Combinatorial study of cofluorescence of rare earth organic complexes doped in the poly(methyl methacrylate) matrix

The luminescence enhancement effect of different kinds and contents of rare earth complexe (RE(DBM)3Phen, RE = Dy, La, Gd, Sm, Y; DBM = dibenzoylmethane; Phen = 1,10-phenanthroline) sensitized Eu(DBM)3Phen doped in poly(methyl methacrylate) (PMMA) matrix was investigated using the combinatorial method. The efficiency of the luminescence enhancement increases with a decrease in the weight percentage of the Eu(DBM)3Phen and an increase in the molecular weight of the PMMA in the systems. Among these sensitization ion complexes, La(DBM)3Phen shows the highest sensitization efficiency. At the optimal content of 5 wt % Eu(DBM)3Phen and 350,000 g/mol weight average molecular weight (Mw) of PMMA, the maximum sensitization efficiency of La(DBM)3Phen is approximately 20 times. We believe that the PMMA with high molecular weight enwraps the rare earth complexes and keeps the donors and acceptors close, which results in the effective intermolecular energy transfer and, consequently, the high sensitization efficiency.     

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.     

Synthesis, crystal structure, and luminescent properties of novel Eu3+ heterocyclic beta-diketonate complexes with bidentate nitrogen donors

New tris(heterocyclic beta-diketonato)europium(III) complexes of the general formula Eu(PBI)3.L [where HPBI = 3-phenyl-4-benzoyl-5-isoxazolone and L = H2O, 2,2'-bipyridine (bpy), 4,4'-dimethoxy-2,2'-bipyridine (dmbpy), 1,10-phenanthroline (phen), or 4,7-diphenyl-1,10-phenanthroline (bath)] were synthesized and characterized by elemental analysis, Fourier transform infrared spectroscopy (FT-IR), 1H NMR, high-resolution mass spectrometry, thermogravimetric analysis, and photoluminescence (PL) spectroscopy. Single-crystal X-ray structures have been determined for the complexes Eu(PBI)3.H2O.EtOH and Eu(PBI)3.phen. The complex Eu(PBI)3.H2O.EtOH is mononuclear, and the central Eu3+ ion is coordinated by eight oxygen atoms to form a bicapped trigonal prism coordination polyhedron. Six oxygens are from the three bidentate HPBI ligands, one is from a water molecule, and another is from an ethanol molecule. On the other hand, the crystal structure of Eu(PBI)3.phen reveals a distorted square antiprismatic geometry around the europium atom. The room-temperature PL spectra of the europium(III) complexes are composed of the typical Eu3+ red emission, assigned to transitions between the first excited state (5D0) and the multiplet (7F0-4). The results demonstrate that the substitution of solvent molecules by bidentate nitrogen ligands in Eu(PBI)3.H2O.EtOH richly enhances the quantum yield and lifetime values. To elucidate the energy transfer process of the europium complexes, the energy levels of the relevant electronic states have been estimated. Judd-Ofelt intensity parameters (Omega2 and Omega4) were determined from the emission spectra for Eu3+ ion based on the 5D0 --> 7F2 and 5D0 --> 7F4 electronic transitions, respectively, and the 5D0 --> 7F1 magnetic dipole allowed transition was taken as the reference. The high values obtained for the 4f-4f intensity parameter Omega2 for europium complexes suggest that the dynamic coupling mechanism is quite operative in these compounds.     

Visible light sensitized attapulgite-based lanthanide composites: microstructure, photophysical behaviour and biological application

Attapulgite, an extremely stable fibrillar mineral present in nature, is a promising new carrier of luminescent lanthanide complexes for further applications. A europium complex Eu(DBM)(3)(H(2)O)(2) (HDBM = dibenzoylmethane) was covalently coupled onto modified attapulgites (or silica nanoparticles) via a ligand exchange reaction, generating attapulgite-based ternary europium complexes. The composites were characterized by CHN elemental analysis, inductively coupled plasma-atomic emission spectroscopy (ICP-AES) for Eu(3+) content, powder X-ray diffraction (XRD), thermogravimetry (TG) and UV-vis absorption spectra. The results indicate that the Eu(3+) complex was grafted covalently to the outer surfaces of attapulgites (or silica nanoparticles) and modifications by coupling agents containing different alkoxide groups (aminopropyltriethoxysilane (APTES) or aminopropylmethyldiethoxysilane (APMDES)) led to different grafting ratios. The structures of these composites were further evidenced by the determination of photophysical behaviours and coordinated water molecules of the complexes linked to matrices. Attapulgite-based lanthanide composites linked by APTES can be excited by visible light, with a wide excitation wavelength range from UV to visible light (a maximum at 398 nm), long luminescence lifetime (503 μs), high quantum yield (48%) and improved exposure durability. When incubated with HeLa cells at 37 °C, the fluorescence of matrix-APTES-cpa-Eu(DBM)(3) is observed on the cell membrane. Moreover, the low cytotoxicity of our present system results in potential applications for cell imaging in biological systems.     

3-Phenyl-4-benzoyl-5-isoxazolonate complex of Eu3+ with tri-n-octylphosphine oxide as a promising light-conversion molecular device

Three new europium complexes, [Eu(PBI)3.3H2O] (1), [Eu(PBI)3.2TOPO] (2), and [Eu(PBI)3.2TPPO.H2O] (3) (where HPBI, TOPO, and TPPO stand for 3-phenyl-4-benzoyl-5-isoxazolone, tri-n-octylphosphine oxide, and triphenylphosphine oxide, respectively), with different neutral ligands were synthesized and characterized by elemental analysis, Fourier transform infrared, (1)H NMR, thermogravimetric analysis, and photoluminescence (PL) spectroscopy. The coordination geometries of the complexes were calculated using the Sparkle/AM1 (Sparkle Model for the Calculation of Lanthanide Complexes within the Austin Model 1) model. The ligand-Eu3+ energy-transfer rates were calculated in terms of a model of the intramolecular energy-transfer process in lanthanide coordination compounds reported in the literature. The room-temperature PL spectra of the europium(III) complexes are composed of the typical Eu3+ red emission, assigned to transitions between the first excited state (5D0) and the multiplet (7F(0-4)). On the basis of emission spectra and lifetimes of the 5D0-emitting level, the emission quantum efficiency (eta) was determined. The results clearly show that the substitution of water molecules by TOPO leads to greatly enhanced quantum efficiency (i.e., 26% vs 92%) and longer 5D0 lifetimes (250 vs 1160 micros). This can be ascribed to a more efficient ligand-to-metal energy transfer and a less nonradiative 5D0 relaxation process. Judd-Ofelt intensity parameters (Omega2 and Omega4) were determined from the emission spectra for the Eu3+ ion based on the 5D0 --> 7F2 and 5D0 --> 7F4 electronic transitions, respectively, and the 5D0 --> 7F1 magnetic-dipole-allowed transition was taken as the reference. A point to be noted in these results is the relatively high value of the Omega2 intensity parameter for all of the complexes. This may be interpreted as being a consequence of the hypersensitive behavior of the 5D0 --> 7F2 transition. The dynamic coupling mechanism is, therefore, dominant, indicating that the Eu3+ ion is in a highly polarizable chemical environment.     

稀土配合物的发光特性及其能量传递研究

利用激光诱导荧光技术研究了稀土铕等金属配合物的发光特性及其能量传递动力学过程．得到了这些稀土配合物中中心离子Eu（3 ）的激发光谱，配体的三线态发时光谱和单线态发射光谱；在实验上观察到由于中心离子Eu（3 ）的5D2←7F0马跃迁吸收造成的配体发射光谱中的凹陷行为     

稀土异硫氰酸盐与二甲基亚砜配合物的合成,性质及热分析研究

合成了15种稀土异硫氰酸盐与二甲基亚砜(DMSO)的配合物,经化学分析和元素分析确定其组成为RE(NCS)_s·mDMSO(RE=La,Ce,Pr,Nd,Sm,Eu,Gd;m=5.RE=Tb,Dy,Ho,Er,Tm,Yb,Lu,Y;m=4).用红外光谱及X射线衍射技术进行了表征.运用TG-DTA-DTG联用技术研究了该系列配合物的热分解过程,求算热重动力学参数发现,第一步热分解阶段的活化能随着中心高子——镧系元素原子序数的依次递增呈现“双峰现象”.     

Thermally stable luminescent composites fabricated by confining rare earth complexes in the two-dimensional gallery of titania nanosheets and their photophysical properties

Fluorescent composite materials of exfoliated titania nanosheets, Ti(0.91)O(2), and rare earth (RE) complexes, Eu(phen)(2)Cl(3).2H(2)O and Tb(phen)(2)Cl(3).2H(2)O (phen = 1,10-phenanthroline), were synthesized via flocculation between them. X-ray diffraction measurements and transmission electron microscopy observations confirmed a restacked lamellar structure for the composites, and elemental analysis revealed a high RE complex content of 15 wt %. The decomposition temperature of the complexes trapped in the composites was improved to 420 degrees C from 250 degrees C for the free form. The restacked composite composed of Ti(0.91)O(2) nanosheets and Eu(phen)(2) exhibited characteristic red emission from the complex, while the composite with Tb(phen)(2) gave featureless emission originated from the ligand. This phenomenon can be explained by a shift of triplet state level of the ligand after encapsulation in the host titania nanosheets. The quantum yield of europium complex in the composite was enhanced 1.6 times more than that of the pure complex.     

Enhanced lasing properties of dissymmetric Eu(III) complex with bidentate phosphine ligands

The luminescent and lasing properties of Eu(III) complexes were enhanced by using an dissymmetric Eu(III) complex. The photophysical properties (the emission spectral shapes, the emission lifetimes, the emission quantum yields, and the stimulated emission cross section (SEC)) were found to be dependent on the geometrical structures of Eu(III) complexes. The geometrical structures of Eu(III) complexes were determined by X-ray single crystal analyses. The symmetrical group of Eu(hfa)3(BIPHEPO) (tris(hexafluoroacetylacetonato)europium(III) 1,1'-biphenyl-2,2'-diylbis(diphenylphosphine oxide)) was found to be C1, which was more dissymmetric than Eu(hfa)3(TPPO)2 (tris(hexafluoroacetylacetonato)europium(III) 1,2-phenylenebis(diphenylphosphine oxide): C2 symmetry) and Eu(hfa)3(OPPO)2 (tris(hexafluoroacetylacetonato)europium(III) 1,2-phenylenebis(diphenylphosphine oxide): C2 symmetry). The analytical data were supported by Judd-Ofelt analysis. The most dissymmetrical Eu(III) complex, Eu(hfa)3(BIPHEPO), showed large electron transition probability and large SEC (4.64 x 10(-20) cm2). The SEC of Eu(hfa)3(BIPHEPO) was superior to even the values of Nd-glass laser for practical use (1.6-4.5 x 10(-20) cm2). The lasing properties of Eu(III) complexes in polymer thin film were measured by photopumping of a Nd:YAG laser (355 nm). The threshold energy of lasing oscillation was found to be 0.05 mJ. The increasing rate of the lasing intensity of Eu(hfa)3(BIPHEPO) as a function of the excitation energy was much larger than that of Eu(hfa)3(TPPO)2 and Eu(hfa)3(OPPO)2. The dissymmetrical structure of Eu(hfa)3(BIPHEPO) promoted the enhancement of the lasing property.     

Electroluminescent properties of three ternary europium complexes with different phenanthroline derivatives

In the past decade a number of lanthanide com-plexes have been designed and synthesized for organic electroluminescent (EL) devices owing to their ex-tremely sharp emission bands and potentially high internal quantum efficiency[113]. This characteristic made the lanthanide complexes one kind of promising candidates for full color flat-panel displays which re-quire pure red, green and blue emissions. So far, how-ever, the devices based on lanthanide complexes as emitters have not demonstrated v…     

Luminescence properties and quenching mechanisms of Ln(Tf2N)3 complexes in the ionic liquid bmpyr Tf2N

The emission properties, including luminescence lifetimes, of the lanthanide complexes Ln(Tf(2)N)(3) (Tf(2)N = bis(trifluoromethanesulfonyl)amide); Ln(3+) = Eu(3+), Tm(3+), Dy(3+), Sm(3+), Pr(3+), Nd(3+), Er(3+)) in the ionic liquid bmpyr Tf(2)N (bmpyr = 1-n-butyl-1-methylpyrrolidinium) are presented. The luminescence quantum efficiencies, η, and radiative lifetimes, τ(R), are determined for Eu(3+)((5)D(0)), Tm(3+)((1)D(2)), Dy(3+)((4)F(9/2)), Sm(3+)((4)G(5/2)), and Pr(3+)((3)P(0)) emission. The luminescence lifetimes in these systems are remarkably long compared to values typically reported for Ln(3+) complexes in solution, reflecting weak vibrational quenching. The 1.5 μm emission corresponding to the Er(3+) ((4)I(13/2)→(4)I(15/2)) transition, for example, exhibits a lifetime of 77 μs. The multiphonon relaxation rate constants are determined for 10 different Ln(3+) emitting states, and the trend in multiphonon relaxation is analyzed in terms of the energy gap law. The energy gap law does describe the general trend in multiphonon relaxation, but deviations from the trend are much larger than those normally observed for crystal systems. The parameters determined from the energy gap law analysis are consistent with those reported for crystalline hosts. Because Ln(3+) emission is known to be particularly sensitive to quenching by water in bmpyr Tf(2)N, the binding properties of water to Eu(3+) in solutions of Eu(Tf(2)N)(3) in bmpyr Tf(2)N have been quantified. It is observed that water introduced into these systems binds quantitatively to Ln(3+). It is demonstrated that Eu(Tf(2)N)(3) can be used as a reasonable internal standard, both for monitoring the dryness of the solutions and for estimating the quantum efficiencies and radiative lifetimes for visible-emitting [Ln(Tf(2)N)(x)](3-x) complexes in bmpyr Tf(2)N.     

三核铕配合物Eu3(DBM)9(TDMB)的星型配体制备与发光性能

用一种星型配体1,3,5-三((4,5-二氮芴-9-肟)甲基))-苯合成了三核铕配合物Eu₃(DBM)₉(TDMB)(DBM=1,3-二苯基-1,3-丙二酮),合成的配合物用元素分析,红外,氢核磁共振进行了表征。研究了配体与配合物的光物理性质。配合物在固态和溶液中具有不同的发光光谱,在二氯甲烷中分别在612 nm和414 nm有荧光峰,固态时只有红光发射,这一结果显示在固态时从TDMB配体到铕离子的能量传递更有效。     

Photophysical Properties of a Novel Organic–Inorganic Hybrid Material: Eu(III)-β-Diketone Complex Covalently Bonded to SiO2/ZnO Composite Matrix

In this article, dibenzoylmethane (DBM) was first grafted with the coupling reagent 3-(triethoxysilyl)-propyl isocyanate (TESPIC) to form precursor DBM–Si, and ZnO quantum dot was modified with 3-mercaptopropyltrimethoxysilane (MPS) to form SiO₂/ZnO nanocomposite particle. Then the precursor DBM–Si and the terminal ligand 1,10-phenthroline (phen) were coordinated to Eu³⁺ion to obtain ternary hybrid material phen–Eu–DBM–SiO₂/ZnO after hydrolysis and copolycondensation between the tetraethoxysilane (TEOS), water molecules and the SiO₂/ZnO network via the sol–gel process. In addition, for comparison, the binary hybrid material with SiO₂/ZnO network and ternary hybrid material with pure Si–O network were also synthesized, denoted as Eu–DBM–SiO₂/ZnO and phen–Eu–DBM–Si, respectively. The results reveal that hybrid material with SiO₂/ZnO network phen–Eu–DBM–SiO₂/ZnO exhibits the stronger red light, the longer lifetimes and higher quantum efficiency than hybrid material with pure Si–O network phen–Eu–DBM–Si, suggesting that SiO₂/ZnO is a favorable host matrix for the luminescence of rare earth complexes.     

Eu(III) emission band changes caused by peripheral C-H/O hydrogen bonding

We synthesized Eu(III) and Sm(III) complexes with tridentate phosphine oxide ligands, Eu(hfa)(3)(TPPM) and Sm(hfa)(3)(TPPM) (hfa: hexafluoroacetylacetonato, TPPM: tris(diphenylphosphinyl)methane), and we then examined their luminescent properties. In the complexes the Eu(III) and Sm(III) centres were fully surrounded by low-vibrational frequency ligands, which led to relatively high emission quantum yields (Φ(Eu) = 30%, Φ(Sm) = 4.7%). The X-ray single crystal structures of the Eu(hfa)(3)(TPPM) revealed nona-coordinated Eu(III) complexes and C-H/O hydrogen bonding formations between the acidic hydrogen atom of the TPPM ligand and oxygen atoms of solvent molecules. The C-H/O hydrogen bonding slightly affected the coordination structure around the Eu(III) ion. Despite the seemingly small effect on the structural change, because the emission band profile of the (5)D(0)→(7)F(2) transition is sensitive to changes in the coordination environment of the Eu(III) complex, we observed a red shift in the emission spectral line.     

Tuning the triplet energy levels of pyrazolone ligands to match the 5D0 level of europium(III)

Three pyrazolone-based ligands, namely 1-phenyl-3-methyl-4-(1-naphthoyl)-5-pyrazolone (HL1), 1-phenyl-3-methyl-4-(4-dimethylaminobenzoyl)-5-pyrazolone (HL2), and 1-phenyl-3-methyl-4-(4-cyanobenzoyl)-5-pyrazolone (HL3), were synthesized by introducing electron-poor or electron-rich aryl substituents at the 4-position of the pyrazolone ring. Their corresponding europium complexes Eu(LX)3(H2O)2 and Eu(LX)3(TPPO)(H2O) (X = 1-3) were characterized by photophysical studies. The characteristic Eu(III) emission of these complexes with at most 9.2 x 10(-3) of fluorescent quantum yield was observed at room temperature. The results show that the modification of ligands tunes the triplet energy levels of three pyrazolone-based ligands to match the 5D0 energy level of Eu3+ properly and improves the energy transfer efficiency from antenna to Eu3+, therefore enhancing the Eu(III) emission intensity. The highest energy transfer efficiency and probability of lanthanide emission of Eu(L1)3(H2O)2 are 35.1% and 2.6%, respectively, which opens up broad prospects for improving luminescent properties of Eu(III) complexes by the modification of ligands. Furthermore, the electroluminescent properties of Eu(L1)3(TPPO)(H2O) were also investigated.     

Judd-Ofelt Analysis on Trifluoroacetate Europium Complexes for Liquid Laser Media

Four europium trifluoroacetate complexes, Eu(CF₃COO)₃·bpy(bpy=2,2′-bipyridine)(1), Eu(CF₃COO)₃· phen(phen=1,10-phenanthroline)(2), Eu(CF₃COO)₃·2bp(bp=benzophenone)(3) and Eu(CF₃COO)₃·2tppo(tppo=triphenyl-phosphine oxide)(4) were synthesized and characterized by elemental analysis, Fourier transform infrared(FTIR) spectroscopy, photoluminescence(PL) spectroscopy and thermogravimetric analysis(TGA). The PL spectra of the complexes at room temperature show the strong typical Eu³⁺ ion red emission, due to the efficient energy “antenna absorption” of ligands and transitions of Eu³⁺ ion between ⁵D₀→⁷F_J(J=0―4). The long lifetime and high quantum yield reflect that the multiphonon relaxations by coupling to O―H and C―H vibrations were reduced. According to the photoluminescent spectra, the Judd-Ofelt parameters Ω₂ and Ω₄ of the complexes were calculated and the radiative properties were also presented. The ⁵D₀ radiative lifetime, quantum yield and the stimulated emission cross-section of the complexes are excellent, which prove that they have promising optical properties for liquid laser. The thermal analyses indicate that they are quite stable to heat.     

Homoleptic imidazolate frameworks [Sr(1-x)Eu(x)(Im)2]--hybrid materials with efficient and tuneable luminescence

Homoleptic frameworks of the formula [Sr(1-x)Eu(x)(Im)(2)] (1) (x = 0.01-1.0; Im(-) = imidazolate anion, C(3)H(3)N(2)(-)) are hybrid materials that exhibit an intensive green luminescence. Tuning of both emission wavelength and quantum yield is achieved by europium/strontium substitution so that a QE of 80% is reached at a Eu content of 5%. Even 100% pure europium imidazolate still shows 60% absolute quantum efficiency. Substitution of Sr/Eu shows that doping with metal cations can also be utilized for coordination compounds to optimize materials properties. The emission is finely tuneable in the region 495-508 nm via variation of the europium content. The series of frameworks [Sr(1-x)Eu(x)(Im)(2)] presents dense MOFs with the highest quantum yields reported for MOFs so far.     

Photo-and Electro-luminescence of the New Ternary Europium(III) Complex

In recent years, the interest in developing luminescent lanthanide complexes has been greatly stimulated by their potential use in electroluminescent displays1. Europium complexes appear most attractive in view of the high photoluminescent efficiency and the high monochromatic red light that are widely exploited in full-color displays2. It has been approved that the second ligand plays an important role in europium complexes, the synergistic complexation of the second ligand can not only lead …     

聚丙烯酸/聚(苯乙烯-丙烯酸)二苯酰基甲烷铕(Ⅲ)配合物的合成及其荧光性能

铕(Ⅲ)和二苯甲酰甲烷(HDBM)形成的有机配合物与聚丙烯酸(PAA)(M_n=5000)、聚(苯乙烯-丙烯酸)(PSAA)(M_n=3000)发生配位反应,分别得到配位聚合物Eu(Ⅲ)-DBM-PAA和NaEu(Ⅲ)-DBM-PSAA,产率分别为89.7%和87.3%.红外光谱、紫外光谱、X光电子能谱测试表明,Eu³⁺分别与PAA,PSAA和DBM-发生配位,元素分析和电导率测定结果证明,1个Eu³⁺分别与PAA中2个链节或PSAA中3个链节的羧基和1个DBM-发生配位.Eu³⁺离子在配位聚合物Eu(Ⅲ)-DBM-PAA和Eu(Ⅲ)-DBM-PSAA中的含量分别为28.46%和12.23%.荧光光谱表明,常温下配位聚合物在紫外光下发出强的红光,主要是Eu³⁺离子的5D0→7F2的能级跃迁.     

Reversible modulation in luminescence intensity of a single vesicle composed of diblock azo-copolymer and tris(dibenzoylmethanate)(phenanthroline)europium(III)

Tris(dibenzoylmethanate)(phenanthroline)europium(III)[Eu(DBM)(3)Phen]-doped amphiphilic vesicles were obtained by self-assembling of poly(N-isopropylacrylamide)-b-poly[6-[4-(4-methylphenyl-azo) phenoxy] hexylacrylate] (PNIPAM(83)-b-PAzoM(20)) in presence of Eu(DBM)(3)Phen in the mixed solvent of THF/H(2)O (50/50 vol.%). Their optical properties were studied by UV-vis and fluorescence spectroscopies. The UV-vis spectrum showed that the electronic transition bands of azobenzene and Eu(DBM)(3)Phen were overlapped at about 365 nm and the main peak of fluorescence emission band appeared at 612 nm. So the vesicles showed obvious red luminescence. It was found that the fluorescence intensity of a single Eu(DBM)(3)Phen-doped vesicle could be modulated by irradiation with UV and visible light due to the reversible trans-cis-trans photoisomerization reaction of azobenzene moiety. Possible energy allocation process for this property was discussed in details.