engleski

Structural Analysis of Iron(III) Complexes with Nicotinic Acid Aroylhydrazones by IR Spectroscopy

Among diverse properties of hydrazones resulting in wide range of their applications, particularly interesting are complexing abilities towards various metal ions.1 Hence three iron(III) complexes, 1, 2 and 3, were synthesized with nicotinic acid aroylhydrazones, which all contained a hydroxyl group at the C2 atom of the phenyl ring, but differed in the position of a methoxy group, being placed at the C3, C4 and C5 atom, respectively. Elemental analysis indicated 1:2 metal to ligand stoichiometry for all the prepared complexes. The proposed structures were based on analysis and assignment of the experimental infrared (IR) spectra of both ligands and complexes, supported by theoretical calculations. IR spectra implied that aroylhydrazones, consisting of the phenyl ring with the methoxy substituent in ortho (1) and para (3) position with respect to the hydroxyl group, coordinated Fe(III) in a similar way, but different from that of aroylhydrazone with the methoxy group in meta (2) position. Based on distinctive IR bands a coordination of the aroylhydrazone ligand in enolimine form was suggested for 2, binding to the metal cation through enolic oxygen, azomethine nitrogen and very likely hydroxyl group oxygen. Intense carbonyl stretching bands, observed in the IR spectra of the Fe(III) complexes 1 and 3, were associated with the carbonyl group not involved in coordination, implying existence of the ligands in ketoamine form.

aroylhydrazones ; Fe(III) complex ; structure ; IR spectroscopy

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