Lanthanide metal(III) ions remarkably catalyze the hydrolysis of phosphodiester linkages in DNA, RNA, and adenosine 3', 5'-cyclic phosphate. The magnitudes of acceleration range from 106 to 10" fold. With the use of Ce(III) ion (0.01 m oldm-3), the phosphodiester linkages in linear DNAs are hydrolyzed for the first time nonenzymatically (half-life 3.6 h at pH 7.2, 50 °C). Furthermore, the linkages in both RNA and adenosine 3', 5'-cyclic phosphate are efficiently hydrolyzed at pH 8.0, 30 °C with the half-lives 10 m in (by Tm(III)) and 36seconds (by Ce(III)), respectively. Non-lanthanide metal ions show virtually no catalysis: the superb catalysis is specific for lanthanide metal ions. These results indicate high potentialities of the metal ions as the catalytic centers for the artificial enzymes which are ap plicable to regulation of various bio-reactions.

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The fluorescence properties of divalent europium complexes with several kinds of crown compounds such as crown ethers, azacrown ethers, N-pivot-lariat azacrown ethers, and cryptands have been systematically investigated under UV irradiation. The most intense emission is yielded by a methanol solution of the Eu2+-15-crown-5 complex, the intensity of which is 690 times greater than that of a methanopc EuC12 solution with the same Eu2+ concentration. The enhancement of the emission intensity can be attributed to "insulation" of the Eu2+ ion from the solvent molecules based on the encapsulation effect and "restriction" of the expansion or vibration of the Eu2+ ion. The peak of the Eu2+ emission located at 489 nm for the Eu2+ion solvated by methanol and in general tend to appear at the shorter wavelength side (417488 nm) as the complexes form. The stoichiometries of several Eu2+ complexes were determined by using the emission intensity molar ratio method and by monitoring the shift and splitting of the proton magnetic resonances for the Sr2+ analogues. Radiative and nonradiative rate constants for the excited states of the -complexes were estimated from quantum yields and luminescence lifetimes. The luminescence enhancement owing to complexation was found to be, not due to an increase in the radiative rate constants, but due to a decrease in the nonradiative ones. The former was almost the same value of order of 105 while the latter changed from 105 to 108s-1. Furthermore, we found that the crown ethers having a bromoalkyl side chain were induced to form complexes with Eu2+ by UV irradiation and that the emission intensity of Eu2+ in the complexes increased significantly. Methacrylate polymers containing cyclic polyether structurrs, su ch as 15-crown-5, 18-crown6 and cryptand[2.2.2], have been prepared and formed complexation with Eu2+ and their luminescence properties studied in a solid state. They generally gave blue bright emissions in the region of ca.420-445 nm under UV irradiation. For the Eu2+ polymer containing cryptand[2.2.2], the peak of the emission spectra was located at 455 n m. The Eu2 + polymer containing the 15-crown-5 ring exhibited the largest intensity of luminescence and its emissigt intensity was ca.20% of that for CaWO4: Pb(NBS 1026). There are supposed to be two types of quenching mechanisms, one is responsible for the Eu2+-Eu2+ distance and another is due to a structural change of complexes. The Eu2+ions in the solid polymer ligands exhibited fairly better stability to air than the Eu2+ ions due to complexing with the monomeric polyethers in a methanol solution. We have studied effects of the coexistence of the several divalent ions with Eu2+ on the luminescence properties and found out the Eu2+-Zn2+doubly-doped polymer containing the 15-crown-5 structure to be twice stronger phosphor than the Eu2+ only doped one.

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2, 6-Pyridine dicarboxylic acid (PDA) and terbium chloride (TbC13) were dissolved in poly (ethylene oxide)s (PEOs) with average molecular weight of 200, 300, or 400. The PDAand TbC13-containing PEO solutions were separately introduced in 2-compartment quartz cell. The Teflon partition plate was then pulled up to contact these two PEO phases to start complex formation. The complexation of TbC13 with PDA was successively analyzed by the fluorescence measurement. The fluorescence intensity (545 nm) increased with vibration. Fluorescence intensity increased more slowly with the increase in the molecular weight of PEO oligomers. The PEO solutions of different viscosity were prepared by adding different amount of LiC104 in the PE0200. The complexation rate was decreased with increasing viscosity. Solution viscosity was revealed to govern the complexation rate. On the other hand, final fluorescence intensity of PDA/Tb complex in LiC104-containing PEO, , , , was the same as that in pure PE0200. Hydroxyl group fraction was revealed to govern the fluorescence intensity. The complexation was further accelerated by applying the potential.

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The effects of crown ethers (12-crown-4, 15-crown-5, and 18-crown-6) and anions (C104-, Cl-, Br-, and I-) on the redox behaviors of europium(III/II) were investigat ed by cyclic voltammetry in an aqueous solution. The complexations of europium(II) with crown ethers were discussed by means of the shifts of redox potential. Addition of 18-crown-6 led to the appearance of a new oxidation wave at 0.28 V and the decrease of the peak height of the oxidation wave at O.55 V. For 15-crown-5 and 12-crown-4, similar behaviors were observed, but the magnitude of the changes for oxidation peak heights was very small. These differences depend upon the relative sizes of europium(II) ion to the internal cavities of crown ethers. As europium(II) forms a stable 1: 1 complex with 18-crown-6, the stabilization of europium(II) is remarkable. The small anion such as Cl- strongly interacts with europium (II) complex with 18-crown-6 to weaken the stabilization effect of europium(II) by crown ether.

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The solubilities of crystalline Nd(III) hydroxide was measured in dilute solutions under anaerobic condition, CO, and 02 partial pressures of O.1 and 1 ppm, respectively. The aim of this work is to get thermodynamic data (equilibrium constant of crystalline Nd(III) hydroxide and hydrolysis constants of Nd(III)) and discuss the similarity of dissolution behavior between Nd(III) and Am(III) which is important element in the view of geological isolation of high level radioactive waste. And another aim is to confirm the reliability of thermodynamic data obtained from this work. The equilibrium was attained from both over- and undersaturation as long as 68 and 64days, respectively. The experiments were carried out at the pH range of 7 to 13 at an ionic strength of O.01 and at room temperature (22 °C). The solid phase was identified as Nd(OH)3 (c) by X-ray diffraction before and after the experiments. From the solubilities of crystalline Nd(III) hydroxide, the equilubrium constant (K810 for Nd(OH)3 (c) +3 H=Nd3+ + 3 H20) and the hydrolysis constants of Nd(111) (pm?, for m N d"-Fn H20=-- Ndm, (OH)(3m-n)+-1-n H+) were estimated. The value for log Ks, is 16. O. The value s for log p, , , log p, 2 and log 1313a re 7.6, 14.3 and < 24.9, respectively. The results indicate both [Nd(OH)]2 and [Nd(OH)4]- a r e not dominant in the pH range 7 to 13. The v a lue of log ign, 7.6, was well agreed with the calculated value of 8.1 by the theory of Brown et al. The dissolution beh a v i o r o f Nd(III) hydroxide was similar to that of Am(111) reported by Rai et al. in aspect of dominant species at different pH.

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Lanthanoid(III) complexes such as Ln2(C604X2)3n H20; (Ln=La, Nd, Sm, Gd, Tb, Ho, Er, X=C1, Br, H) are all polycrystalline fine powders and to which single crystal X-ray structural analysis is not applicable. We applied extended X- ray absorption fine structure (EXAFS) spectroscopy to the above lanthanoid(ll) complexes in order to study the local structure of the complexes. The curve fitting procedure was performed by assuming the single shell model for the parametrization. The coordination- numbers of the lanthanoids(111) were obtained from the relative amplitude of EXAFS signal of the standard compounds Ln(thd), , and were seen to be the same at both Ln2(C604C12)3n H20 and Ln2(C604Br2)3n H20 complexes. These coordination numbers w ere in agreement with those obtained by the thermal analysis. The distance r[Ln(11)-0] between the Ln(III) ion and a coordinated oxygen was also determined. No considerable difference in the distance r[Ln(111)-0] was observed between chloranilates and bromanilates of the individual lanthanoid Ln(ll), and the distances are correlated to the ionic radii of Ln(M) ions very well. The local structures of two complexes are not so different from each other. The behavior of lattice or coordinated water molecules were studied qualitatively by IR spectra. XANES spectra of Br K-edge of bromanilic acid itself give a clearly different feature from those of the lanthanoid(11) complexes.

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X-Ray diffraction and molecular dynamics simulation were carried out to study the structure of DyC18 and equimolecular DyC13-NaC1 in the molten state. The interionic distances of Dy3-C1- and C1--C1- pairs were estimated at 2.67-2.69 and 3.77-3.82A, respectively, and the Dy3+ ion was surrounded by about six Cl- ions. These results suggest that [DyCl6]3appeared to be one of the most abundant short range structure of molten DyCl3 and equimolecular DyC13-NaC1. The geometrical analysis of interionic distance of Dy8+-Dy" allows the existence of dimeric ion Dy2C15- which is formed by linking two octahedra at one C1ion as a common ligand, that is, corner-sharing. The molecular dynamics calculation was used to determine the pair correlation for the respective ion pairs and the angular correlation of Z C1-Dy"--C1- using Born-Mayer-Huggins type potential. The above conclusion was also supported by the molecular dynamics calculation.

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Rare earth(111) complexes of a pentadentate ligand, 2, 6-diacetylpyridine bis(2-pyridylhydrazone)(abbreviated as L), were synthesized and characterized, where rare earths used were La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er and Lu. From the crystal structure of [Eu(L)(NO3)2(CH3OH)](NO3) reported previously, IR spectra and molar conductances in met hanol, it was presumed to be the ten-coordinated structure, [Ln(L)(N08)2(H20)](NO3), for Ln=La-Gd, where the two coordinating nitrate ions function as a bidentate ligand. For the heavier rare earth group of Dy to Lu, the nine- or eight-coordinated structure, [Ln(L)(NO3)(H20)2](NO3)2 or [Ln(L)(NO3)(H20)](N08)2H20, was most probable becau se the absorption intensity around 1380 cm-' attributable to an uncoordinating nitrate ion was more intense in these complexes than that in the complexes of La to Gd. '3C-NMR spectra of the La- and Lu- complexes in DMSO-d6 showed that the ligand, L, was more strongly coordinated to the heavier rare earths compared with the lighter ones.

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The stability constants of lanthanide (M)-ATP (M=Tb, Dy, Er, Tm, Yb) complexes have been determined by a competitive spectrophotometry. The indicator ligand, 5-Br-PAPS (L), as well as its metal complexes, ML, having intense color with sufficient separate absorption peaks permits the analysis of complexation between metal and ATP (A). The stability constants are found to decrease with increasing atomic number: log KmA=5.76 (Tb), 5.57 (Dy), 5.38 (Er), 5.28 (Tm), 5.17 (Yb).

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The complex anions and their vibrational modes in molten GdC1a-KC1 and GdC13-NaC1 were examined by Raman spectroscopy. Each spectrum was deconvoluted into two or three peaks with the Lorentzian-type functions. The peaks in the spectra were assigned to three Raman active modes (v v2, v5) of the GdCle- octahedral complex anion. These peaks shifted toward the lower wavenumber region with increasing mole fraction of GdC13. The peak of vs mode was observed only in the low GdCla concentration region. The clustering of complex anion GdC163 appeared to exist in the melts. However, the clustering might be restrained when the GdC13 concentration became relatively low by adding KC1 or NaCl.

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In tetrahydrofuran (THF) or THF-hexamethylphosphoric triamide (HMPA), diphenylketene ( 1) is reduced with Yb or YbClan to give dimeric compounds (2-5), whereas monomeric products (6-43) are obtained with SmI2, one-electron reductant. Isocyanates (11 a-g) are reduced with SmI2, to produce oxamides (12 a-g) in moderate to good yields. This reaction proceeds via one electron transfer from SmI2, followed by homocoupling of radical intermediates [H]. At room temperature 1-naphthyl isocyanate (11 e) is treated with SmI2 to give 1-naphthylamine as a main product, while at lower temperature, corresponding oxamide (12 e)is obtained as a main product. Higher temperature and longer reaction time are necessary to complete the reaction of aliphatic isocyanates. Furthermore, the SmI2/THF/HMPA system desulfurizes isothiocyanates, R-NCS (13 a-c), under the mild conditions, to give isonitriles (14 ac) in good yields, irrespective of the substituents (R). Thioketone (15) also undergoes desulfurization by Yb metal in THF-HMPA to give olefin (16) at room temperature.

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New low-valent samarium reagents were prepared by the reaction of metallic samarium with bromine in a molar ratio of 4: 3 or by the reaction of samarium(III) bromide with butyllithium. These reagents exhibited reducing ability higher than that of samarium(II)iodide or metallic samarium. Aromatic acid esters were reductively dimerized by these reagents. Diethyl trans-cyclopropane-1, 2-dicarboxylate was subjected to the reductive ringopening reaction on treatment with these reagents. The reaction of dimethyl cyclopropane-1, 1-dicarboxylate with metallic samarium in the presence of mercury halides afforded bis[3, 3-bis (methoxycarbonyl) propyl] mercury.

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Lanthanoid triisopropoxides, [Ln(OPri)8], which were prepared from lanthanoid metals and 2-propanol, were very active catalysts for Meerwein-Ponndorf-Verley reduction an d Oppenauer oxidation. Their activities were higher than that of Al(OPr)8 in the former re action, and various ketones were reduced to the corresponding alcohols in good yields u nder mild conditions. The reduction of aldehydes was very fast even at low temperature, and gave alcohols in moderate yields. At high temperature, however, aldol-type side reactio ns occurred. The analogous side reaction was observed in the Oppenauer oxidation of 1 -phenylethanol with large excess of cyclohaxanone at high temperatures, and gave 2-(1-cy clohexe. nyl)cyclohexanone. The side reaction was repressed by lowering the reaction te mperature and by diluting the ketone concentration with toluene. Thus, the Oppenauer oxidation at 1 0 °C gave acetophenone in a 94% yield. In both reduction and oxidation reactions, the catalyti c activity of lanthanoid triisopropoxides increased in the order La<Nd<Gd=Er=Yb which corresponds with the sequence of metal ion size. This result suggests that the Lewis acidity of the lanthanoid catalysts is the dominant factor in the Meerwein-Ponndorf-Verley/Oppenaue r reactions.

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It has been found that there are some interesting features in the ammonium cerium(W)nitrate mediated nitration of carbon-carbon double bond, and they were investigated in detail. (1) Carboxylic acid such as formic acid is required to promote the reaction. (2) In addition to the substrate, ammonium cerium(N) nitrate, carboxylic acid, and solvent, an appropriate additive such as carbonyl compound which does not have an electron-withdrawing moiety is required. (3) Ammonium cerium(N) nitrate has been converted into cerium(M) formate in the course of the reaction. (4) The present reaction, also, proceeds in the presence of ammonium cerium(ll) nitrate. In this case, the additive is not necessary, but the yields of the products are not satisfactory. These results suggest that, in the present reaction, NO3ligands on the cerium are replaced by formate anions, then resulting free nitrate ion decomposes into the nitroxides in the vicinity of cerium ion, which attack the carbon-carbon double bond in/substrate.

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The reduction of a variety of functional groups with the new samarium diiodide-base system was investigated. This system reduced rapidly ester, lactone, anhydride, acyl halide, ketone, aldehyde, amide and oxime functionalities to the corresponding reduction products in the presence of protic solvent at room temperature in good yields. Benzoic anhydride was reduced with this system to the aldehyde as well as the alcohol and the carbonyl group of aromatic ketone wad partly reduced into the methylene group. Particularly, similarly to the preceding results of carboxylic acid and nitrile, it is of interest that this system reduced ester, anhydride and amided functionalities which are inert with SmI2. These reductions using KOH or LiNH2 in the addition of H2O proceeded smoothly, and the yields of aromatic carbonyl derivatives was generally superior to those of aliphatic carbonyl derivatives. t Lanth a noids in Organic Synthesis. II.

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There has been a growing interest in the surface properties, in particular as catalysts, of lanthanide-3 d intermetallic compounds and lanthanide metal overlayers. By the use of di s solution of lanthanide metals (Ln: EuYb) in liquid ammonia, we have developed metho d s for the preparation of novel lanthanide-containing bimetallic catalysts. The present in v estigation is aimed at unveiling the effects of a lanthanide overlayer on the C-H bond cle avage of cycloalkanes, which is important to determine the activity for the dehydrogenation of hydro carbon. The Ln-Co and Ln-Ni bimetallic catalysts, prepared by the reaction of Co or Ni powders with lanthanide metals dissolved in liquid ammonia, have been characterized by th e dehydrogenation of cyclohexane and methylcyclohexane combined with other catalytic action s. Their catalytic behavior varied markedly with different levels of lanthanide content. First, the rates of cycloalkane dehydrogenation decreased when the loading of lanthanide meta l s on the Co or Ni surface was low and subsequently increased with increasing loading. An analysi s of the initial decrease in the rates of reaction suggested a decrease in catalytically active transition metal sites due to coating with lanthanide metals. The surface is gradually co v ered with the lanthanide metals and simultaneously certain interactions occur to produce newly active centers in the region of high loading, resulting in acceleration of the dehydrogena t ion of cycloalkanes. The presence of lanthanide metals on Co or Ni enhanced the capacity of this surface to dissociate the C-H bond. Furthermore the effects of a lanthanide metal over layer on the catalytic reaction and related properties over an Co or Ni metal surface w ere discussed.

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Samarium diiodide promoted reductive coupling between ethyl 2-(bromomethyl)acrylate (1) and carbonyl compounds (2) was studied. The 2-ethoxycarbonyl allylation with benzaldehyde, hexanal, acetophenane, and benzophenone proceeded in tetrahydrofuran-hexamethylphosphoric triamide at -78 °C to room temperature, and the corresponding a-methylene-rbutyrolactones (3) were produced in moderate yields. However, the reaction with cyclohexanone and diethyl ketone only resulted in a reductive dimerization of 1; no desired 3 were obtained and diethyl 2, 5-bis(methylene)hexanedioate was produced in 50-70% yields. When the reaction was carried out by using ethyl 2-(acetoxymethyl)acrylate 7 instead of 1 as a precursor in the presence of catalytic amount of tetrakis(triphenylphosphine)palladium complex, the corresponding 3 were obtained from the reaction not only with benzaldehyde, hexanal, and acetophenone but also cyclohexanone which did not give 3 in the reaction with 1.

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he catalytic activities of a series of lanthanoid(11) triflates in the glycosylation of 1-0methoxyacety1-2, 3, 4, 6-tetra-0-benzyl-D-glucopyranose with 1-octanol (Eq.1) were investigated. As shown in Table 1, the triflates of some heavy lanthanide(II) salts such as Tb (OTf)3, Ho(OTf)3, Tm(0Tf)3, and Yb(OTf)3, were found to be highly effective. However, there seems to be no clear correlation between the catalytic activity and either the ionic radius or the oxophilicity of the lanthanoid metal ion.

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Eu and Yb among lanthanide metals (Ln) dissolve in liquid ammonia. The dissolved lanthanide metals in liquid ammonia reacted readily with hydroxyl groups of poly(vinyl alcohol)(PVA) at 197 K to form lanthanide-boud PVA (Ln/PVA) which has the structure of -(CH, -CH)7, -. When Ln/PVA was further treated with a solution of TiCl4 in hexane and refluxed 0-Ln-NH2for 6 h, the activity of selective cyclotrimerization of acetylene to benzene newly appeared. The catalytic properties of TiCI4-treated Ln/PVA (Ln/PVA-TiCl4) were investigated by cyclotrimerization of acetylene and characterized by spectrographic measurements.

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The authors report new gadolinium compounds, polysaccharide-gadolinium chelate, that have the enhancement property in magnetic resonance imaging (MRI) as well as a longer half-life time in blood. Dialdehyde starch (DAS; mol. wt.7 x103) and dialdehyde amylose (DAA; mol. wt.3 x108) were synthesized to increase the half-life time in blood. The binding of gadolinium to DAS or DAA was facilitated by the newly synthesized bifunctional chelating agents N-[2-bis(carboxymethyl)arainoethyl]-N-[2-bis (carboxymethyl) amino-2-(p-benzyl) ethyl]glycine (ABDTPA) and 10-[N-(2-amin. oethyl)carbamoyl]methyl-a, a', a"-trimethy1-1, 4, 7, 10tetraazacyclododecane-1, 4, 7-triacetic acid (DO 3 MA). The enhancement properties of resifting gadoli nium compoumds were evaluated for biodistribution, relaxivity and enhancement effect. Biodistribution was dxamined by use of "In labelled complex. Relaxivity was measured at 0.5 T and 1.5 T. Enhancement effect was examined in vivo by using rats that have brain occlusions. Gadolinium(Gd) complexes with DAS or DAA were found to be staying in the blood vessel for a longer period of time than other existing enhancers. The half-life time of DAS-ABDTPA-Gd is 2 h, while as DAA-ABDTPA-Gd is 55 min. eighty to ninety percent of gadolinium complexes bound to DAS or DAA were excreted in urine 24 11 after administration. Relaxivities of the above gadolinium complexes were 1.2-2times as high as those of ABDTPA-Gd or DO 3 MA-Gd. These results demonstrate that gadolinium complexes based on polysaccharide derivatives are promising compounds for future use as MRI enhancers.

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Gadolinium hydrogen a, a', a", a m-tetramethy1-1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10tetraacetate (abbreviated Gd-DOTMA) was developed as a new contrast agent for magnetic resonance imaging. Our study focused on the evaluation of the pharmaceutical properties as in vivo agent. The new modified process by which Gd-DOTMA was synthesized resulted in high yields of this agent. A high stability constant of 10" for Gd-DOTMA was determined at physiological pH. It is more stable than Gd complex with tetraazacyclododecanetetraacetic acid (which is regarded as the most stable Gd complex). The strong T, relaxivities of 4.0and 3.7 (mMs)-1 at O.5 tesla and 1.5 tesla were measured in the aqueous solution. The osmolarity of O.5 M solution, dissolved with equal amounts of meglumine as a solubilizer is 1020 mOsmol/kg. Thi s contrasting agent was studied in vivo by using rats as the experimental group. The agent showed strong enhancement of transplanted tumors within the rat population studied. This compound is rapidly excreted by the kidneys, and has a half-life of 26 min in blood. The median lethal dose (LD, value) of the stable Gd-DOTMA has a favorable tolerance of over 12.3 mmolfkg.

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We have developed a sensitive time-resolved fluoroimmunoassay for secretin and cholecystokinin (CCK). Europium chelate-labeled streptavidin (Eu-SA) was prepared by labeling Euchelate [N'-(p-isothiocyanatobenzyl)diethylenetriamine-N, N N ', N"-tetraacetato]europium (III)]. The assay procedure was as follows: A standard secretin or CCK-8 solution (100 ul), rabbit anti-human secretin or anti-human CCK anti-serum solution (50 pl) and biotinylated secretin or CCK-33 solution (50 ul) were added to the well of microtiter plate coated with coated with goat anti rabbit IgG antibody and incubated for 16 or 72 h at 4 °C. Then, the wells were washed with 0.05 mol/L Tris-HC1 buffered saline containing 0.05% Tween 20(pH 7.7). The solution of Eu-SA (100 pl) was added to the biotinylated secretin or CCK-33bound to the well. After incubation for 90 minutes, the well was washed and then enhancement solution (Pharmacia Co. Ltd. ) (200 AO was added to each well and incubated at room temperature for 10 minutes. The time-resolved fluorescence intensity was measured by Arcus 1230 fluorometer (Pharmacia Co. Ltd. ). A measurable range and fifty percent value of inhibition concentration (IC 50) for secretin and CCK-8 were from 25 to 1000 pg/m/ and 520 pg/m/ and from 62.5 to 32000 pg/m/ and 1450pg/m/, respectively, and the coefficients of variation for within-run was 1.7 -3.30% (n= 8)and 2.34-7.56% (n = 6). Further, the sensitivity of IC 50 value and detection limit for CCK-8 with ELISA amplification system (Daiichi kagakuyakuhin Co. ) was 18.5-fold and 31.3-fold better than that was obtained by without ELISA amplification system.539

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Electron spin resonance of Gd(I11) bound to the two iron specific binding sites (N- and Csites)of chicken ovotransferrin was studied to investigate the difference between these binding sites. From the analysis of the electron spin resonance data and its Gd(III) concent ration dependence, we concluded that the symmetry of the ligand field (E and D) is almost the same for two sites and that the ligand fields (E and D) of the C-site are larger than those of the N-site.

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The abundances of the lanthanoids in waters and lacustrine deposits of Yugama, the crater lake of Mt. Kusatsu-shirane, Gunma, and in a volcanic block erupted by its volcanic activity were determined by the neutron activation analysis. The lanthanoids were detected at ppb levels in water samples and at ppm levels in solid samples, and no exception to the OddoHarkins rule was observed. The lanthanoid patterns in the solid samples normalized to the Leedey chondrite were similar to each other and were typical ones observed in natural rocks, havingn egative slopes which were especially clear in the light lanthanoids. The patterns in the water samples had more moderate negative slopes than those of the solid samples and were very close to the horizontal one. The plot of the partition coefficient, defined as the ratio of the concentration of an element in the water phase to that in the solid phase, against the ionic radius of trivalent metals was found to have a peak at about 90-95 pm, i. e., trivalent metal ions with ionic radii of 90-95 pm were most preferentially fractionated into the water phase in acidic circumstances.

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Adsorption behavior of some chelating resins for rare earth ions was studied. Distribution ratio, Kd of a series of rare-earth ions (M) by Uniselec UR 10 having N-(o-hydroxybenzyl)iminodiacetic acid (HBIDA=FI, A) as the chelating functional group increased with the increase of stability constant of the 1: 1 complex, M(HA) of I-IBIDA with metal ion from lanthanum to europium. However, after europium, it decreased with the increase of atomic number. This trend does not agree with that observed in the monomeric solution, where the stability constant increases with the increase of atomic number. The adsorption behavior of both Dowex A 1 and RGOP having iminodiacetic acid and phosphoric acid as their functional moieties, respectively, was also similar to that of UR 10. RMTP in which phosphonic acid is involved as its functional moiety indicated selective adsorption for heavy but not for 554 * IL.1993 No.5light lanthanoids. On the other hand, RGP having phosphinic acid moiety demonstrated no selectivity for all lanthanoids. These results im plies, therefore, the adsorption behavior of chelating resin for rare-earth ions can not be explained simply by the stability constants of metal complex in the monomeric ligand system. Mutual sepa ration of lanthanum, cerium and europium was successful by the column chromatography according to their K, difference on a column filled with UR 10 (18.5 cm in height and 1.0 cm in diameter) and HC1 solution of pH 1.80 as an eluent.

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Organophosphorus acids have been widely employed for extraction separation of lanthanides owing to their high extractability and large separation factor for lanthanide elements. The extraction behavior of heavier lanthanides, terbium, thulium and lutetium, was investigated by employing three kinds of organophosphorus acids, bis(2-ethylhexyl)hydrogen phosphate (BEHPA), 2-ethylhexyl hydrogen 2-ethylhexylphosphonate (EHEHPA) and bis(2, 4, 4-trimethylpentyl)phosphinic acid (BTMPPA). An organic extractant solution was equilibrated with an equal volume of aqueous solution containing lanthanide ions for 1 h at 25 °C. After centrifugation, the concentration of lanthanide in the aqueous phase and in the acidic strip ping solution from the organic phase was determined by ICP-AES. Lanthanides(M) were extracted as M(HA2)3(HA)2 is the dimer of extractant). The extraction constant (Kex) increased with atomic number owing to lanthanide contraction and decreased in the order, BEHPA>EHEHPA>BTMPPA (see Table 1) in accordance with the decreasing order of their acid dissociation constants. The Kex value greatly depended on the diluent used: hexane>carbon tetrachloride >1, 2-dichloroethane > toluene > b enzene for each lanthanide-EHEHP A complex. Organic phase reactions such as dimerization of extractants and self adduct formation presumably play important roles in extraction equilibria. These regular trends would be useful guide for the selection of suitable diluents.

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Inductively coupled plasma-mass spectrometry (ICP-MS) and-atomic emission spectrometry (ICP-AES) were applied to the determination of rare earth elements (REEs) in rare earth phosphate minerals such as xenotime and monazite. The analytical sensitivities of REEs by ICP-MS and ICP-AES were in the range of ca.2-70 ppt and 1-50 ppb, respectively. Determination of several REEs in phosphate samples by ICP-AES necce ssitated corrections of spectral interferences from coexisting REEs. In ICP-MS, the interferences of coexisting elements in xenotime was scarcely observed, but the intensities of gadolinium and terbium in monazite were changed due to monoxides of coexisting praseodymium or neodymium. These corrections were easily made from the contents of coexisting elements which have been already determined. The sample solutions prepared with hot concentrated sulfuric acid were directly injected into the plasma. REEs contents in the phosphate minerals were determineded by a calibration curve method. The contents of REEs determined by ICP-MS were in good agreement with those determined by ICP-AES, atomic absorption spectrometry or fluorometry.

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The equilibriume xtractionb ehaviorw as investigatedo n trivalent rare earth ions (Lna+), using 1 -phenyl-3-methyl-4-decanoy1-5-pyraz(oHloPn) ea nd sub-ligandsf rom aqueousp hase. Sub-ligandse xaminedw ere 1, 1 0-phenanthrolin(ep hen), t rioctylphosphinoex ide( TOP O), or methyltrioctylammoniucmh lorideC H3(C81117)3N+CT1h-e. chemicals peciese xtracted into chloroform were found to be LnP, in the case of HP as only extractant, whereas LnP8. phen, LnPaTOPO or CH3(C8H17)3N+LnP4- in cases of using phen, TOPO or CH3(C8F117)8N+ C1- as sub-ligand respectively. The values of extraction constant K.., Kex(phen), Kax(TOPO)and K'.. for Ln3+ were determined for the four extraction series, that is, HP only, the coexistence of phen, TOPO or CH3(C8H17)3N+Cl- respectively. The values of extraction constant obtained for the above four series were in the order ICCK'r, <Kei(TOPO)<K(phen). Using these values, the separation factors (S) between the adjacent elements were calculated. The average values of S in cases of coexistence of sub-ligand were larger than that obtained by HP extractant only, in the order HP<HP-I-TOPO<HP+phen<HP+CH. (C61-117)aN+C1-.

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The effect of the addition of diethylenetriaminepentaacetic acid(DTPA) to the stripping phase on the kinetics of permeation of rare earth metal ions, La"-, Pr3+ and Nd3+, through a supported liquid membrane (SLM) containing 2-ethylhexyl hydrogen 2-ethylhexylphosptionate (PC-88 A) was investigated. The flux of Ln3+ steeply decreased with increasing pH in the stripping phase (pHs) and was not detectable above pH 3.0 in the absence of DTPA. On the other hand, in the presence of DTPA, it is worth noting that Ln3+ permeated through the SLM even in the range of pH, where the permeation of Ln3+ was not detractable without DTPA, and that flux remained almost constant between pH, of 1.4 and 3.3. Experimental results on the flux under the various conditions of stirring speeds, pH of feed phase, DTPA concentrations and SLM thickness, led to the assumption that the permeation rate was controlled by the diffusion of Ln complexes in SLM with the concentrations of equilibrium at the extraction interface and zero at the stripping interface. The calculated rates and the average concentrations of Ln in SLM under the above assumption were well coincided with the experimental results, which supports the proposed mechanism. It is also suggested that increasing concentrations of dissociated DTPA species should cause to form complexes with Ln3+ to compensate the decrease in proton activity in the stripping phase with increasing pH.579

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The oxidative decomposition of bastnAsite (LnCO3F: Ln Ce, La, Nd, -) in an equimolar eutectic mixture of NaOH-KOH has been studied to clarify the rate-determining step. The reaction was carried out under the following conditions: 183-220 °C, stirring 260-1050 rpm, atmosphere (1\12, air, and 02), weight ratio of Bastnasite/melt O.02-0.11. BastnAsite was rapidly decomposed to Ce(OH)3, in which the other rare earth metals made a solid solution, and CO32- and F- are fixed in the melt. The resulting hydroxide was easily oxidized to Ce02, in which the other rare earth metals were contained as solid solution. since temperature affected slightly the rate of oxidation of Ce and stirring of both melt and air raised it remarkably, the dissolution of oxygen into the melt was considered to control the rate process. However, the effect of diffusion of oxidizing species in a thin layer of oxidation product was onserved some extent.

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Nitrate produces a polarographic wave in the presence of lanthanoid ion, which accelerates the reduction of nitrate as a catalyst. As the concentration of nitrate or lanthanoid increases, the reduction potential of nitrate changes in the direction of a positive one. The increase of pH favors the reduction of nitrate, in spite that this reaction requires many protons. Multisweep cyclic voltammetry or flow electrolysis with a hanging mercury drop electrode shows that polynuclear complexes of lanthanoid generated with an increase of pH adsorb on the surface of electrode and promote the reduction of nitrate. Current-time curve in a polarographic drop-life or potential-step method is characterized by a sharp peak observed after certain interval, which also substantiates the mechanism stated above. The chief product in the controlled-potential electrolysis is hydroxylamine, and it is inferred that the total reduction of nitrate in the presence of lanthanoid follows the reaction: NO3- + 6 e- + 8 H+ -+ NH30H+ + 2 H20.

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The selective adsorbent for rare-earth ions was prepared by loading bis(2-ethylhexyl) hydrogenphosphate (B 2 EHP) on XAD-7 resin, and the distribution ratios of individual rareearth ions between the resin and the aqueous solution have been determined. The distribution ratio increased with the increase of atomic number of the elements (Fig.2), and the mean separation factor for every neighboring pairs was found to be 2.4. In the chromatographic separation on the B 2 EHP resin column by stepweise elution with O.15 M-3.0 M HCI solution, all of the lanthanoid ions(except prometium) was eluted in the order of their atomic number (Fig.3) and were separated completly.

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Determination of fourteen lanthanides byihigh performance anion-exchange chromatography was studied. A guard column (DIONEX HPIC-CG 5, 8 mm i. d., 10 mm) and a separation column (DIONEX HPIC-CS 5, 4 mm 1. d., 250 mm) were used. The separation was achieved using opposing linear gradients of oxalic acid and diglycolic acid. The gradient was 8 min long and total run time was 25 min. The lanthanide metals were determined by monitoring the absorbance at 520 nm of the complex formed with the postcolumn 4-(2-pyridylazo)resorcinol (PAR) reagent. The detection limits and precisions were in the range 1 to 25 ng and 0, 9 to 6.9%, respectively, as a use of 50 pl sample. This method was applied successfully to the determination of the lanthanides in lanthanide chlorides produced in China.

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The thermal decomposition of samarium(III) acetate tetrahydrate has been studied by means of TG, DTA, X-ray diffraction, IR, gas chromatography, ICP-AES and chemical analysis. The dehydration of tetrahydrate begins at 70 °C. In the process of the dehydration which occurs in three steps, two unknown hydrates are produced. The two unknown hydrates are samarium(la) acetate monohydrate and hemihydrate. Anhydrous samarium(11l) acetate is too hygroscopic to be isolated as a single phase. After several hours in air at room temperature, the anhydrous acetate changes to monohydrate due to the absorption of water vapor. The anhydrous acetate decomposes on heating to samarium (III) carbonate oxide above 280 °C, passing through an intermediate compound, and th en samarium(a) oxide is produced finally. The intermediate compound shows a new X-ray diffraction pattern and is estimated to be Sm (CH3C00) 0.

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Glycothermal treatments of hydrous acetates of lanthanide(Ln) elements in 1, 4-butanediol at 300 °C were examined. Each product was composed of one or a few phases, which varied systematically according to the atomic number of lanthanide elements and four phases having different structure were observed in total (Fig.1 and Table 1). IR spectra (Fig.2) and elemental and thermal analyses (Tables 2 and 5) confirmed that these phases were diacetate hydroxide (Ln(CH3C00)2(OH); phase A), novel acetate dihydroxide (Ln(CH3C00)(OH)2; phase C), and two modifications of acetate oxide (Ln(CH3C00)0; phases B and D), one of which (phase D) has not been reported thus far. One of the modifications of acetate oxide (phase B) was also formed by thermal decomposition of the corresponding acetates while two acetate hydroxide salts and the other modification of acetate oxide (phase D) were not. Glycothermal reaction completely altered the morphology of particles; the produc ts were composed of thin plates (Fig.5), while the original acetates were large (>100 urn) crystals, which suggests that the product is formed via a dissolution-crystallization mechanism, lanthanide acetates being dissolved into a mixture of 1, 4-butanediol and water originated from the crystallization water of the acetates. The modifications of acetat e oxide thermally decomposed into lanthanide oxides uia carbonate oxide salts, while thermal decomposition of the two salts of acetate hydroxide led to dehydration into acetate oxide (phase B) which further decomposed into carbonate oxide and the oxide.

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Glycothermal reaction of acetate hydrates of lanthanide elements with triethyl phosphate in 1, 4-butanediol at 315 °C afforded corresponding lanthanide orthophosphates (LnPO4). The monoclinic modification of the phosphates was obtained from the acetates of La-Eu and the tetragonal one from Tb-Lu. Gadolinium acetate yielded a mixture of the tetragonal and monoclinic modifications; the former form of GdPO4 had been synthesized only by calcination of the monoclinic form at about 1700 °C. With the decrease in the reaction temperature, the proportion of the tetragonal modification decreased. The monoclinic modification of TbPO4 was also formed at the reaction temperature 225 °C together with the tetragonal form. The products were comprised of micro crystals (15-40 nm).

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Thermal decomposition of Ln(C, H, COO) aH2O(Ln: La, Ce, Pr, Nd) was studied by thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The compositions of the starting materials and the products obtained by the thermal decomposition were determined by elemental and chemical analysis and ICP emission spectrometry, and idintified with IR and powder X-ray diffraction measurements. The gaseous products evolved during the thermal decomposition from the anhydride to the oxide were analyzed by gas chromatography. Th e dehydration of the monohydrates took place successively as one step reaction without formation of the intermediate hydrate. The prorionate anhydrides we re fused. The heats of fusion of the anhydr ides of La (ill ), Ce(11), Pr( ill) and Nd(M) were 18.8 2, 9.23, 22.4 9 and 18.3 1 k Jmol-', respectively. The anhydrides release 3-pentan o ne and carbon dioxide to form Ln202CO3(Ln: La, Ce, Pr, Nd) through an intermediate compound in the course of the decomposition. The composition of the intermediate compound was found t o be Ln20(C211, C00)4(Ln: La, Ce, Pr, Nd). Finall y, lanthanide= oxide were produced, but in a case of cerinum cerium (N) oxide was produced.

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The solubilities of crystalline neodymium iodate dihydrate and amorphous neodymium iodate anhydride in water at 298.2 K were measured iodometrically using the supersaturation method. The recommended solubility of neodymium iodate in water at 298.2 K is 1.03 x 1 0-3 moldm-3. Anhydrous iodate of an amorphous type was prepared by thermal dehydration of the iodate dihydrate. During the measurement the amorphous iodate was recrystallized to the crystalline iodate. Thus, the solubility obtained agreed well with the above value.

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In order to obtain pure EuN powder, sponge Eu was prepared by evacuation of NH3 under 10-s Torr from an Eu solution of liquid NH3 a part of impurities in which was removed by dissolution of Eu. The resulting sponge Eu contained 2-3% of Eu(NH2)2 and a small amount of Eu(OH)3. This material was heated in purified NH3 in a silica tube at 700-4000 °C for 15-120 min. Nitridation took place easily at 800-900 °C. The purity of EuN attained 98.5%at 1000 °C for a 30 min heat treatment and the purity decreased gradually when the treatment exceeded 30 min.

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YTa7019 doped with Tm3+ was prepared by a solid state reaction of co-decomposition nitrates as starting materials. The substitution of T m3+ for Y3+ in Y1_, TmsTa7019 was performed in the full compositional region on calcinating at 1200 °C for 24 h in air. The solid solution was isomorphous of CeTa7019 which involved a network of (CO, Ta5+)-02- polyhedra interstratified in a double layer of Ta5+-02- polyhedra. The samples were identified by XRD and the optical measurement was carried out. According to the results of excitation and emission spectra, the intense blue emission of Tm3+ was observed near 460 nm corresponding to twice the intensity of YA103 doped with Trn3+. The unique concentration dependence of emission intensity in Y1_5TmsTa7019 was observed. The maximum of relative intensity was obtained at x=0.2. This profile revealed the concentration quenching of emission. The energy migration of excited Tm3+ was discussed in relation to the low-dimensionality of substituting sites for Tm3+.

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The characteristics of ESR and thermoluminescence (TL) were studied on the X-ray irradiated Rb2Mg2(S04)3: Ln (Ln =La, Eu) prepared by two kinds of procedures as follows. A Rb2Mg2(SO4)3 matrix was synthesized by heating the mixture of Rb2SO4 and MgSO4 at 102 3K for 1 h in a helium flow, mixed well with a fixed amount of Ln2(SO4)8 powder, and heated at 1023 K for 1 h in a helium flow (sample AR). In the other process, the homogeneous mixture of a fixed amount of Rb2SO4, MgSO4 and Ln2(SO4)3 powders were heated at 1023 K for 2 h in a helium flow (sample BR). The X-ray powder diffraction pattern indicated that the crystallization of Rb2Mh2(SO4)3 matrix was suppressed by the coexistence of Ln2(SO4)3. The X-ray irradiated sample AR showed the ESR signal due to S0, - radical and the intensity decreased monotonously with an increase in thel blended amount of Ln2(SO4)3. The X-ray irradiated sample BR showed that the ESR signal intensity had a maximun at 1 mol% La2(SO4)3 doping and that the signal decreased drastically with an increase in the blended amou nt of Eu2(SO4)8. The TL originally arising from Eu2+ (4 f65 d *4f 7 transition) was observed in the samples AR and BR. The maximum of TL intensity of sample AR was higher than that of sample BR. A remarkable difference in the ESR signal and TL intensities for the samples prepared by a different procedure was ascribed to the difficulty of diffusion for a rare earth ion into the crystalline Rb2Mg2(SO4)3 matrix.

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A layered perovskite compound, Ag2La2Ti3010was newly synthesized by an ion exchange reaction of IC2La2Ti8010 with AgNO3 molten salt. The crystal structures of parent compounds K2La2Ti3010. xH20 (x=0, 2) and Ag2La2Ti301were determined by Rietveld analysis. All of the structures were analogous to that of Ruddlesden-Popper phase with a tetragonal crystal system. Although the anhydrous K2La2Ti3010 and Ag2La2Ti3010 had almost the same crystal structure, a drastic difference in the bond character of M-0 (M=K, Ag) was observed between the two compounds, i. e., completely ionic character for the K-0 bond and relatively strong covalent character for the Ag-O bond along the direction of c axis. Such a covalent bond character in Ag2La2Ti3010 was reflected to the conductivity behavior. An almost pure ion conduction of silver was observed at the temperatures below 200 °C, while the mixed conduction with silver ion tranport number of 0.5 was observed over this temperature.

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We measured galvanomagnetic effect of Gd-Co and Gd-Co-Eu amorphous films under ferromagnetic resonance at room temperature. The magnetoresistance effect was dominant in Gd, Coso and Gd21Co79 alloys. On the other hand, the extraordinary Hall effect was dominant in Gd, , Coalloy. The intensity of the magnetoresistance effect increased linearly with increase of magnetization in the Gd-Co system. In Gd-Co-Eu system, the effect of Eu addition on the extraordinary Hall effect was examined. The coefficient of the extraordinary Hall effect in this system increased with increase of Eu concentration. It was understood that the electronic state of Co was varied with the Eu concentration.

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Sintered RE-(Fe, Co, Ni)-B magnets in a regime of RE-Co-B phase diagram were prepared by a powder metallurgical method, and their corrosion behavior as well as magnetic properties were studied in comparison with those of conventional rare earth magnets. NdFe-B magnets substituted with Co and Ni for Fe exhibited no corrosion at all for 1000 h at 70 °C in air with a relative humidity of 95%. They also be resistant to spray salt to the same extent as Sm-Co magnets. The potentiostatic anode polarization curves of the magnets exhibited a remarkable effect of Ni in elevating the corrosion potential in acid- and neutral solutions and in yielding passivation in an alkali solution. Magnets singly substituted with Co displayed only a slight improvement of corrosion over Nd-Fe-B magnets. Microscopic observations of the magnets with analytical TEM and SEM indicated an important role of a Nd(Ni, Co) phase present at the grain boundaries in realizing the good magnetic properties and suitable corrosion resistance at the same time. The influences of replacement of Nd by La, Pr and Dy in the Nd-(Fe, Co, Ni)-B magnets on the corrosion behavior were also studied.

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The luminescence properties of Sr doped yttrium tantalate, ((Y1_xSrx)(Ta1_yNby04_, ) and (Y1_xSrx)Ta04_6) were examined. A single phase of the monoclinic forn with Fergusonite M' structure was obtained in the range 0 < X<0.0015. By doping of Sr ion in the Y(Ta, Nb)04 phosphor, the X-ray excited luminescence was observed. The maximum of luminescence efficiency was obtained at about 0.15 a/o% of Sr content. Also, the addition of Sr ion resuited in the decrease of the afterglow in the Y(Ta, Nb)04 phosphor below 0.15 a/o%. The maximum of conductivity was obtained at O.15 a/o% of Sr content. The electrical conductivity changed as a function of oxygen pressure, especially under the oxygen pressure higher than 10-4 atm. This result indicates that the p-type conduction was closely related to the formation of 02- vacancies in Y(Ta, Nb)04. In addition, it was found that oxygen vacancies significantly contributed to decrease the probability of the non-radiative transition and enhance the luminescence of Sr doped Y(Ta, Nb)04 phosphors.

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Some mechanical, physical and chemical properties of transparent ceramic, Pbo.91La0.09Zro.64Tio.3 4°3; which is one of the so-called PLZT, were investigated and its applica tion to window material of infrared spectrophotometer was attempted. The present PLZT possessed high strength (modulus of rupture at room temperature: 150 MPa), high hardness (Vickers hardness: 5 GPa) and low expansion coefficient (6 x 10-6 IC-') in the range of room temperature to 800 6deg;C. It was very stable in various solvents except for HF solution, as summarized in Tahle 2. The transmittance of 0.5 mm-thick PLZT was about 65% below 6 pm and decreased with increasing wavelength to reach almost 0% at about 9, um. The drop of transmittance of this PLZT at 5, um was less than 10% even at 800 °C. These transparent property made it possible to be utilized as the window material of infrared spectrophotometer in the range of 2.5 to 8 or 9 pm, as shown in Figs.3 and 4. Furthermore, it should be noted that the PLZT is lower in cost compared with the single crystal plates of NaCl, KBr, CaF2, and KRS-6 which are generally used as the window materials.

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We have studied the luminescence of Cu+ ion in CuLa1Gds02. CuLa0.9Gdo.102 showed a green luminescence (Amax-544nm) at room temperature and a red luminescence (Am. -59C nm) at 77 K, respectively. The peak position of the red emission shifted towards lower wavelength with the increase of x in CuLa1_zGd102. It was, therefore, clear that the peak shift was closely related to the sp2 configuration of Cu+ with the size of lattice for CuLa1_sGd. E02.

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A series of chromium lanthanum oxide with the formula LaCr1_xMx03 (M=Cu, Mg, Zn)was synthesized by a conventional solid state reaction at 1350 °C and 1600 6°C for 2 h in air and flowing N2 amd Ar gas. The products were recognized as single phase with orthorhombic perovskite structure in chemical composition range of 0x0.2 for M=Cu and Zn and 0x 0.15 for M=Mg in LaCr1, M, 03. Sinterability was evidently improved by the substit ution of divalent cations. The electrical conductivities increased with increasing the content of divalent cations substituted. This behavior was closely related to the formation of mixed valency state of CO+ and Cr4+ ions due to the substitution of divalent cation for CO+ ions in LaCrO3.

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Perovskite-type LaFe03 powders were prepared by an amorphous citrate process. Lanthanum(E) oxide and iron(E) nitrate as starting materials were mixed with citric acid, then stirred and dried into precursor gel. This gel was calcined at 400--1000 °C for 30 min-5 h. The single phase of LaFe03 powders has been Obtained when calcined at the temperatures above 600 °C. The crystallite sizes of the material were 15--40 nm, and increased as calcining temperature increased. The lattice constants were independent to the calcining conditions and almost the same as the known value. The shape of the grains were plate-like obtained by the amorphous citrate process and rounded by the solid state reaction.

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The single crystal of a ternary intermetallic compound ErRh3B2 was successfully grown by the flux method using a molten metal as a solvent. The choice of the best solvent metal for the crystal growth, the fundamental growth conditions, the crystal structure, and magnetic properties were studied. The crystal structure of the ErRh3B2 belongs to a monoclinic system isomorphous with ErIr3B2 type structure (space group C 2/m): a=5.32(2)A, b=9.21(8)A, c=3.077(6)A, and B = 90.6. This compound shows strongly anisotropic properties an d takes a ferromagnetic ordering at 27 K with its easy axis along the c-direction.

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