Speciation Studies of Bifunctional 3-Hydroxy-4-Pyridinone Ligands in the Presence of Zn2+ at Different Ionic Strengths and Temperatures

Abstract

The acid–base properties of two bifunctional 3-hydroxy-4-pyridinone ligands and their chelating capacity towards Zn2+, an essential bio-metal cation, were investigated in NaCl aqueous solutions by potentiometric, UV-Vis spectrophotometric, and 1H NMR spectroscopic titrations, carried out at 0.15 ≤ I/mol −1 ≤ 1.00 and 288.15 ≤ T/K ≤ 310.15. A study at I = 0.15 mol L−1 and T = 298.15 K was also performed for other three Zn2+/Lz− systems, with ligands belonging to the same family of compounds. The processing of experimental data allowed the determination of protonation and stability constants, which showed accordance with the data obtained from the different analytical techniques used, and with those reported in the literature for the same class of compounds. ESI-MS spectrometric measurements provided support for the formation of the different Zn2+/ligand species, while computational molecular simulations allowed information to be gained on the metal–ligand coordination. The dependence on ionic strength and the temperature of equilibrium constants were investigated by means of the extended Debye–Hückel model, the classical specific ion interaction theory, and the van’t Hoff equations, respectively.

Bifunctional 3-Hydroxy-4-Pyridinones as Potential Selective Iron(III) Chelators: Solution Studies and Comparison with Other Metals of Biological and Environmental Relevance

“…The data presented in the current paper for Cu 2+ and Fe 3+ /(3-hydroxy-4-pyridinones) systems ( Table 1 and Table 2 ) were compared with those already reported in the literature on the interaction of the five ligands with Zn 2+ [ 19 ] and Al 3+ [ 13 ] ( Table S4 ) at I = 0.15 mol L −1 in NaCl (aq) and T = 298.15 K. The speciation models determined for the different systems display a common species, namely the M L (n-z) , which can be used as reference to evaluate and compare the binding ability of the ligands towards the metal cations. The data analysis showed that the log K 110 trend is: Fe 3+ > Al 3+ > Cu 2+ > Zn 2+ , meaning that the 3,4-HPs are featured by a much higher tendency to form very stable complex species with Fe 3+ , followed by Al 3+ , with respect to the M 2+ .…”

“…The data analysis showed that the log K 110 trend is: Fe 3+ > Al 3+ > Cu 2+ > Zn 2+ , meaning that the 3,4-HPs are featured by a much higher tendency to form very stable complex species with Fe 3+ , followed by Al 3+ , with respect to the M 2+ . In addition, considering the stability constants reported in the literature for the Zn 2+ [ 19 ] and Al 3+ /(H 2 ( L2 ) , H( L5 )) systems [ 13 ], the pZn and pAl values were also calculated at physiological pH ( Table 4 ) and compared with the analogous results presented in this paper for Cu 2+ and Fe 3+ . Analysing the data obtained for the different metal cations and the graphs in Figure 10 and Figure S8 , we can conclude that, similarly to the log K 110 behaviour, the pM values follow the trend for the metal ions: Fe 3+ > Al 3+ > Cu 2+ > Zn 2+ .…”

“…Herein, pursuing our previous strategy, we present the results of a potentiometric and UV–Vis (Ultraviolet–Visible) spectrophotometric investigation on the interaction of five bifunctional 3-hydroxy-4-pyridinones ( Figure 1 ) with Cu 2+ and Fe 3+ , metal cations with a borderline and a hard character, respectively, that are carried out at I = 0.15 mol L −1 in NaCl (aq) , T = 298.15 K and 310.15 K. Furthermore, the obtained thermodynamic data are compared with those already reported in the literature on the binding ability and chelating affinity of the five ligands towards Zn 2+ [ 19 ] and Al 3+ [ 13 ], also featured by borderline and hard behaviour, respectively, at the same experimental conditions. The aim of this work was to evaluate whether the 3-hydroxy-4-pyridinones under study could be exploited as selective chelating agents for the treatment of Fe 3+ overload in humans or, alternatively, in environmental matrices.…”

Physicochemical Insight into Coordination Systems Obtained from Copper(II) Bromoacetate and 1,10-Phenanthroline

“…The coordination compound formation in a solution depends on many factors such as stoichiometry, concentration, ionic strength, solvent type, and temperature [ 15 , 16 ]. Typically, different coordination species exist in an equilibrium in a solution, but not necessarily the dominant one can crystallize.…”

Special Issue “Chemical Speciation of Organic and Inorganic Components of Environmental and Biological Interest in Natural Fluids: Behaviour, Interaction and Sequestration”

“…The Special Issue had satisfactory feedback from researchers, with contributions having cross-field character and being of interest for different industrial, pharmaceutical, chemical, and biological fields [7][8][9][10][11][12][13][14][15][16][17].…”