Synthesis of luminescent homo-dinuclear cationic lanthanide cyclen complexes bearing amide pendant arms through the use of copper catalysed (1,3-Huisgen, CuAAC) click chemistry

The design and synthesis of dinuclear-lanthanide complexes possessing triazole-based bridges, formed by using copper catalysed 1,3-cycloaddition reactions between heptadentate alkyne functionalised cyclen europium or terbium complexes and di-azides (CuAAC reactions), are described. While this click reaction worked well for the formation of the homo-Eu(III) and Tb(III) bis-tri-arm cyclen N,N-dimethyl acetamide complexes, 2Eu and 2Tb, and for the homo-Eu(III) chiral N-methylnaphthalene based complexes 3Eu (S,S,S) and 4Eu (R,R,R), the formation of the Eu(III) complex of the primary amide analogue of 2, namely 1Eu, was not successful, clearly demonstrating the effect that the nature of the pendant arms has on this reaction. Furthermore, the click reactions between the free alkyne cyclen bis-derivatives (5-8) and the di-azide were unsuccessful, most likely due to the high affinity of the cyclen macrocycles for Cu(II). The Eu(III) complexes of 2-4 and 2Tb all gave rise to sensitised metal ion centred emission upon excitation of the triazole or the naphthalene antennae in methanol solution, and their hydration states were determined, which showed that while the Eu(III) mono-nuclear complexes had q ～ 2, the click products all had q ～ 1. In the case of 3Eu (S,S,S) and 4Eu (R,R,R), the circular polarised emission (CPL) was also observed for both, demonstrating the chiral environment of the lanthanide centres.     

Rare earth complexes with a novel ligand N-(naphthalen-2-yl)-N-phenyl-2-(quinolin-8-yloxy)acetamide: preparation and spectroscopic studies

Six complexes of rare earth nitrates (Ln=La, Sm, Eu, Gd, Tb, Dy) with a new amide type ligand, N-(naphthalen-2-yl)-N-phenyl-2-(quinolin-8-yloxy)acetamide (L) have been prepared and characterized by elemental analysis, conductivity measurements, IR and and 1H NMR spectra. Under excitation, Eu(III) and Sm(III) complexes exhibited strong red emissions. And the luminescence intensity of Sm(III) complex is higher than that of Eu(III) complex. Thus the Eu(III) and Sm(III) complexes are the potential light conversion agent. However, the Tb(III) and Dy(III) complexes cannot exhibit characteristic emissions of terbium and dysprosium ions, respectively. The results of phosphorescence spectrum show that the triplet-state energy level of the ligand matches better to the resonance level of Eu(III) than Tb(III) ion. In addition, the luminescence of the Eu(III) complex is also relatively strong in highly diluted tetrahydrofuran solution (2 x 10(-4)mol/L) compared with the powder. This is not only due to the solvate effects but also to the changes of the structure of the Eu(III) complex after being dissolved into the solvents. Furthermore, owing to the co-luminescence effect, the proper La(III) or Gd(III) doped Eu(III) complexes show stronger luminescence than the pure Eu(III) complex.     

Synthesis, characterization of the luminescent lanthanide complexes with (Z)-4-(4-methoxyphenoxy)-4-oxobut-2-enoic acid

(Z)-4-(4-Methoxyphenoxy)-4-oxobut-2-enoic acid and its solid rare earth complexes LnL3.2H2O (Ln=La, Eu, Tb) were synthesized and characterized by means of MS, elemental analysis, FTIR, 13C NMR and TG-DTA. The IR and 13C NMR results show that the carboxylic groups in the complexes coordinated to the rare earth ions in the form of a bidentate ligand, but the ester carboxylic groups have not taken part in the coordination. The luminescence spectra of Eu(III) and Tb(III) complexes in solid state were also studied. The strong luminescence emitting peaks at 616nm for Eu(III) and 547nm for Tb(III) can be observed, which could be attributed to the ligand has an enhanced effect to the luminescence intensity of the Eu and Tb.     

Lanthanide macrocyclic quinolyl conjugates as luminescent molecular-level devices.

The Eu(III) tetraazamacrocyclic complexes [Eu.1] and [Eu.2], and the Tb(III) and Yb(III) complexes [Tb.1] and [Yb.2], have been synthesized as luminescent molecular-level devices. The Eu complexes exhibit unique dual pH switching behavior in water under ambient conditions. The delayed Eu emission is reversibly switched on in acid, with an enhancement factor of several hundred for [Eu.1]. These observations are consistent with the protonation of the quinoline aryl nitrogen moiety (pK(a) approximately equal to 5.9 for [Eu.1]). The fluorescence emission spectra of these complexes are unaffected by acid, but pronounced changes occur in alkaline solution due to the deprotonation of the aryl amide nitrogen (pK(a) approximately 9.4 for [Eu.1]). [Tb.1] shows a more intriguing pH dependence; Tb emission is switched "on" only in the presence of H+ and in the absence of molecular oxygen, whereas the fluorescence emission properties are similar to those observed with [Eu.1]. This behavior can be conveniently described as a molecular-level logic gate, corresponding to a two-input INHIBIT function, A wedge B'. The analogous [Yb.2] complex shows no such pH or O(2) dependence.     

Synthesis, characterization and luminescence property of N,N'-di(pyridine N-oxide-2-yl)pyridine-2,6-dicarboxamide and corresponding lanthanide (III) complexes

A new ligand, N,N'-di(pyridine N-oxide-2-yl)pyridine-2,6-dicarboxamide (LH2) and its several lanthanide (III) complexes (La, Eu, Gd, Tb, Y) were synthesized and characterized in detail based on elemental analysis, conductivity measurements, IR, 1H NMR, MS (FAB) and UV spectra and TG-DTA studies. The results indicated that the composition of these binary complexes is [Ln(LH2)(NO3)2.H2O]NO3.nH2O (n=0-1); while the ligand has a good planar structure with strong hydrogen bonds. The fluorescence spectra exhibits that the Tb (III) complex and the Eu (III) complex display characteristic metal-centered fluorescence in solid state while ligand fluorescence is completely quenched. However, the Tb (III) complex displays more effective luminescence than the Eu (III) complex, which is attributed to especial effectivity in transferring energy from the lowest triplet energy level of the ligands (T) onto the excited state (5D4) of Tb (III) than that (5D1) of Eu (III).     

Synthesis and luminescence properties of lanthanide complexes with a new aryl amide bifunctional bridging ligand

A new aryl amide type bifunctional bridging ligand 4,4'-bis{[(2'-benzylaminoformyl)phenoxyl]methyl}-1,1'-biphenyl (L) and its complexes with lanthanide ions (Ln=Pr, Eu, Gd, Tb, Ho, Er) were synthesized and characterized by elemental analysis, infrared spectra, conductivity measurements and thermal analysis. At the same time, the luminescence properties of the Eu and Tb complexes in acetone solutions were investigated. Under the excitation of UV light, these two complexes exhibited characteristic emission of europium and terbium ions. And the lowest triplet state energy level T1 of this ligand matches better to the lowest resonance energy level of Tb(III) than to Eu(III) ion.     

A family of three-dimensional 3d-4f and 4d-4f heterometallic coordination polymers based on mixed isonicotinate and 2-sulfobenzoate ligands: syntheses, structures and photoluminescent properties

Hydrothermal reactions of isonicotinic acid (Hina), 2-sulfobenzoic acid (H(2)sba), d-block metal salts and lanthanide oxides/hydroxides yielded 17 three-dimensional (3D) 3d-4f and 4d-4f heterometallic coordination polymers (HCPs). They are formulated as [LaAg(sba)(ina)(2)](n) (1), [Ln(2)Ag(2)(sba)(2)(ina)(4)(H(2)O)(2)](n) [Ln = Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Tb (7), Dy (8), Ho (9), Er (10)] and [Ln(2)Cu(2)(sba)(2)(ina)(4)(H(2)O)(2)](n) [Ln = La (11), Pr (12), Nd (13), Sm (14), Eu (15), Gd (16), Tb (17)]. Their structures were characterized by single crystal X-ray diffraction, powder X-ray diffraction (XRD), infrared (IR) spectroscopy, elemental analysis (EA), and thermogravimetric analysis (TGA). It reveals that they represent two structural types of 3D HCPs. Furthermore, the investigations of their solid-state photoluminescent (PL) property demonstrate the extraordinary emission behaviors. HCP 1(La-Ag) exhibits tunable blue-to-green PL emissions by variation of excitation light. HCPs 6(Gd-Ag), 11(La-Cu), 12(Pr-Cu) and 16(Gd-Cu) show d(10)-metal-based ligand-to-metal charge transfer (LMCT) or metal-to-ligand charge transfer (MLCT) emissions. HCPs 3(Nd-Ag), 4(Sm-Ag), 5(Eu-Ag), 7(Tb-Ag), 8(Dy-Ag), 13(Nd-Cu), 14(Sm-Cu), 15(Eu-Cu) and 17(Tb-Cu) display characteristic PL emissions of the corresponding Ln(III) ions, while both d(10)-metal-based and 4f-metal-centered emissions are observed in the emission spectra of 4(Sm-Ag), 8(Dy-Ag), 14(Sm-Cu) and 17(Tb-Cu).     

Lanthanide(III) Complexes of Cyclen Triacetates and Triamides Bearing Tertiary Amide-Linked Antennae

The coordination compounds of the trivalent lanthanide ions (Ln(III)) have unique photophysical properties. Ln(III) excitation is usually performed through a light-harvesting antenna. To enable Ln(III)-based emitters to reach their full potential, an understanding of how complex structure affects sensitization and quenching processes is necessary. Here, the role of the linker between the antenna and the metal binding fragment was studied. Four macrocyclic ligands carrying coumarin 2 or 4-methoxymethylcarbostyril sensitizing antennae linked to an octadentate macrocyclic ligand binding site were synthesized. Complexation with Ln(III) (Ln = La, Sm, Eu, Gd, Tb, Yb and Lu) yielded species with overall −1, 0, or +2 and +3-charge. Paramagnetic ¹H NMR spectroscopy indicated subtle differences between the coumarin- and carbostyril-carrying Eu(III) and Yb(III) complexes. Cyclic voltammetry showed that the effect of the linker on the Eu(III)/Eu(II) apparent reduction potential was dependent on the electronic properties of the N-substituent. The Eu(III), Tb(III) and Sm(III) complexes were all luminescent. Coumarin-sensitized complexes were poorly emissive; photoinduced electron transfer was not a major quenching pathway in these species. These results show that seemingly similar emitters can undergo very different photophysical processes, and highlight the crucial role the linker can play.     

[（n—C4H9）4N][EuxM1—x（TTA）4]（M=La、Sm、Gd、Tb）的光致发光

合成了一类组成为[(n-C4H9)4N][EuxM1-x(TTA)4](M=La、Sm、Gd、Tb）的固体配合物，通过测定其红外光谱，X射线粉末衍射谱和荧光光谱，研究了配合物结构和发光性质随Eu^3 浓度变化的规律。红外光谱和XRD谱的分析结果表明，在体系中没有新化合物生成，而荧光光谱分析结果表明发光强度与Eu^3 浓度不成线性关系，不发光的基质配合物组分对发光有不同大小和不同类型的影响，提出一种可能的发光机制解释这一共发光现象。     

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   

Influence of anionic functions on the coordination and photophysical properties of lanthanide(III) complexes with tridentate bipyridines

A series of four ligands based on a 5'-methyl-2,2'-bipyridyl framework substituted in the 6 position by a carboxylic acid, a phosphonic acid, a monoethyl ester phosphonic acid, or a diethyl ester phosphonic acid are described. The pK(a) values of all ligands and their assignments are determined by a combination of UV-vis absorption spectroscopy and (1)H and (31)P NMR spectroscopy. The ability of the tridentate ligands to form complexes with trivalent lanthanide cations (Ln = La, Nd, Eu, and Lu) in buffered water solutions (Tris-HCl, pH = 7.4) is studied by UV-vis absorption spectroscopy and (1)H NMR. While the two ester ligands display a weak coordination ability toward lanthanide cations, the acid ligands form stable complexes with 1:1, 1:2, and 1:3 Ln/L ratios. A weak selectivity is observed for the middle of the lanthanide series, and the complexes of the phosphonic acid derivative are up to 2 orders of magnitude more stable than those of the carboxylic acid ligand. Photophysical properties of the free phosphonic and carboxylic acid ligands and of their complexes with La, Eu, Gd, Tb, and Lu are investigated in buffered aqueous solutions both at room temperature and 77 K. An efficient ligand-to-metal energy transfer is observed for both the Eu and Tb complexes. Despite a relatively large energy gap between the ligand-centered (3)pipi* and the Eu((5)D(0)) or Tb((5)D(4)) emitting states, the metal-centered luminescence is well sensitized with quantum yields reaching up to 45.5 and 42.2% for the Tb 1:3 complexes with carboxylic and phosphonic acid ligands, respectively.     

Thermal and luminescence characterization of lanthanide 2,6-naphthalenedicarboxylates series

The lanthanide 2,6-naphthalenedicarboxylates series of the formulas Ln₂(ndc)₃·nH₂O, where Ln = lanthanides from La(III) to Lu(III); ndc - C₁₀H₆(COO)₂²⁻; n = 4, 4.5 or 5 have been prepared by the precipitation method. All obtained products were examined and characterized by elemental analysis, FTIR spectroscopy, simultaneous thermal analyses TG-DSC and TG-FTIR, X-Ray diffraction patterns as well as luminescence measurements. The crystalline compounds form three isostructural groups: Ce-Sm; La and Eu-Dy; Ho-Lu. In all complexes, the ndc²⁻ ligand appears in the deprotonated form. Heating of the complexes resulted in the multi-steps decomposition process. The dehydration process leads to the formation of stable crystalline Ln₂ndc₃ compounds which further decompose to the corresponding lanthanide oxides (air atmosphere). In argon atmosphere they decompose with releasing of water, carbon oxides and naphthalene molecules. The luminescence properties of Eu(III), Nd(III), Tb(III) and Er(III) complexes were investigated. The complexes of Eu(III) and Tb(III) emitted red and green light when excited by ultraviolet light whereas Nd(III) and Er(III) display emissions in the NIR region.     

Simultaneous spectrophotometric determination of atrazine and cyanazine by chemometric methods

Three novel ligands containing pyridine-2,6-dicarboxylic acid unit, trans-4 -(4'-methoxystyryl) pyridine-2,6-dicarboxylic acid, trans-4-(4'-(dimethylamino)styryl)pyridine-2,6-dicarboxylic acid, and trans-4-(4'-(diphenylamino)styryl)pyridine-2,6-dicarboxylic acid were synthesized and their complexes with Eu(III), Tb(III) ions were successfully prepared. The ligands and the corresponding metal complexes were characterized by means of MS, elemental analysis, IR, (1)H NMR and TG-DTA. The luminescence spectra of Eu(III) and Tb(III) complexes in solid state were studied. The strong luminescence emitting peaks at 615 nm for Eu(III) and 545 nm for Tb(III) can be observed. The applications in cell imaging of the europium and terbium complexes were investigated.     

用非等温DSC曲线确定Ln(NCS)3-·4C3H5CH2NH2的热分解反应机理函数及热分解反应动力学参数

本文利用非等温DSC曲线对十二种镧系元素异硫氰酸盐与苄胺形成的配合物Ln(NCS)3·4C6H5CH2NH2(Ln=La、Pr、Nd、Sm、Eu、Ge、Tb、Dy、Ho、Er、Tm、Yb)进行了非等温动力学研究, 并运用积分法和微分法进行了分析, 推断了它们的热分解反应机理函数。     

Fixation of carbon dioxide by macrocyclic lanthanide(III) complexes under neutral conditions producing self-assembled trimeric carbonato-bridged compounds with μ3-η2:η2:η2 bonding

A series of mononuclear lanthanide(III) complexes [Ln(LH(2))(H(2)O)(3)Cl](ClO(4))(2) (Ln = La, Nd, Sm, Eu, Gd, Tb, Lu) of the tetraiminodiphenolate macrocyclic ligand (LH(2)) in 95 : 5 (v/v) methanol-water solution fix atmospheric carbon dioxide to produce the carbonato-bridged trinuclear complexes [{Ln(LH(2))(H(2)O)Cl}(3)(μ(3)-CO(3))](ClO(4))(4)·nH(2)O. Under similar conditions, the mononuclear Y(III) complex forms the dimeric compound [{Y(LH(2))(H(2)O)Cl}(μ(2)-CO(3)){Y(LH(2))(H(2)O)(2)}](ClO(4))(3)·4H(2)O. These complexes have been characterized by their IR and NMR ((1)H, (13)C) spectra. The X-ray crystal structures have been determined for the trinuclear carbonato-bridged compounds of Nd(III), Gd(III) and Tb(III) and the dinuclear compound of Y(III). In all cases, each of the metal centers are 8-coordinate involving two imine nitrogens and two phenolate oxygens of the macrocyclic ligand (LH(2)) whose two other imines are protonated and intramolecularly hydrogen-bonded with the phenolate oxygens. The oxygen atoms of the carbonate anion in the trinuclear complexes are bonded to the metal ions in tris-bidentate μ(3)-η(2):η(2):η(2) fashion, while they are in bis-bidentate μ(2)-η(2):η(2) mode in the Y(III) complex. The magnetic properties of the Gd(III) complex have been studied over the temperature range 2 to 300 K and the magnetic susceptibility data indicate a very weak antiferromagnetic exchange interaction (J = -0.042 cm(-1)) between the Gd(III) centers (S = 7/2) in the metal triangle through the carbonate bridge. The luminescence spectral behaviors of the complexes of Sm(III), Eu(III), and Tb(III) have been studied. The ligand LH(2) acts as a sensitizer for the metal ions in an acetonitrile-toluene glassy matrix (at 77 K) and luminescence intensities of the complexes decrease in the order Eu(3+) > Sm(3+) > Tb(3+).     

Noncovalent ligand-to-ligand interactions alter sense of optical chirality in luminescent tris(β-diketonate) lanthanide(III) complexes containing a chiral bis(oxazolinyl) pyridine ligand

Highly luminescent tris[β-diketonate (HFA, 1,1,1,5,5,5-hexafluoropentane-2,4-dione)] europium(III) complexes containing a chiral bis(oxazolinyl) pyridine (pybox) ligand--[(Eu(III)(R)-Ph-pybox)(HFA)(3)], [(Eu(III)(R)-i-Pr-pybox)(HFA)(3)], and [(Eu(III)(R)-Me-Ph-pybox)(HFA)(3)])--exhibit strong circularly polarized luminescence (CPL) at the magnetic-dipole ((5)D(0) → (7)F(1)) transition, where the [(Eu(III)(R)-Ph-pybox)(HFA)(3)] complexes show virtually opposite CPL spectra as compared to those with the same chirality of [(Eu(III)(R)-i-Pr-pybox)(HFA)(3)] and [(Eu(III)(R)-Me-Ph-pybox)(HFA)(3)]. Similarly, the [(Tb(III)(R)-Ph-pybox)(HFA)(3)] complexes were found to exhibit CPL signals almost opposite to those of [(Tb(III)(R)-i-Pr-pybox)(HFA)(3)] and [(Tb(III)(R)-Me-Ph-pybox)(HFA)(3)] complexes with the same pybox chirality. Single-crystal X-ray structural analysis revealed ligand-ligand interactions between the pybox ligand and the HFA ligand in each lanthanide(III) complex: π-π stacking interactions in the Eu(III) and Tb(III) complexes with the Ph-pybox ligand, CH/F interactions in those with the i-Pr-pybox ligand, and CH/π interactions in those with the Me-Ph-pybox ligand. The ligand-ligand interactions between the achiral HFA ligands and the chiral pybox results in an asymmetric arrangement of three HFA ligands around the metal center. The metal center geometry varies depending on the types of ligand-ligand interaction.     

Visible and near-infrared intense luminescence from water-soluble lanthanide [Tb(III), Eu(III), Sm(III), Dy(III), Pr(III), Ho(III), Yb(III), Nd(III), Er(III)] complexes

The synthesis of a new ligand (1) containing a single phenanthroline (phen) chromophore and a flexibly connected diethylenetriamine tetracarboxylic acid unit (DTTA) as a lanthanide (Ln) coordination site is reported [1 is 4-[(9-methyl-1,10-phenantrol-2-yl)methyl]-1,4,7-triazaheptane-1,1,7,7-tetraacetic acid]. From 1, an extended series of water-soluble Ln.1 complexes was obtained, where Ln is Eu(III), Tb(III), Gd(III), Sm(III), Dy(III), Pr(III), Ho(III), Yb(III), Nd(III), and Er(III). The stoichiometry for the association was found 1:1, with an association constant K(A) > or = 10(7) s(-1) as determined by employing luminescence spectroscopy. The luminescence and photophysical properties of the series of lanthanide complexes were investigated in both H2O and D2O solutions. High efficiencies for the sensitized emission, phi(se), in air-equilibrated water were observed for the Ln.1 complexes of Eu(III) and Tb(III) in the visible region (phi(se) = 0.24 and 0.15, respectively) and of Sm(III), Dy(III), Pr(III), Ho(III), Yb(III), Nd(III), and Er(III) in the vis and/or near-infrared region [phi(se) = 2.5 x 10(-3), 5 x 10(-4), 3 x 10(-5), 2 x 10(-5), 2 x 10(-4), 4 x 10(-5), and (in D2O) 4 x 10(-5), respectively]. For Eu.1 and Tb.1, luminescence data for water and deuterated water allowed us to estimate that no solvent molecules (q) are bound to the ion centers (q = 0). Luminescence quenching by oxygen was investigated in selected cases.     

Attempted syntheses of lanthanide(III) complexes of the anisole- and anilinosquarate ligands

The polymeric lanthanide complexes (Ln(mu-CH3OC6H5C4O3)(CH3OC6H5C4O3)2 (H2O)4.xH2O)n [Ln=La (1), Eu (2), Gd (3)], formed from the reaction of aqueous solutions of anisolesquarate and Ln(NO3)3.xH2O, are all structurally similar with only subtle differences between the lanthanum complex and the isomorphous pair of europium and gadolinium analogues. The lanthanum atom in 1 has a square antiprismatic coordination geometry comprising two pendant and two mu-1,3-bridging anisolesquarate groups and four aqua ligands. Complexes 2 and 3 have two independent metal atoms in their asymmetric units compared to one for the lanthanum complex. However, the gross structures of 1-3 are essentially the same. The asymmetric unit of the terbium complex ((CH3OC6H5C4O3)3Tb(H2O)4(mu-CH3OC6H5C4O3)(CH3OC6H5C4O3)2Tb(H2O)5).H2O (4) contains two independent binuclear units which hydrogen bond to form an extended structure very similar to those of 1-3. The ionic polymers ([Ln(mu2-C4O4)(H2O)6][C6H5NHC4O3].4H2O)n [Ln=Eu (5), Gd (6), Tb (7)] result from the incomplete hydrolysis of the anilinosquarate ion during the attempted synthesis of Eu(III), Gd(III), and Tb(III) anilinosquarate complexes. However, complete hydrolysis of the substituent is accomplished by La(III) ions, and the neutral polymer (La2(mu2-C4O4)2(mu3-C4O4)(H2O)11.2H2O)n (8) is formed. In complexes 5-7, the central lanthanide atom has a square antiprismatic geometry, being bonded to two mu-1,2-bridging squarate and six aqua ligands. Two anilinosquarate counteranions participate in second-sphere coordination via direct hydrogen bonding to aqua ligands on each metal center. These counteranions, and the included waters of crystallization, serve to link neighboring cationic polymer chains via an extensive array of O-H...O hydrogen bonds to form a 3-dimensional network. The polymeric lanthanum complex 8 contains two different metal environments, each having distorted monocapped square antiprismatic geometry. For one lanthanum atom the coordination polyhedron comprises five aqua and four squarate ligands, while for the other the polyhedron consists of six aqua and three squarate ligands; in each case one of the aqua ligands occupies the capping position. The squarate ligand exhibits two coordination modes in 8 (mu-1,2- and mu-1,3-bridging), and neighboring polymer chains are cross-linked by hydrogen bonds to form a 3-dimensional network.     

Columinescence effect in macromolecular complexes of Eu(III) and Tb(III)

The effect of Y(III) and Gd(III) coactivator ions on the intensity of Eu(III) and Tb(III) luminescence in monomer and polymer mixed-metal complexes was studied. Isomorphic replacement of Eu(III) and Tb(III) ions by Y(III) and Gd(III) ions in macromolecular complexes led to sensitization of Eu(III) and Tb(III) ion luminescence. A mechanism of columinescence was suggested. It involves a charge transfer and the ligand orbitals and the vacant orbitals of Eu(III) and Tb(III) ions and coactivators.     

Synthesis of Eu(III) and Tb(III) complexes with novel pyridine dicarboxamide derivatives and their luminescence properties

A novel ligand, N2,N6-bis[2-(3-methylpyridyl)]pyridine-2,6-dicarboxamide (L2) and the corresponding Eu(III) and Tb(III) hydrochlorate complexes have been synthesized and characterized in detail based on elemental analysis, IR and NMR. The crystal and molecular structure of the complexes was determined by X-ray crystallography. The Eu(III) and Tb(III) ions were found to coordinate to the amido nitrogen atoms and pyridine nitrogen atoms. The luminescence properties of lanthanide complexes in solid state, in different solutions and in different pH value were investigated. The result shows that Tb(III) complexes exhibit more efficient luminescence than Eu(III) complexes, and the ligand (L2) is an excellent sensitizer to Tb(III) ion.