Luminescent Europium Complexes Research Articles

A targetable fluorescent sensor for hypochlorite based on a luminescent europium complex loaded carbon nanotube

A new europium complex covalently modified single-walled carbon nanotube (SWNT) was reported here as an emissive nanosensor for the determination of hypochlorite. FT-IR, UV-vis, TEM and SEM proved that it was successfully linked to the SWNT surface. A luminescence quenching effect of this nanoprobe was rapidly observed in the presence of ClO(-). Moreover, the quenching process can be detected within 1 s and the detection limit could reach 9 × 10(-8) M. We regarded that the ligand exchange process and the high vibration energy of the ClO(-) resulted in this selective recognition behavior.

Structural and Luminescence Properties of Silica-Based Hybrids Containing New Silylated-Diketonato Europium(III) Complex

A new betadiketonate ligand displaying a trimethoxysilyl group as grafting function and a diketone moiety as complexing site (TTA-Si = 4,4,4-trifluoro-2-(3-trimethoxysilyl)propyl)-1-3-butanedione (C4H3S)COCH[(CH2)3Si(OCH3)3]COCF3) and its highly luminescent europium(III) complex [Eu(TTA-Si)3] have been synthesized and fully characterized. Luminescent silica-based hybrids have been prepared as well with this new complex grafted on the surface of dense silica nanoparticles (28 ± 3 nm) or on mesoporous silica particles. The covalent bonding of Eu(TTA-Si)3 inside the core of uniform silica nanoparticles (40 ± 5 nm) was also achieved. Luminescence properties are discussed in relation to the europium chemical environment involved in each of the three hybrids. The general methodology proposed allowed high grafting ratios and overcame chelate release and tendency to agglomeration, and it could be applied to any silica matrix (in the core or at the surface, nanosized or not, dense or mesoporous) and therefore numerous applications such as luminescent markers and luminophors could be foreseen.

In Situ Synthesis and Luminescence Characteristics of Complexes Europium with Schiff Base Ligands

The complexes of europium with two schiff base ligands [2-carboxybenzaldehyde- diethylenetriamine (1), 2-carboxybenzaldehyde-triethylenetetramine (2)] were in-situ synthesized. The formation of complexes was confirmed by the luminescence spectra. The luminescence spectra of two europium complexes were investigated in solid and in DMSO solution, respectively. The results show that two europium complexes exhibit low luminescence emission. And organic solvent DMSO could quench the luminescence of europium complexes.

New technology of production of optically transparent polymer compositions containing capsulated nanosized aggregates of photoactive compounds

The article summarizes the results of the studies performed at the Institute of Chemical Physics, Russian Academy of Sciences, devoted to development of scientific foundations of adding nanosized particles of organic or inorganic photoactive compounds into polymers for production of new polymer nanocomposites of optical application. It is shown that luminescent europium complexes and photochromic indoline spirooxazines can be added to polymer matrices in the solubilized state at a threefold concentration compared to the process without Pluronics. The effect of an increase in the functional activity of solubilized luminescent europium complexes added to polymer compositions of various structures is discovered, which is related with a decrease in the size of aggregates of europium complexes at their solubilization by Pluronics. The solubilization by Pluronics exerts a sharp influence on the maximal content of indoline photochromes in the polymer matrix; the content of the colored form of photochrome in the 3D-crosslinked acryl matrix increases fourfold. This effect is related to both the decrease in the sizes of photochrome aggregates during solubilization and the plasticization of the polymer matrix by Pluronics.

Luminescent europium(III) complexes of tripodal heptadentate N 7 ligands containing three imidazole groups

Luminescent Eu III complexes with tripodal heptadentate N 7 ligands containing three imidazole groups, [Eu III(H 3L 2-H)(ac)](ClO 4) 2·H 2O ( 1), [Eu III(H 3L 2-Me)(ac)](ClO 4) 2·2EtOH ( 2), and [Eu III(H 3L 4-Me)(ac)](ClO 4) 2·H 2O ( 3), were synthesized and characterized, where H 3L 2-H, H 3L 2-Me, and H 3L 4-Me are the tripodal ligands derived from the 1:3 condensation of tris(2-aminoethyl)amine and either 4-formylimidazole, 2-methyl-4-formylimidazole, and 4-methyl-5-formylimidazole, respectively, and ac denotes an acetate ion. Single-crystal X-ray analyses revealed that each Eu III ion is coordinated by a tripodal heptadentate N 7 ligand and two oxygen atoms of the acetate ion as a bidentate ligand. The complexes displayed sharp emission bands based on the f–f transitions by excitation at 261 nm in acetonitrile. The emission intensities increased in the order 1 < 2 < 3 in acetonitrile, while the emission spectra were quenched in aqueous solution due to the partial dissociation of the acetate ion and tripodal ligand.

Electrochemically controllable emission and coloration by using europium(iii) complex and viologen derivatives

We have demonstrated electroswitchable emission and coloration using a novel composite material containing luminescent europium(III) complex Eu(hfa)(3)(H(2)O)(2) and diheptyl viologen HV(2+). The photoluminescence of the Eu(III) complex was controlled by the electrochemical coloration of HV(2+)via intermolecular energy transfer mechanisms.

Artificial luminescent protein as a bioprobe for time-gated luminescence bioimaging

An artificial luminescent protein, apoferritin-encapsulated luminescent europium complex, has been designed/fabricated and displays good biocompatibility and long-lived luminescence, which means it can be used as a bioprobe to image living cells with a time-gated mode.

Intracellular Synchrotron Nanoimaging and DNA Damage/Genotoxicity Screening of Novel Lanthanide-Coated Nanovectors

In cancer therapy, research has focused on the development of nanocarriers that can aid diagnosis, deliver therapeutic agents and monitor treatment progress. This study introduces high-resolution synchrotron x-ray fluorescence microscopy (SR-XFM) to investigate intracellular localization of novel lanthanide-coated nanoparticles in human cells and their genotoxicity screening after internalization. Noble metal nanoparticles coated with cerium and luminescent europium complexes have been developed as platforms for bioimaging and potential biodelivery applications. The intracellular distribution after internalization has been analyzed by ultrasensitive SR-XFM and genotoxicity evaluated using γ-H2AX DNA damage foci phosphorylation assay. We demonstrate the unprecedented capability of SR-XFM for extremely sensitive nanoimaging and intracellular elemental distribution analysis of noble metal nanoparticles in cells. Furthermore, we show that, depending on the charge of the coating complex and the presence of the DNA cargo, the internalization of functionalized nanoparticles by human fibroblasts can cause elevated levels of DNA damage detected by histone H2AX phosphorylation. The variable genotoxic impact of newly designed nanovectors emphasizes the need for careful and comprehensive testing of biological responses of all new nanoconstructs intended for future clinical applications. This can be greatly facilitated by SR-XFM nanoimaging of nanoparticles in cells at very low concentrations.

Theoretical design of highly luminescent europium (III) complexes: A factorial study

In this work, the design of europium (III) complexes exhibiting high quantum yield was accomplished by a systematic study using factorial design and the Sparkle/AM1 model. Eight new complexes derived from the Eu(acac)3.o-phen complex (acac=acetylacetonate acid and o-phen=1,10-phenantroline) were generated through a 23 full factorial design. The ground state geometries of the eight new complexes were predicted using the Sparkle/AM1 model. The singlet and triplet excited levels were calculated using the INDO/S-CIS method, implemented in ZINDO program. Energy transfer rates and quantum yields for each one of the new complexes were calculated using the theoretical model based on the theory of the transitions 4f–4f (Spectrochim. Acta Part A, 1998, 54, 1593). The results strongly suggest that the europium complexes with β-diketone ligands might display a quantum yield increment when strongly electron acceptor groups are added to one of the β-diketone extremities and strongly electron donor groups are added to the opposite side. From the factorial design proposed in this work it was possible to project complexes with quantum yields up to 70%.

Photophysical properties of a series of high luminescent europium complexes with fluorinated ligands

A series of high luminescent europium complexes have been synthesized such as Eu(TFNB)(3)phen (1) Eu(PFNP)(3)phen (2) Eu(HFNH)(3)phen (3) and Eu(PFND)(3)phen (4) which have beta-diketone ligands containing fluorinated alkyl chains with different lengths and conjugated naphthyl groups ie 44 4-trifluoro-1-(2-naphthyl)butane-1 3-dione (TFNB) 445 5 5-pentafluoro-1-(2-naphthyl)pentane-1 3-dione (PFNP) 44 5 5 66 6-heptafluoro-1-(2-naphthyl)hexane-1 3-dione (HFNH) and 445 5 6 67 7 8 8 9 9 10 10 10-pentadecafluoro-1-(2-naphthyl)decane-1,3-dione (PFND) And 10-phenanthroline (phen) is coordinated as the neutral second ligand in 1-4 The crystal structures of 1 and 2 have been studied which are typical and similar to that of 3 The results of TGA-DTA suggest that these Eu complexes have good thermal stabilities By means of absorption and (time resolved) emission spectroscopy including determination of luminescence quantum yields energy transfer dynamics and so on the following results have been obtained first these Eu complexes show characteristic pure red color photoluminescence emission with high quantum efficiencies from the central Eu(3+) ions through the excitation of the ligands secondly photophysical properties of 1 2 3 and 4 especially the lifetimes of excited states (5)D(0) of Eu(3+) ions and quantum efficiencies are influenced by the different lengths of fluorinated alkyl chains though the singlets (S(1)) and triplets (T(1)) of the fluorinated ligands are almost the same (C) 2010 Elsevier B V All rights reserved

Anion-responsive luminescent Eu3+ complexes with ring-like rigid quinoline–amide ligands

Abstract Two novel ring-like rigid quinoline–amide ligands, 2-[2-(1,3-dioxolan-2-yl)quinolin-8-yloxy]-N-benzylacetamide (LI) and 3-[2-(1,3-dioxolan-2-yl)quinolin-8-yloxy]-1,1-diphenylpropan-2-one (LII), were designed to assemble the anion-responsive luminescent europium complexes. Crystallographic studies of the EuLI(NO3)3 and EuLII(NO3)3 revealed that the tetradentate ligands LI and LII cooperatively coordinated with Eu3+ ion and some available sites around central europium ions for guest anions were reserved in the complexes. The luminescent properties of the Eu(III) nitrate complexes in acetonitrile solutions were investigated. And the lowest triplet state energy levels of the ligands are well placed to allow energy transfer to the resonance level of Eu(III). At the same time, the luminescence titration experiments and the Job's plot analysis demonstrated the formation of 1:1 complexes in the solutions. The luminescence intensities at 616 nm were enhanced by addition of NO3− or Cl− anion to the mixed acetonitrile solutions of Eu(CF3SO3)3 and the ligands.

Role of Ligand-to-Metal Charge Transfer State in Nontriplet Photosensitization of Luminescent Europium Complex

We have investigated, by means of steady-state and time-resolved optical spectroscopies, the excited-state dynamics of the luminescent europium complex Eu(III)(tta)(3)dpbt (tta = henoyltrifluoroacetonate; dbpt = 2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine) with Gd(III)(tta)(3)dpbt and Tb(III)(tta)(3)dpbt as the reference complexes that cannot be photosensitized. In the Eu(III)(tta)(3)dpbt complex, the ligand dpbt exhibited biphasic fluorescence decay kinetics; the faster component (decay time constant, 8.5 ps) is ascribed to the rapid conversion of the lowest-lying singlet excited state of dpbt (S(1) or (1)dpbt*) to a ligand-to-metal charge transfer singlet state of the complex ((1)LMCT*), whereas the slower one (1.8 ns) is shown by temperature-dependent luminescence spectroscopy to be delayed fluorescence due to the LMCT-to-dpbt backward energy transfer and represents the time scale of efficient excitation energy flow from the (1)LMCT* state to the (5)D(1) state of Eu(III). On the basis of the spectroscopic results of the Ln(III)(tta)(3)dpbt complexes (Ln = Eu, Gd, and Tb), the crucial role of the (1)LMCT* state in photosensitization of the Eu(III)(tta)(3)dpbt complex is established, and a LMCT-mediated nontriplet sensitization mechanism is proposed, which is advantageous in high efficiency and low excitation photon energy as well as in low susceptibility against oxygen quenching.

Time-resolved fluorescence based DNA detection using novel europium ternary complex doped silica nanoparticles

A two-probe tandem DNA hybridization assay including capture DNA 1, probe DNA 2, and target DNA 3 was prepared. The long-lived luminescent europium complex doped nanoparticles (NPs) were used as the biomarker. The complex included in the particle was Eu(TTA) 3(5-NH 2-phen)-IgG (ETN-IgG), the europium complex Eu(TTA) 3(5-NH 2-phen) linking an IgG molecule. Silica NPs containing ETN-IgG were prepared by the reverse microemulsion method, and were easy to label oligonucleotide for time-resolved fluorescence assays. The luminophores were well-protected from the environmental interference when they were doped inside the silica network. The sequences of Staphylococcus aureus and Escherichia coli genes were designed using software Primer Premier 5.0. Amino-modified capture DNA 1 was covalently immobilized on the common glass slides surface. The detection was done by monitoring the fluorescence intensity from the glass surface after the hybridization reaction with the NPs labeled probe DNA 2 and complementary target DNA 3. The sensing system presented short hybridization time, satisfactory stability, sensitivity, and selectivity. This approach was successfully employed for preliminary application in the detection of pure cultured E. coli, it might be an effective tool for pathogen DNA monitoring.

Effect of Coordination Environment on the Photophysical Properties of Luminescent Europium(III) Complexes

A series of Eu(III) complexes with various neutral ligands (2,2’:6’,2-terpyridine (T), diglyme (D), 1N-(2-dimethylamino)ethyl)-1N, 2N, 2N-trimethylethane-1,2-diamine (PT), di-(2-picolyl)-amine derivative (HT), and multidentate terpyridine derivative (DT)) were synthesized to investigate the effect of coordination environment on the sensitized luminescence of Eu(III) complexes. The nine coordination sites of the Eu 3+ ion are occupied by three bidentate carboxylate moieties and one neutral ligand. The highest emission intensity is obtained for Eu 3+ - [NA]3 (PT), due to the difference in energy transfer efficiency and symmetry of the first coordination sphere of Eu 3+ ion. But, the lowest emission intensity is obtained for Eu 3+ -[NA]3(T). Terpyridine may not play an important role antenna for photosensitizing Eu 3+ ion. It could be attributed to the weak spectral overlap integral J value between its phosphorescence band and Eu 3+ ion absorption band. Therefore, different coordination environment of Ln 3+ ion play an important role in providing sensitization of lanthanide ion emission.

Judd–Ofelt treatment on luminescence of europium complexes with β-diketone and bis(β-diketone)

Eu(DBM) 32H 2O and Eu 2(DDBM) 3H 2O were synthesized by reactions between EuCl 3 and chelating regents of β-diketone (dibenzoylmethane, HDBM) and bis(β-diketone) (1,3-bis(3-phenyl-3-oxopropanoyl)benzene, H 2DDBM), respectively, and their luminescence properties were investigated by the fluorescence spectra and metastable state decay spectra. It was found that the relative intensity ratio of 5D 0→ 7F 2 to 5D 0→ 7F 1transition and the radiative lifetime shows a little change attributing to the different symmetry of europium ions, which Ω 2 of Eu complexes with β-diketone and bis(β-diketone) are 13.08 and 12.24, respectively. Moreover, it was also found that the metastable state lifetime of Eu 2(DDBM) 3H 2O is much longer than that of Eu(DBM) 32H 2O, due to smaller water quenching and lower triplet level of ligands. The Commission Internacionale d’Éclairage (CIE) chromaticity coordinates calculated from emission spectrum are x=0.637 and y=0.343 for Eu 2(DDBM) 3H 2O, which presents high red color purity near 100%.

Calibration beads containing luminescent lanthanide ion complexes

The reliability of lanthanide luminescence measurements, by both flow cytometry and digital microscopy, would be enhanced by the availability of narrowband emitting, UV excited lanthanide calibration beads. 0.5-, 3-, and 5-microm beads containing a luminescent europium-complex are manufactured. The luminescence distribution of the 5-microm beads is measured with a time-delayed light-scatter-gated luminescence flow cytometer to have a 7.0% coefficient of variation (CV) The spacial distribution of the europium-complex in individual beads is determined to be homogeneous by confocal microscopy. Emission peaks are found at 592, 616 (width 9.9 nm), and 685 nm with a PARISS spectrophotometer. The kinetics of the luminescence bleaching caused by UV irradiation of the 0.5- and 5-microm beads measured under LED excitation with a fluorescence microscope indicate that bleaching does not interfere with their imaging. The luminescence lifetimes in water and air were 340 and 460 micros, respectively. Thus, these 5-microm beads can be used for spectral calibration of microscopes equipped with a spectrograph, as test particles for time-delayed luminescence flow cytometers, and possibly as labels for macromolecules and cells.

Synthesis, structures, photo- and electro-luminescent properties of novel oxadiazole-functionlized europium(iii) benzamide complexes

With N-(5-phenyl-1,3,4-oxadiazol-2-yl)-benzamide (HL1) as the first ligand, three new luminescent europium complexes Eu2Na2(L1)6(OH)(2).2C2H5OH.2CHCl3 (1), Eu(L1)3(phen) (phen = 1,10-phenanthroline) (2) and Eu2Na2(L1)6(L2)2(OH)(2).8CHCl3 [L2 = 2,5-bis(2-pyridyl)-1,3,4-oxadiazole] (3) have been prepared and structurally characterized. Each ligand L1 coordinates with a Eu3+ ion through a carbonyl oxygen atom and oxadiazol nitrogen atom, the coordination geometry at europium is a distorted square antiprism. Complexes 1 and 3 have centrosymmetric dimeric structural features with OH- as the bridging ligand, while 2 is mononuclear with phen as the neutral ligand. All these complexes show efficient red emissions typical of Eu3+ ions at room temperature, the overall quantum yields of complexes 1, 2 and 3 were 0.15, 0.37 and 0.23, respectively. Using Eu(L1)3(phen) as the emitting material, an electroluminescent device with the structure ITO/TPD (30 nm)/Eu(L1)3(phen): TPD (1 : 3, 50 nm)/AlQ (30 nm)/Mg(0.9)Ag(0.1)/Ag was fabricated. The device emits sharp red light originating from europium complex, demonstrating that Eu(L1)3(phen) is a promising red emitter with good electron-transporting property.

Novel luminescent europium(III) complexes covalently bonded to bis(phosphino)amine oxide functionalized MCM-41

A novel organo-functionalized mesoporous MCM-41 type of hybrid materials MCM–Si–DPBB was synthesized by co-condensation of bidentate Si(OR) 3 substituted N, N-2-diphenyloxyphosphine-4-bromomethyl-benzenamine (Si–DPBB) and tetraethoxysilane (TEOS) in the presence of the cetyltrimethylammonium bromide (CTAB) surfactant as template. Its ternary europium complex covalently bonded to the silica-based network MCM–Si–DPBB–Eu was also prepared by introduction the Eu(DBM) 3(H 2O) 2 into the hybrid materials. The hybrid material MCM–Si–DPBB–Eu has strong luminescence, and when excited by the ligands absorption wavelength (386 nm), it displays the emission of the Eu 3+ 5D 0- 7F J ( J = 0, 1, 2, 3 and 4) transition lines due to the efficient energy transfer from the ligands to Eu 3+.

MCM‐41 Derivatised with Pyridyl Groups and Its Use as a Support for Luminescent Europium(III) Complexes

AbstractAn organic–inorganic hybrid ligand silica was prepared by reaction of the ordered mesoporous silica MCM‐41 with 3‐triethoxysilylpropyl 4‐pyridylacetamide. Elemental analysis indicated that a pyridyl group loading of 0.93 mmol g–1 was achieved. The derivatised material was further characterised by powder X‐ray diffraction, N2 adsorption, thermogravimetric analysis, FTIR and Raman spectroscopy, and 13C and 29Si CP MAS NMR spectroscopy. Pyridyl‐functionalised MCM‐41 (L″) was treated with chloroform solutions of lanthanide tris‐β‐diketonate complexes Ln(nta)3(H2O)2 [Ln = Eu, Gd; nta = 1‐(2‐naphthoyl)‐3,3,3‐trifluoroacetonate] to give the surface‐bound monosubstituted species Ln(nta)3(H2O)(L″). The residual coordinated water molecules were subsequently replaced by pyridine (py) or methyl phenyl sulfoxide (mpso) to give immobilised Ln(nta)3(py)(L″) and Ln(nta)3(mpso)(L″) species. Photoluminescence studies were carried out at room temperature and 14 K. The emission spectra of the Eu‐modified materials were dominated by the typical Eu3+ red lines ascribed to transitions between the 5D0 excited state and the ground multiplet (7F0–4), and only very weak or negligible emission from the organic ligands are observed. Variation of the excitation wavelength confirmed that all of the Eu3+ ions occupied the same average local environment within each sample. By comparison with the photoluminescence data for the nonsupported Eu(nta)3(py)2 and Eu(nta)3(mpso)2 complexes, it is shown that the interaction between the host and guest has a strong effect on the excited states of the organic ligands; Eu3+ sensitisation occurs exclusively through the ligands rather than by direct intra‐4f6 excitation.(© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2008)

Europium(III) Complexes Containing Organosilyldipyridine Ligands Grafted on Silica Nanoparticles

This work focuses on the grafting of transition metal complexes on silica surface nanoparticles. Nanoscale silica particles in aqueous sols are used as starting silicated materials. We have undertaken the synthesis of europium(III) complexes containing organosilyldipyridine ligands, (EtO)3Si(CH2)3NHCH2-bipy (1) and (EtO)(CH3)2Si(CH2) 3NHCH 2-bipy (2), in view of a direct grafting reaction on silica nanoparticles. Reaction of one molar equivalent of 1 and 2 with Eu(tmhd)3 (tmhd= 2,2,6,6-tetramethyl-3,5-heptanedionato), as precursor, leads to octacoordinated silylated europium(III) complexes [Eu(tmhd)3(1)] (3) and [Eu(tmhd)3(2)] (4) as white solids in 34-54% yields. Europium complexes were characterized by elemental analysis, mass spectrometry, FT-IR, UV, and luminescence spectroscopies. These new complexes are reacting in a 1:10 (v/v) water and ethanol mixture with silica nanoparticles colloidal sol. Elemental analysis and thermogravimetric data indicated grafting ratios of 0.41 and 0.26 mmol of europium(III) complexes per gram of silica. Functionalized silica nanoparticles were characterized by DRIFT spectroscopy and TEM microscopy. The first analysis shows that the chemical integrity of the complexes is retained on the silica surface together with the size and the monodispersity of the nanoscale particles. As expected for europium(III) complexes, luminescence is observed under UV irradiation. Emission and excitation spectra indicate that the metal coordination environment is not modified on the silica surface. Moreover, the sharpness of the luminescence bands and the strong antenna effect are maintained when complexes are covalently bonded to silica. New luminescent europium(III) complexes grafted on silica nanoparticles are therefore obtained from our approach.