Terbium(III) and dysprosium(III) 8-connected 3D networks containing 2,5-thiophenedicarboxylate anion: Crystal structures and photoluminescence studies

Two novel coordination polymers with the formula {[Ln(2)(2,5-tdc)(3)(dmso)(2)].H2O}(n) (Ln = Tb(III) for (1) and Dy(III) for (2)), (2,5-tdc(2-) = 2,5-thiophenedicarboxylate and dmso = dimethylsulfoxide) have been synthesized by the diffusion method and characterized by thermal analysis, vibrational spectroscopy and single crystal X-ray diffraction analysis. Structure analysis reveals that 2,5-tdc(2-) play a versatile role toward different lanthanide ions to form three-dimensional metal-organic frameworks (MOFs) in which the lanthanides ions are heptacoordinated. Photophysical properties were studied using excitation and emission spectra, where the photoluminescence data show the high emission intensity of the characteristic transitions D-5(4 ->) F-7(J) (J= 6, 5, 4 and 3) for (1) and (F9/2 -> HJ)-F-4-H-6 (J = 15/2, 13/2 and 11/2) for (2), indicating that 2,5-tdc(2-) is a good sensitizer. (C) 2012 Elsevier Ltd. All rights reserved.CNPqCNPqCAPESCAPESFAPEMIGFAP-EMIG [CEX-APQ 01565-09

Synthesis, structural characterization and photophysical properties of highly photoluminescent crystals of Eu(III), Tb(III) and Dy(III) with 2,5-thiophenedicarboxylate

Lanthanide compounds of general formula [Ln2(2,5-tdc) 3(dmf)2(H2O)2] ·2dmf·H2O (Ln = Eu(III) (1), Tb(III) (2), Gd(III) (3) and Dy(III) (4), dmf = N,N′-dimethylformamide and 2,5-tdc2- = 2,5-thiophedicarboxylate anion) were synthesized and characterized by elemental analysis, X-ray powder diffraction patterns, thermogravimetric analysis and infrared spectroscopy. Phosphorescence data of Gd(III) complex showed that the triplet states (T1) of 2,5-tdc2- ligand have higher energy than the main emitting states of Eu(III), Tb(III) and Dy(III), indicating that 2,5-tdc2- ligand can act as intramolecular energy donor for these metal ions. An energy level diagram was used to establish the most relevant channels involved in the ligand-to-metal energy transfer. The high value of experimental intensity parameter Ω2 for the Eu(III) complex indicate that the europium ion is in a highly polarizable chemical environment. The emission quantum efficiency (η) of the 5D0 emitting level of Eu(III) was also determined. The complexes act as possible light conversion molecular devices (LCMDs). © 2013 Elsevier B.V. All rights reserved

Structure, characterization and near-infrared emission of a novel 6-connected uninodal 3D network of Nd(III) containing 2,5-thiophenedicarboxylate anion

The novel coordination polymer with the formula {[Nd2(2,5-tdc)3(dmf)2(H2O)2].dmf.H2O}n (2,5-tdc2-=2,5-thiophedicarboxylate anion and dmf=dimethylformamide) has been synthesized and characterized by thermal analysis (TG/DTA), vibrational spectroscopy (FTIR) and single crystal X-ray diffraction analysis (XRD). Structure analysis reveals that Nd(III) ions show dicapped trigonal prism coordination geometry. The 2,5-tdc2- ligands connect four Nd(III) centers, adopting (κ1 - κ1) - (κ1 - κ1) - μ4 coordination mode, generating an interesting 6-connected uninodal 3D network. Photophysical properties were studied using diffuse reflectance spectroscopy (DR) and excitation/emission spectra. The photoluminescence data show the near infrared emission (NIR) with the characteristic 4F3/2→4IJ (J=9/2, 11/2 and 13/2) transitions of Nd(III) ion, indicating that 2,5-tdc2- is able to act as a sensitizer for emission in NIR region. © 2013 Elsevier B.V

Synthesis, structural characterization, luminescent properties and theoretical study of three novel lanthanide metal-organic frameworks of Ho(III), Gd(III) and Eu(III) with 2,5-thiophenedicarboxylate anion

In this paper, the synthesis of three new metal-organic frameworks of lanthanides (LnMOFs) {[Ln(2)(2,5-tdc)(3)(dmso)(2)]center dot H2O}(n) (Ln=Ho (1); Gd (2); Eu (3); 2,5-tdc=2,5-thiophenedicarboxylate anion; dmso=dimethylsulfoxide), and their complete characterization, including single crystal X-ray diffraction, FTIR spectroscopy and thermogravimetric analysis are reported. In especial, photophysical properties of Eu(III) complex have been studied in detail via both theoretical and experimental approaches. Crystal structure of (1) reveals that each lanthanide ion is seven-coordinated by oxygen atoms in an overall distorted capped trigonal - prismatic geometry. The 2,5-tdc(2-) ligands connect four Ln(III) centers, adopting (kappa(1)-kappa(1))-(kappa(1)-kappa(1))-mu(4) coordination mode, generating an 8-connected uninodal 3D network. In addition, theoretical studies for Eu(III) complex were performed using the Sparkle model for lanthanide complexes. (C) 2015 Elsevier Inc. All rights reserved.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Exploring the Intense Lanthanide Luminescence and High Thermal Stability in a New Mixed Eu³⁺/Tb³⁺ Organic Framework Series for Marking in Gunshot Residues

Since their discovery, metal–organic frameworks (MOFs) have attracted increasing interest due to the different applications of these materials. One class of these materials is the mixed lanthanide-organic frameworks (m-LnOFs) formed by more than one type of lanthanide ion. Such compounds have been extensively studied, mainly as luminescent thermometers. However, another very interesting application is the use of mixed LnOFs as markers in gunshot residues (GSR), allowing for the creation of a barcode prototype for each type of ammunition. This work reports the hydrothermal synthesis, complete structural characterization, and photophysical study of nine new mixed LnOFs, of general formula [EuxTb1‑x(Hbtec)]n (0.1 ≤ x ≤ 0.9), and with Hbtec3‑ being the anion from 1,2,4,5-benzenetetracarboxylic acid (H4btec). The mixed compound [Eu0.1Tb0.9(Hbtec)]n1 has excellent thermal stability and interesting optical properties, such as more pronounced dual emission and a characteristic Tb3+ → Eu3+ energy transfer, culminating in high purity of its red emission, when compared to its isostructural homometallic [Eu(Hbtec)]n, previously synthesized. Thus, the compound [Eu0.1Tb0.9(Hbtec)]n1 was selected to act as a potential ammunition marker, more precisely in .380 pistol and 38 caliber revolver, demonstrating satisfactory results and being able to provide support to public safety in the future

Theoretical and experimental spectroscopic studies of the first highly luminescent binuclear hydrocinnamate of Eu(III), Tb(III) and Gd(III) with bidentate 2,2 '-bipyridine ligand

In this paper, the synthesis of three new binuclear lanthanide (III) complexes [Ln(2)(cin)(6)(bpy)(2)] (Ln=Eu (1), Tb (2), Gd (3), cin=hydrocinnamate anion; bpy=2,2'-bipyridine), and their complete characterization, including single crystal X-ray diffraction, FTIR spectroscopy and thermal analysis (TGA/DTA) are reported. In especial, photophysical properties of Eu(III) complex have been studied in detail via both theoretical and experimental approaches. Crystal structures of 1-3 reveal that all compounds are isostructural and that each lanthanide ion is nine-coordinated by oxygen and nitrogen atoms in an overall distorted tricapped trigonal-prismatic geometry. Eu(III) complex structure was also calculated using the Sparkle model for lanthanide complexes and the intensity parameters (Omega(2), Omega(4), and Omega(6)), calculated from the experimental data and from Sparkle/PM3 model. The theoretical emission quantum efficiencies obtained for Sparkle/PM3 structures are in excellent agreement with the experimental values, clearly attesting to the efficacy of the theoretical models. The theoretical procedure applied here shows that the europium binuclear compound displays a quantum yield about 65% suggesting that the system can be excellent for the development of efficient luminescent devices. (C) 2013 Elsevier By. All rights reserved.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Synthesis, crystal structure and photoluminescence of a binuclear complex of europium(III) containing 3,5-dicarboxypyrazolate and succinate

The new europium binuclear complex [Eu2(dcpz)2(suc)(H2O)8] (H2O)1.5 (dcpz = 3,5-dicarboxypyrazolate and suc = succinate) has been synthesized and structurally characterized by single crystal X-ray diffraction methods. The binuclear complex crystallizes in the triclinic space group P 1 and consists of two lanthanide ions linked by two different bridging organic ligands. 3D supramolecular framework is constructed by hydrogen bonds. The compound shows strong red emission under UV excitation at room temperature associated to IL transitions indicating a ligand to metal energy transfer mechanism since the triplet energy level lies higher than that of europium 5D0 level. Magnetic susceptibility studies showed weak temperature dependence characteristic of the Van Vleck paramagnetism.CNPqCAPESFAPES

Photoluminescent and Slow Magnetic Relaxation Studies on Lanthanide(III)-2,5-pyrazinedicarboxylate Frameworks

In the series described in this work, the hydrothermal synthesis led to oxidation of the 5-methyl-pyrazinecarboxylate anion to the 2,5-pyrazinedicarboxylate dianion (2,5-pzdc) allowing the preparation of three-dimensional (3D) lanthanide­(III) organic frameworks of formula {[Ln₂(2,5-pzdc)₃(H₂O)₄]·6H₂O}_<i>n</i> [Ln = Ce (<b>1</b>), Pr (<b>2</b>), Nd (<b>3</b>), and Eu (<b>4</b>)] and {[Er₂(2,5-pzdc)₃(H₂O)₄]·5H₂O}_<i>n</i> (<b>5</b>). Single-crystal X-ray diffraction on <b>1</b>–<b>5</b> reveals that they crystallize in the triclinic system, <i>P</i>1̅ space group with the series <b>1</b>–<b>4</b> being isostructural. The crystal structure of the five compounds are 3D with the lanthanide­(III) ions linked through 2,5-pzdc^2– dianions acting as two- and fourfold connectors, building a binodal 4,4-connected (4·6⁴8)­(4²6²8²)-<b>mog</b> network. The photophysical properties of the Nd­(III) (<b>3</b>) and Eu­(III) (<b>4</b>) complexes exhibit sensitized photoluminescence in the near-infrared and visible regions, respectively. The photoluminescence intensity and lifetime of <b>4</b> were very sensitive due to the luminescence quenching of the ⁵D₀ level by O–H oscillators of four water molecules in the first coordination sphere leading to a quantum efficiency of 11%. Variable-temperature magnetic susceptibility measurements for <b>1</b>–<b>5</b> reveal behaviors as expected for the ground terms of the magnetically isolated rare-earth ions [²F_5/2, ²H₄, ⁴I_9/2, ⁷F₀, and ⁴I_15/2 for Ce­(III), Pr­(III), Nd­(III), Eu­(III), and Er­(III), respectively] with <i>M</i>_<i>J</i> = 0 (<b>2</b> and <b>4</b>) and ±1/2 (<b>1</b>, <b>3</b>, and <b>5</b>). Q-band electron paramagnetic resonance measurements at low temperature corroborate these facts. Frequency-dependent alternating-current magnetic susceptibility signals under external direct-current fields in the range of 100–2500 G were observed for the Kramers ions of <b>1</b>, <b>3</b>, and <b>5</b>, indicating slow magnetic relaxation (single-ion magnet) behavior. In these compounds, τ^–1 decreases with decreasing temperature at any magnetic field, but no Arrhenius law can simulate such a dependence in all the temperature range. This dependence can be reproduced by the contributions of direct and Raman processes, the Raman exponent (<i>n</i>) reaching the expected value (<i>n</i> = 9) for a Kramers system