Crystal structure and magneto-structural investigation of alkoxido bridged dinuclear Fe(III) complexes with 1,3-oxazolidine ligands

Abstract

Four 1,3-oxazolidine based ligands (H2L1−H2L4) were synthesized in solvent-free condition from the reaction of amino alcohols (2-amino-2-(hydroxymethyl)-1,3-propanediol or 2-amino-2-ethyl-1,3-propanediol) and 2-acetylpyridine or 2-pyridinecarboxaldehyde at 110 °C. Four new dinuclear Fe(III) complexes, [Fe2(HL1)(N3)4] (1), [Fe2(HL2)(N3)4] (2), [Fe2(HL3)(N3)4] (3) and [Fe2(HL4)(N3)4] (4), were synthesized with a similar procedure by the reaction of H2L1–4, Fe(NO3)3·9H2O and NaN3 in 1:1:2 molar ratios in methanol. The ligands and complexes were characterized by elemental analysis and spectroscopic methods. The structure of complexes was solved by single-crystal X-ray diffraction analysis which showed complexes 1–4 to be alkoxido-bridged dinuclear Fe(III) complexes. The structural studies indicated that the crystal structure of 2, 3 and 4 consist of a centrosymmetric dinuclear Fe(III) complexes while the asymmetric unit in 1 consists of two halves of the two independent molecules. The Fe(III) ions have similar coordination environments (cis-FeN4O2) in all of 1–4 which can be described as distorted octahedral geometry. The 1,3-oxazolidine ligands act as mononegative tridentate N2O-donor ligand in 1–4. Two azide groups are also coordinated to each Fe(III) ion as terminal monodentate ligands. The alcoholic arms of the 1,3-oxazilidine ligands act as bridging groups between Fe(III) ions and the Fe⋯Fe distances through these bridges are in the range of 3.157–3.198 Å. Magnetic studies in 2–300 K range reveal antiferromagnetic interactions between the Fe(III) ions with values for the magnetic coupling constants in the range −9.4 cm−1 to −9.7 cm−1, with H = −2J(S1S2).