Columinescence effect in macromolecular complexes of Eu(III) and Tb(III)

The effect of Y(III) and Gd(III) coactivator ions on the intensity of Eu(III) and Tb(III) luminescence in monomer and polymer mixed-metal complexes was studied. Isomorphic replacement of Eu(III) and Tb(III) ions by Y(III) and Gd(III) ions in macromolecular complexes led to sensitization of Eu(III) and Tb(III) ion luminescence. A mechanism of columinescence was suggested. It involves a charge transfer and the ligand orbitals and the vacant orbitals of Eu(III) and Tb(III) ions and coactivators.     

Heterobismetal complexes of [26]hexaphyrin(1.1.1.1.1.1)

Au(III)Cu(III) and Au(III)Rh(I) heterobismetal complexes of meso-aryl-substituted [26]hexaphyrin were rationally prepared from a monometal Au(III) complex. The Au(III)Cu(III) complex is an aromatic molecule with a rectangular shape, while Au(III)Rh(I) complexes are out-of-plane macrocycles, being either aromatic or antiaromatic depending upon the number of conjugated pi electrons. The 26pi Au(III)Rh(I) complex was converted into an aromatic and planar 26pi Au(III)Rh(III) complex via double C-H bond activation upon refluxing in pyridine.     

Selective transport of yttrium(III) in the presence of iron(III) through liquid-membrane impregnating acidic organophosphonate mobile carrier

The extraction and stripping behavior of yttrium(III) and iron(III) with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPA) was investigated and applied to liquid-membrane transport for their mutual separation. The extractability of yttrium(III) with EHPA was less than that of iron(III) at equilibrium, but the rates of extraction and stripping of iron(III) were slow. The carrier-mediated transport of yttrium(III) in the presence of iron(III) was investigated through a supported liquid membrane (SLM), impregnated with EHPA as a mobile carrier. Yttrium(III) with fast kinetics was selectively transported across an SLM from a dilute-acid solution into a sulfuric-acid stripping solution, while iron(III) with slow kinetics was hardly transported and was retained in the feed solution. Yttrium(III) was separated from iron(III) through the SLM and quantitative recovery was realized.     

Highly efficient near-infrared-emitting lanthanide(III) complexes formed by heterogeneous self-assembly of Ag(I), Ln(III), and thiacalix[4]arene-p-tetrasulfonate in aqueous solution (Ln(III) = Nd(III), Yb(III))

Heterogeneous self-assembly of thiacalix[4]arene-p-tetrasulfonate (TCAS), Ag(I), and Ln(III) (= Nd(III), Yb(III)) in aqueous solutions conveniently afforded ternary complexes emitting Ln(III)-centered luminescence in the near-infrared (NIR) region. A solution-state study revealed that the Ag(I)-Nd(III)-TCAS system gave a complex Ag(I)(4)·Nd(III)·TCAS(2) in a wide pH range of 6-12. In contrast, the Ag(I)-Yb(III)-TCAS system gave Ag(I)(2)·Yb(III)(2)·TCAS(2) at a pH of around 6 and Ag(I)(2)·Yb(III)·TCAS(2) at a pH of approximately 9.5. The structures of the Yb(III) complexes were proposed based on comparison with known Ag(I)-Tb(III)-TCAS complexes that show the same self-assembly behavior. In Ag(I)(2)·Yb(III)(2)·TCAS(2), two TCAS ligands sandwiched a cyclic array of a Ag(I)-Ag(I)-Yb(III)-Yb(III) core. In Ag(I)(2)·Yb(III)·TCAS(2), Yb(III) was accommodated in an O(8) cube consisting of eight phenolate O(-) groups from two TCAS ligands linked by two S-Ag-S linkages. Crystallographic analysis of Ag(I)(4)·Nd(III)·TCAS(2) revealed that the structure was similar to Ag(I)(2)·Yb(III)·TCAS(2) but that it had four instead of two S-Ag-S linkages. The number of water molecules coordinating to Ln(III) (q) estimated on the basis of the luminescent lifetimes was as follows: Ag(I)(4)·Nd(III)·TCAS(2), 0; Ag(I)(2)·Yb(III)(2)·TCAS(2), 2.4; and Ag(I)(2)·Yb(III)·TCAS(2), 0. These findings were compatible with the solution-state structures. The luminescent quantum yield (Φ) for Ag(I)(4)·Nd(III)·TCAS(2) was 4.9 × 10(-4), which is the second largest value ever reported in H(2)O. These findings suggest that the O(8) cube is an ideal environment to circumvent deactivation via O-H oscillation of coordinating water. The Φ values for Ag(I)(2)·Yb(III)(2)·TCAS(2) and Ag(I)(2)·Yb(III)·TCAS(2) were found to be 3.8 × 10(-4) and 3.3 × 10(-3), respectively, reflecting the q value. Overall, these results indicate that the ternary systems have the potential for a noncovalent strategy via self-assembly of the multidentate ligand, Ln(III), and an auxiliary metal ion to obtain a highly efficient NIR-emissive Ln(III) complex that usually relies on elaborate covalent linkage of a chromophore and multidentate ligands to expel coordinating water.     

Thermal and spectral studies of 2,4,5-trimethoxybenzoates of heavy lanthanides(III) and yttrium(III)

2,4,5-Trimethoxybenzoates of Tb(III), Dy(III), Ho(III), Er(III), Tm(III), Yb(III), Lu(III) and Y(III) are crystalline, hydrated salts with colours typical for M(III) ions. The carboxylate group is a bidenate, chelating ligand. The complexes of Tb(III), Dy(III) and Ho(III) are dihydrates while those of Er(III), Tm(III), Yb(III), Lu(III) and Y(III) are trihydrates. These compounds are characterized by low symmetry. On heating in air to 1273 K, the 2,4,5-trimethoxybenzoates of heavy lanthanides(III) and yttrium(III) decompose in two steps. At first they dehydrate to form anhydrous salts which next are decomposed to the oxides of the respective metals. The values of the enthalpy of dehydration process were determined. The solubility in water at 293 K for all heavy lanthanides(III) and yttrium(III) are in the orders of 10^-3-10^-4 mol dm^-3. The magnetic moments of the complexes were determined in the temperature range 77-300 K.     

Synthesis and electrochemical properties of bipyrimidine bridged triruthenium complexes

A new μ(4)-bpym-bridged dimer of an oxoacetao-triruthenium complex with carbonyl, [{Ru(3)O(CH(3)COO)(5)(CO)(py)}(2)(μ(4)-bpym)], was synthesized. The complex possesses two stable mixed-valence states associated with Ru(3)(III,III,II)/Ru(3)(III,II,II) and Ru(3)(III,III,III)/Ru(3)(III,III,II). The IR-spectroelectrochemistry reveals ν(CO) spectra in five oxidation states, Ru(3)(III,III,III)-Ru(3)(III,III,III) to Ru(3)(III,II,II)-Ru(3)(III,II,II) and both the mixed-valence states show a spectrum indicating medium interaction between the Ru(3) units.     

Study on interaction between Tb(III) and poly(N-isopropylacrylamide)

A new kind of the thermo-sensitive and fluorescent complex of poly(N-isopropylacrylamide) (PNIPAM) and Tb(III) was synthesized by free radical polymerization, in which PNIPAM was used as a polymer ligand. The complex was characterized by using X-ray photoelectron spectroscopy (XPS), ultraviolet-visual (UV), Fourier transform infrared (FT-IR) and fluorescence spectroscopy. The results from the experiments indicated that there is a strong interaction between PNIPAM and Tb(III), leading to a decrease in the electron density of nitrogen and oxygen atoms and an increase in the electron density of Tb(III) in the PNIPAM containing Tb(III) by contrast with PNIPAM and Tb(III), respectively, meanwhile, exhibiting that the Tb(III) is mainly bonded to oxygen atoms in the polymer chain of PNIPAM and formed the complex of PNIPAM-Tb(III). After forming the PNIPAM-Tb(III) complex, the emission fluorescence intensity of Tb(III) in the PNIPAM-Tb(III) complex is significantly enhanced because the effective intramolecular energy transfer from PNIPAM to Tb(III). Especially, the emission intensity of the fluorescence peak at 547 nm can be increased as high as 145 times comparing with that of the pure Tb(III). The intramolecular energy transfer efficiency for fluorescence peak at 547 nm can reach as high as 68%. The fluorescence intensity is related the weight ratio of Tb(III) and PNIPAM in the PNIPAM-Tb(III) complex. When the weight ratio is 1.4%, the maximum fluorescence enhancement can be obtained. Nevertheless, the lower critical solution temperature of PNIPAM containing a low content of Tb(III) has not obviously changed after the formation of the complex of PNIPAM-Tb(III) by the interaction between PNIPAM and Tb(III). This novel thermosensitive and fluorescence characterization of the PNIPAM-Tb(III) complex may be useful in the fluorescence systems and the biomedical field.     

Adsorption behaviour of scandium,yttrium, cerium and uranium from xylenol orange solutions onto anionexchange resins

The effects of concentration, pH and anions on the adsorption behaviour of xylenol orange (XO) on the strong anion exchangers, Amberlite IRA-400 and Hitachi 2632 are described. The adsorption behaviour of the XO complexes of Ce(III), Y(III), Sc(III) and U(VI) on the Amberlite IRA-400 resin as a function of XO concentration and pH is reported. A continuous-flow radiometric detector is used to investigate the separations of the Ce(III)—Sc(III), Y(III)—Sc(III), and Ce(III)—Y(III) pairs on the XO-form Hitachi 2632 resin column by pH control. Satisfactory separations of the Ce(III)—Sc(III) and Y(III)—Sc(III) pairs are achieved.     

Synthesis of two novel macroporous silica-based impregnated polymeric composites and their application in highly active liquid waste partitioning by extraction chromatography

Two kinds of novel macroporous silica-based chelating polymeric adsorption materials, TODGA/SiO2-P and CMPO/SiO2-P, were synthesized by impregnating and immobilizing two chelating agents, N,N,N',N'-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) and octyl(phenyl)-N,N-diisobutylcarbamoylmethylphoshine oxide (CMPO), into the pores of SiO2-P particles. To separate minor actinides (MA(III)) such as Am(III) and Cm(III), the adsorption and elution of 13 typically simulated fission products from a 3 M HNO3 were performed. It was found that in the first column packed with TODGA/SiO2-P, all of the simulated elements were separated effectively into four groups: (1) Cs(I), Mo(VI), and the most portion of Ru(III) (non-adsorption group), (2) Sr(II), small portion of Gd(III) and all of light REs(III) (MA-lRE-Sr group), (3) most of Gd(III) and all heavy RE(III) (hRE group), and (4) Zr(IV), Pd(II), and a little of Ru(III) (Zr-Pd group) by eluting with 3.0 M HNO3, 1.0M HNO3, distilled water, and 0.5 M H2C2O4, respectively, at 298 K. MA(III) was predicted to flow into the second group along with Nd(III) because of their close adsorption-elution onto TODGA/SiO2-P. In the second column packed with CMPO/SiO2-P, MA-lRE-Sr group was separated into (1) Sr(II), (2) middle RE(III) such as Gd(III), Eu(III), Sm(III), and quite small portion of Nd(III) (MA-mRE), and (3) light RE(III) such as La(III), Ce(III), and most of Nd(III) by eluting with 3.0 M HNO3 and 0.05 M DTPA-pH 2.0, respectively, at 323 K. MA(III) was believed to flow into MA-mRE group along with Gd(III) due to their similar adsorption properties towards CMPO/SiO2-P. Based on positions of MA(III) appeared in light and heavy RE(III), an improved MAREC process for MA(III) partitioning from HLW was proposed.     

Visible and near-infrared intense luminescence from water-soluble lanthanide [Tb(III), Eu(III), Sm(III), Dy(III), Pr(III), Ho(III), Yb(III), Nd(III), Er(III)] complexes

The synthesis of a new ligand (1) containing a single phenanthroline (phen) chromophore and a flexibly connected diethylenetriamine tetracarboxylic acid unit (DTTA) as a lanthanide (Ln) coordination site is reported [1 is 4-[(9-methyl-1,10-phenantrol-2-yl)methyl]-1,4,7-triazaheptane-1,1,7,7-tetraacetic acid]. From 1, an extended series of water-soluble Ln.1 complexes was obtained, where Ln is Eu(III), Tb(III), Gd(III), Sm(III), Dy(III), Pr(III), Ho(III), Yb(III), Nd(III), and Er(III). The stoichiometry for the association was found 1:1, with an association constant K(A) > or = 10(7) s(-1) as determined by employing luminescence spectroscopy. The luminescence and photophysical properties of the series of lanthanide complexes were investigated in both H2O and D2O solutions. High efficiencies for the sensitized emission, phi(se), in air-equilibrated water were observed for the Ln.1 complexes of Eu(III) and Tb(III) in the visible region (phi(se) = 0.24 and 0.15, respectively) and of Sm(III), Dy(III), Pr(III), Ho(III), Yb(III), Nd(III), and Er(III) in the vis and/or near-infrared region [phi(se) = 2.5 x 10(-3), 5 x 10(-4), 3 x 10(-5), 2 x 10(-5), 2 x 10(-4), 4 x 10(-5), and (in D2O) 4 x 10(-5), respectively]. For Eu.1 and Tb.1, luminescence data for water and deuterated water allowed us to estimate that no solvent molecules (q) are bound to the ion centers (q = 0). Luminescence quenching by oxygen was investigated in selected cases.     

Complexation studies of iodides of trivalent uranium and lanthanides (Ce and Nd) with 2,2'-bipyridine in anhydrous pyridine solutions

In anhydrous pyridine solution at 294 K, U(III) and Ce(III) triiodides were found to form both 1:1 (ML) and 1:2 (ML(2)) complexes with bipyridine (bipy = L) while Nd(III) triodide formed only a 1:2 complex. The 1:3 (ML(3)) complexes were identified at low temperature with a large excess of L. Conductometry measurements showed for U(III) a large increase in the conductivity when increasing the molar ratio L:U. The complex UL(2) was found to be a 1:1 electrolyte and the species UI(2)(+) was more reactive toward L in comparison with UI(3). For Ce(III) and Nd(III), MI(2)(+) and MI(3) present about the same affinity for L. The stability of the complexes is limited, and U(III) possesses a slightly higher affinity for bipy than the trivalent lanthanides. Interestingly, a preference for the formation of ML(2) complex was shown for all the studied M(III) ions. The driving force for complex formation was always the enthalpy, and, surprisingly for a bidendate ligand (bipy), no favorable entropy contribution to complex formation was observed. The X-ray crystal structures of [CeI(3)(bipy)(2)(py)](4).5py.bipy and UI(3)(bipy)(2)(py).2py were determined. The structures of the molecules MI(3)(bipy)(2)(py) are almost identical for U and Ce. The mean M(III)-N(bipy) bond distances are equal to 2.67(3) A for Ce(III) and 2.65(4) A for U(III). The slightly smaller M(III)-N(bipy) distances observed for U(III) would reflect a slightly more important covalent character of the U(III)-N(bipy) bonds, in agreement with the slightly better affinity of U(III) than Ce(III) or Nd(III) toward bipy observed in solution and with the fact that the enthalpy is the driving force for complex formation.     

Cloud point extraction: an alternative to traditional liquid-liquid extraction for lanthanides(III) separation

Cloud point extraction (CPE) was used to extract and separate lanthanum(III) and gadolinium(III) nitrate from an aqueous solution. The methodology used is based on the formation of lanthanide(III)-8-hydroxyquinoline (8-HQ) complexes soluble in a micellar phase of non-ionic surfactant. The lanthanide(III) complexes are then extracted into the surfactant-rich phase at a temperature above the cloud point temperature (CPT). The structure of the non-ionic surfactant, and the chelating agent-metal molar ratio are identified as factors determining the extraction efficiency and selectivity. In an aqueous solution containing equimolar concentrations of La(III) and Gd(III), extraction efficiency for Gd(III) can reach 96% with a Gd(III)/La(III) selectivity higher than 30 using Triton X-114. Under those conditions, a Gd(III) decontamination factor of 50 is obtained.     

Rare earth complexes with a novel ligand N-(naphthalen-2-yl)-N-phenyl-2-(quinolin-8-yloxy)acetamide: preparation and spectroscopic studies

Six complexes of rare earth nitrates (Ln=La, Sm, Eu, Gd, Tb, Dy) with a new amide type ligand, N-(naphthalen-2-yl)-N-phenyl-2-(quinolin-8-yloxy)acetamide (L) have been prepared and characterized by elemental analysis, conductivity measurements, IR and and 1H NMR spectra. Under excitation, Eu(III) and Sm(III) complexes exhibited strong red emissions. And the luminescence intensity of Sm(III) complex is higher than that of Eu(III) complex. Thus the Eu(III) and Sm(III) complexes are the potential light conversion agent. However, the Tb(III) and Dy(III) complexes cannot exhibit characteristic emissions of terbium and dysprosium ions, respectively. The results of phosphorescence spectrum show that the triplet-state energy level of the ligand matches better to the resonance level of Eu(III) than Tb(III) ion. In addition, the luminescence of the Eu(III) complex is also relatively strong in highly diluted tetrahydrofuran solution (2 x 10(-4)mol/L) compared with the powder. This is not only due to the solvate effects but also to the changes of the structure of the Eu(III) complex after being dissolved into the solvents. Furthermore, owing to the co-luminescence effect, the proper La(III) or Gd(III) doped Eu(III) complexes show stronger luminescence than the pure Eu(III) complex.     

Eu(III) adsorption on rutile: Batch experiments and modeling

Eu(III) adsorption on rutile was investigated as a function of contact time, pH, ionic strength and Eu(III) concentration by using a batch experimental method. The effects of carbonate, sulfate, and phosphate were also studied. It was found that the kinetics of Eu(III) adsorption on rutile could be described by a pseudo-second-order model. The adsorption of Eu(III) on rutile is strongly pH-dependent, but relatively insensitive to ionic strength. A double layer model (DLM) with two inner-sphere Eu(III) surface complexes was applied to quantitatively interpret the adsorption of Eu(III) on rutile. There were no apparent effects of carbonate and sulfate on Eu(III) adsorption, whereas the presence of phosphate promoted Eu(III) adsorption on rutile. The surface complexes of Eu(III) on rutile were evidenced by X-ray photoelectron spectroscopy (XPS).     

Aqueous Ln(III) luminescence agents derived from a tasty precursor

The synthesis, characterization, and photophysical properties are reported for several Ln(III) complexes of a tetradentate chelate, 5LIO-MAM, derived from the common flavor enhancer "maltol". Eu(III), Yb(III), and Nd(III) form stable ML2 complexes in aqueous solution that emit in the red or near-infrared (NIR) upon excitation at ca. 330 nm. The synthesis, aqueous stability, and photophysical properties are reported for a novel tetradentate ligand derived from maltol, a commonly used flavor enhancer. In aqueous solution, this chelate forms stable complexes with Ln(III) cations, and sensitized emission was observed from Eu(III), Yb(III), and Nd(III). A comparison with recently reported and structurally analogous ligands reveals a slightly higher basicity but lower complex stability with Eu(III) [pEu = 14.7(1)]. A very poor metal-centered quantum yield with Eu(III) was observed (Phi(tot) = 0.04%), which can be rationalized by the similar energy of the ligand triplet state and the Eu(III) (5)D0 emissive level. Instead, sensitized emission from the Yb(III) and Nd(III) cations was observed, which emit in the NIR.     

Mutual Influence of Rare-Earth Metals(III) in Their Joint Extraction from Aqueous Solutions with a Toluene Solution of Trialkylbenzylammonium Naphthenate

Extraction of nitrates of lanthanides(III) [La(III)-Lu(III) and also yttrium(III)] from their aqueous multicomponent systems with a toluene solution of trialkylbenzylammonium naphthenate was studied at 298 K and pH 3. Physicochemical and mathematical models describing the distribution and mutual influence of lanthanides(III) [Ln(III)] in their joint extraction from multicomponent aqueous solutions as influenced by the total Ln(III) concentration in the aqueous phase and composition of their mixture was developed.     

Covalency of Sc(III), Y(III), Ln(III) and An(III) as manifested in the enthalpies of solution of anhydrous rare earth halides

The position of scandium and yttrium within lanthanides in respect to the enthalpies of solution of anhydrous rare earth halides has been discussed. It has been indicated that although the respective shift of Sc(III) as a quasi-heavy lanthanide is less pronounced than for Y(III), the overall covalency within the trivalent ions of the scandium group, Ln(III) and An(III) included, is the most pronounced for Sc(III) due to participation of the empty orbitals in bonding: Sc(III)>An(III)>Ln(III)> Y(III). The irregularity of this trend is produced by the superimposed participation of the 5f (An(III)) and, to a lesser extent, of the 4f (Ln(III)) orbitals in bonding. The crucial factor of a maximum difference between the product and substrate coordination number (CN) of the central ion for covalency, separation factor and isotope effect in chemical exchange is emphasized.     

Synthesis and photophysical properties of new Ln(III) (Ln = Eu(III), Gd(III), or Tb(III)) complexes of 1-amidino-O-methylurea

Three new solid lanthanide(III) complexes, [Ln(1-AMUH)₃] · (NO₃)₃ (1-AMUH = 1-amidino-O-methylurea; Ln = Eu(III), Gd(III), or Tb(III)) were synthesised and characterised by elemental analysis, infrared spectra, magnetic moment measurement, and electron paramagnetic resonance (EPR) spectra for Gd(III) complex. The formation of lanthanide(III) complexes is confirmed by the spectroscopic studies. The photophysical properties of Gd(III), Eu(III), and Tb(III) complexes in solid state were investigated. The Tb(III) complex exhibits the strongest green emission at 543 nm and the Eu(III) complex shows a red emission at 615 nm while the Gd(III) complex shows a weak emission band at 303 nm. Under excitation with UV light, these complexes exhibited an emission characteristic of central metal ions. The powder EPR spectrum of the Gd(III) complex at 300 K exhibits a single broad band with g = 2.025. The bi-exponential nature of the decay lifetime curve is observed in the Eu(III) and Tb(III) complexes. The results reveal them to have potential as luminescent materials.     

Separation of gadolinium(III) and lanthanum(III) by nanofiltration-complexation in aqueous medium

A new method is proposed for the separation of gadolinium(III) and lanthanum(III) in aqueous medium by nanofiltration combined with a complexation step. First DTPA was chosen as ligand for a selective Gd(III)/La(III) complexation. Having investigated the influence of three factors (pH, temperature and amount of ligand) for the selective complexation of DTPA towards Gd(III) and La(III), the system is then combined with a nanofiltration separation process to remove 92% of initial Gd(III) and only 12% of initial La.     

Complexation of lanthanides, actinides and transition metal cations with a 6-(1,2,4-triazin-3-yl)-2,2':6',2'-terpyridine ligand: implications for actinide(III)/lanthanide(III) partitioning

The quadridentate N-heterocyclic ligand 6-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2'?:?6',2'-terpyridine (CyMe(4)-hemi-BTBP) has been synthesized and its interactions with Am(III), U(VI), Ln(III) and some transition metal cations have been evaluated by X-ray crystallographic analysis, Am(III)/Eu(III) solvent extraction experiments, UV absorption spectrophotometry, NMR studies and ESI-MS. Structures of 1:1 complexes with Eu(III), Ce(III) and the linear uranyl (UO(2)(2+)) ion were obtained by X-ray crystallographic analysis, and they showed similar coordination behavior to related BTBP complexes. In methanol, the stability constants of the Ln(III) complexes are slightly lower than those of the analogous quadridentate bis-triazine BTBP ligands, while the stability constant for the Yb(III) complex is higher. (1)H NMR titrations and ESI-MS with lanthanide nitrates showed that the ligand forms only 1:1 complexes with Eu(III), Ce(III) and Yb(III), while both 1:1 and 1:2 complexes were formed with La(III) and Y(III) in acetonitrile. A mixture of isomeric chiral 2:2 helical complexes was formed with Cu(I), with a slight preference (1.4:1) for a single directional isomer. In contrast, a 1:1 complex was observed with the larger Ag(I) ion. The ligand was unable to extract Am(III) or Eu(III) from nitric acid solutions into 1-octanol, except in the presence of a synergist at low acidity. The results show that the presence of two outer 1,2,4-triazine rings is required for the efficient extraction and separation of An(III) from Ln(III) by quadridentate N-donor ligands.