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Dissociation of CP20 from Iron( II )(cp20) 3 : A Pulse Radiolysis Study
Author(s) -
Merkofer Martin,
Domazou Anastasia,
Nauser Thomas,
Koppenol Willem H.
Publication year - 2006
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200500821
Subject(s) - chemistry , radiolysis , dissociation (chemistry) , dissociation constant , stereochemistry , inorganic chemistry , aqueous solution , biochemistry , receptor
Deferiprone (CP20), a hydroxypyridine‐4‐one, is used in iron‐chelation therapy. For the iron( III )‐/( II )(cp20) 3 couple, a standard electrode potential of –620 mV was measured by cyclic voltammetry [Templeton et al., Inorg. Chim. Acta 1996 , 245 , 199; Merkofer et al., Helv. Chim. Acta 2004 , 87 , 3021]. On the basis of this value and the overall stability constant for the equilibrium of iron( III ) and three CP20 molecules, ligand dissociation ought to take place after reduction of the iron( III )(cp20) 3 complex. By pulse radiolysis, we show that hydrated electrons reduce the iron( III )(cp20) 3 complex with a rate constant of k = (6.4 ± 0.3) × 10 10 M –1 s –1 , and that the iron( II )(cp20) 3 complex aquates rapidly. The dissociation of the first two CP20 molecules takes place within a few μs after the pulse. The dissociation rate constant for the last CP20 ligand is (8 ± 1) × 10 3 s –1 . The observation of a dissociation illustrates that, under dilute conditions, iron( II ) is not fully complexed by CP20 and could potentially participate in redox cycling to produce oxyradicals. The CO 2 · – radical does not reduce iron( III )(cp20) 3 , which indicates that this complex reacts, as expected, very slowly with inner‐sphere reductants. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)