Affinity of Polypyridines Towards Cd^II and Co^II Ions: a Thermodynamic and DFT Study

Abstract

CdII and CoII complex formation with pyridine (py), 2,2′‐bipyridine (bipy), 2,2′6′,2″‐terpyridine (terpy), 2‐(aminomethyl)pyridine (amp), and bis[(2‐pyridyl)methyl]amine (dpma) was 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 in anaerobic conditions. Potentiometric, UV/Vis spectrophotometric, and calorimetric measurements were carried out to obtain the thermodynamic parameters of the systems investigated. Enthalpy‐stabilized mononuclear MLj complexes are formed, whereas entropy changes counteract complex formation. These results are discussed in terms of different basicities, steric requirements, and solvation, of both the ligands and the resulting complexes. Density functional theory (DFT) calculations were carried out in order to obtain structural information and binding energies in vacuo. The DFT results are correlated with the solution studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Physical Nature of Interactions in ZnIIComplexes with 2,2′-Bipyridyl: Quantum Theory of Atoms in Molecules (QTAIM), Interacting Quantum Atoms (IQA), Noncovalent Interactions (NCI), and Extended Transition State Coupled with Natural Orbitals for Chemical Valence (ETS-NOCV) Comparative Studies

“…clashes are assumed to be also present in a solution and were often used to explain trends in experimental formation constants. [19][20][21][22][23][24][25][26][27] For instance, the unusual trend in the formation constants of Cu II was attributed to steric repulsion between the 3,3-hydrogens already fifty years ago. 19 More recently, the observed difference of about 1.4 log units for a set of metal ions with 1,10-phenanthroline (phen) and 2,2-bipyridyl (the latter ligand forms weaker complexes) was attributed to highly strained ligand in the s-cis conformer (as it is required for coordination to metal ions) because of the steric hindrance between the hydrogen atoms.…”

para-Aminosalicylic acid in the treatment of manganese toxicity. Complexation of Mn2+ with 4-amino-2-hydroxybenzoic acid and its N-acetylated metabolite

“…For the calculations carried out for MnL and [MnL2] 2complexes (L = SAL, PAS, AcPAS), the B3LYP hybrid functional [24,25] was chosen as it is widely demonstrated to provide good structural data for metal complexes, especially for open shell systems [26][27][28][29][30][31][32][33][34]. The Stuttgart-Dresden effective-core potentials [30] with the associated basis set for the valence electrons were employed for Mn within the gaussian-type 6-31+G(d,p) for the other elements.…”

cEST: a flexible tool for calorimetric data analysis

“…In all these applications the stability constant K (and therefore ΔG 0 ) can be obtained by independent experiments, such as potentiometry or spectrophotometry [6][7][8][9][10][11][12][13][14], or be a parameter which is obtained simultaneously to the ΔH 0 in the calorimetric data analysis [6,[14][15][16].…”

“…The reliability of cEST is here checked by applying it to the analysis of published data concerning chemical equilibria in solution, such as Ag + , Co 2+ and Cd 2+ complex formation with terpyridine (terpy) in anhydrous dimethylsulfoxide (DMSO) [8,21] and simulated thermodynamic parameters for multiple overlapping binding equilibria associated to two-or three-binding-site models occurring in biological interactions [22]. Furthermore, new simulated titrations where the formation of polynuclear metal complexes occurs are analyzed to evidence the capability of detecting such type of species by calorimetric data alone.…”