A luminescent dinuclear Eu(III) complex based on 2,8-bis(4′,4′,4′,-trifluoro-1′,3′-dioxobutyl)-dibenzothiophene for light-emitting diodes

A dinuclear Eu (III) complex Eu₂(dbt)₃·4H₂O was synthesized, where H₂dbt was 2,8-bis(4′,4′,4′,-trifluoro-1′,3′-dioxobutyl)-dibenzothiophene. The complex emits the characteristic red luminescence of Eu³⁺ ion due to the ⁵D₀→⁷F_J(J=0-4) transitions under 395 nm-light excitation with a luminescent quantum efficiency of 17%. The complex is thermally stable up to 280 °C. It was found that the complex can be effectively excited by a 395 nm-emitting InGaN chip. Bright red light was obtained using the complex as light color-conversion material.     

Structural and luminescence properties of [Ln(ODA)(phen)·4H2O] complexes (Ln=Sm and Dy, ODA=oxydiacetate, phen=1,10-phenanthroline)

Two novel complexes of Sm(III) and Dy(III) with mixed oxydiacetate (ODA) and 1,10-phenanthroline (phen) ligands were synthesized and their structure and luminescence properties were characterized. The complexes of [Ln(ODA)(phen)·4H₂O]Cl·5H₂O [Ln=Sm and Dy] crystallize in the monoclinic space group P2₁/n with Sm: a=12.3401(14) Å, b=16.821(2), c=12.6847(11) Å, β=107.939(10)°, V=2505.0(5) Å³, Z=4 and ρ=1.841 mg/m³, and with Dy: a=12.289(7) Å, b=16.805(6) Å, c=12.705(4) Å, β=108.144(18)°, V=2493.4(19) Å³, Z=4 and ρ=1.786 mg/m³. The complexes of [Sm(ODA)(phen)·4H₂O]⁺ and [Dy(ODA)(phen)·4H₂O]⁺ excited by UV light produce orange red and lightly white emissions, respectively, via the nonradiative energy transfer from phen to the metals. The quantum yield of the sensitized luminescence of [Dy(ODA)(phen)·4H₂O]⁺ (Q=19%) is much greater than that of [Sm(ODA)(phen)·4H₂O]⁺ (Q=1.4%). The luminescence decay times of the complexes were in a few microsecond range and independent of temperature.     

Photosensitized luminescence of thermostable polynuclear Eu(III) complexes

Tetranuclear europium(III) complexes, [Eu₄(μ-O)(L₁)₁₀] (L₁=2-hydroxy-4-octyloxybenzophenone,1) and [Eu₄(μ-O)(L₂)₁₀] (L₂=2-hydroxy-4-dodecyloxybenzophenone,2) were synthesized by the reaction of lanthanide nitrates with L₁ or L₂ in the presence of triethylamine in methanol. The photosensitized emission bands of the both Eu(III) complexes in THF-d₈ were observed around 579, 590, 615, 653, and 699 nm by the excitation of the ligands at 380 nm, whereas the emission from the mononuclear complex 3 containing ethanol molecules was almost quenched. The emission efficiencies were determined to be 3.1±0.1% for 1 and 3.9±0.1% for 2, respectively. The differential scanning calorimetry (DSC) measurements demonstrated that the decomposition points of 1 and 2 were 309 °C and 320 °C, respectively, indicating high thermostability of these complexes compared to the mononuclear Eu(III) complex 3 (250 °C). New strategy for designing stable rare earth compounds giving strong emission would be emphasized by introducing polynuclear complexes. Polynuclear complexes should open a wide range of molecular design for photosensitized luminescence and thermal stability.     

Correlation between adsorption and thermal properties of lanthanide(III) dinicotinates

Structural and thermal properties of the two isostructural lanthanide metal-organic frameworks: [Er₂(pdc)₃(dmf)₂]·dmf (1) and [Tm₂(pdc)₃(dmf)₂]·dmf (2) where pdc = C₅H₃N(COO)₂²⁻ and dmf = N,N′-dimethylformamide, have been investigated. They are characterized by the BET surface area of 302 and 101 m²/g for 1 and 2, respectively. This paper deals with the influence of activation conditions on sorption properties of the investigated complexes. Thermal investigations of as-made and activated complexes point to their entirely different thermal decompositions.     

Enhanced fluorescence of Tb(III), Dy(III) perchlorate by salicylic acid in bis(benzoylmethyl) sulfoxide complexes and luminescence mechanism

Two novel ternary rare earth perchlorate complexes had been synthesized by using bis(benzoylmethyl) sulfoxide as first ligand (L=C₆H₅COCH₂SOCH₂COC₆H₅), salicylic acid as second ligand (L^′=C₆H₄OHCOO⁻). The compounds were characterized by elemental analysis, TG-DSC and molar conductivities in DMF solution. The composition was suggested as [REL₅L′](ClO₄)₂·nH₂O (RE=Tb, Dy; n=6, 8 ). Based on IR, ¹HNMR and UV spectra, it showed that the first ligand, bis(benzoylmethyl) sulfoxide (L), bonded with Tb(III), Dy(III) ions by the oxygen atom of sulfinyl group. The second ligand, salicylic acid group (L′), not only bonded with RE(III) ions by one oxygen atom of carboxyl group but also bonded with RE(III) ions by oxygen atom of phenolic hydroxyl group. In bis(benzoylmethyl) sulfoxide system, fluorescent spectra of the complexes showed that the luminescence of Tb(III), Dy(III) ions was enhanced by the second ligand salicylic acid. The ternary complexes had stronger fluorescence than the binary ones where only bis(benzoylmethyl) sulfoxide acted as ligand. Phosphorescent spectra of the two ligands indicated that the coordination of salicylic acid resulted in the matching extent increasing between the triplet state of ligand and excited state of the rare earths. The relationship between fluorescence lifetime and fluorescence intensity was also discussed.     

Fluorescence enhancement of lanthanide(III) perchlorate by 1,10-phenanthroline in bis(benzoylmethyl) sulfoxide complexes and luminescence mechanism

Two novel ternary rare earth complexes LnL₅L′(ClO₄)₃2H₂O (Ln=Eu(III), Tb(III); L=bis(benzoylmethyl) sulfoxide, L′=phen) were synthesized and characterized by elemental analysis, coordination titration analysis, molar conductivity, IR, TG-DSC,¹H NMR and UV spectra. The fluorescence spectra illustrated that both the Eu(III) and Tb(III) ternary complexes displayed strong characteristic metal-centered fluorescence in solid state. After the introduction of the second ligand phen group, the relative emission intensities and fluorescence lifetimes of the ternary complex EuL₅L′(ClO₄)₃2H₂O (L=C₆H₅COCH₂SOCH₂COC₆H₅, L′=phen) enhanced more obviously than that of the binary complex EuL₅(ClO₄)₃3H₂O. This indicated that the presence of both organic ligands bis(benzoylmethyl) sulfoxide and the second ligand phen could sensitize fluorescence intensities of Eu(III) ions, and the introduction of phen group was resulted in the enhancement of the fluorescence properties of the Eu(III) ternary rare earth complexes. The phosphorescence spectra are also discussed.     

Synthesis and luminescence of Eu(III) complexes with macrocyclic azacrown ethers and 1,10-phenanthroline

Complexes of Eu(III) with mixed macrocyclic azacrown ethers and 1,10-phenanthroline (phen) were synthesized and their luminescence properties measured. The specific azacrown ethers used were 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetate (TETA) and 1,4,8,12-tetraazacyclopentadecane ([15]aneN₄). The phen-coordinated complexes excited by UV light produced a very bright red emission via an intra-molecular energy transfer from phen to Eu(III). For [Eu(TETA)·(phen)·(H₂O)]⁻ and [Eu([15]aneN₄)·(phen)₂]³⁺, the quantum yields of sensitized luminescence were 8.4% and 7.8%, respectively, and were much greater than those from non-sensitized luminescence of 1.2% and 4.4%, respectively. The decay times of the corresponding phen-coordinated complexes, as measured at room temperature, were 1.6 and 0.6 ms, respectively, and were much longer than those of the phen-uncoordinated complexes of 0.3 and 0.2 ms, respectively.     

Influences of compositions and ligands on photoluminescent properties of Eu(III) ions in composite europium complex/PMMA systems

Three kinds of europium complexes; Eu(phen)₂Cl₃(H₂O)₂, Eu(DN-bpy)phenCl₃(H₂O)₂ and Eu(DB-bpy)phenCl₃(H₂O)₂ (phen: 1,10-phenanthroline, DN-bpy: 4,4′-Dinonyl-2,2′-dipyridyl, DB-bpy: 4,4′-Di-tert-butyl-2,2′-dipyridyl) were prepared and then incorporated into polymethyl methacrylate (PMMA) matrix with different molar ratios of CO groups/Eu³⁺ ions. The final solid composites were formed by a self-assembly process among Eu³⁺ ion, the ligands and PMMA during the solvent evaporation process, and then the ligands re-coordinate to Eu(III). It was found that the ligands affect not only the emission properties of the pure complexes, but also the miscibility of the complexes and PMMA. More than one kind of symmetric sites of Eu³⁺ ions were formed in the composites due to the coordination of CO in PMMA to Eu³⁺ ions. The micro-environments of Eu(III) in the composites were changed with the compositions and the ligands, leading to the change in the crystalline structure, and consequently, the emission characteristics.     

Enhanced luminescence of rare-earthTb (III) by Tm (III) in bis(benzoylmethyl) sulfoxide complexes and intra-molecular energy transfer

Rare-earth complexes [(Tb_xTm_y)L₅(ClO₄)₂](ClO₄)·3H₂O(x:y=1.000:0.000, 0.999:0.001, 0.995:0.005, 0.990:0.010, 0.950:0.050, 0.900:0.100, 0.800:0.200, 0.700:0.300; L=C₆H₅COCH₂SOCH₂COC₆H₅) were synthesized and characterized with elemental analysis, infrared spectra (IR) and ¹H NMR. The photophysical properties of these complexes were studied in detail with ultraviolet absorption spectra, fluorescent spectra and lifetimes. The fluorescence spectra and decay curves of complexes indicated that the fluorescence emission intensity was enhanced and the fluorescence lifetime was prolonged by Tm (III), which may be due to the intra-molecular energy transfer between inert rare-earth ions and active rare-earth ions. The complexes showed the best properties when the mole ratio of Tb (III) to Tm (III) is 0.995:0.005. The intensity of fluorescence can be increased to 208%. Additionally, the energy-transfer mechanisms between the ligand and the central Tb (III) ions were discussed.     

The Studies of Enhanced Fluorescence in the Two Novel Ternary Rare-Earth Complex Systems

Two novel ternary rare-earth complexes SmL₅·L^’·(ClO₄)₂·7H₂O and EuL₅·L^’·(ClO₄)₂·6H₂O (the first ligand L = C₆H₅COCH₂SOCH₂COC₆H₅, the second ligand L^’ = C₆H₄OHCOO⁻) were synthesized and characterized by element analysis, molar conductivity, coordination titration analysis, IR, TG-DSC, ¹HNMR and UV spectra. The detailed luminescence studies on the rare-earth complexes showed that the ternary rare-earth complexes presented stronger fluorescence intensities, longer lifetimes, and higher fluorescence quantum efficiencies than the binary rare-earth materials. After the introduction of the second ligand salicylic acid group, the relative emission intensities and fluorescence lifetimes of the ternary complexes LnL₅·L^’·(ClO₄)₂·nH₂O (Ln = Sm, Eu; n = 7, 6) enhanced more obviously than the binary complexes LnL₅·(ClO₄)₃·2H₂O. This indicated that the presence of both organic ligand bis(benzoylmethyl) sulfoxide and the second ligand salicylic acid could sensitize fluorescence intensities of rare-earth ions, and the introduction of salicylic acid group was a benefit for the fluorescence properties of the ternary rare-earth complexes. The fluorescence spectra, fluorescence lifetime and phosphorescence spectra were also discussed.     

Synthesis,Optical Investigation and Biological Properties of Europium(III) Complexes with 2-(4-Chlorophenyl)-1-(2-Hydroxy-4-Methoxyphenyl)Ethan-1-one and Ancillary Ligands

Synthesis and photoluminescence behaviour of six novel europium complexes with novel β-hydroxyketone ligand, 2-(4-chlorophenyl)-1-(2-hydroxy-4-methoxyphenyl)ethan-1-one (CHME) and 2,2′-bipyridine (bipy) or neocuproine (neo) or 1,10-phenanthroline (phen) or 5,6-dimethyl-1,10-phenanthroline (dmphen) or bathophenanthroline (bathophen) were reported in solid state. The free ligand CHME and europium complexes, Eu(CHME)₃.2H₂O [1] Eu(CHME)₃.bipy [2], Eu(CHME)₃.neo [3], Eu(CHME)₃.phen [4], Eu(CHME)₃.dmphen [5] and Eu(CHME)₃.bathophen [6]were characterized by elemental analysis, FT-IR and ¹H-NMR. The photoluminescence emission spectra exhibited four characteristic peaks arising from the ⁵D₀ → ⁷F_J (J = 1–4) transitions of the europium ion in the solid state on monitoring excitation at λ_ex = 395 nm. The luminescence decay curves of these europium complexes possess single exponential behaviour indicating the presence of a single luminescent species and having only one site symmetry in the complexes. The luminescence quantum efficiency (η) and the experimental intensity parameters, Ω ₂ and Ω ₄ of europium complexes have also been calculated on the basis of emission spectra and luminescence decay curves. In addition, the antimicrobial and antioxidant activities were also studied of the investigated complexes.     

Crystal structure and thermal behavior of two new organic monosulfates NH3(CH2)5NH3SO4 1.5H2O and NH3(CH2)9NH3SO4 H2O

The chemical preparation, the calorimetric studies and the crystal structure are given for two new organic sulfates NH₃(CH₂)₅NH₃SO₄ 1.5H₂O (DAP-S) and NH₃(CH₂)₉NH₃SO₄·H₂O (DAN-S). DAP-S is monoclinic P2₁/n with unit cell dimensions: a=11.9330(2) Å; b=10.9290(2) Å; c=17.5260(2) Å; β=101.873(1)°; V=2236.77(6) Å³; and Z=8. Its atomic arrangement is described as inorganic layers of units and water molecules separated by organic chains. DAN-S is monoclinic P2₁/c with unit cell parameters: a=5.768(2) Å; b=25.890(10) Å; c=11.177(5) Å; β=115.70(4)°; V=1504.0(11) Å³ and Z=4. Its structure exhibits infinite chains, parallel to the [100] direction where the organic cations are interconnected. In both structures a network of strong and weak hydrogen bonds connects the different components in the building of the crystal.     

Synthesis and Fluorescence Properties of Lanthanide (III) Perchlorate Complexes with Naphthyl-Naphthalinesulphonylpropyl Sulfoxide

A ligand with double sulfinyl groups, naphthyl-naphthalinesulphonylpropyl sulfoxide(dinaphthyl disulfoxide, L), was synthesized by a new method and its several lanthanide (III) complexes were synthesized and characterized by element analysis, molar conductivity, coordination titration analysis, IR, TG-DTA, ¹HNMR and UV spectra. The composition of these complexes, were RE₂(ClO₄)₆·(L)₅·nH₂O (RE = La, Nd, Eu, Tb, Yb, n = 2 ∼ 6, L = C₁₀H₇SOC₃H₆SOC₁₀H₇). The fluorescent spectra illustrated that the Eu (III) complex had an excellent luminescence. It was supposed that the ligand was benefited for transferring the energy from ligand to the excitation state energy level (⁵D₀) of Eu (III). The Tb (III) complex displayed weak luminescence, which attributed to low energy transferring efficiency between the average triplet state energy level of ligand and the excited state (⁵D₄) of Tb (III). So the Eu (III) complex displayed a good antenna effect for luminescence. The phosphorescence spectra and the relationship between fluorescence lifetime and fluorescence intensity were also discussed.     

Vibrational Spectra and Structure of Potassium Alum Kal(SO4)2·12[(H2O) x (D2O)1−x ]

The IR spectra and polarization Raman spectra of Kal(SO₄)₂·12(H₂O) and Kal(SO₄)₂·12[H₂O)_0.3(D₂O)_0.7] crystals at 93 K and room temperature have been obtained experimentally. The vibrational spectra of structural elements of potassium alum — the complexes [Al(H₂O)₆ ³⁺ and [Al(D₂O)₆]³⁺ — have been calculated. The vibrational spectra have been interpreted based on the calculation and factor-group analysis data. The spectral data obtained point to the fact that, in the crystals considered, the sulfate ions are partially disordered and there exist two crystallographically different types of water molecules.     

Luminescent Langmuir-Blodgett film of a new amphiphilic Eu β-diketonate

This work reports on the synthesis and characterization of the ligand 3-hexadecylpentane-2,4-dione (Hhdacac) and its Eu³⁺ complexes Eu(hdacac)₆·2H₂O, Eu(hdacac)₆·phen and Eu(hdacac)₆·tta, where phen and tta denote 1,10-phenanthroline and thenoyltrifluoroacetone, respectively. These new compounds present long carbon chains and their expected miscibility into non-polar ambients is confirmed by the emission spectra of Eu(hdacac)₆·tta in hexane. Moreover, the amphiphilic properties of Eu(hdacac)₆ complexes allow the obtainment of thin luminescent films by the Langmuir-Blodgett technique. In both cases (solids and films), the typical antenna effect of β-diketonates is observed. The alluring characteristics of these compounds raise great interest in many fields of Materials Science, like photo- and electro-luminescent materials (mainly thin “organic” films), metal catalysts or probes in non-polar solutions, and Langmuir-Blodgett films of several compositions. For the characterization of these products, nuclear magnetic resonance spectroscopy (¹H NMR), thermogravimetric analysis, elementary analyses (C, H), scanning electron microscopy (energy dispersive X-ray spectroscopy), absorption (UV-vis/FT-IR) and photoluminescence spectroscopies were used.     

Synthesis and structure of the monolayer hydrate K0.3CoO2·0.4H2O

The monolayer hydrate (MLH) K_0.3CoO₂·0.4H₂O was synthesized from K_0.6CoO₂ by extracting K⁺ cations using K₂S₂O₈ as an oxidant and the subsequent intercalation of water between the layers of edge-sharing CoO₆ octahedra. A hexagonal structure (space group P6₃/mmc) with lattice parameters a=2.8262(1) Å, c=13.8269(6) Å similar to the MLH Na_0.36CoO₂·0.7H₂O was established using high-resolution synchrotron X-ray powder diffraction data. The K/H₂O layer in the K-MLH is disordered, which is in contrast to the Na-MLH. At low temperatures metallic and paramagnetic behavior was found.     

Co(II) Complexes of4-((3-ethoxy-2-hydroxybenzylidene)amino)-N-(thiazol-2-yl)benzenesulphonamide and 4-((pyridin-2-ylmethylene)amino)-N-(thiazol-2-tl)benzenesulfonamide: Synthesis,Fluorescence Properties and Anticancer Activity

Two new Co(II) complexes of 4-((3-ethoxy-2-hydroxybenzylidene)amino)-N-(thiazol-2-yl)benzenesulphonamide and 4-((pyridin-2-ylmethylene)amino)-N-(thiazol-2-yl)benzene sulfonamide were synthesised. The structure of the complexes was identified by elemental analysis, FT-IR, electronic, EI mass, Powder XRD spectra and magnetic moment. The TG and DTA patterns of the complexes were supported the structures. The fluorescence quenching of these complexes with alizarin dye were premeditated and the free energy change (?G_et) for electron transfer process was designed by Rehm-Weller equation. The [Co(L₁-H)₂(H₂O)₂] and [Co(L₂)₂(H₂O)₂].2H₂O were submitted for in vitro cytotoxicity studies in human breast cancer cell line (MCF 7).     

Syntheses, structures, fluorescence and thermal properties of three lanthanide coordination polymers built by N-benzoyl-N′-(4-benzoxy)thiourea

Three novel lanthanide 1-D chain coordination polymers, namely {[Tb(μ₂-L)₂(η²-NO₃)(CH₃OH)(H₂O)]·0.5CH₃OH·0.5H₂O}_n (1), {[Dy(μ₂-L)₂(η²-NO₃)(CH₃OH)(H₂O)]·H₂O}_n (2) and {[Ce(μ₂-L)₂(η²-NO₃)(H₂O)₃]·H₂O}_n (3) (HL=N-benzoyl-N′-(4-benzoxy)thiourea), have been prepared and characterized by IR spectroscopy, elemental analysis and single-crystal X-ray diffraction. The luminescence properties and themostabilities of polymers 1-3 have been determined as well.     

Double-stranded helical lanthanide(III) supramolecular networks with rigid diimine ligands: Synthesis, structure, and physical properties

Two lanthanide coordination complexes [Nd(NO₃)₃(CH₃OH)₂(4,4′-bipy)₂] (1) (4,4′-bipy=4,4′-bipyridine) and [4,4′-Hbipy][La(NO₃)₄(H₂O)₂(4,4′-bipy)] (2), with a salt of cationic diprotonated 4,4′-bipy, [2(4,4′-H₂bipy)][4(NO₃)] (3), have been identified and isolated from a methanol solution of Ln(NO₃)₃·6H₂O, 4,4′-bipyridine and pyrazine in 1:2:1 ratio. Their structures have been determined by single-crystal X-ray diffraction analyses, which reveal that 1 has an interesting three-dimensional supramolecular architecture containing 2₁ double-stranded helical chains through hydrogen bonding and π–π interactions, while 2 and 3 have well defined infinite chiral 3D open networks that undergo self-interpenetration. The electrospray ionization mass spectra (ESI-MS) indicate that the covalent complex has higher stability than the electrostatic bonding one. ESI-MS/MS of these ions reveal that the Ln–O bond forms a stronger coordinated bonding than that of Ln–N system and the nitrate anion remains bound to the lanthanide centers after complete dissociation in methanol solution.     

Tautomery and acid-base properties of some azoderivatives of benzoylacetone

The structural, tautomeric and acid-base properties of the new 1-phenyl-2-(2-hydroxy-3-sulfo-5-chlorophenylhydrazo)butane-1,3-dione (H₂L¹), 1-phenyl-2-(2-hydroxy-3,5-disulfophenylhydrazo)butane-1,3-dione (H₂L²), 1-phenyl-2-(2-hydroxy-3-sulfo-5-nitrophenylhydrazo)butane-1,3-dione (H₂L³) and 1-phenyl-2-(2-hydroxy-4-nitrophenylhydrazo)butane-1,3-dione (H₂L⁴) were studied using IR, ¹H and ¹³C NMR spectroscopies and potentiometry. The study reveals that H₂L^1-4 and the known 1-phenyl-2-(2-hydroxyphenylhydrazo)butane-1,3-dione (H₂L⁵) exist in solution as a mixture of Z-enol-azo-II and hydrazo-III tautomeric forms and that an increase in the solvent polarity shifts the tautomeric balance to the enol-azo form. The thermodynamic parameters of the proton dissociation in H₂L^1-5 were determined showing that this process is unspontaneous, endothermic and entropically unfavorable.