Crystal structures and luminescence properties of two new terbium complexes with aromatic carboxylic acid

Two new terbium complexes with aromatic carboxylic acids, [(Tb)₂(L₁)₆(H₂O)₄] (1) and [(Tb)₂(L₂)₆(H₂O)₂(DMF)₂] (2) (HL₁: nicotinic acid; HL₂: 4-hydroxybenzoic acid), with different coordination geometries have been synthesized and their crystal structures determined. The luminescence properties of the two complexes, including the phosphorescence lifetime, have been investigated. The effect of a secondary ligand on luminescence of the ternary terbium complex with carboxylic acid and the relationship between luminescence properties and crystal structure, including coordination mode of the carboxyl groups from HL₁ and HL₂ and coordination mode of a secondary ligand, are discussed.     

Di- and tetracarboxylate ligands for highly luminescent terbium(III) complexes on the basis of sulfonylcalix[4]arene scaffold

New di- (2) and tetracarboxylate ligands (4) were prepared on a sulfonylcalix[4]arene platform by O-alkylation of thiacalix[4]arene with ethyl bromoacetate, followed by hydrolysis of the ester function and oxidation of the sulfide bridges. The sulfonyl-based ligands 2 and 4 formed luminescent 1:1 complexes with terbium(III) ion having higher luminescent quantum yield (Φ = 0.29₁ and 0.28₇, respectively) than 1:1 complexes of the corresponding thiacalix[4]arene-based di- (1) and tetracarboxylate ligands (3) (Φ = 0.03₈ and 0.00₃, respectively), implying higher efficiency of sulfonyl ligands (2 and 4) than those of thia ligands (1 and 3) in the energy transfer process.     

Luminescence detection of cysteine based on Ag-mediated conformational change of terbium ion-promoted G-quadruplex

In this work, we developed a simple and sensitive method for the detection of cysteine (Cys) by employing terbium ion (Tb³⁺)-promoted G-qudraplex (G4/Tb) as a luminescent probe, which is based on Ag⁺-mediated conformational change of G4/Tb. Due to Ag⁺ is able to compete with Tb³⁺ to bind guanine at G4, the presence of Ag⁺ can lead to the formation of G4/Tb–Ag⁺ complex and disrupt the structure of G4/Tb. Meanwhile, the binding of Ag⁺ with G4/Tb will also cause the alteration of the excited state of G4 and more efficient energy transfer from G4 to Tb³⁺, enhancing the luminescence of G4/Tb. However, upon the addition of Cys, Ag⁺ will be released from G4/Tb–Ag⁺ complex because of the high affinity of Cys to Ag⁺. This results in the re-formation of the conformation of G4/Tb and the decrease of the luminescence of G4/Tb. So, Ag⁺-enhanced luminescence of G4/Tb is associated with its conformational transformation. As a luminescent probe for Cys, G4/Tb not only shows excellent selectivity and sensitivity with a detection limit of 20 nM, but also possesses the features of simple preparation, easy reproducibility, and eliminating the interferences from background fluorescence. We envision that the presented strategy might provide new insight into the biosensing applications of lanthanide complex.     

水溶性ZnO/氨丙基-硅氧烷量子点的合成与荧光特性

利用溶胶-凝胶法在非水体系中合成出ZnO量子点,并用3-氨丙基三乙氧基硅烷(APTES)对其进行包覆,制得水溶性ZnO/氨丙基-硅氧烷量子点(ZnO-ASQDs)。通过实验确定最佳包覆条件:t=60℃,T=30min,nSi:nZn=1:1,VPEG/Vtotal=1/9。合成的ZnO量子点分别在348与512nm处有2个荧光发射峰,且激发区域较宽(220~360nm)。经过APTES包覆,ZnO量子点荧光发射强度明显增强,同时具有良好的水溶性与荧光稳定性,稳定时间可达60d之久。由Brus公式计算表明,包覆层对ZnO量子点不但改性还起到保护作用,抑制其团聚。经XRD与TEM证实,ZnO-ASQDs具有核壳结构,ZnO核平均粒径为6nm,整体粒径约为20nm。此外,通过调整ZnO核的粒径可制备出不同荧光颜色的ZnO-ASQDs。     

Preparation of phosphorylated bis-pyrazolyl-pyridine nonadendate ligands and their terbium complexes. Part 2

A series of ligands has been constructed from a central bis-pyrazolyl-pyridine core and various deprotonable chelating pockets based on mixed carboxylate/phosphate or phosphate anionic functions and a central flexible pendent arm for subsequent grafting to biomaterials. For some of these ligands, the sequence of reactions incorporates an additional step introducing a substituted diethynylphenyl residue to increase significantly their solubility in polar organic solvents. The terbium(III) complexes of some of these ligands display outstanding spectroscopic properties with lifetimes ranging from 2.7 to 3.2 ms and quantum yields from 16% to 26% in water.     

Fluorescence and terbium-sensitised luminescence determination of garenoxacin in human urine and serum

Fluorescence and terbium-sensitised luminescence properties of new quinolone garenoxacin have been studied. The fluorimetric method allows the determination of 0.060-0.600 μg ml⁻¹ of garenoxacin in aqueous solution containing HCl/KCl buffer (pH 1.5) with λ_exc=282 nm and λ_em=421 nm. Micellar-enhanced fluorescence was also studied, leading to a higher than 400% increase in analytical signal in presence of 12 mM sodium dodecyl sulphate (SDS), allowing the determination of 0.020-0.750 μg ml⁻¹ of garenoxacin. The terbium-sensitised luminescence method allows the determination of 0.100-1.500 μg ml⁻¹ of garenoxacin in 12 mM SDS solution containing 0.08 M acetic acid/sodium acetate buffer (pH 4.1) and 7.5 mM Na₂SO₃ (chemical deoxygenation agent), with λ_exc=281 nm and λ_em=546 nm. Relative standard deviation (R.S.D.) values for the three methods were in the range 1.0-2.0%. The proposed procedures have been applied to the determination of garenoxacin in spiked human urine and serum.     

Size Effects on the Luminescence Properties of Polymer Nanowires简

Poly（3-（2-methoxyphenyl）thiophene） （PMP-Th） nanowires were fabricated using porous anodic alumina （PAA） as template through electrochemical polymerization by cyclic voltammetry. The control on the size of nanowires was confirmed by electron microscopy. The results indicated that the luminescence spectra of PMP-Th nanowires in PAA nanochannels were blue-shifted and emission intensity was enhanced compared to the emission of the PMP-Th film. Moreover, the luminescent spectra of PMP-Th nanowires were size dependent, which may result from the change in the degree of confinement of nanowires in PAA. F6rster energy transfer from PAA to PMP-Th molecules is considered to be responsible for the enhancement of luminescence from PMP-Th nanowires in PAA. The results show that the emission properties of polymers with nanostructures can be tuned by controlling their size.     

Development of a novel terbium(III) chelate-based luminescent probe for highly sensitive time-resolved luminescence detection of hydroxyl radical

Time-resolved (or time-gated) luminescence detection technique using lanthanide chelates as luminescent probes is a widely used and highly sensitive method for the biological applications. The developments of various functional lanthanide probes that can selectively recognize the biological targets are the essential objective of the technique. In this work, a unique Tb³⁺ chelate-based luminescent probe, N,N,N¹,N¹-[2,6-bis(3′-aminomethyl-1′-pyrazolyl)-4-(p-aminophenoxy)methylene-pyridine] tetrakis(acetate)-Tb³⁺(BMPTA-Tb³⁺), has been designed and synthesized for highly selective and sensitive time-resolved luminescence detection of one highly reactive oxygen species (ROS), hydroxyl radical (OH). The probe is almost non-luminescent, and can selectively react with hydroxyl radical to afford a highly luminescent Tb³⁺ chelate, N,N,N¹,N¹-[2,6-bis(3′-aminomethyl-1′-pyrazolyl)-4-hydroxymethyl-pyridine] tetrakis(acetate)-Tb³⁺ (BHTA-Tb³⁺), accompanied by a 49-fold increase in luminescence quantum yield with a long luminescence lifetime (2.76 ms). The luminescence response of the probe to hydroxyl radical is highly selective and insensitive to pH in the physiological pH range. For loading the probe into the living cells, the acetoxymethyl ester of BMPTA-Tb³⁺ was synthesized and used for the HeLa cell loading. Based on this probe, a background-free time-resolved luminescence imaging method for detecting hydroxyl radical in living cells was successfully established.     

Capillary electrophoresis with post-column addition of terbium and sensitized lanthanide-ion luminescence detection for the determination of diflunisal and salicylic acid

A detection scheme based on the Post-column addition of terbium followed by sensitized luminescence detection has been developed. Two model Compounds- saliculic acid and diflunisa- were separated by capillary electophoresis in an alkaline phosphate buffer. A Solution containing terbium and CTAB was added post-column via a “home-built” reactor resulting in the rapid fromation of the strongly luminescent terbium-salicylic acid and terbium-diflunisal complexes in a reaction capillary. Following complexationn in the reaction capillarty, the 325 nm line from a HeCd laser was used to excite the analytes which efficiently transfer their energy to terebium. Resuulant luminescence of terebium was liner of 2 orders of magnitude. This novel and practical system enables the detection of micromolar concentrations of diflunisal and salicylic acid- a 10 fold improvement over UV absorbance detection in the same system. Post-column addition of terbium also eliminates the problems associated with strong adsorption of the lanthanide ion to the silica walls of the separation capillary and the formation of metal-ligand complexes with different coordination numbers.     

Crystal structure and luminescence property of ternary terbium p-aminobenzoic acid complexes with different second ligands

Ternary terbium complexes with p-aminobenzoic acid (HL), [TbL₃(DMSO)(H₂O)]₂ (1), [TbL₃(DMF)(H₂O)]₂ (2) and [TbL₃(Bpy)(H₂O)]₂·2H₂O (3) (DMSO=dimethyl sulfoxide, DMF=N, N- dimethylformamide, Bpy=2, 2′- bipyridyl) have been synthesized, and their crystal structures determined. The luminescence properties of these complexes, including both the emission quantum yield and the fluorescence lifetime, have been investigated. The effect of a second ligand on the crystal structure and luminescence property of the ternary terbium p-aminobenzoic acid complexes, and the relationship between luminescence properties and crystal structure, including coordination mode of the L⁻ ligand and the characteristics of a second ligand, are discussed.     

Effect of substituent structure on pyrimidine electrophilic substitution

In an investigation into the electrophilic nitrosation reactions of a series of 4,6-disubstituted pyrimidine derivatives, a subtle interplay between the electronic nature of the C-4 and C-6 substituents and reactivity was found where these were chloro-, mono- or disubstituted amino groups. Effects such as the presence of an aryl group or two alkyl groups on the amino moiety impede the progress of the reaction despite the presence of a second activating group.     

Preparation of three terbium complexes with p-aminobenzoic acid and investigation of crystal structure influence on luminescence property

Three new rare earth p-aminobenzoic acid complexes, [Tb₂L₆(H₂O)₂]_n (1), [Tb₂L₆(H₂O)₄]·2H₂O (2) and [Tb(phen)₂L₂(H₂O)₂](phen)L·4H₂O (3) (HL: p-aminobenzoic acid; phen: 1, 10-phenanthroline), with different structural forms are reported in this paper. Complex 1 is a polymolecule with a two-dimensional plane structure. Compound 2 is a binuclear molecule, and 3 appears to be a mononuclear complex. The fluorescence intensity, the fluorescence life-time and emission quantum yield of 2, which has two coordination water molecules, is better than those of 1, which has only one coordination water molecule. This is an unusual phenomenon for general fluorescent rare earth complexes. The fluorescence performance of 3 is the most unsatisfactory among the three complexes. Their crystal structures show that the coordination mode of the ligand is an important factor influencing the luminescence properties of a fluorescent rare earth complex.     

Molecular design and photo-physics of quaternary hybrid terbium centered systems with novel functional di-urea linkages of strong chemical bonds through hydrogen transfer addition

Two kinds of crosslinking reagents, 3-aminopropyl-methyl-diethoxylsiliane (H₂N(CH₂)₃SiCH₃(OC₂H₅)₂, abbreviated as APMES) and N-2-aminoethyl-3-aminopropyltriethoxylsiliane (H₂N(CH₂)₂HN(CH₂)₃Si(OC₂H₅)₃, abbreviated as AEAPES) are modified by 3-(triethoxysilyl)-propyl isocyanate (TESPIC) to afford two novel crosslinking molecular derivatives as bridge ligands. Then the ternary organic-inorganic molecular-based hybrid system with these functional bridge ligands and 1,10-phenanthroline (phen) are constructed with the two components equipped with covalent bonds. The two components of APMES (or AEAPES) and TESPIC is linked through -NHC(O)NH- groups which is applied to coordinate to Tb³⁺ and further formed Si-O backbones after co-hydrolysis and co-polycondensation processes, while phen behaves as the main energy donor for the sensitization of luminescence of Tb³⁺. Luminescence spectra were utilized to characterize the photo-physical properties of the obtained hybrid system and the above spectroscopic data reveal that the phen in this favorable hybrid system behaves the main energy donor for the luminescence of Tb³⁺. In this way, the intra-molecular energy transfer process took place within these molecular-based hybrids and strong green and blue emissions of Tb³⁺ have been achieved.     

A study on terbium sensitized chemiluminescence of ciprofloxacin and its application

A novel rapid flow injection method with chemiluminescence (CL) detection was established for the determination of ciprofloxacin (CPLX), which is an antibiotic commonly used. The method is based on CL of Ce(IV)–SO₃²⁻ sensitized by Tb³⁺–CPLX, and showed the intensive bands characteristic of Tb³⁺ (⁵D₄→⁷F₅). The optimum conditions for CL emission were investigated. The linear relationship between the relative CL intensity and the concentration of CPLX is in the range of 9.0×10⁻⁹–1.0×10⁻⁶ mol/l with a detection limit of 3.1×10⁻¹⁰ mol/l. The relative standard deviation is 2.8% (n=11) for a level of 5.0×10⁻⁸ mol/l. The method was applied to the analysis of CPLX in human serum and urine samples with satisfactory results. The possible mechanism for this sensitized CL reaction is also discussed.     

Structure and luminescence of a nitrate-bridged heterotrinuclear Cu2-Pr complex with compartmental Schiff base ligand

A unique heterotrinuclear nitrate-bridged complex of hexanitrate praseodymium(III) and dicopper(II) compartmental species has been synthesized and characterized by X-ray single crystal structure analysis. The structure determination indicates that the dinuclear copper moiety undergoes a tilted deformation (with respect to the dicopper complex) upon connection to the lanthanide species via a rare nitrate bridge. The trinuclear species is highly fluorescent owing to the presence of praseodymium.     

Studies on molar volume and rheology of terbium soaps in a benzene-DMF mixture

Summary Molar volume (V), apparent molar volume (_v), and fluidity () of terbium soaps in benzene-DMF (7:3 v/v) were evaluated at constant temperature from density and viscosity measurements. The results were used to determine the critical micelle concentration (CMC), soap-solvent and soap-soap interactions, and the effect of the chain length of soap molecules on various parameters. The molar volume and viscosity results are discussed in terms of known relations.

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Untersuchungen zum Molvolumen und zur Rheologie von Terbiumseifen in Benzol-DMF

Zusammenfassung Molvolumen (V), scheinbares Molvolumen (_v) und Fluidität () von Terbiumseifen in einer Mischung aus Benzol undDMF (7:3 v/v) wurden bei konstanter Temperatur aus Dichte-und Viskositätsmessungen ermittelt. Aus den Ergebnissen wurden die kritische Micellenkonzentration (CMC), Seifen-Lösungsmittel- und Seifen-Seifen-Wechselwirkungen sowie der Effekt der Kettenlänge der Seifenmoleküle auf verschiedene Parameter bestimmt. Die Resultate bezüglich Molvolumen und Viskosität werden anhand bekannter Beziehungen diskutiert.

     

Rapid screening detection of fluoroquinolone residues in milk based on turn-on fluorescence of terbium coordination polymer nanosheets

Trace fluoroquinolone residues in milk could be detected based on turn-on fluorescence of AMP/Tb CPNSs. It might provide a new platform for the rapid detection of antibiotic pollutants with the advantages of simple sample pretreatment processes and excellent selectivity.     

Peculiarities of the excitation energy transfer in europium and terbium aromatic carboxylates and nitrate complexes with sulfoxides: Blocking effect

The influence of modification of the aromatic ligands on the excitation energy transfer to Ln³⁺ ions in europium and terbium carboxylates and nitrates was examined. The luminescence excitation spectra of three groups of the europium and terbium compounds: phenyl-, diphenyl-, triphenylacetates, phenoxyacetates and triphenylpropionates; 1- and 2-naphthylcarboxylates and 2-naphthoxyacetates; lanthanide nitrates with diarylsulfoxides (diphenyl- and dibenzylsulfoxides) and dialkylsulfoxides were investigated. The spectra of adducts of terbium phenylcarboxylates with 1,10-phenanthroline were also analyzed. The effect of the aliphatic bridges, which decouple the π–π- or p–π-conjugation in the ligand, on the energy transfer to Ln³⁺ ions (so-called blocking effect) was investigated. It was shown, that this decoupling leads to significant lowering of the energy of “ligand–metal ion” charge transfer states (LM CTS) in the europium carboxylate salts, just down to 27,800 cm⁻¹ in europium 2-naphthoxyacetate. As a consequence, the probability of the LM CTS participation in the excitation energy dissipation processes increases. A channel of the excitation energy dissipation in the region of 31,750 cm⁻¹ related to ligand electronic transitions was found in the europium and terbium nitrates with sulfoxides. It was demonstrated that a part of the energy absorbed by the aromatic ligand having aliphatic bridge can be emitted as the ligand fluorescence.     

Simple, rapid and sensitive spectrofluorimetric determination of diflunisal in serum and urine based on its ternary complex with terbium and EDTA

A very simple, rapid and highly sensitive fluorimetric method for the determination of diflunisal in serum and urine is described. The method is based on the formation of a ternary complex between diflunisal, Tb³⁺ and EDTA in alkaline aqueous solutions. This complex exhibits very intense terbium ion luminescence with a main emission maximum at 546 nm when excited at 284 nm. Optimum conditions for the complex formation have been investigated. The detection limit for diflunisal is 2.4 μg 1⁻¹, while the range of application is 0.01–6.00 mg 1⁻¹. The method has been successfully applied for the determination of diflunisal in untreated human serum and urine samples. Analytical recoveries from serum and urine samples spiked with diflunisal were in the ranges of 96.8–101.2% and 98.0–102.0%, respectively.     

The effects of La doping on luminescence properties of PbWO4 single crystal

X-ray-excited luminescence (XEL), thermoluminescence (TL), photoluminescence under excitation of UV light and X-ray photoelectron spectroscopy (XPS) measurements were conducted on PbWO₄ (PWO) single crystals doped with La³⁺ at a series of concentration levels. With the increase of doping levels, the intensity of PWO in the XEL or the excitation-emission spectra was found to decrease accordingly, especially in the case of heavy doping. TL peaks in the range from room temperature to 200°C disappeared after the doping with La³⁺. A splitting of the La3d XPS peak in the heavy La³⁺-doped samples was observed and proposed to be responsible for that. At a high doping level, La³⁺ would occupy W-sites besides Pb-sites and thus induce a self-compensation via pairs [(La_W³⁺)″′−(La_Pb³⁺)^•]−(V_O)^•• or clusters [3(La_Pb³⁺)^•−(La_W³⁺)″′], where nonradiative recombination was previously reported to occur. The mechanism of the influence on luminescence was also discussed in this paper.