Potentiometric, spectrophotometric and calorimetric study on iron(III) and copper(II) complexes with 1,2-dimethyl-3-hydroxy-4-pyridinone

The iron(III)–1,2-dimethyl-3-hydroxy-4-pyridinone (Deferiprone) system is carefully characterized by a combined potentiometric–spectrophotometric procedure at 25 and 37 °C at different ionic strengths, and by thermochemical and quantum-chemical studies. The main purpose of this work was to determine how the temperature dependence of both complex-formation and protonation constants can affect the pFe values on going from 25 °C (pFe is normally calculated using 25 °C stability constants) to the physiological temperature of 37 °C at which chelating agents are active in vivo. The copper(II)–Deferiprone system is also studied and the iron(III)–Deferiprone distribution diagrams in presence of variable copper(II) amounts are shown so as to explain possible side effects due to a competing metal ion during the chelating therapy of iron overload.