The aqueous geochemistry of the rare-earth elements and yttrium

Two new isomeric bis(trans-fused cyclohexano) substituted 1,4,7,10,13-pentaazacyclopentadecane ligands and their Mn(II) complexes, 3 and 4, have been synthesized, and their activity as superoxide dismutase (SOD) catalysts has been studied. Complex 3 is an excellent SOD catalyst with a second-order rate constant at pH = 7.4 of 1.2 × 10+8 M-1 s-1. In contrast, the isomeric complex 4 has virtually no detectable catalytic SOD activity, implying the need to understand the effect that the position, number, and stereochemistry of substituents exert on the catalytic rate. The crystal structure of the complex 4 was determined and reveals that the Mn(II) ion is coordinated in a pentagonal bipyramid array of the five nitrogens of the macrocyclic ligand and capped by two trans-chloro ligands. Crystal data for MnC18H37Cl2N5 are as follows: triclinic at 20 °C, space group P1--Ci2 (no. 2); a = 9.746(3) A, b = 12.631(6) A, c = 11.311(5) A; α = 73.14(4)°, β = 76.39(3)°, γ = 79.98(3)°, V = 1287(1) A3, and Z = 2 (ρcalc = 1....

Toward the Rational Design of Superoxide Dismutase Mimics: Mechanistic Studies for the Elucidation of Substituent Effects on the Catalytic Activity of Macrocyclic Manganese(II) Complexes

Determination of SO4β1 for yttrium and the rare earth elements at I = 0.66 m and t = 25°C—implications for YREE solution speciation in sulfate-rich waters

Structural studies of lanthanide ions (Nd3+≈Lu3+: about 1 mol/l) in the aqueous chloride (HCl: 0≈6 mol/l) and nitrate (HNO3: 0−13 mol/l) solutions were carried out by extended X-ray absorption fine structure (EXAFS). The radial structural functions appeared to be mainly characterized by hydration in both chloride and nitrate systems and coordination of nitrate ion in nitrate systems. These results indicated that nitrate ion forms inner-sphere complex with lanthanide but chloride ion hardly forms one. The quantitative analyses of EXAFS data have revealed that the total coordination numbers of lanthanide ranged from about 9 for light lanthanides to about 8 for heavy lanthanides in all the samples. The bond distances of Ln−O were from about 2.3 to 2.5 A for Ln−OH2 and from about 2.4 to 2.6 A for Ln−O2NO. Nitrate ion locates at 0.1 A longer position than water, it suggested that nitrate ion ligates more weakly than water.

Structural study of lanthanides(III) in aqueous nitrate and chloride solutions by EXAFS

Chapter 103 Hydration and hydrolysis of lanthanides

Deuterium isotope effects in complexation kinetics. II. Lanthanide(III) sulfate systems

Metal ion association in alcohol solutions—I: Erbium nitrate association in aqueous methanol

Metal ion association in alcohol solutions. III. Erbium chloride in aqueous methanol

A comparison of the ultrasonic relaxation results for erbium chloride complexation in aqueous methanol with those for erbium nitrate demonstrated that the mechanism differs for the two ligands, with a solvation number change occurring for the nitrate and not for the chloride salts.

Jeffry Reidler

Papers

Deuterium isotope effects in complexation kinetics. II. Lanthanide(III) sulfate systems

Metal ion association in alcohol solutions—I: Erbium nitrate association in aqueous methanol

Metal ion association in alcohol solutions. III. Erbium chloride in aqueous methanol

Differences in ErIII complexation with chloride and nitrate ions determined by the ultrasonic relaxation technique