Series Of Lanthanide Ions Research Articles

Controlled Self-Assembly, Isomerism, and Guest Uptake/Release of Charge-Reversible Lanthanide-Organic Octahedral Cages.

Charge plays a crucial role in the function of molecular and supramolecular systems, but coordination hosts capable of orthogonal charge regulation remain elusive so far. In this study, we report the condition-dependent self-assembly of charge-reversible lanthanide-organic tetra-capped octahedral cages, i.e., [Ln6(H3L)4]6+ and [Ln6L4]6-, from a series of lanthanide ions (Ln3+; Ln = Lu, Yb, Eu) and a tritopic tetradentate acylhydrazone ligand (H6L) featuring multiple deprotonation states and propeller conformations. While direct self-assembly under basic conditions produced a mixture of various ΔxΛ6-x-[Ln6L4]6- (x = 0-6) stereoisomers, racemic Δ6- and Λ6-[Ln6L4]6- could be exclusively obtained from the first self-assembly of Δ6- and Λ6-[Ln6(H3L)4]6+ under neutral conditions followed by post-assembly deprotonation. Rich isomerism on the tetra-capped octahedral cages arising from the coupling between the metal-centered Δ/Λ chirality and the ligand conformations has been discussed based on X-ray single-crystal structures of the C3-symmetric Δ3Λ3-Ln6L4 and T-symmetric Δ6/Λ6-Ln6L4 complexes. Host-guest studies confirmed that positively charged rac-Δ6/Λ6-[Ln6(H3L)4]6+ could bind anionic sulfonates, and negatively charged rac-Δ6/Λ6-[Ln6L4]6- exhibited strong encapsulation ability toward ammonium guests, where acid/base-triggered guest uptake/release could be realized taking advantage of the charge reversibility of the cage. Moreover, photophysical studies revealed visible-light-sensitized and guest-encapsulation-enhanced NIR emissions on the rac-Δ6/Λ6-Yb6L4 cage. This work not only enriches the library of functional lanthanide-organic cages but also provides a promising candidate with charge reversibility for the development of smart supramolecular materials.

Single-ion magnet behavior of Ln3+ encapsulated in carbon nanotubes: an ab initio insight.

Single-molecule magnets (SMMs) have attracted large interest owing to their capability to store information at the level of a single molecule, which has great potential for applications in information technology. The key characteristic required for SMM performance is the magnetization blocking barrier, and in the last decade, impressive efforts have been made to increase its height. Herein, we report an ab initio investigation of the SMM behavior of a series of lanthanide ions (Tb3+, Dy3+, Ho3+, Er3+, Tm3+ and Yb3+) encapsulated in zigzag carbon nanotubes (CNTs) of different diameters. The results show that despite the high symmetry of the Ln environment, none of the investigated systems, except for Er3+ encapsulated in the (7,0) CNT, exhibited any blocking behavior. This is mainly attributed to the strong competition between axial and equatorial contributions to the crystal field of these encapsulated ions, resulting in weak or lack of magnetic axiality. The presented results provide useful theoretical guidance for the design of high-performance SMMs via modulating the crystal field of the ligand environment.

High-Efficiency and Wavelength-Tunable Near-Infrared Emission of Lanthanide Ions Doped Lead-Free Halide Double Perovskite Nanocrystals toward Fluorescence Imaging.

Near-infrared (NIR) fluorescent materials show unique photophysical properties, which make them widely used in optical communication, night vision imaging, biomedicine, and other applications. However, the development of high-efficiency and wavelength-tunable NIR nanomaterials is still a challenge. Herein, a series of lanthanide ions doped Cs2AgIn0.99Bi0.01Cl6 double perovskite nanocrystals (DPNCs) with wavelength-tunable NIR light emission (800-1600 nm) have been synthesized. The optimal photoluminescence quantum yield (PLQY) of the DPNCs reaches 66.7%, which is a record value for DPNCs. It is mainly attributed to the contribution of NIR emission of lanthanide ions doped into DPNCs. More importantly, the series of NIR emission wavelengths of lanthanide ions doped Cs2AgIn0.99Bi0.01Cl6 DPNCs include not only shorter-wavelength NIR light (≤900 nm) but also longer-wavelength NIR light (>900 nm), which are more appropriate for foodstuff analysis and medical diagnosis applications. Furthermore, 11.2% Nd3+ doped Cs2AgIn0.99Bi0.01Cl6 DPNCs with the optimal PLQY were embedded in a polymethyl methacrylate (PMMA) polymer matrix (DPNCs@PMMA), and the stability of DPNCs modified by PMMA has been greatly improved. Finally, the 11.2% Nd3+ ions doped Cs2AgIn0.99Bi0.01Cl6 DPNCs@PMMA based NIR LEDs have demonstrated good night vision and human tissue penetration. This work indicates that lanthanide ions doped DPNCs have a potential in NIR light applications and could inspire future research to explore novel lanthanide ions doped semiconductor NCs based NIR LEDs.

Enhanced Photoelectrochemical Activity of TiO2 Nanotubes Decorated with Lanthanide Ions for Hydrogen Production

Highly ordered TiO2 nanotubes (TNTs) decorated with a series of lanthanide ions (Ln3+ = Ho3+, Tb3+, Eu3+, Yb3+, and Er3+) were prepared through an electrochemical process and anodization. The composition, structure, and chemical bond of the as-prepared photocatalysts were characterized through scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and ultraviolet diffuse reflectance spectroscopy. Furthermore, the electrochemical characteristics of the catalysts were analyzed and photoelectrochemical properties were investigated through water splitting. All samples were prepared in the anatase phase without changing the crystal structure. The holmium-doped TNT photocatalyst exhibited the best performance with a hydrogen evolution rate of 90.13 μmol cm−2h−1 and photoconversion efficiency of 2.68% (0 V vs. RHE). Photocatalytic efficiency increased because of the expansion of the absorption wavelength range attributed to the appropriate positioning of the band structure and reduced electron/hole pair recombination resulting from the unhindered electron movement. This study demonstrated the preparation of high-potential solar-active photocatalysts through the synergetic effects of the work function, band edge, and bandgap changes caused by the series of lanthanide combinations with TNTs.

The lanthanide doping effect on toluene catalytic oxidation over Pt/CeO2 catalyst

The present work was undertaken to know the lanthanide doping effect on the physicochemical properties of Pt/CeO2 catalysts and their catalytic activity for toluene oxidation. A series of lanthanide ions (La, Pr, Nd, Sm and Gd) were incorporated into ceria lattice by hydrothermal method, and the Pt nanoparticles with equal quality were successfully loaded on various ceria-based supports. Their catalytic performance toward toluene oxidation shows a remarkable lanthanide-doping effect, and the activity is much dependent on the ion radius and valence state of dopants. Owing to smaller ion radius and low valence state, the dopant of Gd would form more Gd-Ce complex and less GdO8-type complex, generating more oxygen vacancies and then promoting oxygen replenishment. Furthermore, the high concentration of oxygen vacancy would drive electrons to transfer from support to metal, and thus electron-rich and under-coordinated Pt particles that are favorable for toluene adsorption and dissociation are obtained. Attributing to above positive factors, the doping of Gd would effectively enhance the catalytic oxidation of toluene over Pt/CeO2 catalyst. In addition, the Pt/CeGdO2 sample exhibits an excellent reaction stability and resistance of concentration impact.

Building multi-color emitters with tailored lanthanide-based supramolecular metallogels

Multicomponent lanthanide-based metallogel offers unique prospects to access versatile, dynamic supramolecular soft materials with hierarchical stimuli-responsiveness and tunable functions, particularly for applications in the optical display field. In this work, a novel ligand L bearing classical coordinating terpyridine (tpy) and hosting 24-Crown-8 (24C8) moieties was synthesized with a function-oriented design principle, which further allowed the complexation between L and a series of lanthanide ions (Ln). Interestingly, several L-Ln complexes with 1:1 stoichiometry were found to be able to gel the solvent toluene/CH3CN (1:1), and thus lanthanide-based metallogels were successfully prepared. The L-Eu and L-Tb gel was found to be emissive and further utilized to produce a white light emitter through fine adjustment of stoichiometry among Eu, Tb, and L. Importantly, the multicomponent gel strategy was employed, and additional non-coordinating chromophores were introduced into the metallogel system. Thus a broad-spectrum of emission was achieved, and these multicomponent emissive gels were successfully applied as a photo printer. The metallogels also showed multiple stimuli-responsiveness such as pH, guest molecules thanks to the anchoring of predesigned functional moieties such as tpy and 24C8 on the ligand L. It is assumed that our multicomponent metallogel research shown here may open new avenues towards the design and preparation of intelligent and tunable hybrid lanthanide-based optical materials.

Triple NIR light excited up‐conversion luminescence in lanthanide‐doped BaTiO3 phosphors for anti‐counterfeiting

AbstractUp‐conversion luminescent (UCL) materials are excellent candidate for optical anti‐counterfeiting and the exploitation of multi‐wavelength NIR light triggered UC phosphors with tunable color emission is essential for reliable anti‐counterfeiting technology. Herein, a series of lanthanide ions (Er3+, Er3+–Ho3+, and Yb3+–Tm3+) doped BaTiO3 submicrometer particles are synthesized through a modified hydrothermal procedure. XRD and SEM measurements were carried out to identify the structure and morphology of the samples and their UCL properties under 808, 980, and 1550 nm NIR excitation are investigated. Er3+ singly doped sample exhibits Er3+ concentration‐dependent and excitation wavelength‐dependent emission color from green to yellow and orange. The corresponding UC mechanisms under three NIR light excitation are clarified. Pure red emission under 1550‐nm excitation was obtained by introducing small amount of Ho3+ and the fluorescent lifetime test was used to confirm the energy transfer from Er3+ to Ho3+. In addition, Yb3+–Tm3+ co‐doped sample shows intense blue emission from 1G4 → 3H6 transition of Tm3+ under 980‐nm excitation. As a proof of concept, the designed pattern using phosphors with red, green, and blue three primary color emissions under 1550, 808, and 980 nm NIR excitation was displayed to demonstrate their anti‐counterfeiting application.

Sensitizing Full‐Spectrum Lanthanide Luminescence within a Semiconductor CaZnOS Host

Lanthanide ions are appealing for luminescence applications due to their sharp and tunable emission lines spanning the whole spectral range. However, the parity‐forbidden nature of the electronic transition in lanthanide ions typically results in ineffective excitation processes, which is a major obstacle to practical applications of lanthanide‐based luminescent materials. Herein, a general method to sensitize lanthanide luminescence within a semiconductor host of CaZnOS is developed. Efficient energy transfer from the host to a series of lanthanide ions with the assistance of Cu+ or Mn2+ codopants is demonstrated, which introduces intermediate energy states to mediate the energy transfer processes. Accordingly, a wide spectrum of emission is achieved by a single band excitation in the near‐ultraviolet region. Due to the efficient host sensitization, a phosphor‐converted light‐emitting diode (LED) is constructed by integrating the lanthanide‐doped CaZnOS with an ultraviolet LED chip, which is used for near‐infrared studies of biological tissues.

A Family of Highly Emissive Lanthanide Complexes Constructed with 6-(Diphenylphosphoryl)picolinate.

We report a novel family of lanthanide complexes Ln(DPPOP)3 (Ln = Pr, Nd, Sm, Eu, Tb, Dy, Er, and Yb) employing anionic tridentate (O∧N∧O) ligand 6-(diphenylphosphoryl)picolinate (DPPOP). Crystal structures of the complexes reveal that each lanthanide ion is nine-coordinated by three tridentate ligands. In the crystals, 1D channels are found, which can absorb and eliminate water reversibly. DPPOP possesses high triplet energy and can sensitize a series of lanthanide ions. An energy transfer mechanism is proposed through the higher excited states of the lanthanide ions. In the solid state, remarkably high quantum yields in the visible range are obtained: 81% for Eu(III), 97% for Tb(III), 13% for Dy(III), and 4% for Sm(III) complex.

Ytterbium – Doped Prussian blue: Fabrication, photothermal performance and antibacterial activity

The application of photothermal therapy (PTT) to defeat bacterial infections has attracted great attention in the past years. Prussian blue (PB) is a potential photothermal agent in bacteria obliteration. The electron density of cyanide bonds (CN) in PB plays a decisive role on its PTT performance. Meanwhile, recent reports indicated that encapsulating PB shell on lanthanide nanomaterials core could effectively enhance its photothermal efficiency. Hence, a series of lanthanide ions, including erbium (Er3+), dysprosium (Dy3+), thulium (Tm3+), ytterbium (Yb3+), doped PB nanocubes were fabricated by a simple doping method due to the differences between lanthanide and iron on changing electron density of cyanide bond. And the Yb3+ doped PB (PB-Yb) has the best PTT performance of all nanocubes. Structure analyzing results indicate that 9% Fe (Fe2+ or Fe3+) were replaced by Yb3+ in PB-Yb, which could raise its electron density to improve its PTT performance. And the antibacterial test also verified the conclusion. All above results proved that doping proper lanthanide ions into PB is a simple and effective way to improve its photothermal performance.

Structural variations in (CuL)2Ln complexes of a series of lanthanide ions with a salen-type unsymmetrical Schiff base(H2L): Dy and Tb derivatives as potential single-molecule magnets.

A new series of heterometallic trinuclear Cu2Ln complexes [lanthanide ions Ln = Gd (1), Tb (2), Dy (3), Ho (4) and Er (5)] has been synthesized using a Cu(ii)-metalloligand derived from a N2O2 donor unsymmetrical Schiff base, H2L (where H2L = N-α-methylsalicylidene-N'-salicylidene-1,3-propanediamine), and structurally characterized. Among these complexes, [(CuL)2Gd(NO3)3(CH3CN)2] (1), [(CuL)2Tb(NO3)3(CH3CN)2] (2) and [(CuL)2Dy(NO3)3(CH3CN)2] (3) are isomorphic and isostructural. In these complexes two metalloligands coordinate to the central Ln(iii) (Ln = Gd, Tb and Dy respectively) ion in a transoid fashion viaμ2-phenoxido oxygen atoms. The Ln(iii) ions are deca-coordinated with a distorted tetradecahedron geometry. The two terminal Cu(ii) ions of the complexes possess a hexa-coordinated distorted octahedral geometry. In contrast, in complexes [(CuL)2Ho(NO3)3(CH3CN)], (4) and [(CuL)2Er(NO3)3(CH3CN)]·0.5(CH3CN) (5), the two metalloligands coordinated to the Ln(iii) ions in a cisoid fashion. The Ho(iii) ion in 4 is nona-coordinated with a distorted tricapped trigonal prismatic geometry and the Er(iii) ion in 5 is octa-coordinated with a distorted square antiprismatic geometry. The two terminal Cu(ii) ions in complexes 4 and 5 are penta-coordinated with a distorted square-pyramidal geometry. The dc magnetic susceptibilities and field dependent magnetization measurement of complex 1 reveal the occurrence of ferromagnetic interactions between Cu(ii) and Gd(iii) ions as well as intermolecular antiferromagnetic interactions. Both complexes 2 and 3 show ferromagnetic interactions between Cu(ii) and Ln(iii) ions. The ac magnetic susceptibilities of all the complexes were also recorded and it was found that only complexes 2 and 3 exhibit slow relaxation of magnetization reorientation below 10 K at 2000 Oe applied dc field, this being characteristic of single molecule magnets.

Phosphorescent Differential Sensing of Physiological Phosphates with Lanthanide Ions-Modified Mn-Doped ZnCdS Quantum Dots.

Phosphates, both inorganic and organic, play fundamental roles in numerous biological and chemical processes. The biological functions of phosphates connect with each other, analysis of single phosphate-containing biomolecule therefore cannot reveal the exact biological significance of phosphates. Sensor array is therefore the best choice for differentiation analysis of physiological phosphates. Lanthanide ions possess high affinity toward physiological phosphates, while lanthanide ions can also efficiently quench the luminescence of quantum dots (QDs). Taking lanthanide ions as cartridges, here we proposed a sensor array for sensing of physiological phosphates based on lanthanide ions-modified Mn-doped ZnCdS phosphorescent QDs in the manner of indicator-displacement assay. A series of lanthanide ions were selected as quencher for phosphorescent QDs. Physiological phosphates could subsequently displace the quencher and recover the phosphorescence. Depending on their varied phosphorescence restoration, a sensor array was thus developed. The photophysics of phosphorescence quenching and restoration were studied in detail for better understanding the mechanism of the sensor array. The exact contribution of each sensor element to the sensor array was evaluated. Those sensor elements with little contribution to the differentiation analysis were removed for narrowing the size of the array. The proposed sensor array was successfully explored for probing nucleotide phosphates-involved enzymatic processes and their metabolites, simulated energy charge changes, and analysis of physiological phosphates in biological samples.

Lanthanide Complexes of a Calix[4]arene Ligand with Dangling Phosphonate and Picolinamide Arms: Synthesis, Crystal Structures, and Extraction Properties

The coordination behavior of the neutral calix[4]arene‐based ligand L exhibiting dangling phosphonate ester and picolinamide groups in 1,3‐ and 2,4‐distal positions towards a series of lanthanide ions was examined. Reaction of L with Ln(NO3)3 in MeOH afforded mononuclear [LnL(µ1,3‐NO3)2]NO3 complexes [Ln = La (6), Pr (7), Eu (8), Gd (9)]. X‐ray crystallography for 6 and 7 revealed tenfold coordination by phosphoryl O, amide O, and pyridine N atoms from L and four O atoms from two chelating nitrato coligands. Treatment of the [LnL(µ1,3‐NO3)2]NO3 salts with NaBPh4 leads to metathesis of the counterion and, in the case of Pr, Eu, and Gd, to substitution of one nitrato coligand by a methanol molecule yielding [LnL(µ1,3‐NO3)2–n(MeOH)n](BPh4)n+1 for n = 0, Ln = La (10) and n = 1, Ln = Pr (11), Eu (12), Gd (13). X‐ray crystallography of complexes 11–13 revealed an isostructural series of ninefold‐coordinated lanthanide complexes in which one nitrato coligand is exchanged by a methanol molecule. UV/Vis batch titration experiments showed the formation of 1:1 complexes of L with trivalent lanthanides (La3+, Pr3+, Eu3+, Gd3+, Yb3+). The stability constants of the complexes determined by UV/Vis spectroscopic titrations are log K11 = 6.44 ± 0.02 (La), 5.96 ± 0.01 (Pr), 6.37 ± 0.01 (Eu), 7.38 ± 0.3 (Gd), and 9.6 ± 0.2 (Yb). Solvent‐extraction experiments with lanthanide picrates revealed that L is able to extract both La3+ and Eu3+ in 1:1 stoichiometry from aqueous media into chloroform.

First-principles search for efficient activators for LaI3

First-principles calculations were performed using density functional theory with Hubbard corrections or hybrid exchange-correlation functionals, as well as the GW approximation, to predict dopants that could serve as efficient activators for LaI3, a potentially very bright scintillator for which an appropriate activator has not been identified yet. The dopants considered in this work included a series of lanthanide ions (Ce, Pr, Nd, Eu, Gd, and Tb) and several ns2 ions (Tl, Pb, Bi, and Sb). Based on both ground-state calculations and constrained DFT calculations to simulate excited states, the trivalent lanthanide dopants were shown not to constitute an improvement over Ce3+, for which experimental data exist, as they showed occupied 4f states below the valence band maximum (VBM) and 5d states above the conduction band maximum (CBM). In contrast, the only divalent lanthanide considered, Eu2+, displayed occupied 4f states within the band gap of the host, but its 5d states were calculated to be above the CBM. Eu2+ could nonetheless be exploited as an activator by increasing the band gap energy slightly through substitution of iodide ions by bromide ions. Similar results were obtained for Tl+. Finally, Bi3+ and Sb3+ were predicted to be efficient activators in LaI3 by virtue of having unoccupied p states below the CBM, which can serve as electron traps and can combine with holes at the VBM to form localized luminescence centers. Therefore, Bi- and Sb-doped LaI3 should be grown and tested experimentally. Comparison with empirical relationships of the relative positions of the energy levels of rare-earth dopants and implications for efficient doping schemes and scintillation mechanisms in LaI3 are also discussed.

Structural and electrical properties of Na0.5Bi4.0RE0.5Ti4O15 (RE=Tm, Yb and Lu) thin films

In the current study, a series of lanthanide ions, Tm, Yb and Lu, were used for doping at the Bi-site of the Aurivillius phase Na0.5Bi4.5Ti4O15 (NaBTi) to investigate the structural, electrical and ferroelectric properties of the thin films. In this regard, Na0.5Bi4.5Ti4O15 and the rare earth metal ion-doped Na0.5Bi4.0RE0.5i4O15 (RE=Tm, Yb and Lu, denoted by NaBTmTi, NaBYbTi, and NaBLuTi, respectively) thin films were deposited on Pt(111)/Ti/SiO2/Si(100) substrates by using a chemical solution deposition method. Formations of the Aurivillius phase orthorhombic structures for all the thin films were confirmed by X-ray diffraction and Raman spectroscopic studies. Based on the experimental results, the rare earth metal ion-doped Na0.5Bi4.0RE0.5Ti4O15 thin films exhibited a low leakage current and the improved ferroelectric properties. Among the thin films, the NaBLuTi thin film exhibited a low leakage current density of 6.96×10−7A/cm2 at an applied electric field of 100kV/cm and a large remnant polarization (2Pr) of 26.7μC/cm2 at an applied electric field of 475kV/cm.

Ion exchange in hydroxyapatite with lanthanides.

Naturally occurring hydroxyapatite, Ca5(PO4)3(OH) (HAP), is the main inorganic component of bone matrix, with synthetic analogues finding applications in bioceramics and catalysis. An interesting and valuable property of both natural and synthetic HAP is the ability to undergo cationic and anionic substitution. The lanthanides are well-suited for substitution for the Ca(2+) sites within HAP, because of their similarities in ionic radii, donor atom requirements, and coordination geometries. We have used isothermal titration calorimetry (ITC) to investigate the thermodynamics of ion exchange in HAP with a representative series of lanthanide ions, La(3+), Sm(3+), Gd(3+), Ho(3+), Yb(3+) and Lu(3+), reporting the association constant (Ka), ion-exchange thermodynamic parameters (ΔH, ΔS, ΔG), and binding stoichiometry (n). We also probe the nature of the La(3+):HAP interaction by solid-state nuclear magnetic resonance ((31)P NMR), X-ray diffraction (XRD), and inductively coupled plasma-optical emission spectroscopy (ICP-OES), in support of the ITC results.

Optical properties of single crystals of heavy lanthanide chlorides

Studies of heavy lanthanide chlorides may provide important information on the degree of Ln 3+–ligand bond covalency. Monocrystals of LnCl 3·6H 2O, where Ln = Dy, Ho and Er, were grown and spectroscopic investigations were performed at room temperature and at low temperatures down to 4.2 K in order to understand the nature of the Ln 3+–L bonds. The intensities of the electronic lines and the Judd–Ofelt parameters were calculated and compared with those obtained for chlorides of light lanthanides (i.e. Ce(III), Pr(III) and Nd(III)). Room temperature Raman and IR studies of the compounds under investigation were also performed. The relationship between hypersensitivity and covalency is discussed. The change of vibronic coupling strength along the lanthanide ion series does not modify monotonically. The ion-pair interactions are especially visible for the 5I 8 → 5F 2 and 5I 8 → 5F 3 transitions in the HoCl 3·6H 2O low temperature spectra.

Density-functional theory structures of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid complexes for ions across the lanthanide series

The use of organically chelated lanthanides in diagnosis and treatment is a rapidly growing field in medicine. In order to gain a deeper understanding into the properties of these chelates, particularly spectroscopic, density-functional calculations have been performed on a series of lanthanide ions chelated with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid. Based on the results of these calculations, it has been concluded that the local symmetry experienced by the chelated lanthanide ion may be treated as being axial, which will make the interpretation of their spectroscopic properties greatly simplified. It has also been suggested that the so-called "capping" water molecule at the ninth coordination position of the lanthanide is hydrogen bonded to the acetate oxygens of the sidearms, rather than coordinated as the ninth ligand of the lanthanide.

Extraction of Sm(III), Gd(III) and Ho(III) ions with picrolonic acid in methylisobutylketone

Picrolonic acid (HPA) in methylisobutylketone (MIBK) (0.01 mol. dm-3) has been used for the extraction of lanthanide(III) ions such as Sm(III), Gd(III) and Ho(III) (Me) (~3. 10-6mol. dm-3) from pH 1-2 buffer solutions of 0.1 mol. dm-3(H+, Cl-) ionic strength and quantitative extraction (>95%) was found at pH 2. Through slope analysis the composition of the organometallic adduct responsible for the extraction came out to be M(PA)3. The conditional equilibrium constant values, log Kex, were deduced to be 2.60±0.01, 2.09±0.01 and 1.44±0.03 for these lanthanide(III) ions, respectively. The metals in concentration up to ~2.5. 10-4mol. dm-3can be quantitatively extracted by the proposed system. Among the various anions, fluoride, oxalate and cyanide ions (~3.0. 10-4mol. dm-3) and, among the cations, Zn(II) Cu(II), Co(II) and Fe(III) reduced the lanthanide extraction. The extraction of various other metal ions at the optimized conditions of Me extraction for this series of lanthanide ions was also studied and high separation factors (102-103) were obtained showing the good selectivity of this extraction system.

Vibronic coupling in the lanthanide difluoroacetate single crystals

The purpose of this work is to study the spectroscopic behaviour of the europium difluoroacetate single crystal—Eu(HF 2CCOO) 3·3H 2O and to compare it to those for the light (Pr, Nd) and heavy (Er) lanthanide difluoroacetates. Electronic spectroscopic investigations point to low symmetry for the neighbouring surrounding of Ln 3+ ions and, in spite of that, vibronic coupling is experimentally observed in these systems. With view to determine the coupling quantitatively, the calculations of rates R= I VIB/ I 0-phonon from absorption spectra were performed. The emphasis is given to the 3H 4→ 3F 2; 3P 2; 3P 0, 4I 9/2→ 4G 5/2; 2P 1/2, 7F 0→ 5D 2 and 4I 15/2→ 2H 11/2; 4G 11/2; 4F 7/2 transitions of the Pr 3+, Nd 3+, Eu 3+ and Er 3+ ions, respectively. The presented rates for lanthanide difluoroacetate reproduce the known observation that the vibronic coupling is stronger in the beginning (Pr 3+, Nd 3+), weaker at the centre (Eu 3+) and again a little stronger at the end (Er 3+) of the lanthanide ion series. Furthermore, the contribution of both (M and Δ) mechanisms to the intensity of vibronic transitions for Pr 3+ ions was concluded. The results for PrBr 3·7H 2O single crystals are also included in analysis of vibronic coupling for Pr 3+ ion.