K. Nag

Solvent extraction behavior of rare earth ions with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone—II: An examination of gadolinium break, tetrad effect, double-double effect and the relevance of “inclined-W” plot

Abstract Solvent extraction behavior of all rare earth ions (excepting promethium) and yttrium have been investigated using 1-phenyl-3-methyl-4-benzoly-5-pyrazolone (HPMBP) as the extractant in aqueous-chloroform medium at 25 ± 1°C. The initial concentration of HPMBP was 5 × 10−2M, and the aqueous phase was maintained at constant ionic strength 0.1 M (Na, H)+ClO4−. From distribution coefficients (D), extraction equilibrium constants ( K 3,0 ∗ ), for the formation of Ln (PMBP)3, two-phase stability constants (logβ3·PLn(PMBP)3), pH for 50% extraction of metal chelates (pH50) and separation factors (S) between the adjacent elements have been evaluated. These values have been examined in the light of double-double effect and tetrad effect. A plot of log K 3,0 ∗ values against atomic number, Z show tetrad grouping. A similar plot of log K 3,0 ∗ values against L (total angular momentum of rare earth ions) forms an “inclined W”, agreeing with a recent suggestion of Sinha. On the other hand, logβ3·PLn(PMBP)3 values versus r−1 (r, ionic radii of rare earth ions) may be fitted into two straight lines for the lower and higher members of the series with a break at gadolinium.

Chemistry of lanthanons—XVII: Bis-salicylaldehyde ethylenediamine and bis-salicylaldehyde o-phenylenediamine complexes of rare-earths

Abstract A new series of rare-earth metal chelates derived from N-coordinating ligands like bis-salicylaldehyde ethylenediamine (H 2 Salen) and bis-salicylaldehyde o-phenylenediamine (H 2 Salphen) have been prepared with La, Ce, Pr, Nd, Sm, Gd, Dy, Er, Yb and Y. These compounds are of the general formula Ln 2 (Salen) 3 and Ln 2 (Salphen) 3 (where Ln stands for the above lanthanides except Ce). The cerium complex prepared with H 2 Salen has the composition Ce(Salen) 2 . Many compounds of the former series are solvated and contain ethanol or water molecules. These compounds have been characterised by their thermal analyses and i.r. spectra.

Chemistry of lanthanons-XIX ethylenediamine bis-acetylacetone complexes of rare-earths

Ethylenediamine bis-acetylacetone (enac) complexes of rare-earths are described. Compounds of composition Lc(enac)2 X3, where Ln = La, Ce, Pr, Nd and Sm and X = Cl−, NO3− and SCN− and Ln2(enac)3 X6 where Ln = Gd, Dy, Er and Y and X = Cl− and NO3− have been obtained. On the basis of their u.v. visible and i.r. spectra and also from conductance and molecular weight measurements possible structures for the complexes have been proposed.

Studies on rare earth trisoxalatochromates (III), rare earth chromates (V) and rare earth chromites (III)

Abstract Rare earth trisoxalatochromates (III), LnCr(C2O4)3·nH2O (n = 9 for La, and n = 8 for Ce, Pr and Nd) have been isolated and characterized by a number of physicochemical studies. These compounds (except for Ce) serve as precursors for the rare earth chromates (V) and chromites (III). LnCrO4 may be obtained by heating LnCr(C2O4)3·nH2O at 520°C for 4 hr and LnCrO3 at 900°C for a similar period. CeCr(C2O4)3. 8H2O decomposes to a mixture of CeO2 and Cr2O3. The EPR spectra of LaCrO4 are consistent with a tetrahedral geometry of the CrO4 group. Although the unit cell of LaCrO4 is monoclinic and of NdCrO4 is tetragonal, compounds of composition La1−xNdxCrO4 show the presence of only monoclinic phase for x up to 0.23. The electronic spectra of LnCrO3 are compatible with the perovskite structure of these compounds.

Chemistry of lanthanons-XX complexes of the rare earths with 3-mercapto-1-phenylbut-2-en-1-one

Abstract The formation constants of some rare earth complexes of 3-mercapto-1-phenylbut-2-en-1-one have been determined at 0·1 M ionic strength by pH-potentiometric titration in 3:1 ( v/v ) acetone water mixture at 30±0·5°C.

Chemistry of lanthanons—XVIII: Mixed chelates of La, Pr, Nd, Sm and Y containing β-diketone and bis-salicylaldehyde ethylenediamine

Abstract Mixed ligand complexes of lanthanides (La, Pr, Nd, Sm) and Y containing botg β-diketone and bis-salicylaldehyde ethylenediamine (H2 Salen) as the associated ligand molecules have been prepared. By reacting tris-acetyl acetonate and tris-propionyl acetonates of the above lanthanides with the Schiffs base in ammoniacal atmosphere compounds obtained were of the type [Ln(diket)2(Salen)0.5] (I), whereas by refluxing the tris-benzoyl acetonates and tris-dibenzoyl methanides with the Schiffs base, a second series of compound viz., [Ln(diket)(Salen)] (II) were obtained. Sodium salts of tetrakisbenzoyl acetonates and dibenzoyl methanides also yield compounds of the second type.

Thio β-diketonates of lanthanides—I: Solvent extraction behavior of neodymium (III) with 1,1,1-trifluoro-4-(2-thienyl)-4-mercapto but-3-en-2-one (HSTTA) as the extractant

The solvent extraction behavior of Nd3+ using thiothenoyltrifluoroacetone (HSTTA) as extractant has been described. The distribution constant (PHA) and the dissociation constant (Ka) of the reagent in the aqueous-organic phases have been determined. The order of PHA values with respect to the organic solvents are chloroform > cyclohexane > benzene. Among the three solvents the trend in extraction is benzene > cyclohexane > chloroform. The extraction process is predominantly governed by the following reaction equilibrium nNd3+aq+3 HSTTA(o)⇋Nd(STTA)3(o)+3H+(aq) nThe mixed equilibrium constant for extraction (K3,0∗), biphase stability constant (PMA . β3) and pH for 50% extraction have been computed for each solvent systems. The cause of superiority of HTTA over HSTTA as an extractant has been discussed.

Equilibrium studies on metal-peptide systems—I: Polarographic determination of association constants of cadmium(II), zinc(II) and lead(II) complexes of glycylgycine

Abstract The equilibria involved in the association of Cd2+, Zn2+ and Pb2+ with glycylglycine have been investigated polarographically (at 25°C). As the nature of binding depends on solution pH, studies have been made at pH 7 (participation of both the N-terminal amino group and the carbonyl group of the peptide linkage occurs). In the lower range of pH, comparatively weaker (1:1) complexes are formed with Cd2+ and Pb2+ ions (that of Zn2+ could not be detected due to the overlapping hydrogen wave) whereas in the higher range, more stable complexes (both 1:1 and 1:2) are formed for all the metal ions. Stepwise formation constants were determined by DeFord and Humes method. Distribution of different species formed in solution at different pH values (for the cadmium system) and also at the different peptide concentrations studied (for the lead system) is shown graphically.

Studies on rare earth trisoxalatoferrate(III) and rare earth ortho ferrite

Abstract The preparation and characterization of LaFe(C 2 O 4 ) 3 ·9H 2 O is described but the trisoxalatoferrate(III) of other lanthanides could not be isolated. However, the lanthanum ion in LaFe(C 2 O 4 ) 3 ·9H 2 O can be partly replaced by other lanthanide ions, e.g. with Nd(III) doping to the extent of 0.33 mole fraction of the latter has been accomplished. In the compounds La 1− x Nd x Fe(C 2 O 4 ) 3 ·9H 2 O a stron magnetic interaction between Fe 3+ and Nd 3+ is observed. From a comparison of the IR and diffuse reflectance spectra and the X-ray diffraction data it is shown that K 3 Fe(C 2 O 4 ) 3 ·9H 2 O and LaFe(C 2 O 4 ) 3 ·9H 2 O are not isostructural. Thermal analysis (combined TG, DTA and DTG) of LaFe(C 2 O 4 ) 3 ·9H 2 O establishes that this compound is precursor of LaFeO 3 . The LaFeO 3 obtained, has been characterized by its X-ray diffraction pattern, measurement of its magnetic moment, and by its electronic and IR spectra. The thermal behavior of physical mixtures of La 2 (C 2 O 4 ) 3 ·10H 2 O and Fe 2 (C 2 O 4 ) 3 ·5H 2 O and La 2 (C 2 O 4 ) 3 ·10H 2 O and Fe(C 2 O 4 )·2H 2 O has also been investigated and the products of thermal analysis at ∼1000°C in air found to be a mixture of La 2 O 3 and αFe 2 O 3 .

Thio-β-diketonates of lanthanides—III synergistic solvent extraction behavior of neodymium(III) with 1,1,1-trifluoro-4(2-thienyl)-4-mercaptobut-3-en-2-one (HSTTA) and some neutral donors

Abstract The synergistic solvent extraction behavior of Nd(III) with HSTTA and the neutral donors dipyridyl, tributylphosphate (TBP) and tri-n-octylphosphine oxide (TOPO) (≡L) have been investigated using benzene as the organic solvent and an ionic strength 0.1 (NaClO4). The extraction process is governed by the following reaction equilibrium Nd 3 + 3HSTTA (O) +n L (O) ⇆ Nd(STTA) 3 (L) n(O) + 3H + The extraction constants ( K 3,n ∗ ) and the adduct formation constants (β3,n) have been evaluated. With dipyridyl, only mono adduct formation takes place, whereas, with TBP and TOPO, both mono and bis adducts are formed. The β3,n values for HSTTA systems are higher than for the corresponding HTTA systems.