Terbium Complexes Research Articles

Strongly toughened heat‐resistant cyanate ester resin‐based coatings doped by Tb3+‐complex anchored‐uCNTs with green fluorescent properties

AbstractThermally stable polymeric coatings are widely used for metal protection at high temperatures, but their brittle weakness makes them unavailable to durable environment. To overcome that, we report properties of cyanate ester resin (CER) coating doped with unzipped carbon nanotubes (uCNTs) loaded with terbium complex (TBP) as nanofiller. The performance of the coating showed that the bending flexibility, adhesion, and impact resistance of the doped coatings was significantly improved. The cylinder bending test showed that the minimal bending diameter of CER doped with TBP‐uCNTs coating reached 6 mm without failure, which represents a significant improvement compared to the pure CER coating (18 mm). Surprisingly, the impact resistance reached the highest value of 50 cm without any failure of the coating. X‐ray diffraction, Fourier transform infrared spectroscopy, Raman, x‐ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy studies of CNTs, uCNTS, TBP‐uCNTs, and properties of CER indicate that formation of CER/TBP‐uCNTs composite is supported by a chemical reaction between hydroxyl groups of TBP‐uCNTs and the cyanate groups of CER resulting in fabrication of a solid cross‐linked structure. The thermal decomposition temperature of the coating increases from 409°C for pure CER to 453°C for CER/TBP‐uCNTs. The fluorescence spectra show that CER/TBP‐uCNTs exhibits strong luminescence at 550 nm.

Synthesis and characterization of new organometallic lanthanides metal complexes for photodynamic therapy

New Schiff base ligand: 4-methoxy salicaldhyde-2-2-phenyl-hydrazono acetaldehíyde prepared by facile method. The molecular structures characterized by elemental analysis and proton magnetic resonance spectra (1H-NMR spectra). This spectra at the chemical shifts (3.5–10.39 ppm) confirmed the types and the numbers of protons. The sharp melting point at the range 110–112 °C confirmed purity. New optically active metal (samarium, terbium and gadolinium) complexes of the Schiff base synthesized in a one pot reaction. Vibrational IR spectra confirmed functional groups. Scanning electron microscopy micrographs confirmed that the modified microstructure of the metal complexes differed in morphology than the ligand. Powder X-ray diffraction patterns confirmed good crystalline structure. The optically activity of the solid metal complexes confirmed from electronic absorption spectra. The UV absorbance band at the wavelength range 280–390 nm and the intense phosphorescence bands up to 830 nm enabled application in photo dynamic therapy for apoptosis cancer cells by conversion triplet oxygen in the tissues into reactive singlet oxygen. Low charge transfer energy: 2.59–2.61 eV, high molar extinction coefficients (ε) at the order of magnitude \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{10}^{6}$$\\end{document} M− 1 cm− 1 and the intense phosphorescence bands reflected good photodynamic activity. The metal complexes are thermally stable.

Temperature Changes in Luminescence of Mixed Complexes of Terbium and Samarium with Organic Ligands Based on 2,2-bipyridyldicarboxamides

Solutions in acetonitrile of three mixed complexes of rare earth elements (terbium and samarium) with organic ligands with various pyridine substituents were studied in this work. The ratios of ligands and metals in the resulting complexes were determined, and the stability constants of samarium complexes were calculated using the spectrophotometric titration method. Measurements of absorption, emission and excitation spectra of luminescence, luminescence kinetics of solutions of mixed complexes of rare earth elements with an excess of metal relative to the ligand were carried out at various temperatures in the range 298–328 K. An increase of luminescence intensity of a samarium ion in complex upon heating has been discovered for the first time. The dependences of the luminescence quantum yield and lifetime of mixed complexes on temperature were obtained. A thermometric parameter — the ratio of the integral luminescence intensities of samarium and terbium ions — was proposed, and the temperature sensitivity coefficient of this parameter was determined for different complexes.

The interplay between structural features and the efficiency of the energy transfer process in terbium complexes with triarylcyclopentadienyl ligands

Terbium and gadolinium complexes with triarylcyclopentadienyl ligands having electron-donating methoxy substituents in the ortho- (CpPh2Ar−o) and para- (CpPh2Ar−p) positions of one of the phenyl rings have been synthesized. Different structural types, including tetranuclear [{CpPh2Ar−oTb (THF)}2 (μ2-Cl)2(μ3-Cl)3K (THF)]2 (Tb1), [{CpPh2Ar−oTb}2 (μ2-Cl)2 (μ3-Cl)3K]2 (Tb3), [{(CpPh2Ar−oTb)2 (μ2-Cl)3}2 (μ2-Cl)2] (Tb5), [{CpPh2Ar−pTb (THF)}2 (μ2-Cl)2 (μ3-Cl)3K (THF)]2 (Tb6), binuclear [{CpPh2Ar−oTb (THF)Cl}2 (μ2-Cl)2] (Tb4), [{CpPh2Ar−pTb (THF)}2 (μ2-Cl)2 (μ3-Cl)3K (THF)]2 (Tb7), [CpPh2Ar−p2Tb (μ2-Cl) (μ3-Cl)K]2 (Tb8) and mononuclear [CpPh2Ar−o2TbCl] (Tb2) complexes have been obtained and confirmed by single crystal X-ray diffraction analysis. All designed terbium complexes exhibit high quantum yields of the photoluminescence (up to 65 %). The introduction of a methoxy group into one of the phenyl rings of the triarylcyclopentadienyl ligand leads to a more than twofold increase in the quantum yield of the terbium ion luminescence. The estimated values of radiative rate krad of the terbium ion vary in the range of 0.23–0.69 ms. The presence of the methoxy group as well as the mutual disposition of the phenyl rings promotes the appearance of an intraligand charge transfer states involved in the energy transfer process. Due to a lowering of the energy of the interconfigurational 4f −5d transitions caused by the relatively strong crystal field of the Cp ligand in bis(cyclopentadienyl) terbium complexes, the quantum yield of the photoluminescence is high at the short lifetimes of the 5D4 level of the terbium ion.

Solvation structure and thermodynamics for Ln(III), (Ln = Pr, Nd, Tb, and Dy) complexes in phosphonium-based ionic liquids evaluated by Raman spectroscopy and DFT calculation

The coordination states of trivalent praseodymium, neodymium, terbium, and dysprosium complexes in triethyl-n-octylphosphonium bis(trifluoromethylsulfonyl)amide ([P2228][TFSA]) ionic liquid were examined using Raman spectroscopy. In [P2228][TFSA], the concentration dependence of lanthanide (Ln) ions on the Raman spectrum was investigated in the range of 0.24–0.48 mol kg−1 of Ln(III), (Ln = Pr, Nd, Tb, and Dy) in [P2228][TFSA]. Based on classical analysis, solvation numbers n of Ln(III) (Ln = Pr, Nd, Tb, and Dy) in [P2228][TFSA] were determined as 4.80 ± 0.04, 5.08 ± 0.03, 5.15 ± 0.04, and 4.92 ± 0.03, respectively, at 373 K.Based on the temperature dependence of the Raman spectrum measured at temperatures between 298 and 398 K, thermodynamic parameters with ΔisoG, ΔisoH, and ΔisoS for the isomerism of [TFSA]− from the trans- to the cis-coordinated isomer in the bulk and first solvation sphere of the centered Ln3+ (Ln = Pr, Nd, Tb, and Dy) cation in [P2228][TFSA] were evaluated in this study. As indicated by the positive value of ΔisoH(bulk) = 6.86 kJ mol−1, the trans-[TFSA]− was found to be the dominant contributor to enthalpy. In [P2228][TFSA], the value of TΔisoS(bulk) = 7.92 kJ mol−1 was slightly larger than that of ΔisoH(bulk), indicating that cis-[TFSA]− was entropy controlled. Conversely, in the first solvation sphere of the Ln3+ cation, ΔisoH(Ln) became significantly negative, indicating stabilization of cis-[TFSA]− isomers via enthalpic contributions. This result clearly indicates that the cis-[TFSA]− conformer bound to Ln3+ cation is the preferred coordination state of [Ln(III)(cis–TFSA)5]2− in [P2228][TFSA], because ΔisoH(Ln) contributes to a significant decrease in ΔisoG(Ln).Furthermore, DFT calculations using the Amsterdam Density Functional package were used to investigate the optimized geometries and binding energies of [Ln(III)(cis-TFSA)5]2−, (Ln = Pr, Nd, Tb, and Dy) clusters. The bonding energy, ΔEb, was calculated as ΔEb = Etot(cluster) − Etot(Ln3+) − nEtot([TFSA]−), and ΔEb ([Ln(III)(cis-TFSA)5]2−), (Ln = Pr, Nd, Tb, and Dy) were calculated as −4349.2 ± 7.2, −4354.6 ± 7.6, −4278.6 ± 7.2, and −4296.4 ± 7.8 kJ mol−1, respectively. The thermodynamic properties were consistent with the average atomic charges and bond distances of these clusters. Additionally, the highest occupied molecular orbital and lowest unoccupied molecular orbital estimated from DFT methods were consistent with the coordination states of [Ln(III)(cis-TFSA)5]2−, (Ln = Pr, Nd, Tb, and Dy) analyzed by Raman spectroscopy.

Cathodoluminescence of terbium coordination compounds

The cathodoluminescence (CL) of terbium coordination compounds is studied in order to establish its correlation to photoluminescence (PL), as well as to increase its intensity and stability over time. A special setup was designed for this purpose. It is found that terbium complexes anionic carboxylate ligands, as well as NO3, and neutral ligands of different nature display luminescence of various intensities under excitation by fast electrons. Their spectra contain only characteristic narrow bands of terbium f–f transitions. Terbium terephthalate shows the highest CL intensity, as well as high stability over time.

Synthesis and Characterization of Folic Acid-Conjugated Terbium Complexes as Luminescent Probes for Targeting Folate Receptor-Expressing Cells.

Several conjugates between folic acid and a series of kinetically stable lanthanide complexes have been synthesized, using amide coupling and azide-alkyne cycloaddition methodologies to link the metal-binding domain to folate through a variety of spacer groups. While all these complexes exhibit affinity for the folate receptor, it is clear that the point of attachment to folate is essential, with linkage through the γ-carboxylic acid giving rise to significantly enhanced receptor affinity. All the conjugates studied show affinities consistent with displacing biological circulating folate derivatives, 5-methyltetrahydrofolate, from folate receptors. All the complexes exhibit luminescence with a short-lived component arising from ligand fluorescence overlaid on a much longer lived terbium-centered component. These can be separated using time-gating methods. From the results obtained, the most promising approach to achieve sensitized luminescence in these systems requires incorporating a sensitizing chromophore close to the lanthanide.

Syntheses, characterization, luminescent and magnetic properties of polymer bifunctional fibers containing terbium complexes and Fe3O4 nanoparticles

The combination of electrospun nanofibers and nanoparticles is opening up potential in the field of bifunctional materials. Herein, polystyrene (PS, Mw ≈ 260, 000), polyvinyl pyrrolidone (PVP, Mw ≈1, 300, 000), and poly(methyl methacrylate) (PMMA, Mw ≈ 350, 000) bifunctional fibers containing Tb(acac)3phen complexes (acac: acetylacetone, phen: 1,10-phenanthroline) and Fe3O4 nanoparticles (NPs) were synthesized by single-fluid electrospinning method. The structure of bifunctional microfibers was characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy spectrum (EDAX) and infrared spectrum (IR). The average diameters of PS, PVP and PMMA bifunctional fibers are 1.65, 0.313 and 0.571 μm, respectively. The TEM images indicated that Fe3O4 NPs were successfully incorporated into bifunctional fibers. No absorption peaks of terbium complexes and Fe3O4 NPs can be seen in the IR spectra of bifunctional fibers. The luminescent and magnetic properties of bifunctional fibers were also investigated. Due to the change of ligands environment, the main excitation peaks blue shifted about 5–8 nm in the bifunctional fibers. Bifunctional fibers exhibited characteristic emission of Tb3+ ions. The polymers have no effect on the fluorescence lifetimes of terbium complexes. All bifunctional fibers were soft ferromagnetic. In addition, mechanical performances of these nanofibers were also studied. The maximum stress, strain corresponding to the maximum stress and elastic modulus of sample PVP-Fe-Tb is the largest, which indicates that the tensile performance of sample PVP-Fe-Tb is the best.

Temperature Changes in Luminescence of Mixed Complexes of Terbium and Samarium with Organic Ligands Based on 2,2$${}^{\boldsymbol{\prime}}$$-bipyridylcarboxamides

Temperature Changes in Luminescence of Mixed Complexes of Terbium and Samarium with Organic Ligands Based on 2,2$${}^{\boldsymbol{\prime}}$$-bipyridylcarboxamides

Quantitative Structure-Property Relationship of the Rare-Earth Elements-Dibutyl Dithiophosphate Derivative Complexes Using Principal Component Analysis

The separation of rare-earth elements (REEs) has increasingly developed, especially using a complexing ligand of dibutyl dithiophosphate (DBDTP) that has numerous advantages as an extractant in the extraction process. Through technology development, this separation utilizes computational chemistry design to scheme the DBDTP ligand and its derivatives. One of the computational chemistry applications is a quantitative structure-property relationship (QSPR), which is useful for designing ligand derivatives by calculating molecular descriptors and connecting molecular structure with its physicochemical properties. In the present study, we aimed to get a dominant factor affecting complex stability formed from the REEs with DBDTP ligands and the REEs with DBDTP derivative ligands using principal component analysis for the QSPR study. The analysis results demonstrated that the stability of gadolinium, terbium, and dysprosium complex compounds was influenced by seven, seven, and six factors with a total variance of 93.93, 93.17, and 91.63%, respectively.

Polymer-Based Terbium Complex as a Fluorescent Probe for Cancer Antigen 125 Detection: A Promising Tool for Early Diagnosis of Ovarian Cancer.

A novel photoprobe, Tb-acetylacetone (Tb-ACAC) doped within a modified epoxy cellulose polymer immobilized with CA-125 monoclonal antibody, offers an accurate and highly selective method for early ovarian cancer (OC) diagnosis by detecting cancer antigen 125 (CA-125) in serum samples. This approach leverages quenching of the Tb-ACAC luminescence upon binding to CA-125. Characterization of the photoprobe film through UV-vis and fluorescence measurements confirmed the presence of Tb-ACAC within the polymer matrix. In aqueous solution (pH 6.8, λex = 365 nm), the characteristic emission band of Tb-ACAC at λem = 546.2 nm exhibited significant quenching upon CA-125 binding. This quenching effect enabled the sensitive and specific detection of CA-125 in diverse serum samples from OC patients, demonstrating the applicability, simplicity, and effectiveness of this novel approach.

Thermosensitive chameleon films based on polystyrene doped with complexes of europium(III) and terbium(III)

New complexes of Eu(III) and Tb(III) tris(β-diketonates) with Lewis bases were synthesized. The spin-coating technique was used to produce composite films consisting of polystyrene (PS) polymer doped with mixtures of Eu(III) and Tb(III) complexes with different ratio of luminophores. An increase in the content of the Tb(III) complexes in the 5 %Eu x%Tb films intensifies emission of both the Tb3+ and Eu3+ ions due to occurring intermolecular energy transfer and leads to a significant increase in photostability of the material (the loss of luminescence intensity ratio did not exceed 0.5 %/hour). These photostable films were characterized as potential luminescent temperature sensors. The temperature sensitivity of their luminescence intensity and lifetime was investigated in the range of 298–383 K. The maximum absolute sensitivity of the films reaches 6.00 µs/K and exceeds that of all known lanthanide-containing thermal sensors designed for measuring physiological temperatures. In combination with changeable luminescence colors of the films, such a sensitivity makes these materials promising colorimetric thermal sensors for in situ temperature measurements.

Binuclear TbⅢ complex used for the fluorescent detection of 2, 6-pyridindicarboxylic acid, an anthrax biomarker

Anthrax is a potentially highly lethal acute infectious disease caused by the zoonotic bacterium Bacillus anthracis, which poses a threat to human life and health. 2, 6-Pyridinedicarboxylic acid (DPA) is a significant component of bacterial spores as a typical anthrax biomarker. Therefore, it is imperative to develop a simple and efficient detection method for DPA. Here, we successfully synthesized a binuclear terbium complex with formulas [Tb2(DMOMP)2(CH3OH)2(H2O)4Cl2]·2Cl·2CH3OH, which is constructed by 2, 6-dimethoxy-4-methylphenol (DMOMP) and TbⅢ ion. Each TbⅢ ion center is encapsulated by seven O atoms and one Cl− anion. Based on this, the encapsulated coordination environment facilitated efficient ligand energy transfer via the “antenna effect”. Therefore, the complex exhibits interesting luminescence response characteristics, with fast and stable green fluorescence response to DPA, low detection limit Ksv = 1.08 × 10−5 M−1, and fluorescence lifetime τ = 754.93 μs. [Tb2(DMOMP)2(CH3OH)2(H2O)4Cl2]·2Cl·2CH3OH has excellent fluorescence properties and strong immunity to interference and is capable of sensitively detecting the B. anthracis biomarker DPA, allowing it to be potentially used as an effective fluorescent probe and providing a viable strategy for effective anthrax fever prevention.

Structural regulation and luminescence properties of Tb/Zn-Tb complexes based on aliphatic ether Schiff base

Three new Tb(III) complexes containing bis(N-3-methoxysalicylidene)-3- oxapentane-1,5-diamine (H2L) ligand, [Tb(H2L)(NO3)3] (1), [ZnTbL(NO3)2(OAc)(MeOH)] (2), [Zn4Tb2L4(TP)2](NO3)2·DMF (3) (DMF = N,N-dimethylformamide, TP = terephthalate) have been synthesized by ether diffusion and structurally characterized. Complex 1 is a mononuclear, whereas complex 2 forms a heterodinuclear Zn-Tb cluster when introducing zinc ion into the reaction system of Complex 1. Complex 3 is a Zn-Tb heterohexanuclear cluster by adding terephthalic acid into the reaction system of complex 2. Solid-state luminescence studies show that the luminescence peaks of the ligand (π*→π) in the three complexes have undergone significant redshift and enhancement, which may be attributed to the coordination of ligand with metal ions. Moreover, the characteristic emission peak of terbium ions (5D4→7F5, at 545 nm for 2 and 546 nm for 3) appeared in heteronuclear complexes 2 and 3, while complex 1 did not. This indicates that the aliphatic ether Schiff base ligand cannot sensitize terbium ion to luminescence, while the zinc Schiff base complex [ZnL] unit can sensitize terbium ion to luminescence. Finally, the structures and luminescence properties of terbium complexes can be adjusted by the introduction of zinc(II) ion and co-ligand.

Preparation, spectroscopic and anticancer investigations of metal-drug complexes associated between flumequine antibiotic drug with lanthanum(III), samarium(III) and terbium(III) chloride

Flumequine ligand (FLQ) metal complexes of the [M(FLQ)2(Cl)(H2O)].nH2O type, where M are (La(III), Sm(III), and Tb(III)) and FLQ is flumequine have been synthesized. The FLQ metal complexes could be prepared using MCl3 : flumequine in stoichiometry of 1:2 in situ bidentate chelation. The characterization of FLQ complexes obtained have been done using elemental analyses (%C, %H and %N), molar conductivity (Ʌm), infrared spectroscopy (FTIR), electronic spectra (UV-Vis), thermal analysis (TGA), and physicochemical techniques such as X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) measurements at room temperature. Accordingly, these complexes are indicative of an octahedral coordination structure. Flumequine ligand has a bidentate fashion through the oxygen atoms of carbonyl (quinolone) and carboxylic groups. The findings demonstrated the anti-cancer efficacy of these compounds against HepG-2 and MCF-7 cancer cell lines at extremely low doses of up to 58.2 mg/mL. The La(III) complex was shown to have the highest selectivity against cancer cells in comparable with both samarium and terbium(III) complexes.
 KEY WORDS: Flumequine, Lanthanide metal ions, FTIR, EDX, Complexation, Anticancer activity
 Bull. Chem. Soc. Ethiop. 2024, 38(3), 671-684. 
 DOI: https://dx.doi.org/10.4314/bcse.v38i3.10

Examination of the spectroscopic characteristics of bright green emitting, octa coordinated luminescent terbium (III) complexes

Mononuclear heteroleptic green emissive Tb(III) complexes were synthesized utilizing 1,3-diketone and N-based bidentate auxiliary ligands. The structural and photoluminescence characteristics were analyzed employing various spectroscopic and analytical techniques. Band gap values obtained from optical and cyclovoltammetric studies were found in good alignment with each other, illustrating their semiconducting behavior and thereby their potential applications in fabrication of photocells and photovoltaic. The photoluminescent spectra of T1 – T4 complexes exhibited distinct peaks at about 491, 547, 583 and 622 nm. The green emission in these complexes can be attributed to the emission peak observed at approximately 547 nm, which arises from the 5D4→7F5 transition. The thermal investigation revealed their high thermal stability, which further indicates their potential utilization in display devices.

Complexation of Europium(III) and Terbium(III) Ions with Terephthalic Acid in Aqueous Solutions

Complexation of Europium(III) and Terbium(III) Ions with Terephthalic Acid in Aqueous Solutions

Highly efficient co-doped blue phosphorescent organic electroluminescent devices due to improved carriers balance and broadening recombination zone

High performance blue phosphorescent organic electroluminescent devices were realized by utilizing trivalent terbium complex and iridium complex as co-dopant and emitter, respectively. In this case, the co-doped trivalent terbium complex molecules within light-emitting layer function as deeper electron trappers due to its low-lying energy levels. Compared with reference device, co-doped devices displayed relatively higher electroluminescent performances due to improved carriers’ balance as well as broadening recombination zone. Finally, the optimal device with main emission peak at 462 nm obtained the maximum brightness, external quantum efficiency, current efficiency and power efficiency up to 24396 cd/m2, 26.3%, 46.93 cd/A and 50.82 lm/W, respectively. Meanwhile, even at the practical brightness of 1000 cd/m2 (4.3 V), prominent external quantum efficiency and current efficiency as high as 24.0% and 40.73 cd/A, respectively, can still be retained because the broadening recombination zone helps to decrease exciton density thus suppress exciton quenching.

Tridentate Nitrogen Ligand as a Tool for the Construction of Well-Defined Rare Earth Trichloride Complexes.

LnCl3(THF)3 (Ln = Y, La ÷ Nd, Sm ÷ Lu) readily react with the tridentate 1,3,5-trimethyl-1,3,5-triazacyclohexane (Me3tach) ligand to form mono- or binuclear lanthanide trichloride complexes, depending on the stoichiometry of the reaction and the ionic radius of the metal: mononuclear pseudosandwich [LnCl3(Me3tach)2], (Ln = Y, La ÷ Ho) or binuclear complexes [Ln2Cl6(Me3tach)3], or [LnCl3(Me3tach)(THF)]2 (Ln = Sm, Tb). Detailed analysis of the NMR data of [LnCl3(Me3tach)2] complexes with paramagnetic lanthanide ions showed that their structures remained unchanged in the toluene solution. A series of isomorphous complexes [LnCl3(Me3tach)(Py)2] (Ln = La, Sm, Tb, Er, Lu; Py = pyridine) have been obtained by the recrystallization of either mononuclear or binuclear complexes from pyridine. Complexes of terbium and europium ions with the Me3tach ligand exhibit relatively high quantum yields of metal-centered luminescence (0.39 and 0.32, respectively).

Combined performance of circularly polarized luminescence and proton conduction in homochiral cadmium(ii)–terbium(iii) complexes

A pair of Cd2Tb enantiomers shows coexsistence of CPL-active and proton conductive properties, offering a promising strategy for the development of multifunctional materials.