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Two different synthetic pathways were devised in order to graft on silica gel organic moieties, containing macroacyclic or macrocyclic compartimental ligands, formed of an innerN3O2 or N2O2 Schiff base site, able to coordinate d metal ions, and one adjacent O2O2 or O2O4 crown ether-like chamber suitable for hosting f ions, in the terminal part. These materials can bind d metal ions into the amine– imine moiety. Their subsequent reaction with varying amounts of gadolinium(III) invariantly gives a system in which two grafted copper complexes coordinate only one gadolinium(III) ion with their oxygen-containing chambers, giving rise to a trinuclear Cu2Gd entity. According to a third strategy, some mono- and heterobi-metallic macrocyclic complexes were transferred from a water/methanol solution into functionalised silica platforms by coordinating their metal ions to the donor group of one silica-anchored organic residual. UV– Vis spectra of solutions containing these metal complexes gave a clear indication of the selective coordinating ability of the donor group towards 3d or 4f metal ions.

Complexation between thorium(IV) and malonate in 1.05 mol kg(-1) NaClO4 was studied from 10 to 70 degrees C by potentiometry and calorimetry. Three complexes, ThL2+, ThL2 and ThL32-, where L stands for malonate, were identified. The stability constants, the enthalpies and entropies of complexation at variable temperatures were determined. Despite that the enthalpies of complexation become more endothermic, the complexes become more stable due to increasingly larger entropies of complexation that exceed the unfavorable contribution of enthalpies of complexation at higher temperatures. The thermodynamic trends are explained in terms of an electrostatic model and the change in the structure of water with temperature. The data are compared with previous results on the complexation of U(VI) and Nd(III) with malonate and other carboxylate ligands

The protonation of thiodiacetate and its complexation with uranium(VI) in 1.05 mol kg(-1) NaClO4 are studied at variable temperatures (10-85 degrees C). Three U-VI complexes (UO2L, UO2HL+, and UO2HL2-, where L is thiodiacetate) are identified in this temperature range. The formation constants and the enthalpies of complexation are determined by potentiometry and calorimetry. The complexation of uranium(VI) with thiodiacetate becomes more endothermic at higher temperatures. However, the complexes become stronger due to increasingly more positive entropies of complexation at higher temperatures, which exceeds the increase in the unfavorable enthalpy of complexation. The values of the heat capacity of complexation (Delta C-p degrees) are 122 +/- 16, 302 +/- 26, and 242 +/- 23 JK(-1) mol(-1) f or UO2L, UO2HL+, and UO2HL2-, respectively. The effect of temperature on the thermodynamics of the complexation is discussed in terms of the electrostatic model and the change in the solvent structure

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The hydrolysis of uranium(VI) in tetraethylammonium perchlorate (0.10 mol dm-3 at 25 °C) was studied at variable temperatures (10-85 °C).

Neptunium is one of the few radioactive elements that are of great concern in the disposal of nuclear wastes in the geological repository, due to its hazards and the long half-life of the isotope, 237 Np (t1/2 = 2.14 × 106 years). To understand and predict the migration behavior of neptunium in the geological media, it is of importance to study its hydrolysis at elevated temperatures, because the temperature in the waste package and the vicinity of the repository could be high. Moreover, the chemical analogy between neptunium(V) and plutonium(V) adds even greater value to this investigation, because the latter could exist at tracer levels in neutral and slightly oxidizing waters but is difficult to study due to its rather labile redox behavior............

The complexation between Th(IV) and acetate in 1.05 mol kg–1 NaClO4 was studied at variable temperatures (10, 25, 40, 55 and 70 °C). The formation constants of five successive complexes, Th(Ac)j(4–j)+ where Ac = CH3COO– and j= 1–5, and the molar enthalpies of complexation were determined by potentiometry and calorimetry. Extended X-ray absorption fine structure spectroscopy (EXAFS) provided additional information on the complexes in solution. The effect of temperature on the stability of the complexes is discussed in terms of the electrostatic model.

The complexation of uranium(VI) and samarium(III) with oxydiacetate (ODA) in 1.05 mol kg-1 NaClO4 is studied at variable temperatures (25-70 C). Three U(VI)/ODA complexes (UO2L, UO2L22-, and UO2HL2-) and three Sm(III)/ODA complexes (SmLj(3-2j)+ with j = 1, 2, 3) are identified in this temperature range. The formation constants and the molar enthalpies of complexation are determined by potentiometry and calorimetry. The complexation of uranium(VI) and samarium(III) with oxydiacetate becomes more endothermic at higher temperatures. However, the complexes become stronger due to increasingly more positive entropy of complexation at higher temperatures that exceeds the increase in the enthalpy of complexation. The values of the heat capacity of complexation (Cp in J K-1 mol-1) are 95 ± 6, 297 ± 14, and 162 ± 19 for UO2L, UO2L22-, and UO2HL2-, and 142 ± 6, 198 ± 14, and 157 ± 19 for SmL+, SmL2-, and SmL33-, respectively. The thermodynamic parameters, in conjunction with the structural information from spectroscopy, help to identify the coordination modes in the uranium oxydiacetate complexes. The effect of temperature on the thermodynamics of the complexation is discussed in terms of the electrostatic model and the change in the solvent structure.

Complexation of Th(IV) with 2-furoic acid (C4H3OCOOH) and 2-thenoic acid (C4H3SCOOH) in 1.0 mol dm–3 NaClO4 has been studied at 25 °C. The formation constants of successive complexes ThLj(4–j)+, where L stands for the furoate or thenoate anion and j = 1–3 for 2-furoic acid and j = 1–2 for 2-thenoic acid, and corresponding molar enthalpies of complexation were determined by potentiometry and calorimetry. Spectroscopic techniques, including FT Raman and Extended X-Ray Absorption Fine Structure (EXAFS) were used to acquire further information on the interaction between Th(IV) and the ligands. Both the thermodynamic and spectroscopic data are consistent with the formation of ThLj(4–j)+ complexes, in contrast to earlier results in the literature which suggest that the protonated complexes ThL4H22+ and ThL3H23+ are dominant under the experimental conditions. The binding strength of furoic acid and thenoic acid with Th(IV) is discussed in conjunction with the data for other monocarboxylic acids.

The complexation between uranium(VI) and malonate in 1.05 mol kg.1 NaClO4 was studied at variable temperatures (25, 35, 45, 55 and 70 .°C). The formation constants of three successive complexes, UO2(OOCCH2COO), UO2 (OOCCH2COO)2 and UO2(OOCCH2COO)3 ., and the molar enthalpies of complexation were determined by potentiometry and calorimetry. The heat capacity of the complexation, .Cop,m(MLj ), is calculated to be 96±12, 195±15 3, and 267±22 JK.1 mol.1 for j = 1, 2 and 3, respectively. . Extended X-ray Absorption Fine Structure Spectroscopy helped to characterize the coordination modes in the complexes in solution. UV/V is absorption and luminescence spectra at different temperatures provided qualitative information on the temperature effect. The effect of temperature on the complexation between uranium(VI) and malonate is discussed in terms of the electrostatic model and compared with the complexation between uranium(VI) and acetate.

The asymmetric compartmental macrocycles containing one N2O2 or N3O2 Schiff base and one O2O3 or O2O4 crown-ether like chamber, have been obtained by condensation reaction of the formyl precursors 3,3’-(3-oxapentane-1,5-diyldioxy)bis(2-hydroxybenzaldehyde) or 3,3’-(3,6-dioxaoctane-1,8-diyldioxy)bis(2-hydroxybenzaldehyde) with ethylenediamine (H2LA,H2LC) or 1,5-diamino-3-azamethylpentane(H2LB,H2LD), also in the presence of metal ions as templating agents. These ditopic ligands, with dissimilar coordination sites, have been designed and used for the selective complexation of “d” and/or “s” metal ions, respectively into the Schiff base and the crown ether chamber. The selectivity of these processes strongly depends on the size and on the donor atom sets of the sites. The possibility to obtain mononuclear M(L)•nH2O (M = Ni2+, Cu2+, Co2+), Mn(L)(CH3COO)•nH2O or Na(L) and hetero-dinuclear MNa(L)(CH3COO)( M = Ni2+, Cu2+, Co2+) and MnNa(L)(CH3COO)2•nH2O complexes has been successfully tested. The ligands and complexes have been characterized by ir, nmr, mass spectrometry and magnetic susceptibility measurements. Two of the ligands used for the preparation of the solid samples, i.e. to H2LA and H2LB,were employed to study complexation reactions of Co(II) and Na(I) in solution. In order to obtain information on the ligand preorganization effect toward the complex stabilities, a simpler open chain parent compound of H2LB (H2LE) was also prepared and studied. FT-IR spectra show that H2LA is unable to complex Na+ in DMSO while the complexation reactions of Na+ by H2LB and of Co2+ by H2LA take place with slow kinetics. Therefore, thermodynamic data could be obtained only for the systems Co2+/H2LB and Co2+/H2LE The thermodynamic parameters obtained for the complexation reactions show that the pre-organization of the donor atoms in H2LB does not add a significant contribution to the stabilities of the complexes. Both H2LB and H2LE form in DMSO 1:1, 1:2 and 1:3 = M:L complexes with very similar stabilities and almost equal enthalpies of formation. Physico-chemical studies suggest besides that the slow reaction of Na+ with H2LB is probably due to the formation of a 1:1 complex where the metal cation, initially occupying the O3 cage of the ligand, slowly binds also the oxygens of the phenolic moieties. Spectral and calorimetric data on solutions containing H2LB and different Co2+: Na+ ratios evidence that in DMSO no stable heterodinuclear complexes form when the neutral ligand is considered.