Rare earth metal alkyl complexes bearing N,O,P multidentate ligands: Synthesis, characterization and catalysis on the ring-opening polymerization of L-lactide

Alkane elimination reactions of rare earth metal tris(alkyl)s, Ln(CH2SiMe3)3(THF)2 (Ln = Y, Lu) with the multidentate ligands HL1-4, afforded a series of new rare earth metal complexes. Yttrium, complex I supported by flexible amino-intino phenoxide ligand HL1 was isolated as homoleptic product. In the reaction of rigid phosphino-imino phenoxide ligand HL 2 with equintolar Ln(CH2SiMe3)3(THF)2, HL 2 was deprotonated by the metal alkyl and its imino C=N group was reduced to C-N by intramolecular alkylation, generating THF-solvated mono-alkyl complexes (2a: Ln = Y; 2b: Ln = Lu). The di-ligand chelated yttriurn complex 3 without alkyl moiety was isolated when the molar ratio of HL 2 to Y(CH,SiMe3)3(THF)2 increased to 2: 1. Reaction of steric phosphino beta-ketoiminato ligand HL 3 with equimolar Ln(CH2SiMe3)3(THF)2 afforded di-ligated mono-alkyl complexes (4a: Ln = Y; 4b: Ln = Lu) without occurrence of intramolecular alkylation or formation of homoleptic product. Treatment of tetradentate methoxy-amino phenol HL 4 with Y(CH2SiMe3)3(THF)2 afforded a monomeric yttrium bis-alkyl complex of THF-free. The resultant complexes were characterized by IR, NMR spectrum and X-ray diffraction analyses.All alkyl complexes exhibited high activity toward the ring-opening polymerization Of L-lactide to give isotactic polylactide with controllable molecular weight and narrow to moderate polydispersity.

Synthesis and reactivity of rare earth metal alkyl complexes stabilized by anilido phosphinimine and amino phosphine ligands

Anilido phosphinimino ancillary ligand H2L1 reacted with one equivalent of rare earth metal trialkyl [Ln{CH2Si(CH3)(3)}(3)(thf)(2)] (Ln = Y, Lu) to afford rare earth metal monoalkyl complexes [L(1)LnCH(2)Si(CH3)(3)(THF)] (1a: Ln = Y; 1b: Ln = Lu). In this process, deprotonation of H2L1 by one metal alkyl species was followed by intramolecular C-H activation of the phenyl group of the phosphine moiety to generate dianionic species L-1 with release of two equivalnts of tetramethylsilane. Ligand L-1 coordinates to Ln(3+) ions in a rare C,N,N tridentate mode. Complex 1a reacted readily with two equivalents of 2,6-diisopropylaniline to give the corresponding bis-amido complex [(HL1)LnY(NHC(6)H(3)iPr(2)-2,6)(2)] (2) selectively, that is, the C-H activation of the phenyl group is reversible. When 1a was exposed to moisture, the hydrolyzed dimeric complex [{(HL1)Y(OH)}(2)](OH)(2) (3) was isolated. Treatment of [Ln{CH2Si(CH3)(3)}(3)-(thf)(2)] with amino phosphine ligands HL2-R gave stable rare earth metal bisalkyl complexes [(L2-R)Ln{CH2Si(CH3)(3)}(2)(thf)] (4a: Ln=Y, R=Me; 4b: Ln=Lu, R=Me; 4c: Ln=Y, R=iPr; 4d: Ln=Y, R=iPr) in high yields. No proton abstraction from the ligand was observed. Amination of 4a and 4c with 2,6-diisopropylaniline afforded the bis-amido counterparts [(L2-R)Y(NHC(6)H(3)iPr(2)-2,6)(2)(thf)] (5a: R=Me; 5b: R=iPr).

Rare earth metal bis(alkyl) complexes bearing amino phosphine ligands: Synthesis and catalytic activity toward ethylene polymerization

Reactions of neutral amino phosphine compounds HL1-3 with rare earth metal tris(alkyl)s, Ln(CH2SiMe3)(3)(THF)(2), afforded a new family of organolanthanide complexes, the molecular structures of which are strongly dependent on the ligand framework. Alkane elimination reactions between 2-(CH3NH)-C6H4P(Ph)(2) (HL1) and Lu(CH2SiMe3)(3)(THF)(2) at room temperature for 3 h generated mono(alkyl) complex (L-1)(2)Lu(CH2SiMe3)(THF) (1). Similarly, treatment of 2-(C6H5CH2NH)-C6H4P(Ph)(2) (HL2) with Lu(CH2SiMe3)(3)(THF)(2) afforded (L-2)(2)Lu(CH2SiMe3)(THF) (2), selectively, which gradually deproportionated to a homoleptic complex (L-2)(3)Lu (3) at room temperature within a week. Strikingly, under the same condition, 2-(2,6-Me2C6H3NH)-C6H4P(Ph)(2) (HL3) swiftly reacted with Ln(CH2SiMe3)(3)(THF)(2) at room temperature for 3 h to yield the corresponding lanthanide bis(alkyl) complexes L(3)Ln(CH2SiMC3)(2)(THF)(n) (4a: Ln = Y, n = 2; 4b: Ln = Sc, n = 1; 4c: Ln = Lu, n = 1; 4d: Ln = Yb, n = 1; 4e: Ln = Tm, n = 1) in high yields. All complexes have been well defined and the molecular structures of complexes 1, 2, 3 and 4b-e were confirmed by X-ray diffraction analysis. The scandium bis(alkyl) complex activated by AlEt3 and [Ph3C][B(C6F5)(4)], was able to catalyze the polymerization of ethylene to afford linear polyethylene.

Rare earth metal complexes bearing thiophene-amido ligand: Synthesis and structural characterization

2,6-Diisopropyl-N-(2-thienylmethyl) aniline ( H2L) has been prepared, which reacted with equimolar rare earth metal tris( alkyl)s, Ln( CH2SiMe3)(3)( THF)(2), afforded rare earth metal mono( alkyl) complexes, LLn(CH2SiMe3)(THF)(3) ( 1: Ln = Lu; 2: Ln = Y). In this process, H2L was deprotonated by one metal alkyl species followed by intramolecular C-H activation of the thiophene ring to generate dianionic species L2- with the release of two tetramethylsilane. The resulting L2- combined with three THF molecules and an alkyl unit coordinates to Y3+ and Lu3+ ions, respectively, in a rare N,C-bidentate mode, to generate distorted octahedron geometry ligand core. Whereas, with treatment of H2L with equimolar Sc(CH2SiMe3)(3)( THF)(2), a heteroleptic complex ( HL)( L) Sc( THF) ( 3) was isolated as the main product, where the dianionic L2- species bonds to Sc3+ via chelating N, C atoms whilst the monoanionic HL connects to Sc3+ in an S,N-bidentate mode. All complexes 1-3 have been characterized by NMR spectroscopy and X-ray diffraction analysis.

Crystal structure and electrochemical properties of rare earth non-stoichiometric AB(5)-type alloy as negative electrode material in Ni-MH battery

The La0.85MgxNi4.5Co0.35Al0.15 (0.05less than or equal toxless than or equal to0.35) system compounds have been prepared by are melting method under Ar atmosphere. X-ray diffraction (XRD) analysis reveals that the as-prepared alloys have different lattice parameters and cell volumes. The electrochemical properties of these alloys have been studied through the charge-discharge recycle testing at different temperatures and discharge currents. It is found that the La0.85Mg0.25Ni4.5Co0.35Al0.(15) alloy electrode is capable of performing high-rate discharge. Moreover, it has very excellent electrochemical properties as negative electrode materials in Ni-MH battery at low temperature, even at -40degreesC.

Phase behavior of rare earth manganites

Among complex oxides containing rare earth and manganese BaLn(2)Mn(2)O(7)( Ln = rare earth) with the layered perovskite type and Ln(2)(Mn, M)O-7 with pyrochlore-related structure were studied since these compounds show many kinds of phases and unique phase transitions. In BaLn(2)Mn(2)O(7) there appear many phases, depending on the synthetic conditions for each rare earth. The tetragonal phase of so-called Ruddlesden-Popper type is the fundamental structure and many kinds of deformed modification of this structure are obtained. For BaEu2Mn2O7 at least five phases have been identified from the results of X-ray diffraction analysis with the space group P4(2)/mnm, Fmmm, Immm and A2/m in addition to the fundamental tetragonal I4/mmm phase. In the pyrochlore-related type compounds, Ln(2)Mn(2-x)M(x)O(7)(M = Ta, Nb, W etc), there also appear several phases With different crystal structures. With regard to every rare earth, Ln(2)MnTaO(7) phase is stable only for excess Ta and can be obtained under high oxygen partial pressure process. This group has trigonal structure with zirkelite type ( P3(1)21 space group).

Phase behavior of BaLn(2)Mn(2)O(7) (Ln = rare earth) with a layered perovskite structure

Many phases appear in BaLn(2)Mn(2)O(7) family (Ln = rare earth) belonging to one of the Ruddlesden-Popper type compounds, depending upon the experimental conditions such as heating conditions when prepared and composition. Some of these phases were characterized by powder X-ray diffraction method using Rietveld analysis. These phases have only a little difference in crystal structure which has fundamentally K2NiF4 type structure, although the X-ray diffraction patterns are clearly different: a little deformation or tilting of the oxygen octahedron surrounding a central manganese ion composing the main frame of this structure induce these different diffraction patterns. Phase behavior of these compounds, mainly the detailed relation between various phases in BaTb2Mn2O7, was refined including the data of high temperature X-ray diffractometry.

Fabrication, characterization and conductivity of organic-inorganic hybrid Langmuir-Blodgett films based on polyquinoline and rare earth-substituted heteropolymolybdate

The organic/inorganic hybrid Langmuir-Blodgett (LB) films were obtained by the compact organization of poly(1,2-dihydro-2,2,4-trimethyl)quinoline (PQ), octadecylamine (ODA) and rare earth-substituted heteropolymolybdates. They were characterized by surface pressure-area (pi-A) isotherms, absorption spectra, fluorescence spectra, atomic force microscope (AFM) and scanning tunneling microscopy (STM). The atomic force microscope revealed a granular surface texture of nanosized rare earth-substituted heteropolymolybdate. The scanning tunneling microscopy indicated that the hybrid LB films containing rare earth-substituted heteropolymolybdates had the better electrical conductivity than LB film of PQ/ODA.

Fabrication, structure and conductivity of hybrid organic/inorganic Langmuir-Blodgett films of polyquinoline/octadecylamine/rare earth-substituted heteropolyanion

Three kinds of hybrid organic/inorganic Langmuir-Blodgett films are obtained by the compact organization of poly (1, 2-dihydro-2,2,4-trimethyl)quinoline (abridged as PQ), octadecylamine(abridged as OA) and rare earth-substituted heteropolyanions [abridged as RE(PW11,)(2), RE=Ce-II, Eu-II, Gd-II] using the Langmuir-Blodgett technique. They are characterized by the pi-A isotherms, the absorption spectra, the fluorescence spectra and the atomic force microscope. The scanning tunneling microscopy shows that the conductivity of the hybrid LB films is much better after heteropolyanions having been incorporated in the films.

Fabrication and characterization of hybrid Langmuir-Blodgett films of polyquinoline/stearic acid/rare earth-substituted heteropolymolybdate

Three kinds of hybrid Langmuir-Blodgett films are obtained by the organization of poly(1-hydro-2,2,4-trimethyl)quinoline (PQ), stearic acid(SA) and rare earth-substituted heteropolymolybdates (RE(PMo11)(2), RE = Ce-III, Eu-III, La-III) using the Langmuir-Blodgett technique. They are characterized by pi-A isotherms, absorption spectra, fluorescence spectra, IR and atomic force microscope. The absorption spectra indicate that the molecules of PQ and heteropolymolybdates are incorporated into the LB films. The atomic force microscope reveals that heteropolymolybdates aggregate at the surface of the LB film.

Adsorption of heavy rare earth(III) with extraction resin containing bis(2,4,4-trimethylpentyl) monothiophosphinic acid

In the present paper, the adsorption of thulium(Ill) from chloride medium on an extraction resin containing bis(2,4,4-trimethylpentyl) monothiophosphinic acid (CL302, HL) has been studied. The results show that 1.5 h is enough for the adsorption equilibrium. The distribution coefficients are determined as a function of the acidity of the aqueous phase and the data are analyzed both graphically and numerically. The plots of log D versus pH give a straight line with a slope of about 3, indicating that 3 protons are released in the adsorption reaction of thulium(III). The content of Cyanex302 in the resin is determined to be 48.21%. The total amount of Tm3+ adsorbed up to resin saturation is determined to be 82.46 mg Tm3+/g resin. Therefore, the sorption reactions of Tm3+ from chloride medium with CL302 can be described as: Tm3+ + 3HL((r)) <----> TmL3(r) + 3H(+) The Freundlich's isothermal adsorption equation is also determined as: log Q = 0.73 log C + 3.05 The amounts (Q) of Tm3+ adsorbed with the resin have been studied at different temperatures (15-40degreesC) at fixed concentrations of Tm3+, amounts of extraction resin, ion strength and acidities in the aqueous phase.

Spectral properties of rare-earth ions in nanocrystalline YAG : Re (Re = Ce3+, Pr3+, Tb3+)

Bulk and nanoscale powders of YAG:Re (Re = Ce, Pr, Tb) were synthesized by solid-state and sol-gel method. The changes of spectra and energy level were studied. Compared with the bulk YAG:Re (Re = Ce, Pr, Tb) crystals, the lattice parameter of YAG:Re (Re = Ce, Pr, Tb) nanocrystals decreases. It is also found that the excitation peaks of 5d energy levels shift in nanocrystals. The physical reason for spectral and energy level changes is a comprehensive result from the shift of energy centroid of the 5d orbit, the Coulomb interaction between 4f and 5d electrons and the crystal field splitting of the 5d energy level.

A new blue phosphorescent glass-ceramic: Rare-earth-doped calcium aluminoborate

A new blue phosphorescent glass-ceramic, Eu2+ and Nd3+, co-doped CaO-Al2O3-B2O3, was synthesized. After the irradiation with ultraviolet (UV) light, the glass-ceramic emitted blue long-lasting phosphorescence (LLP) with a spectrum peaking at about 464 nm ascribed to the characteristic 4f(6)5d(1) -> 8S(7/2) transition of Eu2+. This phosphorescence can be seen in the dark 1 h after the irradiation. However, the transparent Eu2+ and Nd3+ co-doped CaO-Al2O3-B2O3 glass did not show the phosphorescence. By the X-ray diffraction diffusion (XRD) data, alpha-CaAl2B2O7 was demonstrated to be the crystallites in the glass-ceramic. We think that alpha-CaAl2B2O7:Eu2+ Nd3+ crystallites produced during the heat treatment of the glass contribute to the LLP of the glass-ceramic.

Thermoluminescence studies of rare earth doped Sr2Mg(BO3)(2) phosphor

The Sr2Mg(BO3)(2) phosphors doped respectively with Tm3+, Tb3+ and Dy3+ as activator were prepared by high temperature solid-state reaction. All the thermo luminescence curves of the phosphors consisted of two isolated peaks and the Dy3+ activated sample exhibited the strongest thermo luminescence intensity. The kinetic parameters of the thermoluminescence of Sr2Mg(BO3)(2):0.04 Dy were calculated employing the peak shape method and 3 dimensional thermo luminescent emission spectra were observed peaking at 480, 579, 662 and 755 nm due to the characteristic transition of Dy3+. In addition, the pre-irradiation heat-treatment and the thermoluminescence dose response of Sr2Mg(BO3)(2):0.04 Dy were investigated.

Studies on the roles of different components in Cyanex 302 for rare earth ions extraction and separation

In this paper, the extractabilities of Cyanex 302 and purified Cyanex 302 (hereafter HBTMPTP or HA) in heptane have been compared by extracting the scandium, yttrium, lanthanum, and gadolinium from hydrochloric acid solutions. The roles of the different components in Cyanex 302 on lanthanum extraction have been analyzed. The result demonstrates that the Cyanex 302 has a higher extractability than HBTMPTP, which perhaps originates from the interaction among the components in Cyanex 302. Especially for R3PO, obviously synergistic effect can be observed in the lower pH range and extraction mechanism of lanthanum using the mixture of HBTMPTP and TOPO has been deduced to be:where (HA)(2) and B denote the dimeric form of HBTMPTP and TOPO, respectively. At the same time, the separation abilities of Cyanex 302 and HBTMPTP on the rare earth elements have been compared. Also, the effect of temperature on the extraction with Cyaenx 302, HBTMPTP and the mixture of HBTMPTP and TOPO has also been discussed with thermodynamic functions Delta H, Delta S, and Delta G calculated.