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Abstract: This article provides a short survey on the thermodynamic and kinetic behaviour of cobalt complexes, which are able to bind molecular oxygen in aqueous solutions. The focus is on cobalt complexes with simple polyamines and with polynucleating ligands that share the same basic structure, in terms of them being elements of a sequence with increasing complexity. Ditopic polyazapolyoxalkanes and dicompartimental ligands containing a phenolic moiety are also considered. The aim is to elucidate the relation between the structure of the ligands and the behaviour of their cobalt complexes as donors and acceptors of dioxygen. [Copyright &y& Elsevier]

Abstract: A newly designed calorimetric technique and calculation procedure have been used to obtain partial molar enthalpies, , and excess enthalpies, H E, for binary mixture of hexane+perfluoro-n-alkanes (C5–C8) and perfluorohexane+ n-alkanes (C5–C8), +cyclohexane, and +2-methylheptane. All mixtures are endothermic, and the heat effects increase with the size of the second component. The H E and values found are the largest ever observed for mixtures of non-polar compounds. An estimate of the excess heat capacity for (perfluorohexane+2-methylheptane) has been obtained from at two different temperatures. From at infinite dilution and from the known enthalpies of vaporization, the enthalpies of solvation, Δsolv H ∘, have been evaluated either for alkanes and perfluoroalkanes in both hexane and perfluorohexane solvent. Solute–solvent interactions have been examined by describing the Δsolv H ∘ with an additive scheme of surface interactions and by applying the Scaled Particle Theory. The effects of chain lengthening, branching, and cyclization have been discussed. Perfluoroalkanes proved to be inert molecules that interact weakly with themselves as well as with alkanes. [Copyright &y& Elsevier]

Abstract: The kinetics of binding of Pd(II), initially present as PdCl4 2−, to the azo-dye ligand pyridine-2-azo-p-dimethylaniline (PADA) in dodecyltrimethylammonium chloride (DTAC) micellar solution has been investigated as a preliminary study on palladium micellar extraction and recovery. For comparison, the same investigation has been performed in water. Palladium reacts with PADA forming a strong 1:1 complex both in water and in DTAC micellar solution. Addition of DTAC, at concentrations just above the critical micellar concentration, results in a large enhancement of the rate of complex formation. The analysis of the kinetic behaviour reveals that several reaction paths are present. In water, under the experimental hydrogen ion concentration range investigated, reaction steps involving the protonated ligand forms PADAH+ and PADAH2 ++ are important and the reacting palladium species are PdCl4 2− and Pd(H2O)Cl3 −. In DTAC micellar solution, PADA reacts in its unprotonated form and a new reaction path appears involving the hydroxo species PdCl3OH2− which is about 10-times faster than the other reaction paths. The large catalytic effect produced by DTAC micellar solution provides a promising basis for the extraction of palladium from water using the PADA/DTAC system. [Copyright &y& Elsevier]