Mo2N具有更大的 结构无序性.     

Local order around rare earth ions during the devitrification of oxyfluoride glasses

Erbium L(3)-edge extended x-ray absorption fine structure (EXAFS) measurements were performed on rare earth doped fluorosilicate and fluoroborate glasses and glass ceramics. The well known nucleating effects of erbium ions for the crystallization of cubic lead fluoride (based on x-ray diffraction measurements) and the fact that the rare earth ions are present in the crystalline phase (as indicated by Er(3+) emission spectra) seem in contradiction with the present EXAFS analysis, which indicates a lack of medium range structural ordering around the Er(3+) ions and suggests that the lead fluoride crystallization does not occur in the nearest neighbor distance of the rare earth ion. Molecular dynamics simulations of the devitrification process of a lead fluoride glass doped with Er(3+) ions were performed, and results indicate that Er(3+) ions lower the devitrification temperature of PbF(2), in good agreement with the experimental results. The genuine role of Er(3+) ions in the devitrification process of PbF(2) has been investigated. Although Er(3+) ions could indeed act as seeds for crystallization, as experiments suggest, molecular dynamics simulation results corroborate the experimental EXAFS observation that the devitrification does not occur at its nearest neighbor distance.