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Kinetics and Mechanism of Interactions Between Iron(lll) and Desferrioxamine B. The Formation and Hydrolysis of Ferrioxamine B in Acidic Aqueous Solution

Mladen Biruš ; Department of Chemistry, Faculty of Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia, Yugoslavia
Zdravko Bradić ; Department of Chemistry, Faculty of Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia, Yugoslavia
Nikola Kujundžić ; Department of Chemistry, Faculty of Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia, Yugoslavia
Marijan Pribanić ; Department of Chemistry, Faculty of Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia, Yugoslavia

Sažetak

The kinetics of the formation and hydrolysis of ferrioxamine
B complexes have been studied in acidic aqueous solution (0.001-
-1.0 M HCl) at 25.0 °c, μ = 1.0 M (maintained by NaCl). Two stage
kinetics have been observed in both the formation and in the hydrolysis
reactions. The proposed reaction model involves formation/
hydrolysis of bidentate, tetradentate, and hexadentate bonded
desferrioxamine B to iron(III).
The formation of the bidentate complex occurs by two paths:
one involving unhydrolysed ferric ion yields the rate constant
k1 = 282 M-1 s-1, and the other via hydrolysed ferric species gives
the rate constant k1' = 4.1 X 103· M-1 s-1• The analogous rate constants
for the reverse hydrolysis reactions were obtained; k - 1 =
= 0.65 M-1 s-1 for the acid dependent and k _ 1' = 0.016 s·1 for the
acid independent path.
The formation and hydrolysis rate constants of the tetradentate
linked complex have been calculated using the steady-state approximation
as k 2 = 9 s·1 and k _2 = 2 M-1 s-1, respectively.
The conversion of tetradentate to hexadentate as well as
hydrolysis of the hexadentate to tetradentate bonded species have
been characterized by the rate constants k 3 = 2.2 s-1 and k _ 3 =
= 18 M-1 s-1, respectively.
These results are compared with kinetic data previously
reported. Chloride media increases the rate of formation and hydrolysis
of the bidentate species, and possibly has the same effect
on the tetradentate species but does not affect hydrolysis of the
hexadentate complex. These effects were analyzed in terms of a
labilization of iron(III) coordinated ligands by inner-sphere coordinated
chloride.

Ključne riječi

Hrčak ID:

194241

URI

https://hrcak.srce.hr/194241

Datum izdavanja:

15.4.1983.

Posjeta: 676 *