Interaction of d10 metal ions with thioether ligands: a thermodynamic and theoretical study

Abstract

Thermodynamic parameters of complex formation between d(10) metal ions, such as Zn(2+), Cd(2+), Hg(2+) and Ag(+), and the macrocyclic thioether 1,4,7-trithiacyclononane ([9]AneS3) or the monodentate diethylsulfide (Et(2)S), in acetonitrile (AN) at 298.15 K, were studied by a systematic methodology including potentiometry, calorimetry and polarography. [9]AneS3 is able to form complexes with all the target cations, Et(2)S only reacts with Hg(2+) and Ag(+). Mononuclear ML(j) (j = 1, 2) complexes are formed with all the metal ions investigated, where the affinity order is Hg(2+) > Ag(+) > Cd(2+) ≈ Zn(2+) when L = [9]AneS3 and Hg(2+) > Ag(+) when L = Et(2)S. Enthalpy and entropy values are generally negative, as a consequence of both metal ion interactions with neutral ligands, the reagents' loss of degrees of freedom and the release of solvating molecules. DFT calculations on the complexes formed with [9]AneS3 in vacuum and in AN are also carried out, to correlate experimental and theoretical thermodynamic values and to highlight the interplay between the direct metal-thioether interaction and the solvation effects. Trends obtained for the stability constants and enthalpies of the 1 : 1 and 1 : 2 complexes in solvent well reproduce the experimental ones for all the divalent metal ion complexes with [9]AneS3 and indicate the release of 3 AN molecules in the formation of each consecutive octahedral complex. In addition, calculated and experimental values for Ag(+) complex formation in solution suggest that in AgL(2) species [9]AneS3 ligands are not both tridentate.

Metal Chelation Therapy and Parkinson’s Disease: A Critical Review on the Thermodynamics of Complex Formation between Relevant Metal Ions and Promising or Established Drugs

“…Still much work has to be performed to define the upper and the lower limiting metal K d values required by a CA to disrupt the α-syn complex without causing excessive metal removal, as well as the suitable standard reduction potentials required by the complexes to avoid harmful redox cycling in the brain. Also, available speciation information is in part lacking, especially as regards Cu(I), for which very few stability constants values have been hitherto determined (possible strategies for effective studies of Cu(I) speciations have been proposed [328]), but also for other metal ions and for several complicated or recently proposed CAs. If a complete metal-ligand speciation study (aimed to determine stability constants) cannot be performed, a K d value should at least be determined.…”

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.…”

Thermodynamics of Hg2+ and Ag+ adsorption by 3-mercaptopropionic acid-functionalized superparamagnetic iron oxide nanoparticles

“…Calorimetry is a powerful tool which allows to directly measure the energy exchange occurring when two reagents are mixed in the measurement cell. This technique has been largely used to obtain thermodynamic data for metal complexation reactions occurring in aqueous or non-aqueous media [20][21][22][23][24][25][26][27][28][29], but much less examples of ITC applied to metal ion adsorption studies are present in the literature [30][31][32][33][34][35][36][37]. In many works, metal ion adsorption enthalpy (ΔHads) has been calculated by van't Hoff equation [38,39].…”