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Iron(III) Complexation and Extraction by Aromatic Hydrazones

Aromatic hydrazones, such as salicylaldehyde isonicotinoyl hydrazone, 2’-hydroxyacetophenone isonicotinoyl hydrazone and 2’- hydroxypropiophenone isonicotinoyl hydrazone, have been shown as promising iron-chelating agents [1]. Three methoxy derivatives (L1–L3) of salicylaldehyde nicotinoyl hydrazone (Figure 1) were prepared in this work and their complexation and extraction properties toward iron(III) were studied by UV-Vis spectrophotometry. Complexation of iron(III) was studied in acidic methanol/water 1/1 mixtures (0.01 mol dm–3 HNO3). All hydrazones hydrolyze at these experimental conditions but the iron complexes are stable. The stoichiometries of the formed complexes determined by batch spectrophotometric titrations were 1 : 1 (Fe3+ : L). The extraction of iron(III) from acidic aqueous solutions was performed with chloroform solutions of L1–L3. Optimal experimental conditions for extraction were determined, pH of aqueous phase was 3, concentration of ligand was 4×10–4 mol dm–3 and concentration of iron(III) was 4×10–5 mol dm–3. Stoichiometries of extracted complexes were determined to be 1 : 2 (Fe3+ : L) based on the results obtained by Job’s method and equilibrium shift method. Number of protons released during complexation was three. Molar absorption coefficient of iron(III) complex of L1 at 374 nm was 14091 mol–1 dm3 cm–1. The compound L1 was the most suitable of investigated compounds for extraction of iron(III) from aqueous to chloroform phase due to the least overlapping of absorption maxima of complex and ligand.

aroylhydrazones ; iron(III) ; complexation ; extraction

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