Fluorescent and photochemical properties of TbIII complexes with acrylic acid-based macromolecular ligands

The fluorescent and photochemical properties of Tb^III complexes with macromolecular ligands based on acrylic acid were studied. The photochemical behavior of the macromolecular Th^II complexes with acrylic acid-alkyl methacrylate copolymers differs considerably from those of Tb^III complexes with polyacrylic acid and of low-molecular-weight analogs; in the former case, the intensity of Tb³⁺ photoluminescence noticeably increases during photolysis rather than decreases. It was found that the increase in the length of the alkyl group in the alkyl methacrylate favors the enhancement of the luminescence during the photolysis. The higher efficiency of the enhancement of the Eu³⁺ fluorescence during the photolysis of similar complexes of Eu³⁺ compared to the complexers of Tb³⁺ is due to the nature of the electrodipole hypersensitive⁵D₀–⁷F₂ transition in Eu³⁺.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2007–2010, August, 1996.     

Luminescence of Eu3+ and Tb3+ Complexes of Two Macrobicyclic Ligands Derived from a Tetralactam Ring and a Chromophoric Antenna

Two macrobicyclic ligands derived from an 18‐membered tetralactam ring and 2,2′‐bipyridine or 2,6‐bis(pyrazol‐1‐yl)pyridine moieties, 1 and 2 , respectively, form stable complexes with Gd^III, Eu^III, and Tb^III ions in aqueous solution. The ligand‐based luminescence is retained in the Gd^III cryptates, whereas this radiative deactivation is quenched in the Eu^III and Tb^III cryptates by ligand‐to‐metal energy transfer, resulting in the usual metal‐centered emission spectra. Singlet‐ and triplet‐state energies, emission‐decay lifetimes, and luminescence yields were measured. [Tb⊂ 1 ]³⁺ cryptate shows a long luminescence lifetime (τ=1.12 ms) and a very high metal luminescence quantum yield (Φ=0.25) in comparison with those reported in the literature for Tb³⁺ complexes sensitized by a bipyridine chromophore. By comparison to [Ln⊂ 1 ]³⁺, [Ln⊂ 2 ]³⁺ presents markedly lower luminescence properties, due to worse interaction between the 2,6‐bis(pyrazol‐1‐yl)pyridine unit and the metal ion. Moreover, the luminescent metal and the triplet ligand energy levels of [Eu⊂ 2 ]³⁺ do not match. The effects of H₂O molecules coordinated to the metal centre and of thermally activated decay processes on nonradiative deactivation to the ground‐state are also reported.     

Energy transfer and heat-treatment effect of photoluminescence in Eu-doped TbPO4 nanowires

We have successfully synthesized Eu³⁺-doped TbPO₄ nanowires, which are orderly organized to form bundle-like structure. A thermal treatment up to 600 °C does not modify the size, shape and structure of as-synthesized sample. Due to the energy overlap between Tb³⁺ and Eu³⁺, an efficient energy transfer occurs from Tb³⁺ to Eu³⁺. The effects of Eu³⁺ concentration and thermal treatment on the luminescent properties of Eu³⁺ are investigated. The increase of Eu³⁺ concentration leads to the increase of the energy transfer efficiency from Tb³⁺ to Eu³⁺, but also enhances the probability of the interaction between neighboring Eu³⁺, which results in the concentration quenching. With the heat-treatment, the luminescence of Eu³⁺ presents an obvious increase, but almost no change for the luminescence of Tb³⁺. This difference is explained based on the TGA, DTA, and fluorescent decay dynamics analyses.     

Photodecomposition of Eu3+ complexes with macromolecular ligands based on acrylic acid

The spectroluminescent and photochemical properties of Eu³⁺ complexes with copolymers of acrylic acid and alkyl methacrylates were studied. It was found that the photochemical behavior of the macromolecular complexes differs significantly from that of the lowmolecular analogs: in the course of photodecomposition the luminescence intensity of Eu³⁺ noticeably increases rather than diminishes. The efficiency of the luminescence build up of Eu³⁺ depends on the composition and the structure of the initial macromolecular complexes. A low concentration of the metal, low content of acrylic acid, and increase in the length of the alkyl radical of methacrylate favor the enhancement of the efficiency of luminescence build up of the rare-earth ion.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1559–1562, September, 1993.     

Chemiluminescence and catalysis of decomposition of dispiro(diadamantane-1,2-dioxetane) in solutions of lanthanide perchlorates

Chemiluminescence (CL) accompanying the decomposition of dispiro(diadamantane-1,2-dioxetane) (1) in acetonitrile solutions of Eu^III, Gd^III, Tb^III, Pr^III, and Ce^III perchlorates was studied. In the presence of Eu^III, Tb^III, and Pr^III ions, the chemiluminescence spectra contain the luminescence bands of these ions. In the cases of Gd^III and Ce^III, the chemiluminescence is caused by deactivation of singlet-excited adamantanone (2). The excitation of the lanthanide ion depends on the existence of suitable energy levels at which intracomplex excitation transfer from the³n,π^* of ketone is possible. Chemiluminescence of1 increases in solutions of Eu^III and Tb^III. The yields of CL and excitation of the lanthanide ions in the decomposition of1 in the1·Eu^III and1\Tb^III complexes were determined: φ_Eu · =0.013 ± 0.003 and φ_Tb · =0.08±0.02. The fact that the efficiency for the population of the⁵D₄-level of Tb^III is higher than that for the⁵D₁ and⁵D₀-levels of Eu^III is related to the difference in the energy gap between the triplet level of2 and the excited levels of the lanthanides. For Part I, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 730–735, April, 1997.     

Synthesis,Characterization, and Structural Properties of Luminescent Lanthanide Complexes

The crystal structure of the macrobicyclic europium(III) complex [Eu³⁺ ? 1 ]3Cl^? incorporating a N,N′ - dioxide unit has been determined. It confirms the cryptate nature of this species, the included cation being bound to six N- and two O-sites. The efficient shielding of the bound Eu³⁺ ion may be related to the efficient luminescence of this cryptate and points to the role played by the N-oxide sites. To further explore the effect of such binding groups, the two macrocyclic ligands 4 and 5 bearing two bipyridine N,N′ -dioxide lateral arms have been synthesized and their Eu^III and Tb^III complexes prepared.     

Crystal Structures of the Lanthanum(III), Europium(III), and Terbium(III) Cryptates of Tris(bipyridine) Macrobicyclic Ligands

The crystal structures of the La^III, Eu^III, and Tb^III complexes of macrobicyclic [bpy.bpy.bpy] ligands, [La³⁺ ? 1 ]3 Cl^? ( = 3- La), [Tb³⁺ ? 1 ]3 Cl^? ( = 3- Tb), and [Eu³⁺ ? 2 ]3 C1^? ( = 3- Eu), have been determined. They confirm the cryptate nature of these species, the cations being bound to the eight N-sites of the ligand. The macrobicycle presents two open faces, thus allowing additional coordination of two species, Cl^? ions or H₂O molecules, to the bound cations. These data provide structural support for the photophysical studies of the luminescent properties of the Eu^III and Tb^III cryptates, which indicated residual coordination of H₂O molecules.     

Synthesis and spectroscopic properties of europium(III) and terbium(III) complexes with a pyrano[2,3-b]pyridine ligand

Summary Novel Eu³⁺ and Tb³⁺ complexes with a pyrano[2,3-b]pyridine ligand have been synthesized and characterized. The stability constants in 1:1DMF-water were determined. In solution, various tautomeric forms of the free ligand are present, and their equilibrium is influenced by complexation toLn ³⁺ cations. Both the Eu³⁺ and Tb³⁺ complexes present an intense cation luminescence following the ligand excitation in the UV region. The cation emission quantum yields and life-times are discussed with regard to the mechanism of the ligand-to-metal energy transfer process.

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Synthese und spektroskopische Eigenschaften von Europium(III) und Terbium(III) Komplexen mit einem Pyrano[2,3-b]pyridin als Ligand

Zusammenfassung Es wurden neue Eu³⁺- und Tb³⁺-Komplexe mit einem Pyrano[2,3-b]pyridin-Derivat hergestellt und charakterisiert. Die Stabilitätskonstanten in 1:1DMF-Wasser wurden festgestellt. In Lösung liegen verschiedene tautomere Formen der freien Liganden vor, wobei die entsprechenden Gleichgewichte von der Komplexierung beeinflußt werden. Sowohl die Eu³⁺- als auch die Tb³⁺-Komplexe zeigen eine intensive Kationen-Lumineszenz, die auf die Liganden-Anregung im UV folgt. Die Kationen-Emissionsquantenausbeuten und die Lebenszeiten werden im Hinblick auf den Mechanismus des Prozesses beim Ligand-zu-Metall-Energietransfer diskutiert.

     

A new disordered langbeinite‐type compound,K2Tb1.5Ta0.5P3O12, and Eu3+‐doped multicolour light‐emitting properties

For the first time, a new langbeinite‐type phosphate, namely potassium terbium tantalum tris(phosphate), K₂Tb_1.5Ta_0.5(PO₄)₃, has been prepared successfully using a high‐temperature flux method and has been structurally characterized by single‐crystal X‐ray diffraction. The results show that its structure can be described as a three‐dimensional open framework of [Tb_1.5Ta_0.5(PO₄)₃]_∞ interconnected by K⁺ ions. The Tb^III and Ta^V cations in the structure are disordered and occupy the same crystallographic sites. The IR spectrum, the UV–Vis spectrum, the morphology and the Eu³⁺‐activated photoluminescence spectroscopic properties were studied. A series of Eu³⁺‐doped phosphors, i.e. K₂Tb_1.5–xTa_0.5(PO₄)₃:xEu³⁺ (x = 0.01, 0.03, 0.05, 0.07, 0.10), were prepared via a solid‐state reaction and the photoluminescence properties were studied. The results show that under near‐UV excitation, the luminescence colour can be tuned from green through yellow to red by simply adjusting the Eu³⁺ concentration from 0 to 0.1, because of the efficient Tb³⁺→Eu³⁺ energy‐transfer mechanism.     

Lanthanide-centered inorganic/organic hybrids from functionalized 2-pyrrolidinone-5-carboxylic acid bridge: Covalently bonded assembly and luminescence

A series of organic-inorganic hybrid material with chemically bonding have been prepared through the precursor (PDCA-Si) derived from 2-pyrrolidinone-5-carboxylic acid, which exhibits a self-organization cooperation interaction under the coordination to RE³⁺ (Eu³⁺, Tb³⁺). The pure organic silica hybrids (PDCA-Si) without RE³⁺ presents the small particle size and main blue luminescence with maximum peak 462 nm occupying a broad band from 425 to 550 nm. When Eu³⁺ and Tb³⁺ are introduced, the particle size of the hybrids increases, indicating the coordination effect has influence on the microstructure of hybrids. Besides, the corresponding Eu and Tb hybrids (Eu-PDCA-Si, Tb-PDCA-Si) show the characteristic red and green luminescence of Eu³⁺ and Tb³⁺, respectively, which suggests that the efficient intramolecular energy transfer process take place between carboxylic groups and lanthanide ions take place. The luminescence lifetimes and quantum efficiencies of them are determined and energy transfer efficiency between PDCA-Si and Eu³⁺ (Tb³⁺) is calculated.     

Luminescent Hybrid Materials Based on Laponite Clay

The spectroscopic behavior of ionic Eu³⁺ or Tb³⁺ complexes of an aromatic carboxyl‐functionalized organic salt as well as those of the hybrid materials derived from adsorption of the ionic complexes on Laponite clay are reported. X‐ray diffraction (XRD) patterns suggest that the complexes are mainly adsorbed on the outer surfaces of the Laponite disks rather than intercalated within the interlayer spaces. Photophysical data showed that the energy‐transfer efficiency from the ligand to Eu³⁺ ions in the hybrid material is increased remarkably with respect to the corresponding ionic complex. The hybrid material containing the Eu³⁺ complex shows bright red emission from the prominent ⁵D₀→⁷F₂ transition of Eu³⁺ ions, and that containing the Tb³⁺ complex exhibits bright green emission due to the dominant ⁵D₄→⁷F₅ transition of Tb³⁺ ions.     

A Series of Carboxylic‐Functionalized Ionic Liquids and their Solubility for Lanthanide Oxides

Herein we report the synthesis of propanoic acid functionalized ionic liquids (ILs) with various lengths of alkyl chain on the imidazole ring. The synthesized propanoic acid functionalized ILs were used to dissolve Eu₂O₃ (or Tb₄O₇) due to the formation of europium(III) (or terbium(III)) carboxylate, aimed to get soft luminescent materials combining the properties of ILs and attractive luminescent properties of lanthanide ions. The luminescent behavior of Eu³⁺ and Tb³⁺ in the ILs were investigated by luminescence spectroscopy. The affect of the alkyl chain on the luminescent behavior (the asymmetry parameter (R), the lifetime of ⁵D₀, and the ⁵D₀ quantum efficiency) of Eu³⁺ has been discussed.     

Spectroscopic studies on the interaction of cilostazole with iodine and 2,3-dichloro-5,6-dicyanobenzoquinone

Lanthanide sensitized luminescence and chemiluminescence (CL) are of great importance because of the unique spectral properties, such as long lifetime, large Stokes shifts, and narrow emission bands characteristic to lanthanide ions (Ln³⁺). With the fluoroquinolone (FQ) compounds including enoxacin (ENX), norfloxacin (NFLX), lomefloxacin (LMFX), fleroxacin (FLRX), ofloxacin (OFLX), rufloxacin (RFX), gatifloxacin (GFLX) and sparfloxacin (SPFX), the luminescence and CL properties of Tb³⁺–FQ and Eu³⁺–FQ complexes have been investigated in this contribution. Ce⁴⁺–SO₃²⁻ in acidic conditions was taken as the CL system and sensitized CL intensities of Tb³⁺–FQ and Eu³⁺–FQ complexes were determined by flow-injection analysis. The luminescence and CL spectra of Tb³⁺–FQ complexes show characteristic peaks of Tb³⁺ at 490 nm, 545 nm, 585 nm and 620 nm. Complexes of Tb³⁺–ENX, Tb³⁺–NFLX, Tb³⁺–LMFX and Tb³⁺–FLRX display relatively strong emission intensity compared with Tb³⁺–OFLX, Tb³⁺–RFX, Tb³⁺–GFLX and Tb³⁺–SPFX. Quite weak peaks with unique characters of Eu³⁺ at 590 nm and 617 nm appear in the luminescence and CL spectra of Eu³⁺–ENX, but no notable sensitized luminescence and CL of Eu³⁺ could be observed when Eu³⁺ is added into other FQ. The distinct differences on emission intensity of Tb³⁺–FQ and Eu³⁺–FQ might originate from the different energy gap between the triplet levels of FQ and the excited levels of the Ln³⁺. The different sensitized luminescence and CL signals among Tb³⁺–FQ complexes could be attributed to different optical properties and substituents of these FQ compounds. The detailed mechanism involved in the luminescence and CL properties of Tb³⁺–FQ and Eu³⁺–FQ complexes has been investigated by analyzing the luminescence and CL spectra, quantum yields, and theoretical calculation results.     

Novel bifunctional lanthanide‐centered nanophosphors for latent fingerprint detection and anti‐counterfeiting applications

Production of hybrid organic/inorganic complexes such as lanthanide phosphors in the nanodomain for human fingerprint visualization and anti‐counterfeiting ink under biocompatible UVA and blue light has not yet been studied that thoroughly. This paper presents the preparation of novel, bifunctional, green and red nanophosphors based on Eu³⁺ and Tb³⁺ complexes with quinolinone ligand (H₂L). They have been prepared and characterized for latent fingerprint detection and anti‐counterfeiting ink applications. The analytical data confirm that the ligand acts in a monoanionic bidentate manner through OO donor sites, forming mononuclear complexes, formulated as [Ln(HL)₃(C₂H₅OH)₃] (Ln = Eu³⁺ or Tb³⁺; L = 1‐ethyl‐4‐hydroxy‐3‐(nitroacetyl)quinolin‐2‐(1H)‐one). The Eu³⁺ and Tb³⁺ complexes have nanospherical morphologies with average particle sizes of 17 and 5 nm, respectively. Pure red and green photoluminescence with long lifetime values has been obtained from the Eu³⁺ and Tb³⁺ complexes, respectively, under non‐harmful UVA and blue illumination. Latent fingerprint details, including their characteristic three levels, have been clearly identified from various forensic (non‐porous, semi‐porous, highly fluorescent porous) substrates using red (Eu³⁺) and green (Tb³⁺) nanophosphors. The green nanophosphor powder has a greater capability for visualizing latent fingerprints from highly fluorescent porous surfaces as compared to the red one. Both nanophosphor complexes have been used to develop luminescent ink for anti‐counterfeiting applications.     

Rare earth complexes chemiluminescence catalyzed by gold nanoparticles for fast sensing of Tb3+ and Eu3+

Developing multiplex sensing technique is of great significance for fast sample analysis. However, the broad emissions of most chemiluminescence(CL) luminophores make the multiplex CL analysis be difficult. In this work, a simple and sensitive CL analytical method has been developed for the simultaneous determination of Tb³⁺and Eu³⁺thanking to their narrow band emission. The technique was based on a mixed CL system of periodate(IO₄^-)-hydrogen peroxide(...     

Homogeneous one-dimensional structured Tb(OH)3:Eu nanorods: Hydrothermal synthesis, energy transfer, and tunable luminescence properties

Nearly monodisperse, homogeneous and well-defined one-dimensional Tb_(1−x)(OH)₃:xEu³⁺ (x=0-3 mol%) nanorods have been prepared through hydrothermal method. The size of the Tb(OH)₃:Eu³⁺ rods could be modulated from nano- to micro-scale by using different amount of ammonia solution. They present highly crystallinity in spite of the moderate reaction temperature. Under ultraviolet excitation into the f→f transition of Tb³⁺ at 382 nm, Tb(OH)₃ samples show the characteristic emission of Tb³⁺ corresponding to ⁵D₄→⁷F_{6, 5, 4, 3} transitions; whereas Tb(OH)₃:Eu³⁺ samples mainly exhibit the characteristic emission of Eu³⁺ corresponding to ⁵D₀→⁷F_{1, 2, 4} transitions due to an efficient energy transfer occurs from Tb³⁺ to Eu³⁺. The increase of Eu³⁺ concentration leads to the increase of the energy transfer efficiency from Tb³⁺ to Eu³⁺. The PL colors of Tb(OH)₃:xEu³⁺ phosphors can be easily tuned from green, yellow, orange, to red by changing the doping concentration (x) of Eu³⁺.     

Lanthanide metal polymer complexes. Synthesis,characterization and application

Our recent results on the investigation of lanthanide metal polymer complexes were presented. Luminescence properties of Tb³⁺ or Eu³⁺ -polycarboxylate complexes in aqueous solution were investigated. The excitation band near 300 nm for Tb or Eu(polyacrylate) solutions were drastically enhanced by the addition of hydroxy radical generating reagents as well as ultrasonic irradiation. These spectral changes were attributed to the energy transfer from chromophore molecules formed by generated hydroxy radicals in both systems. Since the increase in the luminescence intensity was proportional to the hydroxy radical concentration, the Eu³⁺ or Tb³⁺ (PAA) system can provide a convenient method for the determination of hydroxy radical concentration in aqueous solution. We have also utilized lanthanide metal ion complexes as a luminescent emitter in electroluminescence (EL) devices. The configuration of the EL cell and experimental results were discussed.     

Electronic excitation energy transfer between Tb3+ and Eu3+ in DMSO

Excitation of Tb³⁺ and Eu³⁺ in DMSO with 487 mμ, which corresponds to the ⁷F₆ → ⁵D₄ transition of Tb³⁺, is accompanied by a reduction in the fluorescence efficiency of Tb³⁺ as [Eu³⁺] increases and by the appearance of a weak emission from Eu³⁺. An average rate constant for both the fluorescence quenching of Tb³⁺ and the energy transfer from Tb³⁺ to Eu³⁺ with subsequent emission from the latter, was found to be (2.2 ± 0.4) × 10³ M^?1 sec^?1.     

Mono- and Mixed Metal Complexes of Eu3+, Gd3+, and Tb3+ with a Diketone,Bearing Pyrazole Moiety and CHF2-Group: Structure,Color Tuning,and Kinetics of Energy Transfer between Lanthanide Ions

Three novel lanthanide complexes with the ligand 4,4-difluoro-1-(1,5-dimethyl-1H-pyrazol-4-yl)butane-1,3-dione (HL), namely [LnL₃(H₂O)₂], Ln = Eu, Gd and Tb, were synthesized, and, according to single-crystal X-ray diffraction, are isostructural. The photoluminescent properties of these compounds, as well as of three series of mixed metal complexes [Eu_xTb_1-xL₃(H₂O)₂] (Eu_xTb_1-xL₃), [EuxGd_1-xL₃(H₂O)₂] (Eu_xGd_1-xL₃), and [Gd_xTb_1-xL₃(H₂O)₂] (Gd_xTb_1-xL₃), were studied. The Eu_xTb_1-xL₃ complexes exhibit the simultaneous emission of both Eu³⁺ and Tb³⁺ ions, and the luminescence color rapidly changes from green to red upon introducing even a small fraction of Eu³⁺. A detailed analysis of the luminescence decay made it possible to determine the observed radiative lifetimes of Tb³⁺ and Eu³⁺ and estimate the rate of excitation energy transfer between these ions. For this task, a simple approximation function was proposed. The values of the energy transfer rates determined independently from the luminescence decays of terbium(III) and europium(III) ions show a good correlation.     

The Series of Rare Earth Complexes [Ln2Cl6(μ‐4,4′‐bipy)(py)6], Ln=Y,Pr, Nd,Sm‐Yb: A Molecular Model System for Luminescence Properties in MOFs Based on LnCl3 and 4,4′‐Bipyridine

A series of 12 dinuclear complexes [Ln₂Cl₆(μ‐4,4′‐bipy)(py)₆], Ln=Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, ( 1 – 12 , respectively) was synthesized by an anhydrous solvothermal reaction in pyridine. The complexes contain a 4,4′‐bipyridine bridge and exhibit a coordination sphere closely related to luminescent lanthanide MOFs based on LnCl₃ and 4,4‐bipyridine. The dinuclear complexes therefore function as a molecular model system to provide a better understanding of the luminescence mechanisms in the Ln‐N‐MOFs ${\hbox{}{{\hfill 2\atop \hfill \infty }}}$ [Ln₂Cl₆(4,4′‐bipy)₃] ? 2(4,4′‐bipy). Accordingly, the luminescence properties of the complexes with Ln=Y, Sm, Eu, Gd, Tb, Dy, ( 1 , 4 – 8 ) were determined, showing an antenna effect through a ligand–metal energy transfer. The highest efficiency of luminescence is observed for the terbium‐based compound 7 displaying a high quantum yield (QY of 86 %). Excitation with UV light reveals typical emission colors of lanthanide‐dependent intra 4f–4f‐transition emissions in the visible range (Tb^III: green, Eu^III: red, Sm^III: salmon red, Dy^III: yellow). For the Gd^III‐ and Y^III‐containing compounds 6 and 1 , blue emission based on triplet phosphorescence is observed. Furthermore, ligand‐to‐metal charge‐transfer (LMCT) states, based on the interaction of Cl^? with Eu^III, were observed for the Eu^III compound 5 including energy‐transfer processes to the Eu^III ion. Altogether, the model complexes give further insights into the luminescence of the related MOFs, for example, rationalization of Ln‐independent quantum yields in the related MOFs.