Thermodynamics of Complex Formation of Silver(I), Cadmium(II) and Cobalt(II) with Open‐Chain Polyamines in Dimethyl Sulfoxide and Molecular Dioxygen Binding to Cobalt(II) Complexes

Abstract

AgI, CdII and CoII complex formation with the primary and tertiary tetraamines 1,4,7,10‐tetraazadecane (trien) and 1,1,4,7,10,10‐hexamethyltriethylenetetraamine (hmtrien) has been studied at 298 K in the aprotic solvent dimethyl sulfoxide (DMSO) and in an ionic medium set to 0.1 mol·dm−3 with Et4NClO4 under anaerobic conditions. UV/Vis spectrophotometric and calorimetric measurements have been carried out to obtain the thermodynamic parameters for the systems investigated. Mononuclear 1:1 complexes are formed for all systems. In addition, trien also forms the ML2 mononuclear complex and a polynuclear M2L3 species with M = Cd2+ and Co2+. All the complexes are enthalpy stabilized, whereas the entropy changes counteract the complex formation. The results are discussed in terms of the different basicities, steric requirements and solvation both of the ligands and of the complexes formed. The influence of N‐alkylation on the selectivity of the ligands towards metal ions is analysed. In the case of the CoII complexes, their ability to take up dioxygen has also been studied by voltammetric and UV/Vis measurements and gasometric absorption. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Thermodynamics of complex formation of silver(I) with N-donor ligands in non-aqueous solvents

“…This trend reflects the prevailing of metal ion solvation effects (see above) on the complexation; the discrepancy observed for water can be explained as due to a strong solvation, via hydrogen bonds, of primary and secondary polyamines in this solvent [6]. This hypothesis is also confirmed by literature data showing that when Ag(I) forms complexes with ligands which are H-bond acceptors only, like pyridines [59] or tertiary amines [8,11], the metal ion solvation prevails and the trend of stability in water and DMSO is reversed. Moreover, similar behaviours in complexation of amines were observed for other metal cations, namely Cd(II) and…”

“…In the last decades many studies have been carried out in the field of the thermodynamics of metal complex formation with nitrogen-donor (N-donor) ligands in water [1][2][3][4] as well as in non-aqueous or mixed solvents [5][6][7][8][9][10][11][12][13]. The main aim of these works has been to investigate the influence both of different basicity and steric properties of the ligands and of the solvents on the stability and nature of the complexes formed.…”

Nickel(II) Complexation with Nitrate in Dry [C4mim][Tf2N] Ionic Liquid: A Spectroscopic, Microcalorimetric, and Molecular Dynamics Study

“…The thermodynamics of metal complex formation has been widely explored in nonaqueous solutions, − while in RTILs very few examples of stability constants determinations are present in the literature for transition metals and f -block elements. − It is also noticeable that no complexation enthalpy (with the exception of Nd 3+ and Eu 3+ ions with nitrate and a calixarene ligand, respectively) , has been previously determined in RTILs, despite the key-role of this parameter for the understanding of the strength of the metal–ligand interaction and the role of the processes occurring in solution upon complexation. From a structural point of view, X-ray absorption spectroscopy (EXAFS), molecular dynamics (MD) simulations, and density functional theory (DFT) calculations have been applied previously to study lanthanides, ,− actinides, ,− alkaline earths, , and transition metals − in RTILs.…”

Thermodynamic and Spectroscopic Studies of Lanthanides(III) Complexation with Polyamines in Dimethyl Sulfoxide

“…The inner-sphere nature of these complexes has also been confirmed by luminescence experiments for Ln(III)−ethylenediamine . For all polyamine ligands, the enthalpies and entropies of complexation are negative, as also found for the complexation of transition metals with the same class of ligands, unlike the situation in water and dimethyl formamide (DMF) with charged ligands. , …”