Excitation and Emission Spectra of Cs2NaLnCl6 Crystals Using Synchrotron Radiation

ABSTRACT

The visible emission and vacuum ultraviolet excitation spectra of the series Cs₂NaLnCl₆ (Ln = Y, Nd, Sm, Eu, Tb, Er, Yb) and Cs₂NaYCl₆:Ln³⁺ (Ln = Sm, Er) have been recorded using synchrotron radiation at room temperature, and in some cases at 10 K. The excitation spectra comprise features associated with charge transfer, excitation from the valence to conduction band, and impurity bands. No d–f emissions were observed for these Ln³⁺ ions, so that the emission bands comprise intraconfigurational 4f ^N –4f ^N transitions and impurity bands, whose natures are discussed. Theoretical simulations of the f–d absorption spectra have been included. The comparison with data from the synchrotron at Desy enables a comprehensive account of the ground (or vibrationally excited ground for Ln²⁺) states of the Ln³⁺ 4f ^N , Ln³⁺ 4f ^N?15d, and Ln²⁺ 4f ^N+1 configurations relative to the valence and conduction bands of Cs₂NaLnCl₆, for which the band gaps are between 6.6 and 8.1 eV.     

Synthesis and Crystal Structure of [（ArO）2Sm（OPPh3）（μ—OH）]2（ArO=2,6—tBu—4—Me—C6H2O）

1 INTRODUCTION In recent years, the syntheses, structures and reactivities of aryloxo lanthanide complexes have attracted a great deal of attention due to their various applications as homogeneous catalysts for organic reactions and precursors for organolan- thanide syntheses[1]. However, the reactivity of divalent lanthanide aryloxides has seldom been studied[2]. We have previously reported that (ArO)2- Sm(THF)4 (ArO = OC6H2-2,6-di-tert-butyl-4-Me) can efficiently initiate the poly…     

Ready Access to Anhydrous Anionic Lanthanide Acetates by Using Imidazolium Acetate Ionic Liquids as the Reaction Medium

Access to lanthanide acetate coordination compounds is challenged by the tendency of lanthanides to coordinate water and the plethora of acetate coordination modes. A straightforward, reproducible synthetic procedure by treating lanthanide chloride hydrates with defined ratios of the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C₂mim][OAc]) has been developed. This reaction pathway leads to two isostructural crystalline anhydrous coordination complexes, the polymeric [C₂mim]_n[{Ln₂(OAc)₇}_n] and the dimeric [C₂mim]₂[Ln₂(OAc)₈], based on the ion size and the ratio of IL used. A reaction with an IL : Ln-salt ratio of 5 : 1, where Ln=Nd, Sm, and Gd, led exclusively to the polymer, whilst for the heaviest lanthanides (Dy−Lu) the dimer was observed. Reaction with Eu and Tb resulted in a mixture of both polymeric and dimeric forms. When the amount of IL and/or the size of the cation was increased, the reaction led to only the dimeric compound for all the lanthanide series. Crystallographic analyses of the resulting salts revealed three different types of metal-acetate coordination modes where η²μκ² is the most represented in both structure types.     

稀土掺杂无机纳米晶及其时间分辨荧光生物检测应用

时间分辨荧光生物标记作为一种灵敏的非放射性标记技术,在科研及医疗机构已获得广泛应用.传统的时间分辨荧光标记以稀土螯合物作为分子探针,存在着光化学稳定性差、长期生物毒性以及价格昂贵等缺点.稀土掺杂无机纳米晶因其优异的光化学与光物理性能,是目前普遍看好且有望成为替代稀土螯合物的新一代时间分辨纳米荧光探针.利用稀土纳米探针的...     

A Copper(II)-Lanthanoid(III)-Glycine Complex with High-Nuclearity, [{La6Cu26gly18(μ 3-OH)30(H2O)24 (ClO4)}(ClO4)21·26H2O] n

The 1-D complex with high-nuclearity [{La₆Cu₂₆gly₁₈( ₃-OH)₃₀(H₂O)₂₄(ClO₄)} (ClO₄)₂₁·26H₂O] _n was synthesized and characterized by X-ray diffraction analysis. The inner core of the basic unit is an octahedron with La³⁺ ions at its vertexes and Cu²⁺ ions at the meddles of the twelve edges. Two additional Cu²⁺ ions are connected to each La³⁺ vertex to form a [La₆Cu₂₄] unit, and adjacent units are interconnected by a pair [Cu(gly)₂] bridges to give a polymeric chain structure.     

Lanthanide Trifluoroacetate Complexes with 2-azacyclononanone. Thermal and kinetic studies

Ln(TFA)₃⋅3AZA (Ln=La, Sm, Er; TFA=trifluoroacetate and AZA=2-azacyclononanone)compounds were synthesized and characterized by microanalytical procedures, IR spectroscopy, X-ray powder diffraction, and thermal analysis. A kinetic study using La, Sm and Er thermogravimetric curves was carried out aiming to proposing a mechanism for the thermal decomposition of such complexes. This revised version was published online in July 2006 with corrections to the Cover Date.     

环辛四烯基稀土金属有机配合物

环辛四烯基稀土配合物是继茂基配合物之后的又一类非常重要的稀土金属有机配合物,本文将就这一领域的发展情况作一个简要的总结和回顾。     

稀土亚磷酸盐GdxTb2-x（HPO3）3（H2O）2（0≤x≤2）的微波合成、表征与性质研究

利用微波辅助合成法,成功地合成出一系列新颖的稀土亚磷酸盐GdxTb2-x(HPO3)3(H2O)2(0≤x≤2).X-射线粉末衍射分析结果表明,它们为同构的化合物.对Gd2(HPO3)3(H2O)2进行X-射线单晶衍射分析得出,该化合物结晶于P21/c空间群,晶胞参数为a=6.9124(6),b=12.8891(12),c=12.3692(11),β=100.1520(10)°.Gd2(HPO3)3(H2O)2是由GdO7多面体,GdO8多面体和[HPO3]假四面体通过共用氧原子相互连接而成的三维骨架.Gd2(HPO3)3(H2O)2和Tb2(HPO3)3(H2O)2的荧光光谱分别显示Gd3+和Tb3+的特征发光.Gd/Tb掺杂的样品中存在Gd3+-Tb3+的能量传递,它们的发光显示Tb3+的绿光发射(5D4→7F3-6),并且5D4→7F3跃迁的强度随着Tb3+掺杂量的增大而增强,这表明Gd2(HPO3)3(H2O)2引入不同浓度的发光中心Tb3+之后可以作为绿光发光材料.磁性研究表明,Gd2(HPO3)3(H2O)2中存在极弱的反铁磁相互作用.     

Adducts of aqua complexes of Ln3+ with a symmetrical octamethyl-substituted cucurbituril: potential applications for isolation of heavier lanthanides

Interaction of a series of lanthanide cations (Ln³⁺) with a symmetrical octamethyl-substituted cucurbituril (OMeQ[6]) has been investigated. X-ray single-crystal diffraction analysis has revealed that the interaction results in the formation of adducts of OMeQ[6] with aqua complexes of lanthanide cations ([Ln(H₂O)₈]³⁺), Ln = Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb in OMeQ[6]–Ln(NO₃)₃–H₂O systems. However, no solid crystals were obtained from systems containing La, Ce, Pr, Nd and Sm. X-ray diffraction analysis has revealed that although the solid adducts fall into two isomorphous groups, there are no significant differences in the interactions between OMeQ[6] and [Ln(H₂O)₈]³⁺ complexes and in the corresponding supramolecular assemblies. Thermodynamic parameters for the interaction between OMeQ[6] and [Ln(H₂O)₈]³⁺ complexes based on isothermal titration calorimetry experiments show two periods corresponding to the above two systems, with the lighter lanthanide cations preferring to remain in solution and the heavier lanthanide cations forming crystalline solids. Electron spectroscopy has shown that interaction of OMeQ[6] with lanthanide cations could provide a means of isolating heavier lanthanide cations from their lighter counterparts.     

DNA binding and antibacterial properties of ternary lanthanide complexes with salicylic acid and phenanthroline

Twelve ternary lanthanide complexes RE(sal)₃phen (RE³⁺ = La³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺, Dy³⁺, Ho³⁺, Tm³⁺, Yb³⁺, Lu³⁺, sal = salicylic acid, phen = phenanthroline) were prepared. Interactions between the complexes and calf thymus DNA (ct‐DNA) were investigated using UV–visible spectrophotometry, fluorescence quench experiment and viscosity measurement. Hypochromicity and red shift of the absorption spectra of complexes were observed in the presence of DNA. The enhanced emission intensity of ethidium bromide (EB) in the presence of DNA was quenched by the addition of lanthanide complexes, which indicated that the lanthanide complexes displaced EB from its binding sites in DNA. Based on the systematic research of the binding constant (K_b) and the fluorescence quenching constant (K_q) of the 12 complexes, we found that the complexes with smaller lanthanide ion radius had stronger binding abilities with DNA. Viscosity measurement showed that the relative viscosity of the DNA solution was enhanced with increasing the amounts of the complexes. All these results suggested that the complexes could bind to DNA and the major binding mode was intercalative binding. Moreover, all these complexes exhibited excellent antibacterial abilities against Escherichia coli. Also, the antibacterial activities of complexes with heavy rare earth were higher than those of complexes with light rare earth. Copyright © 2014 John Wiley & Sons, Ltd.