Iron complexes with sulphate anion or ligand, their thermal behavior and magnetic properties
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Reactions of ferrous or ferric sulphates with the chelating diamine ligands bpy (2,2'-bipyridine) and phen (1,10-phenanthroline) in methanol/water solution yielded two new complexes, a green Fe(III) complex [Fe 2 ( bpy ) 2 (H 2 O) 2 O(SO 4 ) 2 ]·3H 2 O ( 1 ) and dark red complex [Fe( phen ) 3 ](SO 4 )·8.4H 2 O ( 2 ). Both complexes were characterized using chemical and spectroscopic methods (IR, UV-Vis). Single crystal X-ray study showed that 1 exhibit molecular structure formed of dinuclear complex molecules comprising {Fe-O-Fe} structural unit with close distance between the deformed octahedrally coordinated Fe atoms (3.1857(8) Å) and the unit cell content is completed by water solvate molecules. The crystal structure of 2 is ionic and is formed of [Fe( phen ) 3 ] 2+ complex cation, sulphate anions and water solvate molecules. The temperature dependent magnetic study of dinuclear complex 1 revealed strong antiferromagnetic interaction between the two Fe(III) atoms which both are in HS state at all temperatures. The theoretical calculations predict strong antiferromagnetic interaction in dimers, and the analysis of magnetic data yields J/k B = -315.4 K. The thermal behavior of both complexes 1 and 2 was studied in both oxidative (air) and inert (nitrogen) atmospheres. The thermal decomposition in all cases started with dehydration at 90°C (1) and 80°C (2); the dehydrations were followed by temperature dependent IR spectroscopy for complex 2 . In both atmospheres, the solid residues consisted of nanosized oxides (α-Fe 2 O 3 ), as corroborated by SEM analysis, while EDX spectra confirmed the homogeneity of the resulting oxides.
