Synthesis, characterization and luminescence property of N,N'-di(pyridine N-oxide-2-yl)pyridine-2,6-dicarboxamide and corresponding lanthanide (III) complexes

A new ligand, N,N'-di(pyridine N-oxide-2-yl)pyridine-2,6-dicarboxamide (LH2) and its several lanthanide (III) complexes (La, Eu, Gd, Tb, Y) were synthesized and characterized in detail based on elemental analysis, conductivity measurements, IR, 1H NMR, MS (FAB) and UV spectra and TG-DTA studies. The results indicated that the composition of these binary complexes is [Ln(LH2)(NO3)2.H2O]NO3.nH2O (n=0-1); while the ligand has a good planar structure with strong hydrogen bonds. The fluorescence spectra exhibits that the Tb (III) complex and the Eu (III) complex display characteristic metal-centered fluorescence in solid state while ligand fluorescence is completely quenched. However, the Tb (III) complex displays more effective luminescence than the Eu (III) complex, which is attributed to especial effectivity in transferring energy from the lowest triplet energy level of the ligands (T) onto the excited state (5D4) of Tb (III) than that (5D1) of Eu (III).     

Study on interaction between Tb(III) and poly(N-isopropylacrylamide)

A new kind of the thermo-sensitive and fluorescent complex of poly(N-isopropylacrylamide) (PNIPAM) and Tb(III) was synthesized by free radical polymerization, in which PNIPAM was used as a polymer ligand. The complex was characterized by using X-ray photoelectron spectroscopy (XPS), ultraviolet-visual (UV), Fourier transform infrared (FT-IR) and fluorescence spectroscopy. The results from the experiments indicated that there is a strong interaction between PNIPAM and Tb(III), leading to a decrease in the electron density of nitrogen and oxygen atoms and an increase in the electron density of Tb(III) in the PNIPAM containing Tb(III) by contrast with PNIPAM and Tb(III), respectively, meanwhile, exhibiting that the Tb(III) is mainly bonded to oxygen atoms in the polymer chain of PNIPAM and formed the complex of PNIPAM-Tb(III). After forming the PNIPAM-Tb(III) complex, the emission fluorescence intensity of Tb(III) in the PNIPAM-Tb(III) complex is significantly enhanced because the effective intramolecular energy transfer from PNIPAM to Tb(III). Especially, the emission intensity of the fluorescence peak at 547 nm can be increased as high as 145 times comparing with that of the pure Tb(III). The intramolecular energy transfer efficiency for fluorescence peak at 547 nm can reach as high as 68%. The fluorescence intensity is related the weight ratio of Tb(III) and PNIPAM in the PNIPAM-Tb(III) complex. When the weight ratio is 1.4%, the maximum fluorescence enhancement can be obtained. Nevertheless, the lower critical solution temperature of PNIPAM containing a low content of Tb(III) has not obviously changed after the formation of the complex of PNIPAM-Tb(III) by the interaction between PNIPAM and Tb(III). This novel thermosensitive and fluorescence characterization of the PNIPAM-Tb(III) complex may be useful in the fluorescence systems and the biomedical field.     

Chemiluminescence accompanying solid-phase interaction of terbium(III) sulfate with xenon difluoride

It has been found that solid-phase interaction of anhydrous terbium(III) sulfate powder with xenon difluoride at room temperature is accompanied by chemiluminescence (CL). The formation of terbium( IV) and ozone in the course of the reaction has been observed spectrophotometrically. Two CL emitters, xenon in the Xe(I)* oxidation state (540, 580 nm) and Tb(III)* (490, 545, 590 nm), have been revealed. Emission by the former is observed at the beginning of the reaction. After the consumption of xenon difluoride, the emission is due to excited Tb(III) generated as a result of reduction of the Tb(IV) intermediate.     

Synthesis of terbium(III) complex with a biscoumarin derivative and its immobilization in PMMA-based composite thin films with fluorescent properties

An amorphous complex of Tb(III) with the biscoumarin derivative 3,3′-[(4-hydroxyphenyl)methylene)]bis-(4-hydroxy-2H-1-benzopyran-2-one), Tb(H₂L)₃, was successfully synthesized and characterized. IR- and ¹H-NMR-spectroscopy were used to investigate the coordination of the ligand around the Tb(III) ion. Values for the quantum yield and the life time of the excited state of the complex were obtained. The complex was immobilized in transparent and flexible PMMA-based films by a simple casting technique. PMMA/chloroform solutions were used in synthetic procedures that resulted in both glass-supported and self-supporting nanocomposite films. The morphology of the films was studied by scanning electron microscopy, atomic force microscopy and transmission electron microscopy, showing the formation of crack-free films. The presence of the Tb(III) complex in the matrix was proven by the presence of characteristic bands in the IR spectra. Fluorescence microscopy and fluorescence spectroscopy demonstrated the promising optical properties of the films showing the characteristic emission bands of the Tb(III) ions. The longer life time of the excited state of the immobilized complex confirmed the protective role of the PMMA matrix on the optical properties of the complex. The composite films possessing optical properties have the potential for application as active components in optical devices.      

Photosensitized generation of singlet oxygen from rhenium(I) and iridium(III) complexes

Photophysical properties in dilute acetonitrile solution are reported for a number of iridium(III) and rhenium(I) complexes. The nature of the lowest excited state of the complexes under investigation is either metal-to-ligand charge transfer ((3)MLCT) or a ligand centred ((3)LC) state. Rate constants, k(q), for quenching of the lowest excited states by molecular oxygen are in the range 1.5 x 10(8) to 1.4 x 10(10) M(-1) s(-1). Efficiency of singlet oxygen production, f(Delta)(T), following oxygen quenching of the lowest excited states of these complexes, are in the range of 0.27-1.00. The rate constants and the efficiency of singlet oxygen formation are quantitatively reproduced by a model that assumes the competition between a non-charge transfer (nCT) and a CT deactivation channel. The balance between CT and nCT deactivation channels, which is described by the relative contribution p(CT) of CT induced deactivation, is discussed. The kinetic model is found to be successfully applied in the case of quenching of the excited triplet states of coordination compounds by oxygen in acetonitrile, as was proposed for the quenching of pi-pi* triplet states by oxygen.     

Investigations into the synthesis and fluorescence properties of Eu(III), Tb(III), Sm(III) and Gd(III) complexes of a novel bis-beta-diketone-type ligand

A novel bis-beta-diketon ligand, 1,1'-(2,6-bispyridyl)bis-3-phenyl-1,3-propane-dione (L), was designed and synthesized and its complexes with Eu(III), Tb(III), Sm(III) and Gd(III) ions were successfully prepared. The ligand and the corresponding metal complexes were characterized by elemental analysis, and infrared, mass and proton nuclear magnetic resonance spectroscopy. Analysis of the IR spectra suggested that each of the lanthanide metal ions coordinated to the ligand via the carbonyl oxygen atoms and the nitrogen atom of the pyridine ring. The fluorescence properties of these complexes in solid state were investigated and it was discovered that all of the lanthanide ions could be sensitized by the ligand (L) to some extent. In particular, the Tb(III) complex was an excellent green-emitter and would be a potential candidate material for applications in organic light-emitting devices (OLEDs) and medical diagnosis.     

Lanthanide luminescence sensing of copper and mercury ions using an iminodiacetate-based Tb(III)-cyclen chemosensor

The design, synthesis and photophysical evaluation of 1.Tb.Na, a Tb(III)-cyclen-based sensor, possessing a phenyl iminodiacetate-based receptor, for the selective detection of Cu(II) and Hg(II) ions in water is demonstrated. Sensitisation of the Tb(III) ⁵D₄ excited state was achieved by excitation of the phenyl receptor, which in water gave rise to a characteristic time-delayed and line-like Tb(III) emission. The Tb(III) emission was shown to be pH independent over the physiological pH window. The changes in the Tb(III) emission were monitored by carrying out metal titrations using various groups I, II and transition metal ions. Of these, only the titrations of Cu(II) and Hg(II) gave rise to modulations in the Tb(III) emission; resulting in quenching in the Tb(III) emission by ca. 65% and 40%, respectively.     

Visible-light sensitisation of Tb(III) luminescence using a blue-emitting Ir(III) complex as energy-donor

In Ir(III)/Tb(III) dyads in which the excited state energy of the Ir(III) unit lies above 22,000 cm(-1), visible-light excitation of the Ir(III) chromophore results in sensitised emission from Tb(III) following Ir → Tb energy-transfer.     

Neodymium, gadolinium, and terbium complexes containing hexafluoroacetylacetonate and 2,2'-bipyrimidine: structural and spectroscopic characterization

Lanthanide complexes of the form Ln(hfa)3bpm (where Ln=Nd(III), Gd(III), or Tb(III); hfa=1,1,1,5,5,5-hexafluoroacetylacetone and bpm=2,2'-bipyrimidine) have been structurally characterized. The Nd and Gd complexes form one-dimensional arrays when X-ray-quality crystals are grown by the slow evaporation of concentrated solutions of the complexes. Each metal is 10-coordinate with repeating Ln-bpm units. The Tb complex does not form a one-dimensional array under these conditions. Its structure is 9-coordinate with the ninth position occupied by a covalently bonded water molecule that is hydrogen-bonded to the bpm group from another complex in solution. Luminescent studies show that the Nd complex undergoes nonradiative relaxation through solvent vibrational deactivation, while the lowest excited state of the Gd complex, 6P7/2, is higher in energy than the T1 state of the hfa ligand, making luminescence improbable for both of these complexes. In contrast, the Tb complex emits in the visible region of the spectrum when solutions of the complex are excited at 304 nm associated with the pi-pi* transition of the hfa ligand. Emission lines corresponding to transitions from the 5D4 state to the 7FJ manifold of the Tb(III) are observed. The intensity of these emissions decreases as temperature is increased. Lifetime measurements of the Tb monometallic complex fit to a monoexponential with the lifetime decreasing as the temperature is increased.     

Quantum chemistry-based interpretations on the lowest triplet state of luminescent lanthanides complexes. Part 1. Relation between the triplet state energy of hydroxamate complexes and their luminescence properties

In this paper, we evaluate the potential use of theoretical calculations to obtain an energy scale of the lowest ligand-centred triplet excited state in luminescent terbium(III) complexes. In these complexes, non-radiative deactivation of the terbium emitting state via a back-energy transfer process (T1<--Tb(5D4)) is a common quenching process. Consequently the prediction of the energy gap between these two excited states should be useful for programming highly luminescent Tb(III) systems. We report on a strategy based upon experimental and theoretical investigations of the excited state properties of a series of four simple aromatic hydroxamate ligands coordinated to Tb(III) and Gd(III) ions. By using previously reported crystallographic data, the structural and energies properties of these systems were investigated in the ground and first excited triplet states at the density functional theory (DFT) level of calculations. Our theoretical results are consistent with a triplet excited state T1 which is localised on one ligand only and whose the energy level is independent of the lanthanide ion nature (Tb(III), Gd(III)). A good agreement between the calculated adiabatic transition energies and experimental data derived from emission spectra is obtained when a corrective term is considered. These satisfactory results are an indication that this type of modelling can lead to discriminate in terms of the position of the lowest ligand triplet energy level the best antenna among a family of chromophoric compounds. In addition this theoretical approach has provided indications that the difference between the adiabatic transition energies of all the investigated complexes can be mainly explained by metal-ligand electrostatic interactions. The influence of the number of antennae on the quantum yield and the luminescence lifetime is discussed.     

A dinuclear lanthanide complex for the recognition of bis(carboxylates): formation of terbium(III) luminescent self-assembly ternary complexes in aqueous solution

The synthesis and photophysical properties of a coordinatively unsaturated cationic dinuclear terbium complex, 2.Tb(2), that can detect the presence of mono- or bis(carboxylates) in buffered aqueous solution at physiological pH is described. Full ligand synthesis and structural characterization of 2.Na(2) are also described. Spectroscopic measurements determined that each Tb(III) metal center has two metal-bound water molecules (q = 2). The recognition or sensing of N,N-dimethylaminocarboxylic acid, 4, and the bis(carboxylate) terephthalic acid, 5, which can also function as sensitizing antennae, was found to occur through the binding of these carboxylates to the metal center via the displacement of the metal bound water molecules. This gave rise to the formation of luminescent ternary complexes in solution in 2:1 or 1:1 (ion:2.Tb(2)) stoichiometry, respectively. Aliphatic bis(carboxylates) also bind to 2.Tb(2) where the selectivity for the ion recognition and stoichiometry was dictated by the structure of the anion, being most selective for pimelic acid, 6. Binding of either l- or d-tartaric acid gave rise to the formation ternary complex formation, with 2:1 stoichiometry, where the ion recognition resulted in quenching of the lanthanide emission.     

Synthesis and characterization of iridium(III) cyclometalated complexes with oligonucleotides: insights into redox reactions with DNA

Heteroleptic cyclometalated complexes of Ir(III) containing the dipyridophenazine ligand are synthesized through the direct introduction of a functionalized dipyridophenazine ligand onto a bis(dichloro)-bridged Ir(III) precusor and characterized by 1H NMR, mass spectrometry, as well as spectroscopic and electrochemical properties. The excited state of the Ir(III) complexes have sufficient driving force to oxidize purines and to reduce pyrimidine nucleobases. Luminescence and EPR measurements of the Ir(III) complex with an unmodified dppz bound to DNA show the formation of a guanine radical upon irradiation, resulting from an oxidative photoinduced electron-transfer process. Evidence is also obtained indirectly for reductive photoinduced electron transfer from the excited complex to the thymine base in DNA. We have also utilized cyclopropylamine-substituted nucleosides as ultrafast kinetic traps to report transient charge occupancy in oligonucleotides when DNA is irradiated in the presence of noncovalently bound complexes. These experiments establish that the derivatized Ir(III) complexes, with photoactivation, can trigger the oxidation of guanine and the reduction of cytosine.     

咔唑及其衍生物对 9-氰基蒽的荧光猝灭机理的研究

本文研究咔唑及其衍生物对9-氰基蒽(9CNA)的荧光猝灭机理。结果表明, 猝灭过程有以下三种方式:(1)一系列N-烷基咔唑及1,4-二咔唑丁烷、反式1,2-二咔唑环丁烷、N-苄基咔唑等对9CNA的荧光猝灭是通过形成激基复合物。(2)咔唑对9CNA的荧光猝灭是通过形成氢键。(3)1,3-二咔唑丙烷及N-痖烯基咔唑对9CNA的荧光猝灭是属于一般碰撞猝灭过程。以上所有猝灭过程主要都是来自电荷转移相互作用。另外, 还讨论了空间位阻对形成激基复合物的影响。并由稳态和动态荧光实验结果,应用Ware关于激基复合物的形成和解离的动力学公式计算出一系列光物理速率常数。     

Synthesis and photophysical properties of new Ln(III) (Ln = Eu(III), Gd(III), or Tb(III)) complexes of 1-amidino-O-methylurea

Three new solid lanthanide(III) complexes, [Ln(1-AMUH)₃] · (NO₃)₃ (1-AMUH = 1-amidino-O-methylurea; Ln = Eu(III), Gd(III), or Tb(III)) were synthesised and characterised by elemental analysis, infrared spectra, magnetic moment measurement, and electron paramagnetic resonance (EPR) spectra for Gd(III) complex. The formation of lanthanide(III) complexes is confirmed by the spectroscopic studies. The photophysical properties of Gd(III), Eu(III), and Tb(III) complexes in solid state were investigated. The Tb(III) complex exhibits the strongest green emission at 543 nm and the Eu(III) complex shows a red emission at 615 nm while the Gd(III) complex shows a weak emission band at 303 nm. Under excitation with UV light, these complexes exhibited an emission characteristic of central metal ions. The powder EPR spectrum of the Gd(III) complex at 300 K exhibits a single broad band with g = 2.025. The bi-exponential nature of the decay lifetime curve is observed in the Eu(III) and Tb(III) complexes. The results reveal them to have potential as luminescent materials.     

Investigations into the synthesis and fluorescence properties of Tb(III) complexes of a novel bis-beta-diketone-type ligand and a novel bispyrazole ligand

A novel bis-beta-diketone organic ligand, 1,1'-(2,6-bispyridyl)bis-3-(p-methoxyphenyl)-1,3-propanedione (L1) and its derivatives, a novel bispyrazole ligand, 2,6-bis(5-(4-methoxyphenyl)-1H-pyrazol-3-yl)pyridine (L2) were designed and synthesized and their complexes with Tb(III) ion were successfully prepared. The ligands and the corresponding metal complexes were characterized by elemental analysis, infrared, proton nuclear magnetic resonance spectroscopy and TG-DTA. Analysis of the IR spectra suggested that the lanthanide metal ion Tb(III) coordinated to the ligands via the nitrogen atom of the pyridine ring and the carbonyl oxygen atoms for ligand L1 and the nitrogen atom of the pyrazole ring for ligand L2. The fluorescence properties of the two complexes in solid state were investigated and it was discovered that the Tb(III) ions could be sensitized by both the ligand (L1) and ligand (L2) to some extent. In particular, the complex of ligand (L2) is a better green luminescent material that could be used as a candidate material in organic light-emitting devices (OLEDs) since it could be much better sensitized by the ligand (L2), and the fluorescence intensity of Tb(III) complex of L2 are almost as twice strong as L1's.     

Columinescence effect in macromolecular complexes of Eu(III) and Tb(III)

The effect of Y(III) and Gd(III) coactivator ions on the intensity of Eu(III) and Tb(III) luminescence in monomer and polymer mixed-metal complexes was studied. Isomorphic replacement of Eu(III) and Tb(III) ions by Y(III) and Gd(III) ions in macromolecular complexes led to sensitization of Eu(III) and Tb(III) ion luminescence. A mechanism of columinescence was suggested. It involves a charge transfer and the ligand orbitals and the vacant orbitals of Eu(III) and Tb(III) ions and coactivators.     

温度对铽（III）-转铁蛋白溶液构象的影响

在pH 7.4,0.01 mol/L N-2-羟乙基哌嗪-N’-2-乙磺酸（Hepes）条件下,铽 （III）与N,N’-二（2-羟苄基）乙二胺-N,N’-二乙酸（HBED）结合并发生交换 相互作用使铽（III）荧光增强10~4倍,通过监测铽（III）545 nm荧光强度的变化 测定了Tb-HBED配合物的条件稳定常数是lgK = 14.30 ± 0.49;Tb-HBED配合物中 配体、铽（III）荧光强度均随着温度的升高而降低。在pH 7.4,0.01 mol/L Hepes条件下,Tb_N-apoTf-Tb_C配合物中蛋白质的荧光强度随着温度的升高而降 低,而能量受体铽（III）的荧光强度随着温度的升高而增强,主要源于铽（III） 与螺旋5色氨酸残基间的无辐射能量转移;当温度由0 ℃上升到55 ℃时,平均能量 转移效率AE值增加了29%,给体、受体间距离R有约4.2%的减小,温度变化引起 Tb_N-apoTf-Tb_C配合物大的构象变化;铽（III）与人血清脱铁转铁蛋白的结合使 蛋白质的变性温度降低。同样条件下,Tb_N-apoOTf-Tb_C配合物与Tb_N-apoTf- Tb_C配合物有所不同,虽然能量给体的荧光强度随着温度的增加而减小,但铽（ III）荧光强度没有明显的增强;铽（III）对蛋白质的变性温度几乎没有影响。     

Synthesis of Eu(III) and Tb(III) complexes with novel pyridine dicarboxamide derivatives and their luminescence properties

A novel ligand, N2,N6-bis[2-(3-methylpyridyl)]pyridine-2,6-dicarboxamide (L2) and the corresponding Eu(III) and Tb(III) hydrochlorate complexes have been synthesized and characterized in detail based on elemental analysis, IR and NMR. The crystal and molecular structure of the complexes was determined by X-ray crystallography. The Eu(III) and Tb(III) ions were found to coordinate to the amido nitrogen atoms and pyridine nitrogen atoms. The luminescence properties of lanthanide complexes in solid state, in different solutions and in different pH value were investigated. The result shows that Tb(III) complexes exhibit more efficient luminescence than Eu(III) complexes, and the ligand (L2) is an excellent sensitizer to Tb(III) ion.     

Study of terbium(III)–dextran and terbium(III)–α-methyl glucoside interactions

The interaction of dextran with terbium(III) was studied in aqueous solution, pH 3.0–6.6, by fluorescence and optical rotatory dispersion. The polysaccharide enhances Tb(III) fluorescence intensity when the system is excited at the 290-nm hypersensitive transition (⁷F₆ → ⁵H₄). The dextran rotatory power is decreased in the presence of the metal ion. The results indicate that a 38% maximum of the polymer repeat units are coordinated. Complex formation occurs with displacement of water from the cation coordination sphere by hydroxyl groups at the second and third carbon atoms of the pyranoside ring. As the pH increases, a more asymmetric complex is formed. The α-methyl glucoside, low molecular weight dextran analogue, interacts with Tb(III) less strongly than dextran. Fluorimetric titrations indicated that the order of binding ability to polysaccharide is Tb(III) > Al(III) > Ca (II). © 1993 John Wiley & Sons, Inc.     

Luminescence behavior of a water soluble calix[4]arene derivative complex with terbium ion(III) in gelation solution

The complexation luminescence behavior of a water soluble calix[4]arene derivative, 5,11,17,23-tetra-sulfonate-25,26,27,28-tetra-carboxymethoxycalix[4]arene (L) with lanthanoid ion (Tb(3+)) has been investigated in gelation solution at 25 degrees C by using UV-vis and fluorescence spectra. The results obtained indicated that the water soluble calix[4]arene derivative can form an efficient energy transfer complex with terbium ion(III). The fluorescence of L x Tb(3+)complex is partially quenched by gelatin in gelation solution. The quenching intensity is related to the concentration and the hydrolysis degree of gelatin. Absorption and fluorescence spectra analysis show that the -COO(-) groups on gelatin have a definite binding ability to Tb(3+), and then, gelatin could compete binding with calix[4]arene derivative upon complexation with Tb(3+), leading to the relative fluorescence quenching of the formation complex of terbium(III) ion with calix[4]arene derivative.