Sensitized emission from lanthanide-doped nanoparticles embedded in a semiconductor sol-gel thin film.

In(2)O(3) sol-gel thin films made with LaF(3):Ln(3+) (Ln=Er, Nd, and Eu) nanoparticles were prepared and showed sensitized emission of the lanthanide ions after In(2)O(3) matrix excitation. The excitation spectra showed an In(2)O(3) absorption band in addition to the excitation peaks of the lanthanide ions, clearly demonstrating that there is energy transfer from the In(2)O(3) matrix to Ln(3+) (Er(3+), Nd(3+), and Eu(3+)). Similarly, HfO(2) and ZrO(2) sol-gel thin films made with LaF(3):Ln(3+) nanoparticles also showed energy transfer from the semiconductor matrix to the lanthanide ions.     

稀土有机配合物电致发光研究进展

稀土配合物发射带窄, 发射光谱具有类原子光谱性质, 色纯度高(半宽峰<10 nm), 非常适合于全彩色显示. 另外, 稀土配合物发光效率高, 理论上内量子效率可达100%. 因此, 稀土配合物是全色平板显示器件中理想的发光材料之一, 研究稀土配合物电致发光性质具有重要的实际意义和理论意义. 以稀土镧系离子配合物作为发光中心的电致发光器件的研究主要集中于发光效率比较高的Eu3+, Tb3+ 以及近红外的Nd3+, Yb3+和Er3+ 离子. 分类综述了近年稀土配合物电致发光研究的成果及其进展. 总结了不同类型的铕配合物、铽配合物的电致发光特性, 证明配体对于稀土离子的敏化作用非常重要; 总结了近红外的镱、钕、铒配合物在光放大、激光技术、生物医学等方面的潜在应用价值.     

Luminescent ruthenium(II) bipyridine-calix[4]arene complexes as receptors for lanthanide cations

The synthesis and photophysical properties of novel luminescent ruthenium(II) bipyridyl complexes containing one, two, or six lower rim acid-amide-modified calix[4]arene moieties covalently linked to the bipyridine groups are reported which are designed to coordinate and sense luminescent lanthanide ions. All the Ru-calixarene complexes synthesized in this work are able to coordinate Nd(3+), Eu(3+), and Tb(3+) ions with formation of adducts of variable stoichiometry. The absorbance changes allow the evaluation of association constants whose magnitudes depend on the nature of the complexes as well as on the nature of the lanthanide cation. Lanthanide cation complex formation affects the ruthenium luminescence which is strongly quenched by Nd(3+) ion, moderately quenched by the Eu(3+) ion, and poorly or moderately increased by the Tb(3+) ion. In the case of Nd(3+), the excitation spectra show that (i) the quenching of the Ru luminescence occurs via energy transfer and (ii) the electronic energy of the excited calixarene is not transferred to the Ru(bpy)(3) but to the neodymium cation. In the case of Tb(3+), the adduct's formation leads to an increase of the emission intensities and lifetimes. The reason for this behavior was ascribed to the electric field created around the Ru calix[4]arene complexes by the Tb(3+) ions by comparison with the Gd(3+) ion, which behaves identically and can affect ruthenium luminescence only by its charge. However, especially for compounds 1 and 3, it cannot be excluded that some contribution comes from the decrease of vibrational motions (and nonradiative processes) due to the rigidification of the structure upon Tb(3+) complexation. In the case of Eu(3+), compounds 1, 2, and 4 were quenched by the lanthanide addition but the quenching of the ruthenium luminescence is not accompanied by europium-sensitized emission which suggests that an electron-transfer mechanism is responsible for the quenching. On the contrary, compound 3 exhibits enhanced emission upon addition of Eu(3+) (as nitrate salt); it is suggested that the lack of quenching in the [3.2Eu(3+)] adduct is due to kinetic reasons because the electron-transfer quenching process is thermodynamically allowed.     

Cyclam-based dendrimers as ligands for lanthanide ions

We have investigated the complexation of lanthanide ions (Nd3+, Eu3+, Gd3+, Tb3+, Dy3+) with three cyclam-based ligands (cyclam = 1,4,8,11-tetraazacyclotetradecane), namely 1,4,8,11-tetrakis(naphthylmethyl)cyclam (1), and two dendrimers consisting of a cyclam core appended with four dimethoxybenzene and eight naphthyl units (2) and twelve dimethoxybenzene and sixteen naphthyl units (3). In the free ligands the fluorescence of the naphthyl units is strongly quenched by exciplex formation with the cyclam nitrogens. Complexation with the metal ions prevents exciplex formation and revives the intense naphthyl fluorescence. Fluorescence and NMR titration experiments have revealed the formation of complexes with different metal/ligand stoichiometries in the case of 1, 2 and 3. Surprisingly, the large dendrimer 3 gives rise to a stable [M(3)3]3+ species. Energy transfer from the lowest singlet and triplet excited states of the peripheral naphthyl units to the lower lying excited states of Nd3+, Eu3+, Tb3+, Dy3+ coordinated to the cyclam core does not take place.     

A cyclam core dendrimer containing dansyl and oligoethylene glycol chains in the branches: protonation and metal coordination

We have synthesized a dendrimer (1) consisting of a 1,4,8,11-tetraazacyclotetradecane (cyclam) core, appended with four benzyl substituents that carry, in the 3- and 5-positions, a dansyl amide derivative (of type 2), in which the amide hydrogen is replaced by a benzyl unit that carries an oligoethylene glycol chain in the 3- and 5-positions. All together, the dendrimer contains 16 potentially luminescent moieties (eight dansyl- and eight dimethoxybenzene-type units) and three distinct types of multivalent sites that, in principle, can be protonated or coordinated to metal ions (the cyclam nitrogen atoms, the amine moieties of the eight dansyl units, and the 16 oligoethylene glycol chains). We have studied the absorption and luminescence properties of 1, 2, and 3 in acetonitrile and the changes taking place upon titration with acid and a variety of divalent (Co2+, Ni2+, Cu2+, Zn2+), and trivalent (Nd3+, Eu3+, Gd3+) metal ions as triflate and/or nitrate salts. The results obtained show that: 1) double protonation of the cyclam ring takes place before protonation of the dansyl units; 2) the oligoethylene glycol chains do not interfere with protonation of the cyclam core and the dansyl units in the ground state, but affect the luminescence of the protonated dansyl units; 3) the first equivalent of metal ion is coordinated by the cyclam core; 4) the interaction of the resulting cyclam complex with the appended dansyl units depends on the nature of the metal ion; 5) coordination of metal ions by the dansyl units follows at high metal-ion concentrations; 6) the effect of the metal ion depends on the nature of the counterion. This example demonstrates that dendrimers may exhibit complete functionality resulting from the integration of the specific properties of their component units.     

Liquid-liquid extraction of some lanthanide metal ions by polyoxyalkylene systems

Polyoxyalkylene systems, namely, polypropylene glycol (PPG-1025), polyethylene glycol (PEG-600) and polybutadieneoxide (PBDO-700) dissolved in either nitrobenzene or 1,2-dichloroethane have been tested as prospective extractants for some lanthanide metal ions (Eu(3+), Pr(3+) and Er(3+)) from their aqueous solutions in the presence of picrate anions. The metal ions were quantified before and after extraction using the inductively coupled plasma emission spectrophotometry technique. The percent extraction and the distribution coefficients have indicated that pH of the aqueous phase, picrate concentration and the organic solvent are the major parameters that affect the extraction efficiency of the metal ions. The optimum pH range was found to be 3.5-5.5 and the picrate concentration should be as high as possible; however, a picrate concentration of about 0.05 M proved to be adequate for a near quantitative extraction. In all cases, nitrobenzene enhanced a higher percent extraction compared to 1,2-dichloroethane. The efficiency of the polyoxyalkylene systems to extract certain lanthanide metal ions was in the order PBDO-700>PPG-1025>PEG-600 when nitrobenzene was the organic solvent and in the order PPG-1025>PBDO-700 approximately PEG-600 when 1,2-dichloroethane used as the solvent in the organic phase. The extractability of PPG-1025 towards the lanthanide metal ions was in the order Pr(3+)>Eu(3+)>Er(3+) irrespective of the organic solvent used. The stoichiometry of the extracted polyoxyalkylene ion-pairs with the lanthanide metal ions has been estimated. Each mole of metal ions is associated with three moles of picrate anions and 13 to 14 moles of propyleneoxide units in the case of PPG-1025, and about 9 to 10 moles of ethyleneoxide units in the case of PEG-600 and 10 moles of butadieneoxide units in the case of PBDO-700.     

Azulene-moiety-based ligand for the efficient sensitization of four near-infrared luminescent lanthanide cations: Nd3+, Er3+, Tm3+, and Yb3+

The ML(4) complexes formed by reaction between the bidentate azulene-based ligand diethyl 2-hydroxyazulene-1,3-dicarboxylate (HAz) and several lanthanide cations (Pr(3+), Nd(3+), Gd(3+), Ho(3+), Er(3+), Tm(3+), Yb(3+), and Lu(3+)) have been synthesized and characterized by elemental analysis, FT-IR vibrational spectroscopy and electrospray ionization mass spectroscopy. Spectrophotometric titrations have revealed that four Az(-) ligands react with one lanthanide cation to form the ML(4) complex in solution. Studies of the luminescence properties of these ML(4) complexes demonstrated that Az(-) is an efficient sensitizer for four different near-infrared emitting lanthanide cations (Nd(3+), Er(3+), Tm(3+), and Yb(3+)); the resulting complexes have high quantum yield values in CH(3)CN. The near-infrared emission arising from Tm(3+) is especially interesting for biologic imaging and bioanalytical applications since biological systems have minimal interaction with photons at this wavelength. Hydration numbers, representing the number of water molecules bound to the lanthanide cations, were obtained through luminescence lifetime measurements and indicated that no molecules of water/solvent are bound to the lanthanide cation in the ML(4) complex in solution. The four coordinated ligands protect well the central luminescent lanthanide cation against non-radiative deactivation from solvent molecules.     

稀土元素对人肝癌细胞SMMC-7721增殖的影响

用MTT法研究了14种稀土元素(La，Ce，Pr，Nd，Sm，Eu，Gd，Tb，Dy，Ho，Er，Tm，Yb和Lu)对人肝癌细胞SMMC-7721增殖的影响。他们对肝癌细胞的生长作用可分为3类。其中La^3 、Ce^3 和Eu^3 对肝癌细胞的增殖有剂量依赖性正效应，能够在一定浓度范围内刺激细胞生长；Sm^3 ，Gd^3 ，Ho^3 ，Er^3 ，Yb^3 对肝癌细胞生长的刺激作用没有剂量依赖性特征；而Pr^3 ，Nd^3 ，Tb^3 ，Dy^3 ，Tm^3 和Lu^3 则表现出对肝癌细胞的增殖具有不用程度的抑制。推测14种稀土元素作用方式的不同与他们的原子结构有一定的关系，它们对肝癌细胞的相对增殖率随着原子序数的增加呈现出一定的规律性。     

Highly luminescent Eu(3+) and Tb(3+) macrocyclic complexes bearing an appended phenanthroline chromophore

A two-component ligand system (1) containing 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) as the hosting unit for the lanthanide cations and an appended asymmetrically functionalized 1,10-phenanthroline (phen) as the chromophore was synthesized. The 1:1 complexes with Eu(3+), Gd(3+), Tb(3+), and Yb(3+) have been prepared and studied in aqueous solution. For Gd.1, a relaxivity value of 2.4 mM(-1) s(-1) has been measured at 20 MHz and 25 degrees C, which indicates that there are no water molecules in the first coordination sphere of the metal ion. The analysis of high resolution (1)H NMR spectra of Yb.1 supports this view and suggests the direct involvement of the phen moiety in the coordination of the metal ion. For Eu.1 and Tb.1, the absorption and luminescence spectra, the overall luminescence efficiencies, and the metal-centered (MC) lifetimes were obtained; coordination features were also determined by comparing luminescence properties in water and deuterated water. For Eu.1 and Tb.1, the overall emission sensitization (se) process in air-equilibrated water was found to be notably effective with phi(se) = 0.21 and 0.11, respectively. A detailed study of the steps originating from light absorption at the phen unit and leading to MC sensitized emission was performed.     

Selective colorimetric sensing of Cu2+ using triazolyl monoazo derivative

Although the high sensitivity, high selectivity and fast response make emission (fluorescence) based technique as one of the most promising tool for developing the chemosensors for metal ions, the past few years have witnessed a demand for the absorption based chemosensors for paramagnetic heavy metal ions, especially Cu(2+). Being paramagnetic, Cu(2+) leads to the low signal outputs ("turn-off") caused by decreased emission which may sometimes give false positive response, rendering the emission based technique less reliable for analytical purposes. Herein, we report synthesis and characterization of a hetarylazo derivative, characterized by a strong charge-transfer band which gets attenuated convincingly in the presence of Cu(2+) leading to distinct naked-eye color change (yellow to purple), and to a lesser extent in the presence of Cd(2+), Zn(2+), Co(2+), Pb(2+), Fe(2+), Ni(2+), Fe(3+) and Hg(2+) for which the naked eye sensitivity was comparatively (w.r.t. Cu(2+)) much less. No response was observed for the other metal ions including Li(+), Na(+), K(+), Mg(2+), Ca(2+), Ba(2+), Mn(2+), Ag(+), Zn(2+), Cd(2+), Pb(2+), and lanthanides Ce(3+), La(3+), Pr(3+), Eu(3+), Nd(3+), Lu(3+), Yb(3+), Tb(3+), Sm(3+), Gd(3+). The proposed sensing mechanism has been ascribed to the stabilization of LUMO after complexation with Cu(2+) and a 1:1 stoichiometry has been deduced.     

Assembly of robust and porous hydrogen-bonded coordination frameworks: isomorphism, polymorphism, and selective adsorption

By using the tripodal ligand ntb (tris(benzimidazole-2-ylmethyl)amine) and lanthanide nitrate, three isomorphous series of coordination frameworks of the general formula [Ln(ntb)(NO(3))(3)]·solvents (series 1: monoclinic C2/c, Ln = Gd(3+) and Yb(3+); series 2: hexagonal P3(1)/c, Ln = Nd(3+), Eu(3+), Gd(3+), and Er(3+); series 3, cubic Pa3?, Ln = Gd(3+) and Er(3+); solvent = H(2)O or CH(3)OH) have been assembled and characterized with IR, elemental analyses, and single crystal and powder X-ray diffraction methods. In all isomorphous complexes, analogous [Ln(ntb)(NO(3))(3)] coordination monomers of the same structure act as the building blocks to be assembled via hydrogen bonds into three-dimensional (3D) frameworks. So the complexes of the same lanthanide ion (for example, the Gd(3+) ion) from three isomorphous series form polymorphs, for example, monoclinic polymorph 1-Gd, hexagonal polymorph 2-Gd, and cubic polymorph 3-Gd. The single-crystal analyses revealed that the polymorphism was related to different fashions of hydrogen bonding interactions, which was caused by different crystallization conditions, leading to the formation of different 3D hydrogen-bonded frameworks showing distinct porous and topological structures. The monoclinic and hexagonal crystals contain 1D channels, while the cubic crystal is nonporous. The thermogravimetric analyses indicated that all polymorphic crystals have high thermal stability against the removal of guest molecules, and the robust porosity of the hexagonal crystals has been verified by temperature-dependent single-crystal-to-single-crystal measurements upon guest removal/uptake. The solvents adsorption study disclosed that the porous frameworks show high selectivity of benzene against toluene and xylene, while the gas adsorption measurements indicated a moderate H(2), CO(2), and MeOH storage capacity in contrast to low N(2) uptake. The solid-state photoluminescence of the Eu(3+) and Nd(3+) complexes in the near-infrared and visible region has also been investigated, offering examples with optical properties tunable by means of isomorphous replacement.     

Synthesis and characterization of heterodinuclear Ln(3+)-Fe3+ and Ln(3+)-Co3+ complexes,bridged by cyanide ligand (Ln3+ = lanthanide ions). Nature of the magnetic interaction in the Ln(3+)-Fe3+ complexes

The reaction of Ln(NO3)3.aq with K3[Fe(CN)6] or K3[Co(CN)6] in N,N'-dimethylformamide (DMF) led to 25 heterodinuclear [Ln(DMF)4(H2O)3(mu-CN)Fe(CN)5].nH2O and [Ln(DMF)4(H2O)3(mu-CN)Co(CN)5].nH2O complexes (with Ln = all the lanthanide(III) ions, except promethium and lutetium). Five complexes (Pr(3+)-Fe3+), (Tm(3+)-Fe3+), (Ce(3+)-Co3+), (Sm(3+)-Co3+), and (Yb(3+)-Co3+) have been structurally characterized; they crystallize in the equivalent monoclinic space groups P21/c or P21/n. Structural studies of these two families show that they are isomorphous. This relationship in conjunction with the diamagnetism of the Co3+ allows an approximation to the nature of coupling between the iron(III) and the lanthanide(III) ions in the [Ln(DMF)4(H2O)3(mu-CN)Fe(CN)5].nH2O complexes. The Ln(3+)-Fe3+ interaction is antiferromagnetic for Ln = Ce, Nd, Gd, and Dy and ferromagnetic for Ln = Tb, Ho, and Tm. For Ln = Pr, Eu, Er, Sm, and Yb, there is no sign of any significant interaction. The isotropic nature of Gd3+ helps to evaluate the value of the exchange interaction.     

Lanthanide-containing photoluminescent materials: from hybrid hydrogel to inorganic nanotubes

Functional photoluminescent materials are emerging as a fascinating subject with versatile applicability. In this work, luminescent organic-inorganic hybrid hydrogels are facilely designed through supramolecular self-assembly of sodium cholate, and lanthanide ions such as Eu(3+), Tb(3+), and Eu(3+)/Tb(3+). Fluorescence microscopy and TEM visualization demonstrates the existence of spontaneously self-assembled nanofibers and 3D networks in hybrid hydrogel. Photoluminescence enhancement of lanthanide ions is realized through coordination with cholate and co-assembly into 1D nanofibers, which can successfully shield the Eu(3+) from being quenched by water. The photoluminescence emission intensity of a hybrid hydrogel exhibits strong dependence on europium/cholate molar ratio, with maximum emission appearing at a stoichiometry of 1:3. Furthermore, the emission color of a lanthanide-cholate hydrogel can be tuned by utilizing different lanthanide ions or co-doping ions. Moreover, photoluminescent lanthanide oxysulfide inorganic nanotubes are synthesized by means of a self-templating approach based on lanthanide-cholate supramolecular hydrogels. To the best of our knowledge, this is the first time that the lanthanide oxysulfide inorganic nanotubes are prepared in solution under mild conditions.     

Studies on the extraction and separation of lanthanide ions with a synergistic extraction system combined with 1,4,10,13-tetrathia-7,16-diazacyclooctadecane and lauric acid

1,4,10,13-Tetrathia-7,16-diazacyclooctadecane (ATCO) and its binary extraction system containing lauric acid were studied extensively as extractants of lanthanide (M(3+)=La(3+), Ce(3+), Pr(3+), Nd(3+), Sm(3+), Eu(3+) and Gd(3+)) in 1,2-dichloroethane solution. The percentage extraction of Ce(3+) and Eu(3+) by ATCO were only measured to be less than 5% during a pH range 5.5-7.0 in NCS(-), ClO(4)(-) and PF(6)(-) mediums respectively, which indicates that ATCO alone has very low extractability to lanthanide, due to the bad fit of metal ions in its cavity. However, when lauric acid was added to the ATCO organic phase, because of forming rare earth adduct, the percentage extraction for lanthanide until Gd(3+) was enhanced in the binary system in comparison with that did not adopt the lauric acid within the pH range 6-7. The extraction species and extraction equilibrium constants logK(ex) were found to be CeLA(3)3HA, -8.5, EuLA(3)HA, -6.7, and GdLA(2)NO(3)2HA, -1.8, respectively. The separation factor between Eu(3+) and Ce(3+) was found to be 2.5, however, poor selectivity for lanthanide was observed. From Gd(3+) to Er(3+) and Lu(3+), the synergistic effect of the binary extraction system decreases with increasing atomic number. For gadolinium, the synergistic effect becomes much weaker than that of Ce(3+) and Eu(3+), no synergistic effect existed for erbium and lutetium. Thermodynamic data for synergistic solvent extraction are also reported in this paper. The order of organic phase stability constants of the extraction species is Sm (5.8)>Pr (5.7)>Eu (5.6)>Ce (5.3)>La (5.2)>Gd (2.8).     

Calix[4]azacrowns as novel molecular scaffolds for the generation of visible and near-infrared lanthanide luminescence

Two calix[4]azacrowns, capped with two aminopolyamide bridges, were used as ligands for the complexation of lanthanide ions [Eu(III), Tb(III), Nd(III), Er(III), La(III)]. The formation of 1:2 and 1:1 complexes was observed, and stability constants, determined by UV absorption and fluorescence spectroscopy, were found to be generally on the order of log beta(11) approximately 5-6 and log beta(12) approximately 10. The structural changes of the ligands upon La(III) complexation were probed by 1H NMR spectroscopy. The two ligands were observed to have opposite fluorescence behaviors, namely, fluorescence enhancement (via blocking of photoinduced electron transfer from amine groups) or quenching (via lanthanide-chromophore interactions) upon metal ion complexation. Long-lived lanthanide luminescence was sensitized by excitation in the pi,pi band of the aromatic moieties of the ligands. The direct involvement of the antenna triplet state was demonstrated via quenching of the ligand phosphorescence by Tb(III). Generally, Eu(III) luminescence was weak (Phi(lum) 相似文献   

Bright white light through up-conversion of a single NIR source from sol-gel-derived thin film made with Ln3+-doped LaF3 nanoparticles

White light was generated from a single silica thin film made with Yb0.75La0.2Eu0.05F3, La0.45Yb0.5Er0.05F3, and La0.75Yb0.2Tm0.05F3 nanoparticles by exciting with a single source near-infrared light (980 nm CW diode laser). Eu3+ and Tm3+ ions are responsible for red and blue emission, respectively. Er3+ ion is responsible for green as well as red emission. The Commission Internationale de l'Eclairage (CIE) coordinates of the resulting light were easily adjusted by controlling the concentration of Ln3+ (Eu3+, Er3+, Tm3+) ions in the nanoparticles as well as the concentration of Ln3+-doped nanoparticles in the sol-gel thin layer.     

General synthesis and structural evolution of a layered family of Ln8(OH)20Cl4 x nH2O (Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Y)

The synthesis process and crystal structure evolution for a family of stoichiometric layered rare-earth hydroxides with general formula Ln(8)(OH)(20)Cl(4) x nH(2)O (Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Y; n approximately 6-7) are described. Synthesis was accomplished through homogeneous precipitation of LnCl(3) x xH(2)O with hexamethylenetetramine to yield a single-phase product for Sm-Er and Y. Some minor coexisting phases were observed for Nd(3+) and Tm(3+), indicating a size limit for this layered series. Light lanthanides (Nd, Sm, Eu) crystallized into rectangular platelets, whereas platelets of heavy lanthanides from Gd tended to be of quasi-hexagonal morphology. Rietveld profile analysis revealed that all phases were isostructural in an orthorhombic layered structure featuring a positively charged layer, [Ln(8)(OH)(20)(H(2)O)(n)](4+), and interlayer charge-balancing Cl(-) ions. In-plane lattice parameters a and b decreased nearly linearly with a decrease in the rare-earth cation size. The interlamellar distance, c, was almost constant (approximately 8.70 A) for rare-earth elements Nd(3+), Sm(3+), and Eu(3+), but it suddenly decreased to approximately 8.45 A for Tb(3+), Dy(3+), Ho(3+), and Er(3+), which can be ascribed to two different degrees of hydration. Nd(3+) typically adopted a phase with high hydration, whereas a low-hydration phase was preferred for Tb(3+), Dy(3+), Ho(3+), Er(3+), and Tm(3+). Sm(3+), Eu(3+), and Gd(3+) samples were sensitive to humidity conditions because high- and low-hydration phases were interconvertible at a critical humidity of 10%, 20%, and 50%, respectively, as supported by both X-ray diffraction and gravimetry as a function of the relative humidity. In the phase conversion process, interlayer expansion or contraction of approximately 0.2 A also occurred as a possible consequence of absorption/desorption of H(2)O molecules. The hydration difference was also evidenced by refinement results. The number of coordinated water molecules per formula weight, n, changed from 6.6 for the high-hydration Gd sample to 6.0 for the low-hydration Gd sample. Also, the hydration number usually decreased with increasing atomic number; e.g., n = 7.4, 6.3, 7.2, and 6.6 for high-hydration Nd, Sm, Eu, and Gd, and n = 6.0, 5.8, 5.6, 5.4, and 4.9 for low-hydration Gd, Tb, Dy, Ho, and Er. The variation in the average Ln-O bond length with decreasing size of the lanthanide ions is also discussed. This family of layered lanthanide compounds highlights a novel chemistry of interplay between crystal structure stability and coordination geometry with water molecules.     

Studies on hydrolytic polymerization of rare-earth metal ions-V Hydrolytic polymerization of Dy(3+)

The hydrolytic polymerization of Dy(3+) was determined by the equilibrium-pH method. The concentration of Dy(3+) was varied from 0.1 to 0.6M. The composition and hydrolysis constants of the Dy(3+) hydrolysis products were obtained by a graphical method and then refined by computer fitting and pq analysis. The results show that the species in the Dy(3+) solution are Dy(OH)](2+), [Dy(2)(OH)(2)](4+) and [Dy(3)(OH)(3)](6+), but the last of these is a minor species. The behaviour of Dy(3+) is the same as that of Er(3+) and Yb(3+) but different from that of the medium lanthanide ions Sm(3+), Eu(3+) and Gd(3+).     

Metal complexes with a new N(4)O(3) amine pendant-armed macrocyclic ligand: synthesis, characterization, crystal structures, and fluorescence studies

The synthesis of a new oxaaza macrocyclic ligand, L, derived from O(1),O(7)-bis(2-formylphenyl)-1,4,7-trioxaheptane and tren containing an amine terminal pendant arm, and its metal complexation with alkaline earth (M = Ca(2+), Sr(2+), Ba(2+)), transition (M = Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+)), post-transition (M = Pb(2+)), and Y(3+) and lanthanide (M = La(3+), Er(3+)) metal ions are reported. Crystal structures of [H(2)L](ClO(4))(2).3H(2)O, [PbL](ClO(4))(2), and [ZnLCl](ClO(4)).H(2)O are also reported. In the [PbL] complex, the metal ion is located inside the macrocyclic cavity coordinated by all N(4)O(3) donor atoms while, in the [ZnLCl] complex, the metal ion is encapsulated only by the nitrogen atoms present in the ligand. pi-pi interactions in the [H(2)L](ClO(4))(2).3H(2)O and [PbL](ClO(4))(2) structures are observed. Protonation and Zn(2+), Cd(2+), and Cu(2+) complexation were studied by means of potentiometric, UV-vis, and fluorescent emission measurements. The 10-fold fluorescence emission increase observed in the pH range 7-9 in the presence of Zn(2+) leads to L as a good sensor for this biological metal in water solution.     

含2，2＇-联嘧啶桥Ir^III-Ln^III（Ln=Nd，Yb，Er）双金属配合物的合成和光物理性质

选择具有（N^N）（N^N）位点的四齿配体2,2’-联嘧啶fbpm）作为桥联配体,利用铱配合物Ir（dfppy）2（bpm）Cl作为配体与稀土配合物Ln（TTA）3·2H2O配位,得到了Ir^III-Ln^III（Ln=Nd,Yb,Er）双金属配合物[Ir（dfppy）2（bpm）Ln（TTA）3]Cl．通过荧光滴定的方法,测定了该铱配合物与稀土离子之间的络合稳定常数．通过对铱配合物及Ir^III-Ln^III（Ln=Nd,Yb,Er）双金属配合物在可见区光谱的测定,可以观察到明显的铱配合物发光的猝灭,说明从铱中心到稀土中心发生了能量传递．同时,利用可见光选择性激发铱配合物可以获得在稀土Nd^III,Yb^III,E^III离子红外区的发光．说明了铱配合物Ir（dfppy）2（bpm）Cl作为配体可以较好地敏化稀土离子的红外发光．