Synthesis, characterization and spectroscopic studies of copolymer of styrene with 4-oxe-4(P-hydroxyl phenylamino) but-2-enoic acid and corresponding fluorescent macromolecular lanthanide(III) complexes

Copolymer of styrene with 4-oxe-4(P-hydroxyl phenylamino) but-2-enoic acid (PSHPEA) and its luminescent lanthanide complexes Ln-PSHPEA (Ln = La, Eu, Tb and Y) were synthesized and characterized by means of elemental analysis, FT-IR, thermogravimetric analysis and fluorescence determination. The results showed that the carboxylic groups on the chain of the copolymer acted as bidentate ligands coordinated to lanthanide ions, but the amido carbonyl groups, amino N and hydroxy groups had not taken part in coordination; the coordination degree of -COO⁻/Ln³⁺ which determined the content of metal ions in the macromolecular complexes, was closely dependent on both the pH value of the solution and the molar ratio of St to 4-oxe-4(P-hydroxyl phenylamino) but-2-enoic acid in the polymer ligand. The fluorescence determination showed that the complexes exhibited characteristic fluorescence with comparatively high brightness and good mono-chromaticity. Typical relationship between emission intensity and Ln³⁺ ions content in macromolecular complexes exhibited some extent of fluorescence concentration quenching in our studies. The emission intensity of Tb-PSHPEA complexes was much stronger than that of Eu-PSHPEA complexes, which was attributed to especial effectivity in transferring energy from the lowest triplet energy level of the ligand onto the excited state (⁵D₀) of Tb³⁺ ion than that (⁵D₄) of Eu³⁺ ion.     

Experimental and density functional theory insights into the effect of withdrawing ligands on the fluorescence yield of Ru(II)‐based complexes

The quality of emission spectra of metal complexes gives good insights into their performance in many optoelectronic applications. Herein, the effect of the number and position of various ligand structures on the emission spectra of Ru bipyridine complexes was studied. Specifically, the use of a different number of withdrawing groups (COOH) was investigated in detail. The complexes were first investigated using density functional theory (DFT) and time‐dependent DFT calculations and then confirmed experimentally. The bandgap energy, reactivity, emission spectra and Stokes shift were found to depend on the number and position of the withdrawing groups attached to the Ru(bpy)₂²⁺ complexes. Upon increasing the number of withdrawing groups, the electrons were found to be withdrawn from the carbon orbitals and resonated to reach the metal, and accumulated around it, thus enhancing the metal‐to‐ligand charge transfer mechanism instead of the ligand‐to‐ligand charge transfer mechanism. The complexes with more withdrawing groups showed spectra with more intense emission peaks with shorter lifetime, indicating the enhancement in the photoactivity of the complexes. Ligands with ring nitrogens with two COOH groups showed the greatest effect on the enhancement of the emission spectra with a lifetime of 0.5359 ns. The resulting collective emission spectra covered a wide wavelength range, making the investigated complexes a good choice for many optoelectronic applications.     

Synthesis,crystal structure,antioxidation and fluorescence of two lanthanide complexes with a noncyclic polyether Schiff base ligand

Two lanthanide (Sm and La) complexes with the Schiff base ligand bis(3-methoxysalicylidene)-3-oxapentane-1,5-diamine (Bod) have been synthesized and characterized by physico-chemical and spectroscopic methods. [Sm(Bod)(NO₃)₃] {bis(3-methoxysalicylidene)-3-oxapentane-1,5-diamine samarium(III) trinitrate} (1) is a discrete mononuclear species and [La(Bod)(NO₃)₃(DMF)]_n {bis(3-methoxysalicylidene)-3-oxapentane-1,5-diamine dimethylformamide lanthanum(III) trinitrate}_n (2) formed an inorganic coordination polymer. In the two complexes, the metal ions are both ten-coordinate and the geometric structure around the Ln(III) ions can be described as distorted hexadecahedral. An antioxidant assay in vitro shows that complexes 1 and 2 exhibit better scavenging activity than both the ligand and the usual antioxidants on hydroxyl and superoxide radicals. Under excitation at room temperature, a red shift in the fluorescence band of the ligand in the complexes compared with that of the free ligand can be attributed to coordination of the rare earth ions to the ligand. Furthermore, 1 produced characteristic Sm(III) luminescence, which indicates the ligand Bod is a good organic chelator to absorb energy and transfer it to the Sm³⁺ ion.     

Fluorescent lanthanide chelates for biological systems

Certain lanthanide chelate complexes are known to emit strong fluorescence with very distinct physical properties that are different from those of organic fluorescent compounds: the fluorescence of lanthanide complexes is long-lived with the half decay-time of several hundreds microseconds to 2 ms. The complexes are excited by UV light and emit fluorescence in the visible region. The emission profile is very sharp and the wavelength is specific to each metal, for instance, Eu³⁺ complexes emit at 615 nm and Tb³⁺ at 545 nm regardless of the ligand. These properties show that the complexes can be excellent fluorescence labels for proteins and DNAs and, when time-resolved fluorometry is employed, provide highly sensitive detection methods in biotechnology. Among many labels we have developed, BHHCT-Eu³⁺ and BPTA-Tb³⁺ are suitable for immunoassay, DNA hybridization assay, and DNA chip technology. Homogeneous DNA hybridization assay systems using fluorescence resonance energy transfer and fluorescence intercalators will be introduced.     

芳环上硝基取代基对苯甲酸功能化聚苯乙烯-Eu（Ⅲ）配合物光致发光性能的双重影响

将硝基苯甲酸配基(NBA)键合在聚苯乙烯侧链,制得了硝基苯甲酸功能化的聚苯乙烯(PS-NBA),在此基础上使大分子配体PS-NBA与Eu(III)离子配位,制备了二元高分子-稀土配合物PS-(NBA)3-Eu(III),也以邻菲罗啉(Phen)为小分子配体,制备了三元高分子-稀土配合物PS-(NBA)3-Eu(III)-Phen1,重点研究了芳环上硝基取代基对高分子-稀土配合物光致发光性能的影响.研究结果表明,芳环上的硝基取代基对以Eu(III)为中心离子的苯甲酸功能化聚苯乙烯-稀土配合物的发光性能具有双重影响.硝基取代基通过配基内的电荷转移(ILCT),耗损配基激发单线态的能量,有效降低苯甲酸配基的三线态能量,使配基NBA最低三线态能级与Eu(III)离子共振能级之间的匹配程度显著增强,对Eu(III)离子的荧光发射发生强敏化作用,使配合物PS-(NBA)3-Eu(III)以及PS-(NBA)3-Eu(III)-Phen1产生了高强度的荧光发射,显现出硝基取代基对配合物发光性能的正性影响.另一方面,即使在稀溶液中,随着高分子-稀土配合物浓度从4.0×10-6mol·L-1增大至4.0×10-4mol·L-1,配合物的荧光发射也会逐渐变弱,这是由激发态的配合物向硝基发生荧光共振能量转移(FRET)的淬灭作用所导致的,表现出硝基取代基对配合物发光性能的负性影响.     

Synthesis and photophysical properties of Ir<Superscript>III</Superscript>-Ln<Superscript>III</Superscript> (Ln = Nd,Yb, Er) bimetallic complexes containing bipyrimidines as bridging ligands

Bipyrimidines have been chosen as (N∧N)(N∧N) bridging ligands for connecting metal centers. Ir^III-Ln^III (Ln = Nd, Yb, Er) bimetallic complexes [Ir(dfppy)₂(μ-bpm)Ln(TTA)₃]Cl were synthesized by using Ir(dfppy)₂(bpm)Cl as the ligand coordinating to lanthanide complexes Ln(TTA)₃·2H₂O. The stability constants between Ir(dfppy)₂(bpm)Cl and lanthanide ions were measured by fluorescence titration. The obvious quenching of visible emission from Ir^III complex in the Ir^III-Ln^III (Ln = Nd, Yb, Er) bimetallic complexes indicates that energy transfer occurred from Ir^III center to lanthanides. NIR emissions from Nd^III, Yb^III, and Er^III were obtained under the excitation of visible light by selective excitation of the Ir^III-based chromophore. It was proven that Ir(dfppy)₂(bpm)Cl as the ligand could effectively sensitize NIR emission from Nd^III, Yb^III, and Er^III.     

Intramolecular energy transfer in actinide complexes of 6-methyl-2-(2-pyridyl)-benzimidazole (biz): comparison between Cm and Tb systems

Coordination of the 6-methyl-2-(2-pyridyl)-benzimidazole ligand with actinide and lanthanide species can produce enhanced emission due to increased efficiency of intramolecular energy transfer to metal centers. A comparison between the curium and terbium systems indicates that the position of the ligand's triplet state is critical for the enhanced emission. The energy gap between the ligand's triplet state and the acceptor level in curium is about 1000 cm⁻¹, as compared to a ~600 cm⁻¹ gap in the terbium system. Due to the larger gap, the back transfer with curium is reduced and the radiative yield is significantly higher. The quantum yield for this “sensitized” emission increases to 6.2%, compared to the 0.26% value attained for the metal centered excitation prior to ligand addition. In the terbium case, the smaller donor/acceptor gap enhances back transfer and the energy transfer is less efficient than with the curium system.     

Three Isostructural 4‐Sulfophthalate‐Based Lanthanide Complexes: Syntheses,Crystal Structures,and Luminescent Properties

Three lanthanide complexes with the ligand 4‐sulfophthalate (sp^3–), [Ln(H₂O)₂(sp)]_n [Ln = Dy ( 1 ), Tb ( 2 ), and Er ( 3 )], were solvo‐/hydrothermally synthesized by changing the rare earth cations, and were characterized structurally and photophysically. Complexes 1 – 3 are isostructural, exhibiting a two‐dimensional layered structure with centrosymmetric dinuclear subunits infinitely extended by 4‐connected sp^3– connectors. Photoluminescence spectra of 1 – 3 demonstrate that anionic sp^3– ligand can serve as a functionalized chromophore to sensitize the luminescent emission of the lanthanide ion, suggesting that the sp^3–‐involved lanthanide complexes can be used as novel optical materials.     

Lanthanide metal polymer complexes. Synthesis,characterization and application

Our recent results on the investigation of lanthanide metal polymer complexes were presented. Luminescence properties of Tb³⁺ or Eu³⁺ -polycarboxylate complexes in aqueous solution were investigated. The excitation band near 300 nm for Tb or Eu(polyacrylate) solutions were drastically enhanced by the addition of hydroxy radical generating reagents as well as ultrasonic irradiation. These spectral changes were attributed to the energy transfer from chromophore molecules formed by generated hydroxy radicals in both systems. Since the increase in the luminescence intensity was proportional to the hydroxy radical concentration, the Eu³⁺ or Tb³⁺ (PAA) system can provide a convenient method for the determination of hydroxy radical concentration in aqueous solution. We have also utilized lanthanide metal ion complexes as a luminescent emitter in electroluminescence (EL) devices. The configuration of the EL cell and experimental results were discussed.     

Ytterbium(III) Porpholactones: β‐Lactonization of Porphyrin Ligands Enhances Sensitization Efficiency of Lanthanide Near‐Infrared Luminescence

The near‐infrared (NIR) luminescence efficiency of lanthanide complexes is largely dependent on the electronic and photophysical properties of antenna ligands. Although porphyrin ligands are efficient sensitizers of lanthanide NIR luminescence, non‐pyrrolic porphyrin analogues, which have unusual symmetry and electronic states, have been much less studied. In this work, we used porpholactones, a class of β‐pyrrolic‐modified porphyrins, as ligands and investigated the photophysical properties of lanthanide porpholactones Yb‐1 a – 5 a . Compared with Yb porphyrin complexes, the porpholactone complexes displayed remarkable enhancement of NIR emission (50–120 %). Estimating the triplet‐state levels of porphyrin and porpholactone in Gd complexes revealed that β‐lactonization of porphyrinic ligands lowers the ligand T₁ state and results in a narrow energy gap between this state and the lowest excited state of Yb³⁺. Transient absorption spectra showed that Yb^III porpholactone has a longer transient decay lifetime at the Soret band than the porphyrin analogue (30.8 versus 17.0 μs). Thus, the narrower energy gap and longer lifetime arising from β‐lactonization are assumed to enhance NIR emission of Yb porpholactones. To demonstrate the potential applications of Yb porpholactone, a water‐soluble Yb bioprobe was constructed by conjugating glucose to Yb ‐ 1 a . Interestingly, the NIR emission of this Yb porpholactone could be specifically switched on in the presence of glucose oxidase and then switched off by addition of glucose. This is the first demonstration that non‐pyrrolic porphyrin ligands enhance the sensitization efficiency of lanthanide luminescence and also display switchable NIR emission in the region of biological analytes (800–1400 nm).     

稀土离子及其配合物对二棕榈酰磷脂酰乙醇胺相变性质的影响

用差示扫描量热研究了金属离子和稀土配合物对二棕榈酰磷脂酰乙醇胺(DPPE)脂双层由凝胶态向液晶态相转变的影响T~m的影响。发现加入金属离子提高了DPPE脂双层的相转变温度。其中, Na^+＜Ca^2^+＜Ln^3^+。Pr^3^+的影响较La^3^+强。在pH 7.4时, 柠檬酸镧对T~m影响很小, 相反在pH 2.0时, 则降低相变温度T~m。乳酸稀土在pH 2.0和pH 7.4时都显著提高T~m, 在中性条件下, 对T~m影响更大。同时, 乳酸稀土较相同浓度下的稀土离子影响大, 说明乳酸稀土中稀土离子和乳酸根配体存在协同作用。我们初步探讨了金属离子以及稀土配合物对DPPE脂双层相变温度影响的原因。     

The Series of Rare Earth Complexes [Ln2Cl6(μ‐4,4′‐bipy)(py)6], Ln=Y,Pr, Nd,Sm‐Yb: A Molecular Model System for Luminescence Properties in MOFs Based on LnCl3 and 4,4′‐Bipyridine

A series of 12 dinuclear complexes [Ln₂Cl₆(μ‐4,4′‐bipy)(py)₆], Ln=Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, ( 1 – 12 , respectively) was synthesized by an anhydrous solvothermal reaction in pyridine. The complexes contain a 4,4′‐bipyridine bridge and exhibit a coordination sphere closely related to luminescent lanthanide MOFs based on LnCl₃ and 4,4‐bipyridine. The dinuclear complexes therefore function as a molecular model system to provide a better understanding of the luminescence mechanisms in the Ln‐N‐MOFs ${\hbox{}{{\hfill 2\atop \hfill \infty }}}$ [Ln₂Cl₆(4,4′‐bipy)₃] ? 2(4,4′‐bipy). Accordingly, the luminescence properties of the complexes with Ln=Y, Sm, Eu, Gd, Tb, Dy, ( 1 , 4 – 8 ) were determined, showing an antenna effect through a ligand–metal energy transfer. The highest efficiency of luminescence is observed for the terbium‐based compound 7 displaying a high quantum yield (QY of 86 %). Excitation with UV light reveals typical emission colors of lanthanide‐dependent intra 4f–4f‐transition emissions in the visible range (Tb^III: green, Eu^III: red, Sm^III: salmon red, Dy^III: yellow). For the Gd^III‐ and Y^III‐containing compounds 6 and 1 , blue emission based on triplet phosphorescence is observed. Furthermore, ligand‐to‐metal charge‐transfer (LMCT) states, based on the interaction of Cl^? with Eu^III, were observed for the Eu^III compound 5 including energy‐transfer processes to the Eu^III ion. Altogether, the model complexes give further insights into the luminescence of the related MOFs, for example, rationalization of Ln‐independent quantum yields in the related MOFs.     

Stepwise Increase of NdIII-Based Phosphorescence by AIE-Active Sensitizer: Broadening the AIPE Family from Transition Metals to Discrete Near-Infrared Lanthanide Complexes**

We designed two near-infrared (NIR) lanthanide complexes [( L )₂-Nd(NO₃)₃] ( L =TPE₂-BPY for 1 , TPE-BPY for 2 ) by employing aggregation-induced emission (AIE)-active tetraphenylethylene (TPE) derivatives as sensitizers, which possessed matched energy to Nd^III, prevented competitive deactivation under aggregation, even shifted the excitation window toward 600 nm by twisted intramolecular charge transfer. Furthermore, benefiting from the 4 f electron shielding effect and antenna effect, the enhanced excitation energies of the AIE-active sensitizers by structural rigidification transferred into the inert Nd^III excited state through ³LMCT, affording the first aggregation-induced phosphorescence enhancement (AIPE)-active discrete NIR-emitting lanthanide complexes. As 1 equipped with more AIE-active TPE than 2 , L →Nd energy transfer efficiency in the former was higher than that in the latter under the same conditions. Consequently, the crystal of 1 exhibited one of the longest lifetimes (9.69 μs) among Nd^III-based complexes containing C−H bonds.     

Adsorption of cadmium(II) onto goethite and kaolinite in the presence of benzene carboxylic acids

The effect of benzene carboxylic acids on the adsorption of Cd(II) (5×10⁻⁵ M) by goethite and kaolinite has been studied in 0.005 M NaNO₃ at 25°C. The concentrations of phthalic (benzene-1,2-dicarboxylic acid), hemimellitic (1,2,3), trimellitic (1,2,4), trimesic (1,3,5), pyromellitic (1,2,4,5) and mellitic (1,2,3,4,5,6) acids varied from 2.5×10⁻⁵ to 1×10⁻³ M. Mellitic acid complexes Cd(II) strongly above about pH 3, but the other acids only at higher pH, phthalic acid forming the weakest complexes. Phthalic, trimesic and mellitic acids adsorbed strongly to goethite at pH 3, but adsorption decreased at higher pH; however, mellitic acid was still about 50% adsorbed at pH 9, by which the other two were almost entirely in solution. At 10⁻³ M all the acids enhanced the adsorption of Cd(II) to goethite, the higher members of the series being the most effective. The higher members of the series suppressed Cd(II) adsorption onto kaolinite, but phthalic and trimesic acids caused slight enhancement. The effects of mellitic acid on Cd(II) adsorption depended strongly on its concentration. The maximum enhancement of Cd(II) adsorption onto goethite was at 10⁻⁴ M. The greatest suppression of Cd(II) adsorption onto kaolinite was at 10⁻³ M, and at 2.5×10⁻⁵ M mellitic acid enhanced Cd(II) adsorption onto kaolinite at intermediate pH. The results are interpreted in terms of complexation between metal and ligand (acid), metal and substrate, ligand and substrate, and the formation of ternary surface complexes in which the ligand acts as a bridge between the metal and the surface.     

Dependence of the Lifetime upon the Excitation Energy and Intramolecular Energy Transfer Rates: The 5D0 EuIII Emission Case

In many Eu^III‐based materials, the presence of an intermediate energy level, such as ligand‐to‐metal charge transfer (LMCT) states or defects, that mediates the energy transfer mechanisms can strongly affect the lifetime of the ⁵D₀ state, mainly at near‐resonance (large transfer rates). We present results for the dependence of the ⁵D₀ lifetime on the excitation wavelength for a wide class of Eu^III‐based compounds: ionic salts, polyoxometalates (POMs), core/shell inorganic nanoparticles (NPs) and nanotubes, coordination polymers, β‐diketonate complexes, organic–inorganic hybrids, macro‐mesocellular foams, functionalized mesoporous silica, and layered double hydroxides (LDHs). This yet unexplained behavior is successfully modelled by a coupled set of rate equations with seven states, in which the wavelength dependence is simulated by varying the intramolecular energy transfer rates. In addition, the simulations of the rate equations for four‐ and three‐level systems show a strong dependence of the emission lifetime upon the excitation wavelength if near‐resonant non‐radiative energy transfer processes are present, indicating that the proposed scheme can be generalized to other trivalent lanthanide ions, as observed for Tb^III/Ce^III. Finally, the proper use of lifetime definition in the presence of energy transfer is emphasized.     

Peculiarities of metal—ligand bonding in europium trinitrate complexes: a viewpoint of comparative charge density analysis in crystals

The results of high-resolution X-ray diffraction studies of the charge density distribution in crystals of three europium trinitrate complexes, including those with N-donor "antenna"-ligands are summarized. It is shown that the charge transfer between lanthanide ion and "antenna" correlates with the energy of interaction between the metal and nitrate anion, and the total stabilization energy of the metal polyhedron depends weakly on the coordination number of the metal and the nature of the ligands. The statistical treatment of the crystal structural data for similar complexes and the energies of the corresponding metal—ligand interactions allowed us to suggest the stability of mer-arrangement of the coordinated nitrate anions and to propose a semiempirical relationship to estimate the energy of Eu—O interactions. The influence of vibration processes on the electron density distribution in the EuO₂NO fragment was additionally considered, and a feasibility to estimate the energy of interaction between the ligand and lanthanide ion at non-stationary points on the potential energy surface was validated.     

稀土-异烟酰肼席夫碱配合物的设计、合成与结构

由异烟酰肼和2-吡啶甲醛合成了席夫碱配体HL,并和稀土离子合成组装得一系列稀土配合物。用X-射线单晶衍射对配合物的结构进行了测定。通过荧光测试发现La配合物有荧光,而Eu,Dy则使配体的荧光淬灭。     

Experimental and computational studies of the binding properties of lower rim tetra- and di-substituted calix[4]arene amide derivatives with metal ions

Abstract

Experimental and theoretical binding studies of representative alkali, alkaline earth, transition, heavy metal and lanthanide cations by tetra- and di-substituted calix[4]arene amide derivatives (diethyl amide 1a–c and morpholide amide 2a–c) in the cone conformation were carried out. Binding was assessed by extraction experiments of the metal picrates from water to dichloromethane and proton NMR titrations. Density functional theory calculations were also performed to determine the binding energy of the complexes formed and to analyse the host–guest interaction modes. In the cases of ligands 1b and 2c with Na⁺ and Ag⁺ picrates, the extraction energy was also determined using the polarisable continuum model. The results are discussed in terms of the nature of the amide residue and the substitution pattern (1,3 vs. 1,2). Both tetra-amide derivatives are good extractants, showing preference for Na⁺, Ca²⁺, Ag⁺ and Pb²⁺ cations, mainly di-ethylamide 1a. Concerning di-amide derivatives, the relative position of the substituents seems to be more important than the nature of the amide group in the extraction process. Proton NMR studies indicate the formation of 1:1 complexes between the amides and the cations studied, and DFT data show that all ligands form the most stable complexes with La³⁺.     

硫杂蒽酮类稀土配合物的合成、表征及与DNA的作用(I)

合成了新的O-(硫杂蒽酮-[2]-基)-氧乙酸及其稀土配合物. 通过元素分析, IR, ¹H NMR, UV, DTA-TG和¹³C NMR谱对其结构进行了表征. 研究表明: 配体羧羰基脱质子后与金属离子配位, 2位氧原子也与金属离子配位, 配合物中含有一定量的配位水, 配合物为非电解质类型. 同时, 研究了O-(硫杂蒽酮-[2]-基)-氧乙酸稀土配合物对质粒DNA的切割作用. 结果表明: 铕的配合物对DNA的切割较明显, 且当配合物浓度增加时, 质粒DNA的超螺旋构型逐渐减少, 而缺刻、开环型构型逐渐增多. 在相同条件下, Eu(III)离子对质粒pBR322DNA几乎没有切割作用; 配体O-(硫杂蒽酮-[2]-基)-氧乙酸对质粒pBR322DNA也有切割作用, 但配合物EuL₃对质粒pBR322DNA的切割作用明显强于配体, 表明稀土离子Eu(III)与配体生成配合物后有较好的协同切割作用.     

含2，2＇-联嘧啶桥Ir^III-Ln^III（Ln=Nd，Yb，Er）双金属配合物的合成和光物理性质

选择具有（N^N）（N^N）位点的四齿配体2,2’-联嘧啶fbpm）作为桥联配体,利用铱配合物Ir（dfppy）2（bpm）Cl作为配体与稀土配合物Ln（TTA）3·2H2O配位,得到了Ir^III-Ln^III（Ln=Nd,Yb,Er）双金属配合物[Ir（dfppy）2（bpm）Ln（TTA）3]Cl．通过荧光滴定的方法,测定了该铱配合物与稀土离子之间的络合稳定常数．通过对铱配合物及Ir^III-Ln^III（Ln=Nd,Yb,Er）双金属配合物在可见区光谱的测定,可以观察到明显的铱配合物发光的猝灭,说明从铱中心到稀土中心发生了能量传递．同时,利用可见光选择性激发铱配合物可以获得在稀土Nd^III,Yb^III,E^III离子红外区的发光．说明了铱配合物Ir（dfppy）2（bpm）Cl作为配体可以较好地敏化稀土离子的红外发光．