Terbium Complexes Research Articles

A Dendrimer-Based Time-Gated Concentric FRET Configuration for Multiplexed Sensing

Förster resonance energy transfer (FRET) is widely used for the development of biological probes and sensors. In this context, the norm for multiplexed detection is deployment of multiple probes, each a discrete donor-acceptor pair. Concentric FRET (cFRET) probes enable multiplexed sensing with a single vector but, to date, have only been developed around semiconductor quantum dots, which may limit the scope of biological applications for such probes. Here, we demonstrate that dendrimers labeled with a luminescent terbium complex (Tb) are a viable and advantageous alternative platform for cFRET probes. Polyamidoamine dendrimers were functionalized with Tb, biotin, NeutrAvidin, and three types of dye-labeled oligonucleotide probes to establish a network of competitive and sequential Tb-to-dye and dye-to-dye FRET pathways. These probes were characterized physically and photophysically, and a time-gated multiplexed assay for DNA targets was demonstrated. The time-gating offered by the Tb allowed the rejection of background autofluorescence from serum. More broadly, this dendrimer-based architecture shows that cFRET is a general concept and is an important step toward a new generation of probes for biological sensing.

Rapid and Wash-Free Time-Gated FRET Histamine Assays Using Antibodies and Aptamers.

Histamine (HA) is an indicator of food freshness and quality. However, high concentrations of HA can cause food poisoning. Simple, rapid, sensitive, and specific quantification can enable efficient screening of HA in food and beverages. However, conventional assays are complicated and time-consuming, as they require multiple incubation, washing, and separation steps. Here, we demonstrate that time-gated Förster resonance energy transfer (TG-FRET) between terbium (Tb) complexes and organic dyes can be implemented in both immunosensors and aptasensors for simple HA quantification using a rapid, single-step, mix-and-measure assay format. Both biosensors could quantify HA at concentrations relevant in food poisoning with limits of detection of 0.19 μg/mL and 0.03 μg/mL, respectively. Excellent specificity was documented against the structurally similar food components tryptamine and l-histidine. Direct applicability of the TG-FRET assays was demonstrated by quantifying HA in spiked fish and wine samples with both excellent concentration recovery and agreement with conventional multistep enzyme-linked immunosorbent assays (ELISAs). Our results show that the simplicity and rapidity of TG-FRET assays do not compromise sensitivity, specificity, and reliability, and both immunosensors and aptasensors have a strong potential for their implementation in advanced food safety screening.

The incorporation of upper vs lower rim substituted thia- and calix[4]arene ligands into polydiacethylene polymeric bilayers for rational design of sensors to heavy metal ions

1,3-Diketone calix [4]arene (CA) and thiacalix [4]arene (TCA), with the hydrophobic substituents introduced onto lower or upper rims respectively, form mixed aggregates with 10,12-pentacosadiynoic acid (PCDA) through the thin film hydration technique. Computer simulations, showing the arrangement of TCA and CA molecules in supramolecular clusters with PCDA molecules, suggest that PCDA assemblies with both cyclophanes are a convinient basis for the coordination of metal ions. However, photopolymerization of mixed aggregates reveals more disruption of the vesicular nanostructure of polydiacetylene (PDA) when CA molecules are included compared to TCA. The incorporation of the TCA and CA ligands influences the ability of the mixed PDA-bilayers to conformational and spectral changes and provides tight coordination of Tb3+ ions and efficient sensitizing of the Tb3+-centered luminescence. The PDA-bilayers incorporated by terbium TCA complex provide more sensitive response on the series of heavy metal ions vs their CA-based analogues. The surface exposed TCA rims and carboxylate moieties of PDA provide two different binding sites for Tb3+ and heavy metal ions. Both distribution of Tb3+ and heavy metal ions between these sites and heterometallic complex formation are revealed as the factors affecting the luminescence response of PDA-TCA terbium complex in the solutions of heavy metal ions. The interplay between these factors is the reason for the different luminescence response of PDA-TCA terbium complex on Cd2+, Hg2+ and Pb2+ ions. The PDA-vesicles incorporated by terbium TCA complex exhibit easier phase separation vs the PDA vesicles themselves, which favors the extraction of Pb2+ ions.

Synthesis, Optoelectronic and Photoluminescent Characterizations of Green Luminous Heteroleptic Ternary Terbium Complexes

This article presents four ternary terbium complexes based on fluorinated 2-thenoyltrifluoroacetone (TTFA) and N donor bidentate neutral ligands. The prepared complexes were examined by elemental study, electrochemical analysis, spectroscopically and thermo-gravimetrically. Spectral analysis shows the bonding of Tb3+ ion with oxygen and nitrogen atom of diketone and neutral ligand respectively. Upon excitation in UV region, synthesized terbium complexes show luminescence in green region of electromagnetic spectrum. Photoluminescence emission spectra of complexes do not show any ligand based peak suggesting the effective transferal of energy from ligand to metal ion. Green emanation by terbium complexes is owing to intense peak ~547nm (5D4 → 7F5). The outcome of emission data and CIE coordinates correlate with each other and affirms the utility of green luminous complexes as potential emissive material for optoelectronic gadgets applied in lighting system.

Preparation and photoluminescent characteristics of green Tb(III) complexes with β-diketones and N donor auxiliary ligands

This paper presents four octa coordinated ternary terbium complexes based on 2-benzoylacetophenone (BAP) and other auxiliary ligands. For characterization purpose, elemental analysis, electrochemical study, thermal analysis and spectroscopic investigations were carried out in detail. Optical band gap (3–4 eV) of complexes was determined from Tauc’s relation. Upon excitation in UV region, emission spectra of complexes demonstrate peaks of Tb3+ ion at ∼616 nm, 589 nm, 548 nm, and 492 nm, attributed to 5D4 → 7FJ (J = 3 to 6) respectively due to energy transfer from ligand to Tb(III) ion via antenna effect. Peak at 548 nm corresponding to 5D4 → 7F5 is responsible for bright green emission of synthesized terbium complexes. CIE color coordinates and color purity further corroborate the green emission of Tb3+ complexes. The complexes were found to be quite stable as studied by thermal analysis. The outcomes of characterizations have demonstrated that these complexes could behave as good contenders in lighting systems and displays owing to their photometric characteristics.

Preparation and optical investigation of green luminescent ternary terbium complexes with aromatic β-diketone

Green luminescent complexes of terbium based on derivatives of 1,10-phenanthroline auxiliary ligand and 1-phenyl-1,3-butanedione (PBD) with general formula [Tb(PBD)3L] were synthesized. The complexes were characterized by spectroscopic and thermal methods. Photoluminescence spectra demonstrated that on excitation under UV radiations, four emission peaks were displayed in the emission spectra. These characteristic peaks appeared due to transition from the energized (5D4) to the ground state (7FJ) positioned at 491, 547, 584, 622 nm, where J = 6–3 respectively. The hypersensitive peak located at 547 nm is responsible for the characteristic green emission of terbium ion. Absorption and electrochemical analytical results point out the application of synthesized complexes in lighting and displays. Optical and electronic band gap in 3–4 eV range were also found comparable to each other and revealed the use of ternary terbium complexes as semiconductor material.

Terbium complexes of an asymmetric β-diketone: Preparation, photophysical and thermal investigation

Chromophoric 1,3-diketone ligand has been utilized to prepare novel ternary complexes of terbium with differently substituted 2,2′-bipyridines as auxiliary ligands. These prepared complexes were thoroughly investigated with the help of numerous spectroscopic techniques. Infrared spectral analysis has suggested the coordination of diketone and ancillary ligand to the Tb(III) ion through oxygen and nitrogen atom respectively. Photoluminescence emission spectra of complexes have displayed only characteristic peaks of Tb3+ ion suggesting the efficient sensitization of metal ion by chromophoric ligands. Emission spectra of all complexes have displayed the ligand sensitized green emission due to the 5D4→7F5 transition situated at around 548 nm. Colorimetric investigation and color purity of complexes reveal the green luminous character of synthesized complexes. Thermogravimetric measurements have revealed the thermal stability of the complexes. Optical and electronic band gaps are found to be in good agreement with each other that shows their importance as semiconductor material. These trivalent complexes of terbium could be utilized as the green component in displays and light emissive materials.

Spectroscopic and optical investigation of 1,10-phenanthroline based Tb(III) β-diketonate complexes

A series of luminescent ternary terbium complexes based on fluorinated ligand 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione (TFNB) and other auxiliary ligands were synthesized and explored. Optical and photophysical characteristics of complexes were examined spectroscopically. Thermal and electrochemical behavior of complexes is also reported. In emission spectra of complexes, four characteristic peaks of Tb3+ ion at 492 nm, 548 nm, 586 nm and 615 nm accredited to 5D4 → 7FJ (J = 6–3) transitions appeared upon excitation in UV region. Most intense peak at 548 nm is accountable for bright green emission of ternary complexes. Color purity and CIE parameters also suggest the green luminous behavior of complexes. Our investigation has revealed that the synthesized complexes could be used in preparing lighting system, OLEDs and display devices owing to their luminescent characteristics.

Models of radiovoltaic batteries based on organo-lanthanide complexes

The complexes of Eu(III) and Tb(III) with beta-diketonate ligands were tested as donor materials in heterojunction radiovoltaic planar devices. The compounds revealed weak ability to directly convert the energy of cathode and X-ray radiation into electricity. However, the use of these complexes as additional radioluminescent layers in radiovoltaic devices has led to design an efficient radio-photovoltaic battery. The highest energy conversion efficiency was achieved when terbium complex with pyrasolonate and triphenylphosphine oxide ligands (Tb(pmip)3(TPPO)2) was used as a phosphor. The device with Tb(pmip)3(TPPO)2 outer layer under cathode radiation of 100 KeV gave output power 94 nW. Under X-ray radiation with photon energy 10 KeV the same device exhibited power of 0.95 nW. In both cases, the energy of accident electrons or X-ray photons causes the emission of the phosphor layer in the visible region, which penetrate through the glass substrate and the anode to the donor/acceptor heterojunction where it is converted into electric current. Thus, the devices operate as radio-photovoltaic devices, although the contribution of the radio-voltaic effect to the overall energy conversion process is very small.

Multi-Functional Silver Nanoparticles for High-Throughput Endospore Sensing.

In spore-forming bacteria such as Bacillus and Clostridium, the vegetative cells form highly durable hard shells called endospores inside the bacteria to survive as the growth environment deteriorates. Because of these properties, endospores can cause food poisoning and medical accidents if they contaminate food, medicine, or other products, and it is required for technology to detect the spores at the manufacturing site. In this study, we focused on the surface-enhanced Raman scattering (SERS) method for the sensitive detection of dipicolinic acid (DPA), a molecular marker of endospores. We constructed Fe3O4/Ag core–shell functional silver nanoparticles that specifically bind to DPA, and investigated a method for the qualitative detection of DPA by SERS and the quantitative detection of DPA by fluorescence method using a terbium complex formed on the surface. As a result, the concentration of the functional silver nanoparticles constructed could detect spore-derived DPA by fluorescence detection method, and SERS was several tens of nM. The functionalized nanoparticles can detect DPA quantitatively and qualitatively, and are expected to be applied to detection technology in the production of food and pharmaceuticals.

Novel versatile europium and terbium complexes as bioprobes and anticancer agents

Focusing on the pertinent research on dual activity (as probes and cancer inhibitors), two novel Eu and Tb lanthanide complexes were prepared in this work alongside their binuclear counterparts holding Cu as the secondary metal.

Synthesis of Europium and Terbium Complexes with Photophysical and Potential Bioprobe Properties

Synthesis of Europium and Terbium Complexes with Photophysical and Potential Bioprobe Properties

Effect of gold and silver nanoparticles on the detection of Ciprofloxacin in clinical wastewater by europium and terbium complexes

Effect of gold and silver nanoparticles on the detection of Ciprofloxacin in clinical wastewater by europium and terbium complexes

Magnetic interaction of photoexcited terbium-porphyrin complexes with non-aromatic ligands having different symmetries.

Interaction between the total angular momentum (J) of 4f electrons in lanthanides and the orbital angular momentum (L) of porphyrins in the photoexcited states was investigated by temperature-dependent and magnetic circular dichroism (MCD) for 5,10,15,20-tetraphenylporphyrinato (TPP) terbium(III) complexes with two different non-aromatic ligands i.e. 12-crown-4(1,4,7,10-tetraoxacyclododecane) and 1-aza-12-crown-4(1,4,7-trioxa-10-azacyclododecane). The two cases with different ligands were examined in order to understand how magnetic interaction depends on the symmetry of the non-aromatic ligands. The three absorption bands in the visible region, B(0,0), Q(1,0), and Q(0,0) bands, showed temperature-dependent MCD A term. For each band, the J-L interaction was determined from the simulation-based fitting to experimental ratios. An increase in the magnitude of the J-L interaction was observed when the second ligand was the aza-crown with a lower symmetry. Ab initio RASSCF/RASSI calculations were performed to explore the effect of the difference in the second ligand to the ligand centred excited states and the ligand-field-splitting structure on the metal-centred ground multiplet of J = 6.

Synthesis, structure, phase controlled colour tuning of dinuclear Pr(III) and Tb(III) complexes with fluorinated β-diketone and heterocyclic Lewis base as UV light converters

Heteroleptic homo dinuclear complexes, [Pr(fod)3(μ-bpp)Pr(fod)3] and [Tb(fod)3(μ-bpp)Tb(fod)3] (fod is the anion of 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione (Hfod) and bpp is 2,3-bis(2-pyridyl)pyrazine) have been synthesized and thoroughly characterized. The 1H NMR spectra of the complexes are consistent with the dinuclear complex formation. In the absorption spectra, the 3P2 ← 3H4, 3P1 + 1I6 ← 3H4 and 1D2 ← 3H4 transitions of Pr(III) complex show considerable sensitivity towards the host medium and prominent stark splitting of these transitions is observed in chloroform and dichloromethane. The effect of phase change on photophysical properties of Pr(III) and Tb(III) complexes is investigated by observing the steady state and time resolved fluorescence spectra of the solid complexes, their solutions and PMMA doped thin hybrid films. Intense emission is observed for the PMMA doped hybrid materials of the complexes. In the case of [Pr(fod)3(μ-bpp)Pr(fod)3] complex doped PMMA, additional emission peaks are observed from the high energy excited states (3P2, 1I6, 3P1 and 3P0), indicating that the PMMA facilitates emission from the higher emitting levels. The emitting colour of Pr(III) complex shows phase dependence with the emission of blue and purple light in the solutions, orange in solid state and in the case of PMMA doped hybrid films at a doping concentration of 5 % and 10 %, the Commission Internationale de l'Eclairage (CIE) colour coordinates are in the white region x = 0.351, y = 0.377 and light blue region x = 0.313, y = 0.319, respectively. Intense green light emission is observed for the terbium complex in all media. The semiempirical theoretical tool of Sparkle/PM7 has been used for obtaining the geometry of the complexes.

Thermal Dependence of the Luminescent Properties of Mononuclear TbIII Macrocyclic Complexes

AbstractA family of six terbium(III) complexes with hexaaza macrocyclic ligands, together with the isostructural yttrium(III) species, is reported and the thermal dependence of the photophysical properties of the terbium(III) complexes is analysed. The coordination number is defined by the anions, nitrate or isothiocyanate, which act as secondary ligands. While complexes with nitrate anions are decacoordinated species, presenting a N6O4 first coordination sphere, complexes derived from isothiocyanate are nonacoordinated with exclusively nitrogen donor atoms. Regarding the optical properties, only the macrocyclic ligands derived from aliphatic amines act as sensitizers for the terbium(III) cations, and the complexes emit in the green region, according to the obtained CIE coordinates. The isothiocyanato ligand plays a detrimental role on the luminescence of the corresponding complexes, since their emission is weaker as compared to that of the nitrato counterparts. The greater achieved thermal sensitivity for one of the studied terbium(III) complexes was 3.2 %K−1 at 300 K.

Lanthanide-based complexes as efficient physiological temperature sensors

A new molecular thermometric sensor based on the terbium(III) complex [C2mim][Tb(fod)4] (C2mim – 1-methyl-3-ethylimidazolium, fod− - tetrakis-6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate), doped with 0.015% of its europium(III) analogue (1, [C2mim][Tb(fod)4]0.99985:[C2mim][Eu(fod)4]0.00015), was prepared and its thermochromic behaviour evaluated from ambient temperature up to 75 °C, including in the physiological range (35–45 °C). It was found that the intensity ratio of the 5D4→7F5 (TbIII) and 5D0→7F2 (EuIII) transitions is correlated with temperature having three different linear regimes. Visual colorimetry allowed the evaluation of the temperature in different ranges from green at ambient temperature, to yellow and finally red at higher temperatures. The TbIII complex emission intensity is extremely sensitive to small temperature variations, particularly between 25 and 35 °C, were it reaches only 40% of the initial intensity.Confinement of the dopped TbIII tetrakis-complex in the organic polymeric matrix poly(methylmethacrylate) (PMMA) induced higher thermal stability in 1, together with a strong temperature dependence of the most intense emissive transition of the TbIII complexes. The photoluminescence quantum yield of polymer-lanthanide hybrid materials increased significantly compared with that of 1. Under 366 nm irradiation, the hybrid material presents a green colour at 25 °C that evolves to yellow at 30 °C and to a white tone at 35 °C.

Bright and stable luminescent probes for target engagement profiling in live cells.

The pace of progress in biomedical research directly depends on techniques that enable the quantitative interrogation of interactions between proteins and other biopolymers, or with their small-molecule ligands. Time-resolved Förster resonance energy transfer (TR-FRET) assay platforms offer high sensitivity and specificity. However, the paucity of accessible and biocompatible luminescent lanthanide complexes, which are essential reagents for TR-FRET-based approaches, and their poor cellular permeability have limited broader adaptation of TR-FRET beyond homogeneous and extracellular assay applications. Here, we report the development of CoraFluors, a new class of macrotricyclic terbium complexes, which are synthetically readily accessible, stable in biological media and exhibit photophysical and physicochemical properties that are desirable for biological studies. We validate the performance of CoraFluors in cell-free systems, identify cell-permeable analogs and demonstrate their utility in the quantitative domain-selective characterization of Keap1 ligands, as well as in isoform-selective target engagement profiling of HDAC1 inhibitors in live cells.

High-throughput sensor microtiter plate of new terbium complexes for the determination of anthracene in seawater

A new fluorescent sensing microtiter plate (MTP) was developed for high sensitivity monitoring of anthracene in seawater samples. For this purpose, two ternary complexes of Tb(III) ions with dibenzoylmethane and neocuproine [Tb(DBM)2(MePhen)] or with dibenzoylmethane and bathocuproine [Tb(DBM)2(PhMePhen)] were synthesized. Elemental analysis, energy dispersive X-ray analysis, X-ray diffraction, infrared and ultraviolet–visible emission, and thermal analysis were conducted on the Tb(III) complexes. The limits of detection (DL) were 0.14 and 1.05 μmol L−1 for [Tb(DBM)2(MePhen)] and [Tb(DBM)2(PhMePhen)], respectively. [Tb(DBM)2(PhMePhen)] MTP is embedded in a membrane made of cellulose acetate. The first high-throughput anthracene sensor MTP, based on [Tb(DBM)2(PhMePhen)] sensor showed a linear range, from 0.2 to 20 μmol L−1. [Tb(DBM)2(PhMePhen)] MTP was validated for accurate and precise monitoring of anthracene using gas chromatography. The selectivity of the [Tb(DBM)2(PhMePhen)] MTP toward anthracene was examined. The data indicated that [Tb(DBM)2(PhMePhen)] MTP is suitable for rapid and direct detection of anthracene.

Rational design of efficient nanosensor for glyphosate and temperature out of terbium complexes with 1,3-diketone calix[4]arenes

The temperature and substrate dependent luminescence of terbium complexes with calix[4]arene derivatives makes them promising building blocks of nanosensors. Thus, calix[4]arene 1,3-diketones in 1,3-alternate and cone isomeric forms bearing buthyl, dodecyl, nonyl and bromine substituents are introduced as ligands forming luminescent Tb3+ complexes in basified DMF solutions. The structure variation of the ligands allows to highlight buthyl-substituted derivative of calix[4]arene 1,3-diketone in 1,3-alternate isomeric form as the optimal structure. The detailed studies of the complex stoichiometry by means of UV-Vis and H1 NMR diffusion spectroscopy methods reveal 2:2 stoichiometry as the main for the calix[4]arene 1,3-diketones in 1,3-alternate isomeric form. The predominance of 2:2 over 1:1 and 1:2 (Tb:L) complex stoichiometries for the buthyl-substituted ligand was confirmed by comparison of the quantum chemically calculated thermochemical parameters of their complex formation. However, the 2:2 complex formation is either restricted for their dodecyl-substituted derivative or interferes with the 1:2 stoichiometry for the bromo-substituted counterpart. The conversion of the Tb3+ complexes from the DMF solutions to the PSS-stabilized colloids through the solvent-exchange procedure reveals the unfavorable effect of the nonyl- and dodecyl-substituted ligands on aggregation behavior of the colloids. Thus, 2:2 terbium complex with buthyl-substituted ligand in 1,3-alternate isomeric form is the optimal basis for production of the luminescent PSS-colloids with high colloid stability. The Tb3+- luminescence of the colloids exhibit the enhanced sensitivity to both environmental pollutant glyphosate with LOD = 1.97 nM and temperature changes within the physiological temperature range with SI = −4.67 K-% at 323 K.