MOSSBAUER-EFFECT STUDIES OF A NEW ORGANOEUROPIUM COMPLEX [EU(ETA-6-C6ME6)(ALCL4)2]4

The Mossbauer spectrum of a new organoeuropium complex with a neutral pi-ligand, Eu(eta6-C6Me6) (AlCl4)2, is measured at 88 K. The Mossbauer parameters derived from the spectrum show the divalent nature of the europium ion in this organoeuropium complex. The calculations of the electric field gradient at the Eu nucleus in the crystal indicate that the Eu-Cl bond in the compound may possess a certain covalent character. The low Debye temperature of this complex may be attributed to weak and delocalized pi-bonding between the Eu atom and the benzene ring of hexamethylbenzene, and a slow paramagnetic relaxation is suggested by the Mossbauer effect.

Electron transfer between Eu3+ and Ce3+ in SrM-F-4 matrix

Emissions of europium (II) and europium (III) have been observed in SrMgF4:Eu and SrMgF4:Eu,Ce phosphors which are synthesized in Ar flow, It is notable that the intensity of the ESR peaks corresponding to Eu2+ is increased when cerium ion is incorporated which can be explained by electron transfer mechanism.

Electron Transfer and its Equilibrium between Eu and Tb in SrMgF4 System

Emission of europium(II) and europium(III) have been observed in SrMgF4 xEu, yTb phosphors winch are synthesized in Ar flow. The valence state of En is influenced by terbium, It is noted that the intensities of the ESR peaks corresponding to Eu2+ are increased when terbium ion is codopech this can be explained by electron transfer mechanism which is Eu3++Tb3+-->Eu2++Tb4+. And its equilibrium constant is calculated.

SYNTHESIS AND CHARACTERIZATION OF POLYMER-SUPPORTED LANTHANIDE COMPLEXES AND BUTADIENE POLYMERIZATION BASED ON THEM

Poly(styrene-acrylic acid)-lanthanide (Ln.PSAA) and poly(ethylene-acrylic acid)-neodymium (NdPEAA) complexes have been prepared and characterized. The infrared and X-ray photoelectron spectra indicate that the lanthanide complexes possess the bidentate carboxylate structure Ln-O-C(R)-O (see structure B in text). The catalytic behavior of the complexes has been described. The catalytic activities of Nd.PSAA and Nd.PEAA are much greater than that of the corresponding low molecular weight catalyst for butadiene polymerization. The activities of various individual lanthanide elements are quite different from one another. Neodymium shows the highest activity. Europium, samarium and the heavy elements exhibit very low or no activities. The cis-1,4 content of the polybutadiene obtained is not affected by different lanthanide elements in the series. The complex with the intermediate content of the functional group has a higher activity than the others. The polymer-supported lanthanide complexes having different constitutions have different catalytic activities. When the molar ratio of lanthanide to the functional group is ca. 0.2, the activity of the complex is in the optimum state. The activity is influenced by the dispersion of the lanthanide metal immobilized on the polymer chain. Catalytic activity can be improved by adding other metals to the catalyst system.

MOSSBAUER-EFFECT STUDIES OF THE DIMER OF A BIMETALLIC EU-AL COMPLEX

Mossbauer spectra of the dimer of a bimetallic Eu-Al complex, [(CF3COO)3EuHAl(C2H5)2 . 2 THF]2 are measured at different temperatures (81 to 166 K) and some Mossbauer parameters, such as isomer shift, electric quadrupole splitting and asymmetric parameter, are derived from the experimental spectra. The Debye temperature of the compound determined by a Debye model is 128 K. The results indicate that europium in the organo-europium compound is trivalent and that a bridging hydrogen atom between two europium atoms exists in the dimer. The low Debye temperature implies that the weaker binding force between the europium atom and the lattice may be related to the structure and the chemical bonding in the organometallic compound of europium.