Complexation of Eu(III), Am(III) and Cm(III) with Dicarboxylates: Thermodynamics and Structural Aspects of the Binary and Ternary Complexes

The complexation of Eu(III), Am(III) and Cm(III) with dicarboxylate anions with O, N or S donor groups was measured in I=6.60 mol⋅kg⁻¹ (NaClO₄) at temperatures of 0–60 °C by potentiometry and solvent extraction. The complexation thermodynamics of these complexes show that their stability is due to highly favorable complexation entropies because the complexation enthalpies are endothermic. Luminescence studies with Eu(III) and Cm(III) were used to measure the hydration numbers of the complexes. NMR spectra of ¹H and ¹³C were used to determine the binding modes of La(III) with the ligands. The formation of 1:1:1 ternary complexes of M(EDTA)⁻ with the dicarboxylate ligands was studied to determine changes in coordination of the metal cation with formation of the ternary species. The complexation of ternary complexes changes from bidentate to monodentate as the chain length between the binding sites of the dicarboxylates increases from 1 (malonate) to 4 (adipate). DFT computations were used to confirm the structural aspects of the interaction of these complexes.     

The precipitation of some actinide element complex ions by using hexammine cobalt(III) cation—VI The precipitation of Np(IV), (V) and (VI) sulfate complex ions with hexammine cobalt(III) cation

Precipitation behaviors of Np(IV), (V) and (VI) in sulfuric acid and ammonium sulfate solutions with hexammine cobalt(III) ion have been studied. The optimum conditions of precipitating Np as crystalline compounds are 0.4 M H₂SO₄ and 0.06 M [Co(NH₃)₆]Cl₃ for Np(IV), larger than 0.5 M (NH₄)₂SO₄ and 0.03 M [Co(NH₃)₆]Cl₃ for Np(V), and the higher the concentrations the better for Np(VI). Np(IV) is completely removed from ammonium sulfate solution.Composition of the Np(IV) compound from the sulfuric acid solution is [Co(NH₃)₆]₂[Np(SO₄)₅]·nH₂O. And composition of the Np(V) compounds is possibly [Co(NH₃)₆][NpO₂(SO₄)₂]·α[Co(NH₃)₆]₂(SO₄)₃·nH₂O (α = 2.20−0.32). Solubilities of the Np(IV), (V) and (VI) compounds in water are found to be 4.9 mgNp/l, 520 mgNp/l, and 250 mgNp/l, respectively.     

Kinetics of oxidation of 4,4′-biphenyldiol and of 4,4′-biphenoquinone by metal ions in aqueous perchlorate media: Reactions with Mn(III), Ce(IV) and Ag(II)

The kinetics and mechanisms of the oxidation of 4,4′-biphenyldiol ([1,1′-biphenyl]-4,4′-diol, I) to 4,4-biphenoquinone ([bi-2,5-cycloexadiene-(1,1′-cycloexadiene-(1,1′-ylidene)]-4,4′-dione, II) as well as the oxidative decomposition of II by means of some metal ions (Mn^III, Ce^IV and Ag^II) have been investigated in aqueous perchlorate media at different temperatures and acidities. The oxidation of I follows the empirical rate law: $\text{−}\text{d[I}\text{]}\text{d}\text{t}\text{= k[}\text{I][M}\text{]f([}\text{H}{}^{\mathrm{+}}\text{])}$, where M represents the oxidizing metal ion, and the decomposition of II: $\text{−}\text{d[II]}\text{d}\text{t}\text{= k′[}\text{II}\text{][}\text{M}\text{]}{}^{\mathrm{a}}\text{f′([}\text{H}{}^{\mathrm{+}}\text{])}$, where a = 1 for Ag^II and a = 0 for Ce^IV and Mn^III. The reaction mechanisms are proposed.     

Synthesis,crystal structures and magnetism of lanthanide(III) binuclear complexes [Ln2(μ1 ,3-CH3CO2)2(SCN−)4L2(H2O)6] (Ln = Gd(III) and Eu(III), L = 4-methylpyridine N-oxide)

Two lanthanide(III) binuclear complexes have been synthesized with acetate as bridging ligand and 4-methylpyridine N-oxide (L), SCN^? and H₂O as terminal ligands and structurally determined by X-ray crystallography. Both crystals [Gd₂(μ_1,3-CH₃CO₂)₂(SCN^?)₄(L)₂(H₂O₆) (1) and [Eu₂(μ_1,3-CH₃CO₂)₂(SCN^?)₄(L)₂(H₂O)₆] (2) belong to monoclinic with space group P2₁/n. The relevant cell parameters are as follows: a?=?9.0034(12)?Å, b?=?15.998(2)?Å, c?=?12.1277(17)?Å, β?=?100.625(2)° for complex 1; and a?=?9.0168(18)?Å, b?=?15.990(3)?Å, c?=?12.142(2)?Å, β?=?100.734(3)° for complex 2; The two lanthanide(III) ions are bridged by two acetate anions forming a binuclear unit, in which L, SCN^? and H₂O as unidentate terminal ligands take part in the coordination. The variable-temperature magnetic susceptibility of 1 was measured in the 4–300?K range; fitting for the susceptibility data reveals that there is no magnetic interaction between the bridged Gd(III) ions.