Spectra analysis of Nd(DBM)3(TPPO)2 in MMA solution and PMMA matrix

The absorption spectra of Nd(DBM)3(TPPO)2 (DBM = dibenzoylmethane; TPPO = triphenylphosphine oxide) in methyl methacrylate (MMA) and polymethyl methacrylate (PMMA) were measured. Slater-Condon parameters (F2, F4, F6), Lander parameter (zeta4f), nephelauxetic effect parameters (beta, delta) and Judd-Ofelt parameters (Omega2, Omega4, Omega6) were calculated on the basis of the absorption spectra. Analysis of the relationship between the structure of rare-earth complexes and the nephelauxetic effect, Judd-Ofelt parameter Omega2 was carried out. The radiative properties of Nd(DBM)3(TPPO)2 in PMMA were also predicted according to the Judd-Ofelt theory. The values of the radiative lifetime and the emission cross-section of 4F3/2 --> 4I11/2 fluorescence transition are comparable with those shown by glasses used in the solid-state laser applications.     

Optical properties of a tetradentate bis(beta-diketonate) europium(III) complex

Eu₂(BPOPB)₃H₂O, an europium complex chelated with bis(β-diketone), was synthesized. Its properties have been investigated by absorption spectrum, emission spectrum and luminescence lifetime measurement. The complex displays strong red luminescence upon irradiation at the ligand band around 355 nm, which indicates that the bis-β-diketonate ligand BPOPB is an efficient sensitizer. The Judd–Ofelt parameters obtained from the emission spectrum of Eu₂(BPOPB)₃H₂O have been used to calculate the total spontaneous emission probabilities (A), the radiative lifetime (τ_rad), the fluorescence branching ratio (β) and the stimulated emission cross-sections (σ). The luminescence lifetimes are determined to be 402 and 169 μs for Eu₂(BPOPB)₃H₂O and Eu(DBM)₃(H₂O)₂, respectively. The relationship between the structures of rare-earth complexes and luminescence lifetimes was analyzed. The radiative properties reveal that Eu₂(BPOPB)₃H₂O is potential to be an efficient luminescent material.     

Efficient sensitization of europium, ytterbium, and neodymium functionalized tris-dipicolinate lanthanide complexes through tunable charge-transfer excited states

A series of push-pull donor-pi-conjugated dipicolinic acid ligands and related tris-dipicolinate europium and lutetium complexes have been prepared. The ligands present broad absorption and emission transitions in the visible spectral range unambiguously assigned to charge-transfer transitions (CT) by means of time-dependent density functional theory calculations. The photophysical properties (absorption, emission, luminescence quantum yield, and lifetime) of the corresponding europium complexes were thoroughly investigated. Solvatochromism and temperature effects clearly confirm that Eu(III) sensitization directly occurs from the ligand CT state. In addition, modulation of the energy of the CT donating state by changing the nature of the donor fragment allows the optimal energy of the antennae for europium sensitization to be determined, and this optimal energy was found to be close to the (5)D 1 accepting state. Finally, this CT sensitization process has been successfully extended to near-infrared emitters (neodymium and ytterbium).     

Two-photon absorption and photoluminescence of europium based emissive probes for bioactive systems

Observation of two-photon excitation (760 nm) and emission of two responsive water soluble europium complexes is reported with cross-sections of up to 2 GM. Two-photon excitation spectra have also been measured, acquisition being achieved by the use of a cavity-dumped mode locked Ti-sapphire laser. Time-gated detection is used to differentiate the ligand fluorescence and metal centred emission in these europium complexes.     

Preparation and Characterization of Ternary Europium ComplexDoped Thin SolGel Hybrid Film by Fluorescence Spectroscopy*

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Fluorescence study of Eu chelates in solution and polymer matrix

The fluorescence spectra of Eu chelates with different neutral ligand in methyl methacryate (MMA) solution were measured and the influence of the neutral ligand was analyzed. The chelate Eu(DBM)3(TOPO)2, which shows the strongest fluorescence intensity in the solution, has been incorporated into the poly(methyl methacryate) (PMMA) matrix. According to the fluorescence emission spectrum, its radiative properties were also predicted.     

Fluorescent properties of a dendritic ligand europium complex incorporated in polymethylvinylsiloxane

A dendritic europium complex, Eu(BCPD)₃Phen, has been incorporated into polymethylvinylsiloxane (PMVS). Its fluorescent properties have been investigated by fluorescence emission spectra and lifetime measurements. According to the fluorescence emission spectra, the Judd–Ofelt parameters Ω₂, Ω₄ of Eu(BCPD)₃Phen/PMVS have been calculated. The radiative decay rate A_rad, the non-radiative rates A_nrad, the lifetime τ and the luminescent quantum yield η were analyzed also.     

多羧酸根铕二元配合物的合成及光谱分析

分别以1,3,5-苯三甲酸(H₃BTC)、苯六甲酸(H₆MTA)和1,2,3,4,5,6-环己六甲酸(H₆CCA)为配体合成了Eu(III)的二元发光配合物Eu(BTC)·2H₂O, Eu₂(MTA)·4H₂O 和Eu₂(CCA)·4H₂O. 通过元素分析、红外光谱和等离子体原子发射光谱对其化学组成进行了结构表征, 表征结果与理论吻合良好. 利用荧光分度计, 研究了所制备配合物室温条件下的荧光性能(荧光激发光谱、发射光谱、荧光寿命和量子效率), 结果表明: 该三种配合物在紫外光照射下, 均发射Eu(III)离子的特征红光, 其中Eu₂(MTA)·4H₂O(量子效率＝10.25%, 荧光寿命＝0.36 ms)的荧光性能最好, 这说明配体H₆MTA 的能级与Eu³⁺离子能级匹配程度很好. 另外, 通过热分析对配合物的热稳定性进行了分析, 结果表明: 该三种配合物均具有良好的热稳定性, 主要分解温度远高于其他β-二酮配合物.     

Synthesis and spectroscopic behavior of highly luminescent Eu(3+)-dibenzoylmethanate (DBM) complexes with sulfoxide ligands

In this paper the synthesis, characterization and photoluminescent behavior of the [RE(DBM)3L2] complexes (RE=Gd and Eu) with a variety of sulfoxide ligands; L=benzyl sulfoxide (DBSO), methyl sulfoxide (DMSO), phenyl sulfoxide (DPSO) and p-tolyl sulfoxide (PTSO) have been investigated in solid state. The emission spectra of the Eu(3+)-beta-diketonate complexes show characteristics narrow bands arising from the 5D0-->7F(J) (J=0-4) transitions, which are split according to the selection rule for C(n), C(nv) or C(s) site symmetries. The experimental Judd-Ofelt intensity parameters (Omega2 and Omega4), radiative (A(rad)) and non-radiative (A(nrad)) decay rates, and R02 for the europium complexes have been determined and compared. The highest value of Omega2 (61.9x10(-20)cm2) was obtained to the complex with PTSO ligand, indicating that Eu3+ ion is in the highly polarizable chemical environment. The higher values of the experimental quantum yield (q) and emission quantum efficiency of the emitter 5D0 level (eta) for the Eu-complexes with DMSO, DBSO and PTSO sulfoxides suggest that these complexes are promising Light Conversion Molecular Devices (LCMDs). The lower value of quantum yield (q=1%), for the hydrated complex [Eu(DBM)3H2O], indicates that the luminescence quenching occurs via multiphonon relaxation by coupling with the OH-oscillators from water molecule coordinated to rare earth ion. The pure red emission of the Eu-complexes has been confirmed by (x, y) color coordinates.     

Synthesis and color of 2-(N,N-diethyl-p-quinonediimine)-indazolones

A number of substituted 2-(N, N-diethyl-p-quinonediimine)indazolones have been synthesized, and their optical properties investigated. It has been shown that introduction of electrophilic substituents into the benzene ring of an indazolone gives rise to a bathochromic shift in the absorption spectra of 2-(N, N-diethyl-p-quinonediimine)indazolones in alcohol and benzene solution.     

Spectral and luminescence properties of derivatives of 2-aryl[9,10]phenanthroxazole

Certain 2-aryl derivatives of [9,10]phenanthroxazole have been synthesized and their spectral and luminescence properties have been investigated. It has been shown that the introduction of acceptor substituents into the para position of the 2 -phenyl radical changes the nature of the fluorescence state, resulting in a nearly two-fold increase of the rate constant of fluorescence emission and a 50% increase of the quantum yield of fluorescence. Special features of the spectral and luminescence properties have been examined for derivatives with an intramolecular hydrogen bond (aryl = o-hydroxyphenyl) and with considerable steric hindrance (aryl = 9-anthryl).Khar'kov State University, Khar'kov 310077. Institute of Single Crystals, National Academy of Sciences of the Ukraine, Khar'kov 310001. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 558–566, April, 1995. Original article submitted February 23, 1994.     

Preparation,Characterization of Ternary Europium Complex-Doped Thin Sol-Gel Hybrid Film by Fluorescence Spectroscopy

ernary europium complex with dibenzoylmethane(DBM), 1,10-phenanthroline(phen) was in-situ syn thesized in thin SiO₂/polyvinyl butyral(PVB) hybrid films by a two-step sol-gel process, characterized by means of fluorescence spectroscopy. The luminescence spectra, fluorescence lifetimes, photostability were all investigated. The results showed that the hybrid films exhibited the characteristic emission bands of the central rare earth Eu³⁺. In addition, Eu³⁺ presented longer fluorescence lifetime than in an ethanol solution, the complex had a higher photostability in the hybrid film than in the PVB film containing the corresponding pure complex.     

Luminescent Properties of Europium(III) Complexes with Quinaldic Acid and Sulfur–Containing Neutral Ligands

The luminescent heteroligand complexes of europium(III) with quinaldic acid and sulfur-containing neutral ligands Eu(Quin)3∙D∙3H2O (Quin–quinaldic acid, D–dimethyl sulfoxide or dihexyl sulfoxide) and Eu(Quin)3∙3H2O have been obtained. Their composition and structure have been determined. The thermal and spectral-luminescent properties of the heteroligand europium(III) complexes have been studied. The quinaldate ion has been found to coordinate to the europium(III) ion as a bidentate ligand. The Stark structure of 5D0–7Fj (j = 0, 1, 2) transitions in the low-temperature luminescence spectra of the europium(III) complexes has been analyzed     

The synthesis and the solvent and substituent effect on the spectroscopic characteristic of 3-ethyl-2-(p-substitued styryl)benzothiazolium iodides

The photophysical and photochemical properties of p-substitued 2-styryl-ethylbenzothiazolium iodides, possessing different electron-withdrawing or electron-donating groups are described. The dyes were prepared by the condensation of 3-ethyl-2-methylbenzothiazole salts with p-substituted benzaldehydes. The synthesis of suitable substrates is presented as well. We describe here the absorption, emission spectra and the luminescence quantum yield of hemicyanine dyes (SH) measured in 11 different organic solvents of varying polarity. Molecular structure of the synthesized dyes was established by (1)H NMR, electronic absorption and fluorescence spectrometry. The spectral data confirmed that all the compounds exist in E-configuration of their styryl residues. The planar molecular conformation is typical for the compounds with five-membered side aromatic moieties (for example benzothiazole). The compounds possessing N-alkyl substituent in phenyl ring, in contrast to the compounds with other substituents, exhibit low fluorescence quantum yield in THF solution. This indicates that for N-alkyl derivatives the non-radiative processes are much more effective than the radiative ones. The electronic absorption and fluorescence emission spectra of tested dyes demonstrate high sensitivity to the nature of substituent introduced into the aromatic ring.     

Crystal structure and luminescence property of ternary terbium p-aminobenzoic acid complexes with different second ligands

Ternary terbium complexes with p-aminobenzoic acid (HL), [TbL₃(DMSO)(H₂O)]₂ (1), [TbL₃(DMF)(H₂O)]₂ (2) and [TbL₃(Bpy)(H₂O)]₂·2H₂O (3) (DMSO=dimethyl sulfoxide, DMF=N, N- dimethylformamide, Bpy=2, 2′- bipyridyl) have been synthesized, and their crystal structures determined. The luminescence properties of these complexes, including both the emission quantum yield and the fluorescence lifetime, have been investigated. The effect of a second ligand on the crystal structure and luminescence property of the ternary terbium p-aminobenzoic acid complexes, and the relationship between luminescence properties and crystal structure, including coordination mode of the L⁻ ligand and the characteristics of a second ligand, are discussed.     

Luminescence studies on europium-strontium phthalate system

New lanthanide luminescence materials were prepared. The main component lanthanide chelates generally need a relatively high content of rare earth. Inorganic luminescence materials only need low rare earth concentration using doped method. Similarly, lanthanide chelates can be added to complex matrix by doped method. In this way, low rare earth concentration emission was successful in the lanthanide chelates system as well. The influence of europium ion concentration on luminescence intensities was discussed. When the europium ion weight in the complex is only about 0.6%, the sample exhibits good luminescence properties. The fluorescence, Fourier transform infrared spectra, micro-Raman and electron spin resonance spectra of the samples were measured. And a possible luminescence mechanism was suggested by the inorganic doped mechanism and the luminescence of lanthanide complexes together.     

Extraction of europium from nitrate solutions in the presence of tris(hydroxymethyl)aminomethane and characterization of the products of pyrolysis of extracts

The extraction of europium by neat benzene and benzene solutions of tributyl phosphate (TBP) and benzoic acid (BA) was studied in the presence of tris(hydroxymethyl)aminomethane (THMAM). Based on europium distribution in these extraction systems in combination with the IR and luminescence spectra of extracts, we infer that well-extractable europium complexes with THMAM are formed. We demonstrate that introduction of THMAM into aqueous nitrate solutions considerably enhance europium extraction. The compositions are determined and some magnetic properties of pyrolysis products of extracts are studied.     

Two-photon microscopy and spectroscopy of lanthanide bioprobes.

The linear and non-linear photophysical properties of tris-dipicolinate europium and terbium complexes (absorption, emission, lifetime, luminescence induced by two-photon absorption) are studied in the crystalline state as well as in protein derivative crystals and compared to those in solution. Upon laser irradiation at 532 nm, luminescence of terbium is induced by a two-photon antenna effect, whereas luminescence of europium results from one-photon absorption in forbidden f-f transitions. Finally, linear and two-photon microscopy imaging experiments on biological and bio-inspired crystals are performed. These first proof-of-concept experiments open the way for the development of time-resolved non-linear microscopy that should combine the advantages of lanthanide luminescence (long lifetime, sharp emission bands, insensitivity to oxygen) with those of confocal biphotonic excitation (near-IR excitation, 3D resolution and reduced photodamage).     

Effect of Aliphatic Chain Length in the Ligand on Photophysical Properties and Thin Films Morphology of the Europium Complexes

Chelating ligands based on polydentate diamides of 2,2'-bipyridyl-6,6'-dicarboxylic acid with a high affinity for lanthanide ions have been synthesized. The effect of the size of lipophilic aliphatic substituents in the ligand on the photophysical characteristics of europium complexes in acetonitrile solutions and in the solid state, as well as on the morphology of thin films obtained by the spin-coating method, was studied. The external and internal luminescence quantum yields have been measured, the luminescence lifetimes at 300 and 77 K were determined, and the sensitization efficiency values for europium complexes were calculated. The phosphorescence of gadolinium(III) complexes was used to determine the energy difference between the triplet level of the ligand and the resonance level of europium.     

An alternative route to highly luminescent platinum(II) complexes: cyclometalation with N=C=N-coordinating dipyridylbenzene ligands

The remarkable luminescence properties of the platinum(II) complex of 1,3-di(2-pyridyl)benzene, acting as a terdentate N=C=N-coordinating ligand cyclometalated at C2 of the benzene ring ([PtL(1)Cl]), have been investigated, together with those of two new 5-substituted analogues [PtL(2)Cl] and [PtL(3)Cl] [HL(2) = methyl-3,5-di(2-pyridyl)benzoate; HL(3) = 3,5-di(2-pyridyl)toluene]. All three complexes are intense emitters in degassed solution at 298 K (lambda(max) 480-580 nm; phi(lum) = 0.60, 0.58, and 0.68 in CH(2)Cl(2)), displaying highly structured emission spectra in dilute solution, with lifetimes in the microsecond range (7.2, 8.0, and 7.8 micros). On the basis of the very small Stokes shift, the highly structured profiles, and the relatively long lifetimes, the emission is attributed to an excited state of primarily (3)pi-pi character. At concentrations >1 x 10(-)(5) M, structureless excimer emission centered at ca. 700 nm is observed. The X-ray crystal structure of [PtL(2)Cl] is also reported.