Thermodynamic, spectroscopic, and computational studies of lanthanide complexation with diethylenetriaminepentaacetic acid: temperature effect and coordination modes

Stability constants of two DTPA (diethylenetriaminepentaacetic acid) complexes with lanthanides (ML(2-) and MHL(-), where M stands for Nd and Eu and L stands for diethylenetriaminepentaacetate) at 10, 25, 40, 55, and 70 °C were determined by potentiometry, absorption spectrophotometry, and luminescence spectroscopy. The enthalpies of complexation at 25 °C were determined by microcalorimetry. Thermodynamic data show that the complexation of Nd(3+) and Eu(3+) with DTPA is weakened at higher temperatures, a 10-fold decrease in the stability constants of ML(2-) and MHL(-) as the temperature is increased from 10 to 70 °C. The effect of temperature is consistent with the exothermic enthalpy of complexation directly measured by microcalorimetry. Results by luminescence spectroscopy and density functional theory (DFT) calculations suggest that DTPA is octa-dentate in both the EuL(2-) and EuHL(-) complexes and, for the first time, the coordination mode in the EuHL(-) complex was clarified by integration of the experimental data and DFT calculations. In the EuHL(-) complex, the Eu is coordinated by an octa-dentate H(DTPA) ligand and a water molecule, and the protonation occurs on the oxygen of a carboxylate group.     

Time-resolved laser fluorescence spectroscopy and extended X-ray absorption spectroscopy investigations of the N3- complexation of Eu(III), Cm(III), and Am(III) in an ionic liquid: differences and similarities

The complexation of the lanthanide Eu(III) and the actinides Cm(III) and Am(III) by N3- was investigated by application of time-resolved laser fluorescence spectroscopy (TRLFS) and X-ray absorption spectroscopy (XAFS) in the ionic liquid solution of C4mimTf2N (1-butyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imide). TRLFS measurements show that the interaction of azide with Eu(CF3SO3)3 and Eu(ClO4)3 results in both dynamic luminescence quenching by collisional encounters of N3- with Eu(III) and static luminescence quenching by inner-sphere complexation of Eu(III) by N3-. Hereby, the complexation of Eu-triflate by azide starts at a lower N3- concentration as compared to the perchlorate salt. The authors ascribe this phenomenon to a stronger bonding of ClO4- toward the metal ion than triflate, as well as to a stronger electrostatic repulsion of N3- by the perchlorate ligand. In both actinide samples (Cm(ClO4)3, Am(ClO4)3), the complexation with azide exhibits a clear kinetic hindrance. Nevertheless, mixed actinide-perchlorate-azide complexes are formed after several days in C4mimTf2N. The different reaction kinetics for the Ln- and An-complexation by azide may provide the opportunity for an effective separation of lanthanides from actinides in the nuclear fuel cycle by the use of N-based extractants in ionic liquid solution.     

The effect of temperature on the complexation of Cm(III) with nitrate in aqueous solutions

The complexation of curium(III) with nitrate was studied at different temperatures (10-85 °C) by luminescence spectroscopy. The stability constants of CmNO(3)(2+) were calculated from the luminescence emission spectra. The specific ion interaction approach (SIT) was used to obtain the stability constants of CmNO(3)(2+) at infinite dilution and variable temperatures. The complexation is weak and little effect of temperature on the complexation was observed over the temperature range 10-85 °C. Data on the luminescence lifetime indicate that each nitrate ligand replaces two water molecules from the inner coordination sphere of Cm(3+), forming a bidentate inner-sphere complex with Cm(3+) in aqueous solutions.     

Highly luminescent, triple- and quadruple-stranded, dinuclear Eu, Nd, and Sm(III) lanthanide complexes based on bis-diketonate ligands

The bis(beta-diketone) ligands 1,3-bis(3-phenyl-3-oxopropanoyl)benzene, H(2)L(1) and 1,3-bis(3-phenyl-3-oxopropanoyl) 5-ethoxy-benzene, H(2)L(2), have been prepared for the examination of dinuclear lanthanide complex formation and investigation of their properties as sensitizers for lanthanide luminescence. The ligands bear two conjugated diketonate binding sites linked by a 1,3-phenylene spacer. The ligands bind to lanthanide(III) or yttrium(III) ions to form neutral homodimetallic triple stranded complexes [M(2)L(1)(3)] where M = Eu, Nd, Sm, Y, Gd and [M(2)L(2)(3)], where M = Eu, Nd or anionic quadruple-stranded dinuclear lanthanide units, [Eu(2)L(1)(4)](2-). The crystal structure of the free ligand H(2)L(1) has been determined and shows a twisted arrangement of the two binding sites around the 1,3-phenylene spacer. The dinuclear complexes have been isolated and fully characterized. Detailed NMR investigations of the complexes confirm the formation of a single complex species, with high symmetry; the complexes show clear proton patterns with chemical shifts of a wide range due to the lanthanide paramagnetism. Addition of Pirkle's reagent to solutions of the complexes leads to splitting of the peaks, confirming the chiral nature of the complexes. Electrospray and MALDI mass spectrometry have been used to identify complex formulation and characteristic isotope patterns for the different lanthanide complexes have been obtained. The complexes have high molar absorption coefficients (around 13 x 10(4) M(-1)cm(-1)) and display strong visible (red or pink) or NIR luminescence upon irradiation at the ligand band around 350 nm, depending on the choice of the lanthanide. Emission quantum yield experiments have been performed and the luminescence signals of the dinuclear complexes have been found to be up to 11 times more intense than the luminescence signals of the mononuclear analogues. The emission quantum yields and the luminescence lifetimes are determined to be 5% and 220 micros for [Eu(2)L(1)(3)], 0.16% and 13 micros for [Sm(2)L(1)(3)], and 0.6% and 1.5 micros for [Nd(2)L(1)(3)]. The energy level of the ligand triplet state was determined from the 77 K spectrum of [Gd(2)L(1)(3)]. The bis-diketonate ligand is shown to be an efficient sensitizer, particularly for Sm and Nd. Photophysical studies of the europium complexes at room temperature and 77 K show the presence of a thermally activated deactivation pathway, which we attribute to ligand-to-metal charge transfer (LMCT). Quenching of the luminescence from this level seems to be operational for the Eu(III) complex but not for complexes of Sm(III) and Nd(III), which exhibit long lifetimes. The quadruple-stranded europium complex has been isolated and characterized as the piperidinium salt of [Eu(2)L(1)(4)](2-). Compared with the triple-stranded Eu(III) complex in the solid state, the quadruple-stranded complex displays a more intense emission signal with a distinct emission pattern indicating the higher symmetry of the quadruple-stranded complex.     

Characterization and comparison of Cm(III) and Eu(III) complexed with 2,6-di(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine using EXAFS, TRFLS, and quantum-chemical methods

The complexation of Cm(III) and Eu(III) with 2,6-di(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine (n-C3H7-BTP) in nonaqueous organic solution is studied with extended X-ray absorption spectroscopy. Bond lengths are the same in both complexes. Quantum-chemical calculations performed at different levels support this finding. On the other hand, the Cm.(n-C3H7-BTP)3 complex is formed at much lower ligand-to-metal concentration ratio than the Eu.(n-C3H7-BTP)3 complex, as shown by time-resolved laser-induced fluorescence spectroscopy. This is in good agreement with n-C3H7-BTP's high selectivity for trivalent actinides over lanthanides in liquid-liquid extraction.     

Synthesis and luminescence properties of the Pr(III), Sm(III), Eu(III), Nd(III), and Yb(III) complexes with propane-1,3-dione derivatives

The luminescence method, mass spectrometry, and elemental analysis are used to reveal that under optimal conditions (pH 5–8) Ln³⁺ ions (Ln = Pr, Sm, Eu, Nd, and Yb) with 1-(2-hydroxy-4-methylphenyl)-3-(5-methyl-1-phenyl-¹ H-1,2,3-triazol-4-yl)propane-1,3-dione form complexes with the mole ratio Ln: ligand = 2: 3. According to the IR spectral data, Ln³⁺ ions coordinate three oxygen atoms of two carbonyl groups and one hydroxyl group. In the IR spectra of the complexes, an intense band at 628.7 cm^?1 is assigned to the Ln-O bond vibrations. The X-ray diffraction patterns of the complexes contain no lines corresponding to the ligand. The luminescence intensity of the complexes in the visible spectral range changes in the series Eu(III) > Sm(III) > Pr(III), whereas in the IR region the order is Yb(III) > Nd(III). In all cases, luminescence of the solid complexes is considerably more intense than that of their solutions.     

IR luminescence of neodymium(III) and ytterbium(III) complexes with acylpyrazolones in solutions

Acylpyrazolones (L1–L5) have been synthesized and the conditions of their complexation with neodymium(III) and ytterbium(III) ions in aqueous solutions have been elucidated. The component ratio in the synthesized complexes is Nd(Yb): L = 1: 1. The conditions of excitation and luminescence of the ligands and complexes have been studied. The formation of mixed-ligand complexes upon the introduction of trioctyl- or triphenylphosphine oxide leads to a considerable rise of neodymium and ytterbium. In the presence of 1,10-phenanthroline and bathophenanthroline, competing complexation leads to a 20–70% decrease in luminescence intensity. The introduction of water-miscible organic solvents (30 vol %) decreases the Nd(III) and Yb(III) luminescence intensity by a factor of 9–20.     

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.     

Luminescent materials of annealed Eu3+-exchanged zeolite L crystals

In this work, we report the luminescence behavior of Eu(3+)-exchanged zeolite L microcrystals annealed at different temperatures. SEM and XRD techniques were employed to characterize the samples. UV-vis absorption spectroscopy and luminescence spectroscopy were used to study the luminescence properties of the annealed materials. It is shown that Eu(3+)-exchanged zeolite L crystals are structurally stable at 800 °C, and that its structure is completely collapsed when annealed at 1100 °C. Calcination of Eu(3+)-exchanged zeolite L crystals at 700 °C leads to a strong violet-blue emission, while a strong red emission is observed when the sample is annealed at 1100 °C.     

Thermodynamic study of Eu(III) complexation by pyridine monocarboxylates

The thermodynamic parameters (log K, ΔG, ΔH and ΔS) of complexation of Eu(III), a chemical analogue of trivalent actinides, with pyridine monocarboxylates, namely, picolinic acid (pyridine-2-carboxylic acid), nicotinic acid (pyridine-3-carboxylic acid), isonicotinic acid (pyridine-4-carboxylic acid) have been studied at 1.0 M ionic strength adjusted by NaClO₄ and 298 K by potentiometry, fluorescence spectroscopy and calorimetry. The potentiometric results revealed formation of four complexes, ML_i (i = 1–4) in case of picolinate whereas only ML complexes in case of nicotinate and isonicotinate. The log K_ML for Eu(III) picolinate complex is higher than that for complexes of Eu(III) with the other two acids. The complexation reaction between Eu(III) and picolinate was found to be exothermic due to chelate formation via pyridyl nitrogen. In case of complexation of Eu(III) with nicotinate and isonicotinate, the enthalpy changes are similar as in the case of simple mono carboxylates and are positive. Life time measurements by time resolved fluorescence spectroscopy, for the decay of ⁵D₀ state of Eu(III) also indicated the formation of ML₄ with picolinate and formation of ML only with the other two acids. The experimental observations on the stability and binding mode of the complexes are corroborated by theoretical calculations using the TURBOMOLE software. The detail analysis of calculated charge values of the free ligands and the complexes indicates that charge polarization is more in the isonicotinate than in nicotinate upon complexation.     

Complexation of uranium(VI) and samarium(III) with oxydiacetic acid: temperature effect and coordination modes

The complexation of uranium(VI) and samarium(III) with oxydiacetate (ODA) in 1.05 mol kg(-1) NaClO(4) is studied at variable temperatures (25-70 degrees C). Three U(VI)/ODA complexes (UO(2)L, UO(2)L(2)(2-), and UO(2)HL(2)(-)) and three Sm(III)/ODA complexes (SmL(j)((3-2)(j)+) with j = 1, 2, 3) are identified in this temperature range. The formation constants and the molar enthalpies of complexation are determined by potentiometry and calorimetry. The complexation of uranium(VI) and samarium(III) with oxydiacetate becomes more endothermic at higher temperatures. However, the complexes become stronger due to increasingly more positive entropy of complexation at higher temperatures that exceeds the increase in the enthalpy of complexation. The values of the heat capacity of complexation (Delta C(p) degrees in J K(-1) mol(-1)) are 95 +/- 6, 297 +/- 14, and 162 +/- 19 for UO(2)L, UO(2)L(2)(2-), and UO(2)HL(2)(-), and 142 +/- 6, 198 +/- 14, and 157 +/- 19 for SmL(+), SmL(2)(-), and SmL(3)(3-), respectively. The thermodynamic parameters, in conjunction with the structural information from spectroscopy, help to identify the coordination modes in the uranium oxydiacetate complexes. The effect of temperature on the thermodynamics of the complexation is discussed in terms of the electrostatic model and the change in the solvent structure.     

Synthesis, characterisation and biological evaluation of lanthanide(III) complexes with 3-acetylcoumarin-o-aminobenzoylhydrazone (ACAB)

Lanthanide(III) complexes of the general formula [Ln(ACAB)(2)(NO(3))(2)(H(2)O)(2)].NO(3).H(2)O where Ln=La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III) and Y(III), ACAB=3-acetylcoumarin-o-aminobenzoylhydrazone have been isolated and characterised based on elemental analyses, molar conductance, IR, (1)H- and (13)C-NMR, UV, TG/DTA and EPR spectral studies. The ligand behaves in bidentate fashion coordinating through hydrazide >C=O and nitrogen of >C=N. A coordination number of ten is assigned to the complexes. Antibacterial and Antifungal studies indicate an enhancement of activity of the ligand on complexation.     

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   

稀土冠醚类配合物的研究 XX: 三价及二价稀土硫氰酸盐与辛二酰双(4'-苯并-15-冠-5)配合物的合成和性质

在乙腈和二氯甲烷混合溶液中合成了三价稀土元素(La, Nd, Eu, Dy, Er, Yb)硫氰酸盐与辛二酰双(4'-苯并-15-冠-5)的六个新配合物。并在氩气氛中, 以四氢呋喃为溶剂, 锂-萘为还原剂, 制得了二价铕硫氰酸盐与辛二酰双(4'-苯并-15-冠-5)的固体配合物。通过元素分析、红外光谱、差热热重分析、荧光光谱、穆斯堡尔谱、电子自旋共振谱、还原性实验等研究了双冠醚与稀土离子的配位作用, 并讨论了三价和二价稀土配合物在物理化学性质上的差别。     

Thermodynamic study on the complexation of Am(III) and Eu(III) with tetradentate nitrogen ligands: a probe of complex species and reactions in aqueous solution

A thermodynamic investigation has been performed to study the complexation of trivalent metal (M) ions (M = Am(III), Eu(III)) with tetradentate ligands (L), 6,6'-bis(5,6-dialkyl-1,2,4-triazin-3-yl)-2,2'-bipyridines (BTBPs), by using relativistic quantum mechanical calculations. The structures and stabilities of the inner-sphere BTBPs complexes were explored in the presence of various counterions such as NO(3)(-), Cl(-), and ClO(4)(-). According to our calculations, Am(III) and Eu(III) can chelate eight or nine water molecules at most, whereas more stable species like M(NO(3))(3)(H(2)O)(4) tend to be formed in the presence of nitrate ions. The inner sphere of the BTBPs complexes can accommodate four water molecules or three nitrate ions based on our calculations, forming species such as [ML(H(2)O)(4)](3+) and ML(NO(3))(3). Compared with Eu(III) complexes, the Am(III) counterparts have obviously lower binding energies in both the gas phase and solution. In addition, the solvent effect significantly decreases the binding energies of the BTBPs complexes. It has been found that the complexing reactions, in which products and reactants possess the same or close number of nitrate ions, are more favorable for formation of the BTBPs complexes. In short, the reactions of M(NO(3))(3)(H(2)O)(4) → ML(NO(3))(3) and [M(NO(3))(H(2)O)(7)](2+) → [ML(2)(NO(3))](2+) are probably the dominant ones in the Am(III)/Eu(III) separation process.     

Synthesis, characterization, antioxidant activity, and DNA-binding studies of 1-cyclohexyl-3-tosylurea and its Nd(III), Eu(III) complexes

A new ligand, 1-cyclohexyl-3-tosylurea (H(2)L), was prepared by condensation ethyl N-(3-tossulfonyl) carbamate and cyclohexanamine. Its two lanthanide(III) complexes, Ln(H(2)L)(3) . 3NO(3) [Ln=Nd (1), and Eu (2)], have been synthesized and characterized on the base of element analyses, ESI-MS, molar conductivities, IR spectra and thermogravimetry/differential thermal analysis (TG-DTA). In addition, the DNA-binding properties of the ligand and its complexes have been investigated by electronic absorption spectroscopy, fluorescence spectroscopy, circular dichroic (CD) spectroscopy and viscosity measurements. The experiment results suggest that the ligand and its two complexes bind to DNA via a groove binding mode, and the binding affinity of the complex 2 is higher than that of the complex 1 and the ligand. Furthermore, the antioxidant activity (superoxide and hydroxyl radical) of the ligand and its metal complexes was determined by using spectrophotometer methods in vitro. These complexes were found to possess potent antioxidant activity and be better than standard antioxidants like vitamin C and mannitol. In particular, complex 2 displayed excellent activity on the superoxide and hydroxyl radical.     

Tethered dinuclear europium(III) macrocyclic catalysts for the cleavage of RNA

Dinuclear europium(III) complexes of the macrocycles 1,3-bis[1-(4,7,10-tris(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane]-m-xylene (1), 1,4-bis[1-(4,7,10-tris(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane]-p-xylene (2), and mononuclear europium(III) complexes of macrocycles 1-methyl-,4,7,10-tris(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane (3), 1-[3'-(N,N-diethylaminomethyl)benzyl]-4,7,10-tris(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane (4), and 1,4,7-tris(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane (5) were prepared. Studies using direct excitation ((7)F0 --> (5)D0) europium(III) luminescence spectroscopy show that each Eu(III) center in the mononuclear and dinuclear complexes has two water ligands at pH 7.0, I = 0.10 M (NaNO3) and that there are no water ligand ionizations over the pH range of 7-9. All complexes promote cleavage of the RNA analogue 2-hydroxypropyl-4-nitrophenyl phosphate (HpPNP) at 25 degrees C (I = 0.10 M (NaNO3), 20 mM buffer). Second-order rate constants for the cleavage of HpPNP by the catalysts increase linearly with pH in the pH range of 7-9. The second-order rate constant for HpPNP cleavage by the dinuclear Eu(III) complex (Eu2(1)) at pH 7 is 200 and 23-fold higher than that of Eu(5) and Eu(3), respectively, but only 7-fold higher than the mononuclear complex with an aryl pendent group, Eu(4). This shows that the macrocycle substituent modulates the efficiency of the Eu(III) catalysts. Eu2(1) promotes cleavage of a dinucleoside, uridylyl-3',5'-uridine (UpU) with a second-order rate constant at pH 7.6 (0.021 M(-1) s(-1)) that is 46-fold higher than that of the mononuclear Eu(5) complex. Methyl phosphate binding to the Eu(III) complexes is energetically most favorable for the best catalysts, and this supports an important role for the catalyst in stabilization of the developing negative charge on the phosphorane transition state. Despite the formation of a bridging phosphate ester between the two Eu(III) centers in Eu2(1) as shown by luminescence spectroscopy, the two metal ion centers are only weakly cooperative in cleavage of RNA and RNA analogues.     

Aqueous Ln(III) luminescence agents derived from a tasty precursor

The synthesis, characterization, and photophysical properties are reported for several Ln(III) complexes of a tetradentate chelate, 5LIO-MAM, derived from the common flavor enhancer "maltol". Eu(III), Yb(III), and Nd(III) form stable ML2 complexes in aqueous solution that emit in the red or near-infrared (NIR) upon excitation at ca. 330 nm. The synthesis, aqueous stability, and photophysical properties are reported for a novel tetradentate ligand derived from maltol, a commonly used flavor enhancer. In aqueous solution, this chelate forms stable complexes with Ln(III) cations, and sensitized emission was observed from Eu(III), Yb(III), and Nd(III). A comparison with recently reported and structurally analogous ligands reveals a slightly higher basicity but lower complex stability with Eu(III) [pEu = 14.7(1)]. A very poor metal-centered quantum yield with Eu(III) was observed (Phi(tot) = 0.04%), which can be rationalized by the similar energy of the ligand triplet state and the Eu(III) (5)D0 emissive level. Instead, sensitized emission from the Yb(III) and Nd(III) cations was observed, which emit in the NIR.     

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.     

Europium(III) Acrylatodibenzoylmethanate: Synthesis,Spectroscopy (IR,Luminescence), and Polymerization Properties

Eu(III) acrylatodibenzoylmethanate was synthesized with the aim of obtaining luminescent macromolecular Ln(III) complexes with chromophores. It was homo- and copolymerized with methyl methacrylate. The compounds formed were characterized by elemental analysis, luminescence, and IR spectroscopy. The luminescence intensity of the macromolecular Eu(III) complexes containing dibenzoylmethanate ions was shown to exceed the intensity of the monomeric complex by several times. The increase in the luminescence intensity when going from the monomer to copolymers is explained by the weakening of the quenching effect of the low state of the metal–ligand charge transfer.