Lanthanide Ions Research Articles

Unearthing the Real-Time Excited State Dynamics from Antenna to Rare Earth Ions Using Ultrafast Transient Absorption.

The conventional energy transfer pathway in organic lanthanide complexes is purported to be from the excited singlet state of the chromophore to the triplet state and subsequently directly to the emitting state of the trivalent lanthanide ion. In this work, we found that the energy transfer occurs from the triplet state to the nearest energy level, instead of directly to the emitting state of the lanthanide ion. The triplet decay rate for different lanthanide ions follows an energy gap law from the triplet level to the receiving level of the lanthanide ion. Three different categories of complexes were synthesized and inspected using different techniques, demonstrating the universality of our findings. This work renews the insights to conventional findings, highlighting the importance of the energy gap between the triplet state and the nearest lanthanide energy level in optimization of light harvesting. The rationale of ligand design of chromophores should be reconsidered, leading to various applications of lanthanide complexes with enhanced quantum yield and brightness.

Structure and photoluminescence properties of coordination compound [Eu2(o-MBA)6(phen)2] with high quantum yield

An europium(III) coordination binuclear compound [Eu2(o-MBA)6(phen)2] (o-MBA = ortho-methylbenzoate, phen = 1,10-phenantroline) has been synthesized and investigated by X-ray diffraction method, thermogravimetric analysis (TGA), infrared (IR) and photoluminescence (PL) spectroscopy. The single crystal X-Ray diffraction measurements show that the compound crystallizes in the triclinic centrosymmetric space group P-1. The PL excitation spectrum displays a broad band between 300 and 420 nm and a number of sharp transitions between 384 and 590 nm, which can be attributed to the Eu3+ 4f6 intra-shell excitation transitions. The complex exhibits characteristic narrow, metal-centred emission bands, which are determined by the radiative transitions of the Eu3+ ion, from the first excited non-degenerate 5D0 level to the 7FJ (J = 0–4) manifold. The compound shows intense hypersensitive transition 5D0→7F2 which dominates the PL emission spectrum. The dipole strengths of the transitions were determined from the emission spectra in terms of Judd-Ofelt (JO) intensity parameters Ωλ (λ = 2, 4). The high intensity bright-red emission of the complex can be attributed to highly polarizable ligands environment and the low site symmetry (Ci) around the lanthanide ions. We suppose that the J-mixing effect in the Eu(III) ions is responsible for enhanced peak maximum of the 5D0→7F0 transition.

Low-potential anodic electrochemiluminescence of terbium metal-organic frameworks for selective microRNA-155 detection

High excitation potential is recognized as a harmful factor for the biological activity of biomacromolecules, such as proteins and nucleic acids, in electrochemiluminescence (ECL) biosensing. Developing low-potential ECL luminophores is vital for improving ECL accuracy in actual sample sensing. In this work, based on porous metal-organic framework (MOF) structure with multiple active sites and energy transfer between the excited ligands and Ln nodes, we designed a series of Ln-MOFs and observed ECL emission at low potential, providing a novel method to realize low-potential ECL. The MOF nanoemitters were prepared using 1,3,5-tri (4-carboxyphenyl)benzene ligand and several lanthanide ions as nodes through mild hydrothermal reaction. Interestingly, strong ECL emission at +0.75 V of peak potential was observed in the ECL-potential curve of Tb-based MOF using 2,2′,2″-nitrilotriethanol as coreactant, which was beneficial for reducing background interference in biosensing, and this ECL emission was attributed to the energy transfer between Tb and excited ligand. This low-potential ECL was then applied to construct an ECL biosensor with newly developed Cas12a-based method for selective detection of microRNA-155 without the help of strand displacement or reverse transcription. For this ECL system, the limit of detection was 0.78 nM, and the overall detection time was 2.5 h. The Ln-MOF nanoemitter provides a robust ECL platform to selectively detect various targets by integrating new bio-related techniques.

A few examples of cis trans isomerization in complexes involving the oxamide function

Synthesis of heterodinuclear 3d transition metal complexes in which two metal ions are introduced in equivalent coordination sites of a ligand is quite uncommon. We have previously shown that the application of the cis–trans isomerization of the oxamido group was able to furnish such a possibility. In the present paper we demonstrate that this synthetic pathway, relying on the possibility of changing the conformation (cis vs trans) of the oxamido group, can be extended to other ligands. Although we have not been able to characterize these complexes by structural determinations, FAB-MS, EPR and magnetic data do confirm the efficiency of this reaction pathway. We also demonstrate that the cis–trans isomerization of the oxamido group is not due to a particular property of the ion involved in the reaction. In fact, isomerization is governed by the basicity of the reaction medium. According to the reaction condition, it is possible to favor or not this phenomenon, and to increase the accessibility to a larger number of novel genuine complexes. But the oxophilic character of the lanthanide ions limits the use of this synthetic pathway because it impedes this isomerization. Eventually, the very weak magnetic interactions observed in these Cu-Gd complexes can be explained thanks to spin polarization.

Recent progress in lanthanide-based fluorescent nanomaterials for tetracycline detection and removal.

Tetracycline (TC) has been widely used in clinical medicine and animal growth promotion due to its broad-spectrum antibacterial properties and affordable prices. Unfortunately, the high toxicity and difficult degradation rate of TC molecules make them easy to accumulate in the environment, which breaks the ecological balance and seriously threatens human health. Rapid and accurate detection of TC residue levels is important for ensuring water quality and food safety. Recently, fluorescence detection technology of TC residues has developed rapidly. Lanthanide nanomaterials, based on the high luminescence properties of lanthanide ions and the high matching with TC energy levels, are favored in the real-time trace detection of TC due to their advantages of high sensitivity, rapidity, and high selectivity. Therefore, they are considered potential substitutes for traditional detection methods. This review summarizes the synthesis strategy, TC response mechanism, removal mechanism, and applications in intelligent sensing. Finally, the development of lanthanide nanomaterials for TC fluorescence detection and removal is reasonably summarized and prospected. This review provides a reference for the establishment of a method for the accurate determination of TC content in complex food matrices.

Elucidating the Mechanism of Efficient Eu(III) and Yb(III) Sensitisation from a Re(I) Tetrazolato Triangular Assembly.

The reaction of Re(CO)5Br with deprotonated 1H-(5-(2,2':6',2''-terpyridine)pyrid-2-yl)tetrazole yields a triangular assembly formed by tricarbonyl Re(I) vertices. Photophysical measurements reveal blue-green emission with a maximum at 520 nm, 32 % quantum yield, and 2430 ns long-lived excited state decay lifetime in deaerated dichloromethane solution. Coordination of lanthanoid ions to the terpyridine units red-shifts the emission to 570 nm and also reveals efficient (90 %) and fast sensitisation of both Eu(III) and Yb(III) at room temperature, with a similar rate constant kET on the order of 107 s-1. Efficient sensitisation of Eu(III) from Re(I) is unprecedented, especially when considering the close proximity in energy between the donor and acceptor excited states. On the other hand, comparative measurements at 77 K reveal that energy transfer to Yb(III) is two orders of magnitude slower than that to Eu(III). A two-step mechanism of sensitisation is therefore proposed, whereby the rate-determining step is a thermally activated energy transfer step between the Re(I) centre and the terpyridine functionality, followed by rapid energy transfer to the respective Ln(III) excited states. At 77 K, the direct Re(I) to Eu(III) energy transfer seems to proceed via a ligand-mediated superexchange Dexter-type mechanism.

(Invited) Near-Infrared Triggered Theranostics

In the last decade, the field of luminescent lanthanide doped nanoparticles has had a meteoric rise, progressing from the basic understanding of the photophysical properties governing their nanoscale luminescence, in particular upconversion, to their use in a plethora of applications, with considerable focus in biology and medicine. This interest stems primarily from the ability to stimulate these luminescent nanoparticles with near-infrared (NIR) light as well as their diverse emission wavelengths spanning the UV to the NIR. Therefore, with a single NIR excitation wavelength, it is possible to observe higher energy multiphoton luminescence, known as upconversion, or single photon NIR emission (known as down-shifted luminescence). The former upconversion process proceeds through the sequential absorption of multiple NIR photons through the long-lived 4f electronic energy states of the tri-positive lanthanide ions. As a result, upconversion is several of orders more efficient than conventional multiphoton absorption processes. This is especially interesting for applications in theranostics (therapy + diagnostics on the same platform) where the upconverted light can be used to trigger another light activated modality (therapy) while the NIR luminescence can be used for bioimaging and nanothermometry (diagnostics). Here, we present our work on the synthesis and development of various NIR excited (and emitting) core/shell lanthanide-doped nanostructures/nanoplatforms and demonstrate how their various emissions could be harnessed for applications in biology and nanomedicine.

Octocrylene carboxylate as an antenna in a luminescent Europium(III) complex: Experimental and theoretical insights

A new carboxylic acid, 2-cyano-3,3-diphenyl-2-propenoic acid, CLN, a chromophore ligand, was obtained by an alkaline hydrolysis reaction from the octocrylene, a commercial type B ultraviolet (UVB) radiation absorber. The CLN structure was elucidated by single-crystal X-ray diffraction (SCXRD) as being tetragonal with space group P4‾21/c and the presence of a carboxylic acid group was confirmed by mass, infrared (IR), and proton nuclear magnetic resonance (1H NMR) spectroscopy. In this way, coordination compounds were developed between CLN and Ln(III), Ln = being Gadolinium (Gd) and Europium (Eu), with a stoichiometry of 4:13 metal:ligand, confirmed by thermal and elemental analyses, corroborating with the metal cluster predicted by Sparkle/AM1 semi-empirical model. Photoluminescence data indicated that Eu(III) is efficiently sensitized by CLN due to its triplet excited state, determined using the emission spectrum of the Gd(III) mimic complex (T = 25,477 cm−1), being suitable for this purpose. Therefore, the emission spectrum of the Eu(III) complex exhibited a 5D0 → 7FJ transitions characteristic of the lanthanide ion. Furthermore, the Judd-Ofelt intensity parameters, the radiative and non-radiative decay rates, and the intrinsic quantum yield evaluated using the software LUMPAC software were in good agreement with the experimental values.

A De Novo Metalloenzyme for Cerium Photoredox Catalysis.

Cerium photoredox catalysis has emerged as a powerful strategy to activate molecules under mild conditions. Radical intermediates are formed using visible light and simple complexes of the earth-abundant lanthanide. Here, we report an artificial photoenzyme enabling this chemistry inside a protein. We utilize a de novo designed protein scaffold that tightly binds lanthanide ions in its central cavity. Upon visible-light irradiation, the cerium-dependent enzyme catalyzes the radical C-C bond cleavage of 1,2-diols in aqueous solution. Protein engineering led to variants with improved photostability and metal binding behavior. The photoenzyme cleaves a range of aromatic and aliphatic substrates, including lignin surrogates. Surface display of the protein scaffold on Escherichia coli facilitates whole-cell photobiocatalysis. Furthermore, we show that also natural lanthanide-binding proteins are suitable for this approach. Our study thus demonstrates a new-to-nature enzymatic photoredox activity with broad catalytic potential.

Lanthanide-based F-MOFs: Structure, hydrolytic stability, spectral and magnetic properties

A series of five novel lanthanide-based fluorinated metal-organic frameworks (Ln-F-MOFs) have been synthesized under solvothermal conditions by the reaction of 3,3′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-dicarboxylic acid (H2L) and lanthanide Ln(III) ions (Ln(III)La, Ce, Pr, Nd and Eu). Powder X-ray diffraction (PXRD) analysis revealed that all prepared complexes are isostructural. A single-crystal X-ray crystallographic study of one representative of the isostructural group, namely {[La2(L)3(DMF)2(H2O)2]}n showed, that compound crystallizes in a triclinic system with space group P-1. The lattice parameter values are a = 8.563(2) Å, b = 13.199(3) Å, c = 16.008(4) Å, α = 104.588(7) °, β = 92.904(7) ° and γ = 92.717(7) °, with two formula units in the unit cell. The overall structure is formed by 2D polymeric layers, which are arranged into a semi-3D supramolecular structure through hydrogen bonds and other intramolecular interactions. The study of the hydrophobic properties of the complexes showed that the complexes exhibit surface hydrophobicity with a “rose petal effect” and a contact angle of approximately 107°. However, the structures are not hydrolytically stable in the long term and the structure starts to delaminate after two days in water. This is a manifestation of the fact that the complexes do not form a 3D polymer network, it is made up of 2D layers connected only by weak non-bonding interactions. The photoluminescence properties of the Ln(III) complexes are determined by the characteristic 5d-4f or 4f-4f electron transitions for the individual lanthanide ions. The magnetic properties of Nd(III), Pr(III) and Eu(III) variants were studied. The magnetic properties of {[Pr2(L)3(DMF)2(H2O)2]}n are characterized by the presence of a low-lying quasi-doublet with 15.6 cm−1 energy splitting, whereas Eu(III) variant is nonmagnetic at low temperatures, but the magnetic 7F1 state is accessible by thermal excitation. For Nd(III) complex, the X-band EPR measurements were performed. Since 1D channels with dimensions of 4.90 × 7.23 Å2 are present within the structure, the adsorption of N2, CO2 and H2 gases was also studied.

Salicylic Acid-Modified Sm-TiO2 for Photoluminescence and Photocatalysis under Real Sunlight: Synergistic Effects between Ligand-to-Metal Charge Transfer (LMCT) and Sm3+ Dopant.

A salicylic-acid (SA)-modified samarium-doped TiO2 complex (Sm-TiO2/SA) was synthesized via a sol-gel method followed by impregnation. A Raman Fourier transform IR and X-ray photoelectron spectroscopic study showed that SA (as an electron donor) forms a surface complex on the Sm-TiO2 surface through its phenolic/carboxylic functional groups. In the Sm-TiO2/SA complex, a ligand-to-metal charge transfer (LMCT) is active, inducing a marked red-shift in the absorption spectrum of TiO2, which extends to 550-600 nm. The synergetic effect between the LMCT process and the luminescent properties of the lanthanide ions (Sm3+) is discussed and supported by the photoluminescence spectra. Further photocatalytic experiments (under sunlight) and the study of the effect of different scavengers show the presence of competitive reactions between de-ethylation and cleavage of Rhodamine B (RhB) during its degradation. With the Sm-TiO2/SA complexes, the superoxide radical ion (O2 •-) is the main active species responsible for the N-de-ethylation pathway under sunlight irradiation. The cleavage of RhB by the hydroxyl radical (•OH) appears, instead, to dominate with the Sm-TiO2 photocatalysts.

Controlled labelling of tracer antibodies for time-resolved fluorescence-based immunoassays

Tracer antibodies, which are labelled with fluorescent or other type of reporter molecules, are widely employed in diagnostic immunoassays. Time-resolved fluorescence immunoassay (TRFIA), recognized as one of the most sensitive immunoassay techniques, utilizes tracers labelled with lanthanide ion (Ln) chelates. The conventional approach for conjugating isothiocyanate (ITC) Ln-chelates to antibodies involves random chemical targeting of the primary amino group of Lys residues, requiring typically overnight exposure to an elevated pH of 9–9.3 and leading to heterogeneity. Moreover, efforts to enhance the sensitivity of the assays by introducing a higher number of Ln-chelates per tracer antibody are associated with an elevated risk of targeting critical amino acid residues in the binding site, compromising the binding properties of the antibody. Herein, we report a method to precisely label recombinant antibodies with a defined number of Ln-chelates in a well-controlled manner by employing the SpyTag/SpyCatcher protein ligation technology. We demonstrate the functionality of the method with a full-length recombinant antibody (IgG) as well as an antibody fragment by producing site-specifically labelled antibodies for TRFIA for cardiac troponin I (cTnI) detection with a significant improvement in assay sensitivity compared to that with conventionally labelled tracer antibodies. Overall, our data clearly illustrates the benefits of the site-specific labelling strategy for generating high-performing tracer antibodies for TRF immunoassays.

6-(6-Methyl-1,2,4,5-Tetrazine-3-yl)-2,2'-Bipyridine: A N-Donor Ligand for the Separation of Lanthanides(III) and Actinides(III).

Here, we report the synthesis of the 6-(6-methyl-1,2,4,5-tetrazine-3-yl)-2,2'-bipyridine (MTB) ligand that has been developed for lanthanide/actinide separation. A multimethod study of the complexation of MTB with trivalent actinide and lanthanide ions is presented. Single-crystal X-ray diffraction measurements reveal the formation of [Ce(MTB)2(NO3)3], [Pr(MTB)(NO3)3H2O], and [Ln(MTB)(NO3)3MeCN] (Ln = Nd, Sm, Eu, Gd). In addition, the complexation of Cm(III) with MTB in solution was studied by time-resolved laser fluorescence spectroscopy. The results show the formation of [Cm(MTB)1-3]3+ complexes, which occur in two different isomers. Quantum chemical calculations reveal an energy difference between these isomers of 12 kJ mol-1, clarifying the initial observations made by time-resolved laser fluorescence spectroscopy (TRLFS). Furthermore, quantum theory of atoms in molecules (QTAIM) analysis of the Cm(III) and Ln(III) complexes was performed, indicating a stronger covalent contribution in the Cm-N interaction compared to the respective Ln-N interaction. These findings align well with extraction data showing a preferred extraction of Am and Cm over lanthanides (e.g., max. SFAm/Eu = 8.3) at nitric acid concentrations <0.1 mol L-1 HNO3.

Six-Coordinated CoII Single-Molecule Magnets: Synthetic Strategy, Structure and Magnetic Properties.

The pursuit of molecule-based magnetic memory materials contributes significantly to high-density information storage research in the frame of the ongoing information technologies revolution. Remarkable progress has been achieved in both transition metal (TM) and lanthanide based single-molecule magnets (SMMs). Notably, six-coordinated CoII SMMs hold particular research significance owing to the economic and abundant nature of 3d TM ions compared to lanthanide ions, the substantial spin-orbit coupling of CoII ions, the potential for precise control over coordination geometry, and the air-stability of coordination-saturated structures. In this review, we will summarize the progress made in six-coordinated CoII SMMs, organized by their coordination geometry and molecular structure similarity. Valuable insights, principles, and new mechanism gleaned from this research and remaining issues that need to be addressed will also be discussed to guide future optimization.

Newly synthesised diglycolamide functionalised silica gel with terminal 2-ethylhexyl alkyl chain, Silica-DGA (2EH) having high ligand density for adsorption of trivalent actinide and lanthanide from acidic medium

A novel diglycolamide resin with 2-ethylhexyl terminal alkyl chain functionalised to silica gel was synthesised and characterised by ATR-FTIR, SEM, TG/DSC, &13C (CP/MAS) solid state NMR techniques. Effective functionalization of the organic ligand upon silica gel was confirmed from the two carbonyl stretching frequencies at 1735 cm−1 and 1619 cm−1 in the FTIR spectrum and carbonyl carbon atom signal at 170 ppm in 13C (CP/MAS) solid state NMR spectrum. Thermo gravimetric measurement showed 17.3 ± 0.2 % (W/W) weight loss corresponding to the ligand loading value of 425 µmol/g. The resin showed very high uptake of trivalent lanthanide and actinide ions from 4.0 M HNO3 medium and very low distribution of Cs & Sr; Kd ∼ 1.1×103 mL/g for Am(III), ∼ 1.41×103 mL/g for Eu(III), ∼2.5 mL/g for Sr and 1.53 mL/g for Cs. FTIR spectroscopic study of the Eu3+ adsorbed resin showed single carbonyl stretching frequency at 1654 cm−1, instead of the two carbonyl stretching frequencies in fresh silica-DGA(2EH) resin indicating complexation through carbonyl oxygen. Very low Kd of ∼1.2–5.1 mL/g for lanthanides/actinides from 4.0 M HNO3 containing water soluble DGA namely N, N, N, N, Tetraethyldiglycolamide (TEDGA) in the concentration range 0.3–0.1 M indicates 99 % back adsorption feasibility.

Intra-lanthanide separation performance of DOTP: Solid-phase extraction and selective precipitation studies

The applicability of 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetra(methylene phosphonic acid) (DOTP) for intra-lanthanide (Ln) separation was investigated through two approaches: the synthesis of inorganic–organic hybrid sorbents and selective precipitation in an aqueous solution. Hybrid sorbents combining zirconium oxide and DOTP were fabricated through post-synthetic grafting and hydrothermal synthesis. The successful syntheses were verified by FTIR and 31P magic-angle spinning (MAS) NMR spectroscopies. All the hybrid sorbents showed a lanthanide uptake of approximately 10–20 μmol/g at pH 3 and displayed only moderate selectivity, with the highest separation factor (SF) of about 10 for Lu3+ over La3+. In contrast, the selective precipitation of lanthanides by DOTP in an aqueous solution was successful in the presence of Cu2+. When a Cu-DOTP complex was introduced into a La/Lu equimolar solution, lanthanide ions were selectively precipitated with an SF of approximately 30–190. When the initial stoichiometry was set to Ln:Cu-DOTP = 8:1, roughly 95 % of the lanthanides in the precipitate were Lu3+, regardless of the pH ranging from 3 to 5. This precipitation process demonstrated selectivity even for adjacent lanthanide pairs. The selectivity is assumed to be a result of structural variations in the precipitates of Ln-Cu-DOTP, which is supported by the characterization results obtained from X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and UV–Vis spectroscopy. The findings presented in this study indicate that DOTP has the potential for use in the selective extraction of lanthanides, which may offer promising advancements in intra-lanthanide separation.

Negative thermal expansion enhanced upconversion emission in Y2Mo3O12:Er3+/Yb3+ phosphor

Volume shrinkage upon heating is an uncommon phenomenon known as negative thermal expansion (NTE). NTE host Y2Mo3O12 (YMO) codoped with Er3+/Yb3+ and Er3+/Yb3+/Li+ ions were successfully synthesized for upconversion (UC) emission and optical thermometry studies. Upconversion using 980 nm laser stimulation resulted characteristic emissions of Er3+ion. The Li + codoping enhanced the UC emissions at room temperature by modifying the local environment around lanthanide ions. UC emission of both the phosphors were recorded at increasing temperature from 301 to 773K. The YMO: Er3+/Yb3+ phosphor shows enhanced UC emission with temperature due to the NTE feature of host lattice. Whereas, no such enhancement in UC emissions was observed for YMO: Er3+/Yb3+/Li+. Further, FIR based optical thermometry was studied for YMO: Er3+/Yb3+ phosphor using 2H11/2 (522 nm) and 4S3/2 (546 nm) levels of Er3+ ion. The maximum absolute and relative sensitivities are determined to be 22.60 × 10−3 K−1 and 11.16 × 10−3 K−1 at 303 K respectively. Results indicate that prepared phosphor can be used in prevention of thermal quenching as well as in temperature sensors.

Highly efficient detection of aspirin using novel lanthanide-xanthan gum hydrogels

A commonly employed method for identifying aspirin involves the use of either HPLC or electrochemical analysis. In this article, a highly selective and ultrasensitive fluorescent sensor with convenient synthesis steps for the detection of aspirin was reported. This study introduced a novel hybrid organic-inorganic optical network hydrogel achieved through the integration of a complex of Tb-xanthan gum (XG) into the backbone of polyvinyl alcohol (PVA). This hydrogel fabricated in a water-based environment, exhibits weak green luminescence at the beginning owing to the chelation and sensitization of lanthanide (Tb3+) ions by ligands. Interestingly, the green emission intensity observed at λ ex = 346 nm, is enhanced by dual energy-transfer channels from XG and aspirin. We experimentally demonstrate that luminescent Tb3+-XG complex-binding aptamer hydrogels can selectively detect aspirin from 250 nM to 1 μM with a detection limit of 150 nM in this study. Furthermore, we discuss the resulting structure, thermal stability, excellent swelling properties, mechanical characteristics, and morphology of this light-emission material in detail. The success of this method will open up new opportunities for the use of hydrogels in visual fluorescence sensing applications.

Ultrafast synthesis and luminescence properties of rare earth orthoniobates RENbO4 (RE = La, Eu, Gd, Yb, Lu)

Rare earth orthoniobates (RENbO4) are one kind of important functional materials due to its applications in solid-state phosphors, thermal barrier coatings, and microwave dielectric ceramics. The synthesis of rare earth niobates often needs high reaction temperatures (1300 °C–1700 °C) and long processing times (from hours to tens of hours) in solid-state reactions, which can increase the study time of the relationship between structure and properties. In this work, we used ultrafast high-temperature sintering method to synthesize RENbO4 (RE = La, Eu, Gd, Yb, Lu), and found specific structure and properties in these materials obtained with specific synthetic techniques. Based on the electronegativity scale, the charge transfer energy of lanthanide ions in the YNbO4 crystal was calculated. The rapid synthesis of RENbO4 in a vacuum atmosphere generated more oxygen vacancies, and the structures of [REO8] and [NbO6] were distorted. The shortening of the fluorescence lifetime of LaNbO4 and EuNbO4 was related to the formation of self-trapped excitons facilitated by lattice distortion. The emission peak of LuNbO4 at about 530 nm is attributed to the oxygen vacancy in the niobate group. The reported synthetic methods can provide a fast materials screening route for high melting point inorganic materials.

Indole-derivative β-diketone samarium and terbium compounds modified by ancillary ligand: Syntheses, crystal structures, and photoluminescence properties

EIFD, LnCl3·6H2O (Ln = Sm, Tb) and ancillary ligand are developed to synthesize a sequence of six new β-diketone Sm-based and Tb-based compounds modified to enhance the photoluminescence property, namely Sm(EIFD)3(H2O)·CH2Cl2 (1), Sm(EIFD)3(bpy) (2), Sm(EIFD)3(phen)·CH2Cl2 (3), Tb(EIFD)3(H2O)·CH2Cl2 (4) and Tb(EIFD)3(bpy) (5), Tb(EIFD)3(phen)·CH2Cl2 (6) (EIFD: 1-(1-ethyl-1H-indol-3-yl)-4,4,4-trifluorobutane-1,3‑dione, bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline). The crystal structures of compounds 1−6 with the lanthanide(III) ions of seven (1, 4)/eight (2, 3, 5, 6) coordinated configuration are determined by single-crystal X-ray diffraction. Different non-covalent interactions (NCIs) and their% contribution to the compounds structures and their roles in stabilizing the structure are determined by Hirshfeld surface analysis. The photoluminescence properties of compounds 1−6 by substituting the solvent H2O with bpy and phen contained nitrogen ancillary ligands are then studied experimentally, leading to a rationalization of their central lanthanide(III) ions emission lifetime.