RING-OPENING POLYMERIZATION OF TETRAHYDROFURAN WITH RARE EARTH-CONTAINED CATALYSTS

Rare earth trifluoroacetates, Ln(CF3CO2)(3) (Ln = thirteen rare earth elements), combined with R(n)AlH(3-n) (R = methyl, octyl, n = 3; R = ethyl, i-Butyl, n = 2, 3) were used as catalysts for the polymerization of tetrahydrofuran (THF). The activity increased by adding propylene oxide (PO), as a promoter, to the polymerization system, producing high molecular weight polytetrahydrofuran (PTHF). The effects of Ln, PO/Ln, and Al/Ln, and others on the polymerization of THF were also studied. (C) 1993 John Wiley & Sons, Inc.

SYNTHESES, CHARACTERIZATION AND CRYSTAL-STRUCTURES OF THE COMPLEXES OF RARE-EARTH WITH O-CHLOROBENZOIC ACID

REL3.H2O (RE=Y, La is similar to Lu; HL = o-chlorobenzoic acid) were synthesized. Their thermal decomposition and IR spectra were studied. The crystal structures of the complexes of neodymium, terbium and lutetium were determined by X-ray diffraction method. They crystallize in the monoclinic space group P2(1)/n and show infinite chain structures. The coordination numbers of rare earth ions are nine.

X-RAY PHOTOELECTRON-SPECTRA OF SOME BIOINORGANIC COMPLEXES OF THE RARE-EARTHS WITH N-ACETYLALANINE

X-Ray photoelectron spectra of some bioinorganic complexes of La, Ce, PT, Nd, Sm and Eu with N-acetylalanine have been measured and the 3d5/2 and 3d3/2 main peaks and their satellites have also been assigned. ne spin-orbit splitting between the 3d5/2 and 3d3/2 core-level of the rare earth ion in these complexes becomes slightly larger than that of the free rare earth atom due to the effect of the crystal field. The satellite for the 3d main peaks of La in the solid state complex are in higher binding energy region and may be attributable to the L --> 4f charge-transfer shake-up process. The satellites for the 3d main peaks of Ce, Pr, Nd, Sm and Eu are in the lower binding energy region and may be attributable to the 4f --> L charge-transfer shake-down process.

SYNTHESES, CHARACTERIZATION AND CRYSTAL-STRUCTURES OF THE COMPLEXES OF RARE-EARTH WITH M-METHYLBENZOIC ACID

REL3(RE=Y, La approximately Lu; HL = m-methylbenzoic acid) were synthesized, and their IR spectra were studied. The crystal structures of the complexes of neodymium and terbium were determined by X-ray diffraction method. Both of them crystallize in the monoclinic space group P2(1)/n and show infinite chain structures. The coordination numbers are nine (Nd3+) and eight (Tb3+), respectively.

CRYSTALLIZATION OF RARE-EARTH OXIDE-FILLED POLYPROPYLENE

A study has been made of the crystallization behavior of polypropylene (PP) filled with rare earth oxides under isothermal conditions. These rare earth oxides include lanthanum oxide (La2O3), yttrium oxide (Y2O3), and a mixture of rare earth oxides containing 70% Y2O3 (Y2O3-0.70). A differential scanning calorimeter was used to monitor the energetics of the crystallization process from the melt. During isothermal crystallization, dependence of the relative degree of crystallinity on time was described by the Avrami equation. It has been shown that the addition of any of the three rare earth oxides causes a considerable increase in the overall crystallization rate of PP but does not influence the mechanism of nucleation and growth of the PP crystals. The analysis of kinetic data according to nucleation theories shows that the increase in crystallization rate of PP in the composites is due to the decrease in surface energy of the extremity surfaces. The relative contents of the beta-form in the composites are somewhat higher than that in the plain PP. However, the contents of the beta-form in the plain PP and the composites are all very low relative to those of the alpha-form and the influence of the formation of the beta-form on the crystallization kinetics can be neglected.

SYNTHESES AND CRYSTAL STRUCTURES OF THE COMPLEXES OF RARE EARTH WITH FUMARIC ACID

Six compounds of M2F3 center dot 1.2H(2)O (M=EU, Ga, Tb, Y, Er, LU: H2F=Fumaric acid) have been synthesized. The structures of Eu(III), T b(III), Y(III), Er(III) and Lu(III) compounds have been determined by singal crystal X-ray diffraction method. The complex of Eu(III) crystallizes in tri-clinic space group P (1) over bar, and the coordination number of Eu3+ is ten. The other four complexes crystallize in monclinic space P2(1)/c, and the coordination numbers of the metal ions are eight. Each of the complexes shows a three-dimensional net structures.

A NEW HYDROGEN SENSOR WITH RARE-EARTH COMPLEX FLUORIDE

A new type of solid-state galvanic cell for detecting a small amount of hydrogen in air at room temperature is proposed. The sensor cell is a potentiometric cell using Ce0.95Ca0.05F2.95 as solid-state electrolyte. The cell exhibits good sensing properties to hydrogen in air at room temperature.

STUDY ON COMPLEXES OF RARE-EARTH WITH L-PHENYLALANINE BY POTENTIOMETRY WITH CALORIMETRY

The stability constants and thermodynamic functions for complexes of rare earth with L-phenylalanine have been determined by potentiometry and calorimetry at 25-degrees-C and ionic strength of 0.15mol.dm-3(NaCl). Stability of the complexes shows the "Tetrad effect". The entropy change makes a predominant contribution to the stability of these complexes. The ligand is coordinated to rare earth ions through its -CO2- and -NH2 group, and dehydration of ions plays an important role in coordination reaction.

INVESTIGATION OF THE PHOTOELECTRONIC PROPERTIES OF RARE-EARTH MONOPHOSPHIDES

The optical, electrical and photoelectronic properties of rare earth monophosphides (LnP, Ln = La, Nd, Sm and Y) have been studied. The experimental results indicate that their resistivities are low, the electric conduction in all of them is N-type, the energy gaps of LaP, NdP, SmP and YP are 1.46eV, 1.15eV, 1.1eV and 1.0eV, respectively. The SmP/Si and YP/Si junctions exhibit the photovoltaic effect. They may be used as photoelectronic sensors.

THE PHOTOELECTRIC PROPERTIES OF THIN-FILMS OF RARE-EARTH MONOPHOSPHIDES

The optical, electrical and photoelectric properties of rare earth monophosphides (LnP, Ln = La, Nd, Sm, Y, Dy and Yb) have been studied in thin films. The films exhibit semiconducting behaviour with energy gaps of 1.0-1.46 eV and n-type electrical conduction. Their resistivities are 10(-2) OMEGA-cm with corresponding Hall mobilities of 8.5-400 cm2 V-1 s-1. The films are deposited on a p-type silicon substrate in vacuum. Voltage-current characteristic measurements show that a p-n junction has been formed between LnP and silicon. Spectral sensitivity and a photovoltaic effect have been observed in LnP-Si junctions. They may be useful photoelectric materials.

XPS STUDY ON RARE-EARTH PHTHALOCYANINE COMPLEXES

The rare earth monophthalocyanine complexes, LnPcCl and LnPc(OAc)2 (Ln = Tb, Ho, Tm, Lu, Pc=Phthalocyanine, OAc = Acetate), were synthesized. The electronic structures of the complexes have been studied by means of XPS. The experimental results of binding energies for the complexes indicate that the bonds of the complexes have a certain covalent character depending on L-->Ln charge transfer. This L-->Ln charge transfer process of phythalocyanine complexes differs from that of crown ether complexes. Both coordination and substitution are included in the former case, but only coordination in the latter. Phthalocyanine ring is an electrophilic group and its electronegativity is large. So, the O1s binding energies of coordinating oxygen atoms of acetate in LnPc(OAc)2 are larger than those of Ln(OAc)3. The magnitude of valent charge delocalized from ligand onto metal atom is dependent on electronegativity, coordination number, valence state and so on. Because coordination number of Ln in LnPc(OAc)2 is larger than that in LnPcCl and electronegativity of Clin LnPcCl is larger than that of O in LnPc(OAc)2, the Ln4d5/2 binding energies of LnPc (OAc)2 are less than those of LnPcCl.

DIELS-ALDER REACTION CATALYZED BY RARE-EARTH CHLORIDES

Rare earth chlorides were used to catalyze the synthesis of 2-butoxy-3, 4-dihydro-2H-pyran using equimolar acrolein and vinyl butyl either. The cycloadduct is unstable which undergoes catalytic ring opening oligomerization. The way to stabilize the cyclo adduct has been studied, thus high yields of 90-95% were obtained.

DETERMINATION OF TRACE AMOUNT OF 14 RARE-EARTH IMPURITIES IN HIGH-PURITY YTTRIUM-OXIDE WITH ICP-AES

A method of analysis of high purity yttrium oxide with ICP-AES was described with emphasis on the study of Y_2O_3 matrix effects. The results showed that the line intensities of ana]ytes decreased with the increase of Y_2O_3 concentration in solution because of following factors. (1) The presence of matrix resulted in the decrease of the amount of analytes reaching ICP. (2) Matrix Y_2O_3 entering the plasma decreased the excitation temperature of the plasma and depressed the ionization of analytes in the pl...