Synthesis Of Lanthanum Research Articles

Synthesis of lanthanum(III)-containing heteropoly compounds with a Peacock-Weakley type anion from aqueous-organic solutions

Conditions necessary for the formation of La(III)-containing polyoxotungstates in solutions of the system Na2WO4 – HNO3 – La(NO3)3 – H2O/Solvent (Solvent = acetone, acetonitrile, ethanol; 50/50 vol.% Н2О: Solvent ratio) acidified to acidity Z = ν(H+)/ν(WO42–) = 0.80 were elaborated. It was established that during salting out, the addition of an organic solvent leads to the crystallization of normal salts, Na9[La(W5O18)2]·nH2O (n = 32–35). Using FT-IR spectroscopy, it was shown that the anion [La(W5O18)2]9– in the composition of the isolated salts belongs to the Peacock–Weakley type of structure and the absence of solvent molecules in the composition of the crystalline product was established. Using the method of scanning electron microscopy, the single-phase nature of the synthesized salts was established (according to the uniform contrast of the surface of the samples during scanning in the backscattered electron mode and according to the results of energy dispersive X-ray microanalysis), and the grain sizes were determined (from 140–300 nm for the salt isolated from the H2O: acetone medium, to 300–450 nm for the salt isolated from the H2O: ethanol system). Microphotographs of powders of Na9[La(W5O18)2]·nH2O salts powders in characteristic X-ray emission do not show zones with different surface morphology, and demonstrate uniform distributions of Na, La, W, and O without segregation, which confirms the single–phase nature of the samples isolated from aqueous-organic solutions. The conducted research made it possible to expand the list of organic solvents that can be used for the synthesis of normal salts with a heteropoly anion with a Peacock–Weakley type of structure from aqueous-organic solutions. The use of acetonitrile and ethanol for Na9[La(W5O18)2 ]·nH2O isolating can be extended to the synthesis of salts with other lanthanide heteroatoms.

Synthesis of lanthanum – cerium - terbium condensed phosphates and their fluorescence properties for redox environments

Rare earth phosphates are known as a relatively stable matrix for fluorescent materials. However, uncondensed orthophosphates were mostly studied until recently. Therefore, in this work, lanthanum – cerium – terbium condensed phosphates were investigated for the green fluorescence properties and their redox responses. These fluorescence peaks became weaker by oxidation process for cerium cations, and then recovered by the reduction process. The fluorescence intensity decreased by increasing the concentration of oxidant and the time. In addition, this fluorescence intensity was recovered by using reducing agent having a corresponding concentration and by increasing the time correspondingly. These condensed phosphates have a possibility to use as a sensing material for redox environments.

Nano- and microsized Eu3+ and Tb3+-doped lanthanide hydroxycarbonates and oxycarbonates. The influence of glucose and fructose as stabilizing ligands

Europium and terbium-doped lanthanum hydroxycarbonate and lanthanum oxycarbonate nanoparticles were fabricated under two different reaction conditions using lanthanide acetate and urea as the starting materials. The photoluminescence properties of these hydroxycarbonate and oxycarbonate particles, and of their colloidal suspensions in water, were studied. The Eu(3+) (5)D(0)→(7)F(J) and Tb(3+) (5)D(4)→(7)F(J) emission spectra and the luminescence lifetimes in the two carbonate matrices were measured. Terbium-doped cerium oxycarbonate particles were synthesized, and the energy transfer process from Ce(3+) to Tb(3+) was investigated. The synthesis of lanthanum and cerium oxycarbonates was also carried out in the presence of stabilizing ligands: glucose and fructose. The influence of these ligands on the structure and luminescence was explored.

REE-ferrite based ceramic

Fine REE-ferrite powders were obtained by wet burning. The solid-phase synthesis of lanthanum – gadolinium ferrite was studied. It was shown that the desired phase can be obtained at temperatures to 750°C. Firing regimes making it possible to obtain REE-ferrite based ceramic with low open porosity and relative density to 99% of the theoretical value were found.

Effect of Phase Composition on Magnetoresistive Properties of LaMnO3+x

We have studied the magnetoresistivity, thermoelectric power, and magnetic susceptibility of lanthanum manganite LaMnO3+x with different γ-Mn2O3 contents at 77–300 K. The specimens were obtained by high-temperature direct synthesis of lanthanum and manganese oxides. For all the specimens, we established ferromagnetic ordering with Curie point 220–245 K, accompanied by appearance of negative magnetoresistivity, catastrophic growth of magnetic susceptibility, and semiconductor conductivity. The maximum negative magnetoresistivity (δH ≈ −13%) is characteristic for two-phase samples with the lowest oxygen content.

Lanthanide bis(trifluoromethanesulfonyl)amides, synthesis, characterization and catalytic activity

The synthesis of lanthanum, neodymium and ytterbium bis(trifluoromethanesulfonyl)amides, named triflimidates, from acetates, carbonates and oxides is investigated. When the synthesis is performed in water, all the salts contain one molecule of water and the lanthanum and neodymium salts synthesized from the acetates also contain one molecule of acetic acid. After removal of the water and acetic acid in refluxing ethanol, the salts are obtained anhydrous but associated for lanthanum and neodymium, whereas the ytterbium salt is monomeric and volatile. When the synthesis is performed directly in ethanol, the neodymium salt contains two molecules of coordinated ethanol. In non-hazardous solvents, these triflimidates are better catalysts than the analogous triflates toward either Friedel–Crafts acylations, or Fries transpositions or Baeyer–Villiger oxidations. Unexpectedly, the cerium(IV) triflimidate catalyzes the oxidation of aromatic ketones to give the corresponding acids.

Synthesis and solution properties of lanthanum(III), europium(III), and lutetium(III) THP complexes and an x-ray diffraction study of a crystal containing four stereoisomers of a europium(III) THP complex (THP = 1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane). Methyl groups impart rigidity to S,S,S,S-THP macrocyclic complexes

The macrocycle 1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane (THP) prepared from racemic propylene oxide and cyclen (1,4,7,10-tetraazacyclododecane) consists of a mixture of stereoisomers that arise from the chiral {alpha}-carbons of the hydroxypropyl groups. {sup 13}C NMR studies suggest that five different diastereomers are formed. Lanthanum(III), europium(III), and lutetium(III) THP complexes are synthesized from the mixture of THP stereoisomers. Europium(III) THP complexes containing R,R,R,S and S,S,S,R configurations at the {alpha}-carbons of the hydroxypropyl groups cocrystallize from solution. The complex [Eu(THP)(H{sub 2}O)]{sub 2}(CF{sub 3}SO{sub 3}){sub 6}{center_dot}2EtOH{center_dot}H{sub 2}O crystallizes in the centrosymetric monoclinic space group P2{sub 1}/c (No. 14). Four stereoisomers (two enantiomeric pairs) of the complex appear in the crystal. Each asymmetric unit consists of two different diastereomers of the europium(III) cation, six triflate anions, two ethanol molecules, and one water molecule of solvation. The structure was solved and refined to R = 5.54% and R{sub w} = 5.72% for those 3351 reflections with {vert_bar}F{sub o}{vert_bar} > 6{sigma}{vert_bar}F{sub o}{vert_bar}. In addition, synthesis of the THP stereoisomer with all hydroxypropyl groups containing the S-configuration (S-THP) is accomplished by use of S-propylene oxide. The synthesis of lanthanum(III), europium(III), and lutetium(III) complexes of S-THP is reported; {sup 1}H and {sup 13}C NMR spectra of the lanthanum and lutetium complexes indicatemore » that only one diastereomer is present in solution.« less

Synthesis of Lanthanum(III), Praseodymium(III), Neodymium(III), Samarium(III), Gadolinium(III), Dysprosium(III) and Ytterbium(III) Metal Picrates and their Spectral, Magnetic and Pharmacological Studies

Synthesis of Lanthanum(III), Praseodymium(III), Neodymium(III), Samarium(III), Gadolinium(III), Dysprosium(III) and Ytterbium(III) Metal Picrates and their Spectral, Magnetic and Pharmacological Studies