Formation and characterization of heteropolyacid/polycation multilayer films on gold electrode

Ultrathin multilayer films of a polybasic lanthanide heteropoly tungstate-molybdate complex and a cationic polymer of quaternized poly(4-vinylpyridine) partially complexed with osmium bis(2,2'-bipyridine) have been fabricated on a gold electrode precoated with a cysteamine self-assembled monolayer. The multilayer films have been characterized by optical spectroscopy, small-angle X-ray diffraction, and electrochemical methods (cyclic voltammetry and electrochemical impedance). Especially, the electrochemical impedance spectroscopy is developed to monitor the layer deposition processes. It provides important information such as double-layer capacitance and charge-transfer resistance. All obtained results reveal regular film growth with each layer adsorption. (C) 2001 The Electrochemical Society.

Spectroscopic study of the photophysical properties of rare earth ions encapsulated: Water soluble functional calixresorcin[4]arene

A novel macrocyclic compound-water soluble functional calixresorcin[4]arenes-tetra para sulfo-phenylmethyl-calixresorcin[4]are was synthesized for the first time. The photophysical properties of terbium and europium ions encapsulated in the macrocyclic ligand were studied in detail. The triplet state energy of the calixresorcin[4]arene was determined to be 24400 cm(-1) by the low temperature phosphorescence spectrum and it was found that it can sensitize both terbium ion and europium ion. The possible energy transfer process between the functional calixresorcin[4]arene and the encapsulated Tb3+ and Eu3+ was discussed. The luminescence quantum efficiency of Tb3+- calixresorcin[4]arene was calculated.

New development of organolanthanide complexes containing chalcogenide ligands

This article is to present and outline new approaches to chalcogen coordination chemistry from the organolanthanides point of view.

Bright green organic electroluminescent devices based on a novel thermally stable terbium complex

A navel thermally stable terbium carboxylate complex, Tb(MTP)(3)(phen) (MTP=monotetradecyl phthalate, phen=1,10-phehanthroline), was synthesized and characterized. The device structure of glass substrate/indium-tin-oxide/poly(p-phenylenevinylene) (PPV)/poly (N-vinycarbazole) (PVK):Tb(MTP)(3)(phen): 1,3,4-oxadizole derivative (PBD)/tris(8-hydroxyquinoline) (Alq(3))/aluminum (Al) was employed to study the electroluminescent properties of Tb(MTP)(3)(phen). A green emission with extremely sharp spectral band of less than 10 nm at 544 nm peak wavelength was observed. A maximum luminance of 152 cd/m(2) and an external quantum efficiency of 0.017% were achieved at a drive voltage of 24 V. A possible mechanism of energy transfer based on the polymer doped with lanthanide organic complex was also proposed.

Effects of La3+ and Gd3+ on Ca2+ influx in rat hepatoma H-35 cells

Effects of La3+ and Gd3+ on Ca2+ influx were investigated in rat hepatoma H-35 cells by measuring the initial rate of Ca-45(2+) uptake. It was found that the maximum initial rate of Ca2+ uptake was increased six- to ten-fold at low concentrations of La3+ and Gd3+. Kinetic analyses by measuring the initial rate of Ca2+ influx at different external Ca2+ concentrations indicated the existence of two intracellular exchangeable components in the basal Ca2+ system, with low and high affinities for Ca2+, and only one class of Ca2+ binding sites was observed in the La3+- or Gd3+-treated cells. For high affinity, La3+ and Gc(3+) increased both kinetic parameters K-m and V-max of basal Ca2+ influx. La3+ and Gd3+ compete directly with Ca2+ for Ca2+ binding site for low affinity. The kinetics is competitive.

A novel rare earth coordination catalyst for polymerization of biodegradable aliphatic lactones and lactides

A novel rare earth coordination system composed of lanthanide trifluoroacetates Ln(CF3COO)(3) (Ln = Y, Yb, Nd, Tm, Ho, La, Pr) and triisobutylaluminium Al(i-Bu)(3) was used as catalyst for the polymerization of epsilon-caprolactone (CL), D,L-lactide (DLLA) and their copolymerization. The influence of temperature, time and catalyst concentration on polymerization yields and molecular weights of the polyesters have been studied. It was shown that the ring-opening polymerization of cyclic esters catalysed by Ln(CF3COO)(3)/Al(i-Bu)(3) has some living character and the molecular weight of the polyester could be controlled by adjusting the molar ratio of monomer to catalyst. The DLLA/CL copolymer was synthesized by sequential addition of monomers and the structure of the copolyester was characterized by GPC, NMR and DSC. (C) 1998 SCI.

Synthesis, extraction and electronic structure of Ce@C-2n

In view of the growing interest in endohedral lanthanide fullerenes, Ce, as a typical +4 oxidation state lanthanide element, has been systematically studied. The synthesis, extraction and electronic structure of Ce@C-2n are investigated. Soot containing Ce@C-2n was synthesized in high yield by carbonizing CeO2-containing graphite rods and are back-burning the CeC2-enriched cathode deposit in a DC are plasma apparatus. Ce@C-2n, dominated by Ce@C-82, can be efficiently extracted from the insoluble part of the soot after toluene Soxhlet extraction by pyridine at high temperature and high pressure in a closed vessel. About 60% Ce@C-2n (2n = 82,80,78,76) and 35% Ce@C-82 can be enriched in the pyridine extract. This fact is identified by desorption electron impact mass spectrometry (DEI MS). The electronic structure of Ce@C-2n is analyzed by using X-ray photoemission spectroscopy (XPS) of pyridine-free film. It is suggested that the encapsulated Ce atom is in a charge state close to +3 and was effectively protected from reaction with water and oxygen by the enclosing fullerene cage. Unlike theoretical expectation, the electronic state of Ce@C-82 is formally described as Ce+3@C-82(3-). (C) 1997 Elsevier Science Ltd.

Mass spectral study of extractable La- and Lu-containing fullerenes

Mass spectra of LaxC2n (x = 1,2), well known endohedral metallofullerenes, and Lu2C2n (2n = 76-112), new members of extractable metallofullerenes, were studied. Positive-ion laser desorption/ionization (LDI) and electron impact (EI) mass spectra indicated that lutetium is a special lanthanide that prefers to form dilutetium fullerenes by the are-burning method. However, the signals for Lu2C2n become very weak in negative-ion LDI-MS, this is different from La-2@C-80, which has close relative abundances in positive- and negative-ion MS. The distinction between Lu2C2n and La-2@C-80 in the negative-ion LDI mass spectra may be due to the different structures of La- and Lu-containing fullerenes. (C) 1997 by John Wiley & Sons, Ltd.

Study on the interaction of rare earth with 3,5,3'-triiodothyronine

The stability constants for rare earth complexes with 3,5,3'-triiodothyronine were determined at 37 degrees C end an ionic strength of 0.15 mole/L NaCl. The lanthanide induced shifts were measured for H-1 nuclei of 3,5,3'-triiodothyronine. The coordination of rare earth with 3, 5, 3'-triiodothyronine was discussed.

Interaction of La3+ and cholesterol with dipalmitoylphosphatidylglycerol bilayers by FT-Raman spectroscopy

The interaction of La3+ and cholesterol with the negatively charged phospholipid dipalmitoylphosphatidylglycerol bilayers was studied by Fourier transform-Raman spectroscopy. La3+ was shown to increase interchain order and intermolecular ordering of the lipid lattice, cholesterol exhibited less of an effect, the La3+-DPPG-cholesterol complex was more ordered than cholesterol=DPPG nd less ordered than La3+-DPPG complexes, cholesterol modulates the order/disorder parameters of DPPG bilayers.

Efficient cleavage of ribonucleoside 3',5'-cyclic phosphates and deoxyribonucleoside 3',5'-cyclic phosphate by lanthanides

The cleavage of 3',5'-cAMP, 3',5'-cGMP and 3',5'-dcAMP by lanthanides has been investigated by HPLC and H-1 NMR. Rapid cleavage of cAMP, cGMP and dcAMP by Ce(III) under air at pH 8 and 37 degrees C has been observed. Regioselective cleavage of P-O(5') bond in cAMP, cGMP and dc;aMP tu give the corresponding 3'-AMP, 3'-GMP and 3'-dAMP by lanthanide chlorides has been achieved, and 3'-AMP and 3'-GMP are cleaved to adenosine(A) and guanosine(CT) more slowly, respectively, The notable difference in reactivity between Ce(III) and the other lanthanide ions under air has also been studied. The cleavage is enhanced with the increase in the molar fraction of Ce(IV). The fast cleavage of cAMP by Ce(III) under air at pH 8 is ascribed to the resultant Ce(IV) in the reaction mixture.

Syntheses and crystal structures of [(C6H5CH2C5H4)(2)GdCl center dot THF](2) and (C6H5CH2C5H4)(2)ErCl center dot THF

[(C6H5CH2C5H4)(2)GdCl . THF](2) (1) and (C6H5CH2C5H4)(2)ErCl . THF (2) were prepared by the reaction of LnCl(3) (Ln=Gd, Er) with benzylcyclopentadienyl sodium in THF and characterized by elemental analysis, IR, H-1 NMR, C-13 NMR, MS and thermal gravimetry. The crystal structures of both compounds were determined. Complex 1 is dimeric and its structure belongs to the monoclinic, P2(1)/c space group with a=1.1432(2), b=1.2978(2), c=1.7604(3) nm, beta=108.75(2), V=2.4732(9) nm(3), Z=2(four monomers), D-c=1.54 g . cm(-3). R=0.0342 and R(w)=0.0362. Complex 2 is monomer and its structure belongs to the orthorhombic, P2(1)2(1)2(1) space group with a=0.8645(2), b=1.1394(3), c=2.5289(4) nm, V=2.4919(9) nm(3), Z=4, D-c=1.56 g . cm(-3). R=0.0514, R(w)=0.0529. The determination of the crystal structure shows that in complex 1 the benzyl groups on the cyclopentadienyls coordinated to Gd3+ are located in the opposite direction (139 degrees); in complex 2 the benzyl groups on the cyclopentadienyls coordinated to Er3+ are located in the same direction (6.5 degrees).

W-183 NMR characterization of rare earth heteropolymetalates in aqueous solution

W-183 NMR spectra were obtained for [La(AsW11O39)(2)](11-), [La(As2W17O61)(2)](17-), [La(SiW9Mo2O39)(2)](13-), [LaSb9W21O86](16-), [LaAs4W40O140](25-) and alpha-, beta-[(CeO)(3) . (SiW9O34)(2)](14-) complexes, Tungsten NMR studies showed that the C-s symmetry of the square antiprism for [La(ASW(11)O(39))(2)](11-) and [La(As2W17O61)(2)](17-) anions keep constant in aqueous solution; the lanthanide accupied the central S-1 site in [LnSb(9)W(21)O(86)](16-) and [LnAs(4)W(40)O(140)](25-) complexes, respectively, and lanthanide metal cations gave [(CeO)(3) . (SiW9O34)(3)](14-) type of complexes with SiW9O3410-.

Preparation and characterization of polymer-supported rare earth complexes

The polymers containing different ligand groups of atoms (mainly O, N, and S) and their rare earth complexes were prepared, characterized and classified based on the type of metal-ligand tending. The catalytic activities of the complexes are briefly discussed. The polymer-supported rare earth complexes showed much greater activities than the corresponding complexes with a low molecular weight.

FT-RAMAN SPECTROSCOPIC STUDIES ON THE INTERACTION OF METAL-IONS WITH SPHINGOMYELIN BILAYER

The interaction of trivalent lanthanide ions and divalent calcium ions with sphingomyelin bilayer has been studied by FT-Raman spectroscopy. The results showed that the bonding of metal ions to the phosphate group of sphingomyelin bilayer, either La3+ or Ca2+, did not change the conformation of the choline group, that is, O-C-C-N+ is still in its gauche conformation. The presence of metal ions changed the states of the interfacial region from liquid-like to amorphous state and even to crystalline. They increased the fluidity of acyl chains of sphingomyelin bilayer and made them packed disorderly.