The Fluorescent Properties and Electronic Structure of Nd(111) Complexes with Carboxylic Acids

Mixed-ligand neodymium(III) complexes with carboxylic acids and nitrogen- and phosphorus-containing neutral ligands, which luminesce in the near-IR region, are studied by luminescence and X-ray photoelectron spectroscopies. It is found that coordination of neutral ligands through the nitrogen donor atom leads to an increase in the electron density at the neodymium(III) ion.     

Low-vibrational luminescent polymers including tris(bis-perfluoromethane and ethanesulfonylaminate)neodymium(III) with 8 coordinated DMSO-d6

Novel Nd(III) complexes, tris(bis-perfluoromethane and ethanesulfonylaminato)neodymium(III)octa(deuterated dimethylsulfoxide) were designed and synthesized to apply to luminescent materials in plastic optical fiber. The IR and the near-IR spectra analyses has been done to estimate the radiationless transition via vibrational excitation of the Nd(III) complexes. [Nd(pms)₃(DMSO-d₆)₈] and [Nd(pes)₃(DMSO-d₆)₈] in polyhexafluoroisopropylmethacrylate gave a emission quantum yield of 1.3% and 1.6%, which was the largest in luminescent Nd(III) polymers. A research field for telecommunication network using 1.3 μm light would be achieved by luminescent Nd(III) materials encapsulated low-vibrational coordination sites.     

Co-fluorescence effect of rare earth complexes with 4-aminobenzoic acid in a silica matrix

Terbium(III), yttrium(III), and neodymium(III) complexes with 4-aminobenzoic acid have been co-doped into silica matrix. For the samples, the characteristic emissions of terbium(III) increase obviously with the addition of yttrium(III) complex, while the reverse is true with the addition of neodymium(III) complex. Compared with terbium(III) complex doped silica sample, the photoacoustic signal of the ligand decreases for terbium(III)–yttrium(III) complexes co-doped sample, and increases for terbium(III)-neodymium(III) complexes co-doped sample. The fluorescence quantum yields and lifetimes of the samples have been determined. The co-fluorescence mechanism has been discussed from radiative and nonradiative relaxations. The nephelauxetic parameters and photoacoustic branching vectors of neodymium(III) in the silica samples have also been calculated. The spectral result indicates that heteronuclear complexes may form in the silica matrix upon a suitable heat treatment. The co-fluorescence effect found in the inorganic matrix can contribute to the better design and application of rare earths containing fluorescent materials.     

Near-IR Luminescent Rare Earth Ion–Sensitizer Complexes

Rare earth ions, with relatively long luminescence lifetimes, have significant advantages for application in fields as varied as diagnostics and optical amplification. In diagnostics the long luminescence lifetimes allow for extremely sensitive time-gated detection, where the difference in temporal behavior of scatter and background fluorescence and the long-lived rare earth luminescence is utilized. In optical amplification the long excited-state lifetime makes it easier to obtain population inversion, a requirement for effective stimulated emission. Unfortunately the absorption cross section of rare earth ion transitions is extremely low. However, via sensitized excitation by means of a suitable organic molecule, efficient excitation is obtained. It is shown that excitation in the visible part of the spectrum can be used to excite rare earth ions which luminesce in the near-IR, such as ytterbium, neodymium, and erbium, via a fluorescein-derivative as sensitizer. The advantages of this approach are manifold. Low-cost light sources are available for the visible part of the spectrum, and interferences from the matrix (scatter, absorption) are minimal. Detection in the near-IR is almost interference-free. For optical amplification the wavelength regions around 1300 and 1550 nm, which can be covered with the neodymium and erbium complexes, respectively, are the most important for applications in optical telecommunication.     

Photoacoustic Spectra Studies on Neodymium Complexes

A series of neodymium complexes crystals were synthesized and their photoacoustic spectra were determined. The excited state energy levels of Nd(III) in different complexes were discussed and their relaxation processes were studied. The different coordination environments were shown by comparing the band due to Nd(III) ⁴19/2 – ⁴G5/2, C7/2 transitions in different complexes. The fine structure of this absorption shows that the Nd-0 bond forms a stronger coordinated bond than that of Nd-N system.     

Near-infrared luminescence emitted by an electrically switched liquid crystal cell

Switching of near-infrared emission was observed for liquid crystal (LC) cells filled with a chiral nematic liquid-crystal mixture (mixture of E7 and cholesteryl nonanoate) doped with luminescent neodymium(III) or ytterbium(III) β-diketonate complexes. The operating principle of the LC cell is based on an electrically induced phase transition from a chiral nematic to a nematic phase. The chiral nematic phase scatters the excitation light more strongly, resulting in more efficient light absorption and intenser photoluminescence.     

Inert and stable erbium(III)-cored complexes based on metalloporphyrins bearing aryl-ether dendron for optical amplification: synthesis and emission enhancement

We have developed novel inert and stable erbium (Er)(III)-cored complexes based on metalloporphyrins for optical amplification. The functionalized metalloporphyrin ligands have been designed and synthesized to provide enough coordination sites for the formation of inert and stable 9-coordinated Er(III)-cored complexes. Er³⁺ ions were encapsulated by the metalloporphyrin ligands, such as Zn(II)- and Pt(II)-porphyrins. The near-infrared (IR) emission intensity of Er³⁺ ion is much stronger in the Er(III)-cored complex based on Pt(II)-porphyrin than Er(III)-cored complex based on Zn(II)-porphyrin. Furthermore, we have incorporated a G2-aryl-ether functionalized dendron into the Er(III)-cored complex, yielding an Er(III)-cored dendrimer complex bearing the Pt(II)-porphyrin. The Er(III)-cored dendrimer complex shows the stronger near-IR emission intensity than the corresponding complex based on Pt(II)-porphyrin by seven times in solid state. The lifetimes of the emission band of Pt(II)-porphyrin ligands in the visible region were found to be 30 and 40 μs for the Er(III)-cored complex and the Er(III)-cored dendrimer complex based on Pt(II)-porphyrin in deoxygenated THF solution samples, respectively. Also, in both cases, the sensitized luminescence intensity is increased in deoxygenated solution. Therefore, it indicates that the energy transfer from the metalloporphyrins to Er³⁺ ions takes places through the triplet state. In this paper, the synthesis and photophysical properties of novel Er(III)-cored complexes based on metalloporphyrins and Er(III)-cored dendrimer complex based on metalloporphyrin will be discussed.     

Theoretical and spectroscopic studies of 5‐aminoorotic acid and its new lanthanide(III) complexes

The complexes of cerium(III) and neodymium(III) were synthesized by reaction of the respective inorganic salts with 5‐aminoorotic acid (H₄L) in amounts equal to the metal:ligand molar ratio of 1:3. The structures of the final complexes were determined by means of spectral (IR, Raman, ¹H NMR and ¹³C NMR) and elemental analysis. Significant differences in the IR spectra of the complexes were observed as compared to the spectrum of the ligand. A comparative analysis of the Raman spectra of the complexes with that of the free H₄L allowed a straightforward assignment of the vibrations of the ligand groups involved in coordination. The geometry of H₄L was computed and optimized for the first time with the Gaussian03 program using the B3PW91/6‐311++G**, B3PW91/LANL2DZ, B3LYP/6‐311++G** and B3LYP/LANL2DZ methods. The experimental IR and Raman bands of the ligand were assigned to normal modes on the basis of DFT calculations. The vibrational analysis performed for the studied species, H₄L and its complexes, helped to explain the vibrational behavior of the ligand vibrational modes sensitive to interaction with the lanthanides. The vibrational study gave evidence for the coordination mode of the ligand to lanthanide ions and was in agreement with the other theoretical prediction. Copyright © 2006 John Wiley & Sons, Ltd.     

Raman,FT‐IR,and DFT studies of 3,5‐pyrazoledicarboxylic acid and its Ce(III) and Nd(III) complexes

3,5‐Pyrazoledicarboxylic acid was used as a ligand for the synthesis of its Ce(III) and Nd(III) complexes. The complexes of Ce(III) and Nd(III) with 3,5‐pyrazoledicarboxylic acid were synthesized and their compositions were determined by elemental analysis. Vibrational study in the solid state of 3,5‐pyrazoledicarboxylic acid and its new Ce(III) and Nd(III) complexes was performed by IR and Raman spectroscopy. The changes observed between the IR and Raman spectra of the ligand and of the complexes allowed us to establish the coordination mode of the metal in both complexes. The comparative vibrational analysis of the free ligand and its lanthanide(III) complexes gave evidence that 3,5‐pyrazoledicarboxylic acid binds Ln(III) through the deprotonated carboxylic oxygens. The density functional theory (DFT) calculated geometries, harmonic vibrational modes and Raman scattering activities of the ligand were in good agreement with the experimental data, and a complete vibrational assignment is being proposed. The experimental IR and Raman bands of the ligand were assigned to normal modes on the basis of DFT calculations. The effect of the intramolecular hydrogen bonds in the ligand on vibrational mode positions is also discussed. The characteristic IR and Raman bands of 3,5‐pyrazoledicarboxylic acid and its lanthanide complexes were specified and discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Sensitized Near-Infrared Luminescence From NdIII, YbIII and ErIII Complexes by Energy-Transfer From Ruthenium 1,3-Bis([1,10]Phenanthroline-[5,6-d]-Imidazol-2 -yl)Benzene

The luminescent ruthenium 1,3 -bis([1,10]phenanthroline-[5,6 -d]- imidazol-2 -yl)benzene (bpibH₂) complex, a potentially useful bridging ligand with a vacant diimine site, has been used as ‘metallo ligand’ to make heterodinuclear d–f complexes by attachment of a {Ln(dik)₃} fragment (dik?=?1,3-diketonate) at the vacant site. When Ln?=?Nd, Yb, or Er the lanthanide centre has low-energy f–f excited states capable of accepting energy from the ³MLCT excited state of the Ru(II) centre, there is quenching in the ³MLCT luminescence of the Ru(II) centre, that affords sensitized lanthanide(III) based luminescence in the near-IR region. Nd(III) was found to be the most effective at quenching the ³MLCT luminescence of the ruthenium component because of the high density of f–f excited states of the appropriate energy which make it as effective energy-acceptor compared to Er and Yb complexes.     

邻苯二甲酸铕—铽络合体系的荧光性能和红外光谱研究

本文对在３６５ｎｍ波长紫外光激发下均可发出特征荧光的铕、铽邻苯二甲酸固体络合物以机械混合和化学作用两种混合方式，研究了这两系列混合络合物的荧光光谱和红外光谱。结果表明，无论其荧光发射波长还是其发射强度，铕、铽之间均存在相互影响；其中荧光发射峰位的变化较小，而荧光强度变化较大，铕、铽的荧光性能之间即存在相互敏化作用，又存在相互猝灭作用。红外光谱结果表明机械混合和化学作用都使络合物的结构发生了变化。     

全氟羧酸钕2,2’-联吡啶配合物的合成及其光学特性

合成了一系列全氟羧酸钕2,2’-联吡啶配合物:Nd(CF3COO)3.Dipy,Nd(C2F5COO)3.Dipy和Nd(C3F7COO)3.Dipy,并通过红外光谱、元素分析、热分析、紫外可见近红外吸收光谱和荧光光谱对其进行了表征。配合物的分解温度都高于260℃,最大失重温度超过340℃,说明它们具有良好的热稳定性。全氟羧酸的碳链长度和钕离子配位结构的差异,引起配合物的吸收跃迁强度的变化。根据紫外可见近红外吸收图谱,计算获得了Judd-Ofelt参数和受激辐射跃迁特性。配合物的受激发射面积分别为:3.63×10-20,2.36×10-20和1.49×10-20 cm2,可以和文献报道的无机材料媲美,它们将是非常有潜力的液体激光介质。     

EPR Studies of DOPA–Melanin Complexes with Fe(III)

Paramagnetic centers in 3,4-dihydroxyphenylalanine–melanin and its complexes with Fe(III) were examined by electron paramagnetic resonance (EPR) spectroscopy. Paramagnetic centers of melanin play an important role in detoxification of environment and they reveal high activity in binding of metal ions. Two different signals were observed in EPR spectra: lines of o-semiquinone free radicals and lines of paramagnetic Fe(III). Amplitudes of EPR lines of both free radicals and iron ions decrease with increasing Fe(III) content in melanin–metal ion complexes. Free radical concentrations in the melanin samples, g-factors, amplitudes and line widths of EPR spectra were determined. It was stated that fast spin–lattice relaxation processes exist in both free radical system and paramagnetic iron ions in melanin complexes.     

钕、铽(Ⅲ)硝酸盐、水杨醛乙二胺双席夫碱、二甲亚砜三元配合物的NMR研究

用NMR的方法研究了新型稀土配合物：钕、铽（Ⅲ）硝酸盐与N，N-二亚水杨基乙二胺双席夫碱、二甲亚砜三元配合物的结构，并利用二维质子NOE谱和异核多量子相关谱完全归属了它们的质子和13C信号．     

钕、铽(Ⅲ)硝酸盐、水杨醛乙二胺双席夫碱、二甲亚砜三元配合物的NMR研究

用NMR的方法研究了新型稀土配合物:钕、铽(Ⅲ)硝酸盐与N,N-二亚水杨基乙二胺双席夫碱、二甲亚砜三元配合物的结构,并利用二维质子NOE谱和异核多量子相关谱完全归属了它们的质子和¹³C信号.     

Luminescence of phthalocyanine thin films

The near-IR luminescence in thin films of metal-free phthalocyanine and phthalocyanine complexes is investigated at room temperature. It is shown that the intensity of the luminescence peaks depends on the polymorphic modification and the structure of the complexes, whereas the peak positions remain virtually unchanged.     

Synthesis and Luminescent Properties of Lanthanide Complexes with Structurally Related Novel Multipodal Ligands

To explore the relationship between the structure of the ligands and the luminescent properties of the lanthanide complexes, a series of lanthanide nitrate complexes with two novel structurally related multipodal ligands, 1,3-bis{[(2’-(2-picolylaminoformyl))phenoxyl]methyl}benzene (L ^I ) and 1,2-bis{[(2’-(2-picolylaminoformyl))phenoxyl]methyl}benzene (L ^II ), have been synthesized and characterized by elemental analysis, infrared spectra and molar conductivity measurements. At the same time, the luminescent properties of the Eu(III) and Tb(III) nitrate complexes in solid state and the Tb(III) nitrate complexes in solvents were investigated at room temperature. Under the excitation of UV light, these complexes exhibited characteristic emissions of central metal ions. The lowest triplet state energy levels T₁ of these ligands both match better to the lowest resonance energy level of Tb(III) than to Eu(III) ion. The influence of the structure of the ligands on the luminescent intensity of the complexes was also discussed.     

Syntheses and Fluorescence Properties of Two Novel Lanthanide (III) Perchlorate Complexes with Bis(benzylsulfinyl)methane

A novel ligand with double sulfinyl groups, bis(benzylsulfinyl)methane, was synthesized by a new method and its two lanthanide (III) complexes were synthesized and characterized by element analysis, molar conductivity, coordination titration analysis, IR, TG-DSC, ¹HNMR and UV spectra. The results indicated that the composition of these complexes was REL_2.5(ClO₄)₃·3H₂O (RE = Tb (III), Dy (III), L = C₆H₅CH₂SOCH₂SOCH₂C₆H₅). The FT-IR results revealed that the perchlorate group was bonded with the lanthanide ion by the oxygen atoms, and the coordination was bidentate. The fluorescent spectra illustrated that both the Tb (III) and Dy (III) complexes displayed characteristic fluorescence in solid state, especially for the Tb (III) complex, the peak of ⁵D₄ → ⁷ F₅ of the Tb (III) ion in 544 nm was stronger than that of others. It indicated that the Tb (III) complex could emit purer green fluorescence. By analysis fluorescence and phosphorescence spectra, it was found that the ligand had the advantage to absorb energy and transfer it to the Tb (III) and Dy (III) ions. The phosphorescence spectra and fluorescence lifetimes of the complexes were also measured.     

Investigation on damage of BSA molecules under irradiation of low frequency ultrasound in the presence of FeIII-tartrate complexes

The interaction between bovine serum albumin (BSA) and Fe(III)-tartrate complexes ([Fe(III)(tar)(H(2)O)(3)](-) and [Fe(III)(tar)(2)](5-)) as well as the damage of BSA in the presence of Fe(III)-tartrate complexes under ultrasonic irradiation was studied by UV-vis and fluorescence spectra. In addition, the influences of ultrasonic irradiation time, Fe(III)-tartrate complex concentration, ionic strength and solution acidity (pH value) were also examined on the damage of BSA. The results showed that the fluorescence quenching of BSA caused by the Fe(III)-tartrate complexes belonged to the static quenching. The BSA and Fe(III)-tartrate complexes interacted with each other mainly through weak interaction and coordinate actions. The corresponding binding association constants (K) and the binding site numbers (n) were calculated. The results were as follows: K(1)=1.67x10(3)Lmol(-1) and n(1)=0.9699 for [Fe(III)(tar)(H(2)O)(3)](-), K(2)=1.54x10(3)Lmol(-1) and n(2)=0.8754 for [Fe(III)(tar)(2)](5-). Otherwise, under ultrasonic irradiation the BSA molecules were obviously damaged by the Fe(III)-tartrate complexes. The damage degree rose up with the increase of ultrasonic irradiation time, Fe(III)-tartrate complex concentration, pH value and ionic strength. And that, [Fe(III)(tar)(H(2)O)(3)](-) exhibited higher sonocatalytic activity in a way than [Fe(III)(tar)(2)](5-).     

Spectroscopic studies of lanthanide(III) ion complexes with diethyl(phthalimidomethyl) phosphonate

Complexation and photophysical properties of complexes of lanthanide ions, Ln(III), with diethyl(phthalimidomethyl)phosphonate ligand, DPIP, were studied. Interactions between Ln(III) and DPIP were investigated using Nd(III) absorption and Eu(III) and Tb(III) luminescence (emission and excitation) spectra, recorded in acetonitrile solution containing different counter ions (NO₃^-, Cl^- and ClO₄^-). Results of the absorption spectroscopy have shown that counter ions play a significant role in the complexation of Ln(III)/DPIP complexes. Studies of luminescence spectra of Eu(III) and Tb(III) ions proved that the formation of Ln(III)/DPIP complexes of stoichiometry Ln:L=1:3 is preferred in solution. Based on the results of elemental analysis, Nd(III) absorption spectra and IR and NMR data, it was shown that the DPIP ligand binds Ln(III) ions via oxygen from phosphoryl group, forming complexes of a general formula Ln(DPIP)₃(NO₃)₃·H₂O, in which the NO₃^- ions are coordinated with the metal ion as bidentate ligands. Luminescent properties and energy transfer, from the ligand to Ln(III) ions in the complexes formed, were studied based on the emission and excitation spectra of Eu(III) and Tb(III). Their luminescent lifetimes and emission quantum yields were also measured.