Synthesis, crystal structures and thermal properties of heteroleptic acetylacetonato iron(III) complexes with aromatic N,N-donor ligands

Using solvothermal syntheses three heteroleptic neutral complex molecules [Fe(acac)(bpy)Cl-2] (1), [Fe(acac) Cl-2(phen)] (2) and [Fe(acac)Cl-2(4dmbpy)] (3) (bpy = 2,2 '-bipyridine, phen = 1,10-phenanthroline, 4dmbpy = 4,4 '-dimethyl-2,2 '-bipyridine) were prepared from the acetylacetonate solution and characterized by chemical analyses and spectroscopic methods (IR and UV-Vis). All three complexes exhibit molecular structures with Fe(III) central atoms which are deformed octahedrally coordinated by one chelating N,N '-donor ligand (bpy, phen or 4dmbpy), one chelating O,O '-donor ligand acac and two olyhedr ligands. The crystal structures are stabilized by hydrogen bonds (complexes 1-3) and p- p interactions (complexes 1 and 2). The complexes exhibit rather high thermal stability up to about 200 degrees C. The first weight loss for 1, 2 and 3 may correspond to decomposition of acac ligand. The residues of the thermal decompositions of the respective complexes 1-3 were formed by alpha-Fe2O3 as shown by a combination of PXRD, SEM and EDX methods.