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 (H 2 L 1 −H 2 L 4 ) 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, [Fe 2 (HL 1 )(N 3 ) 4 ] ( 1 ), [Fe 2 (HL 2 )(N 3 ) 4 ] ( 2 ), [Fe 2 (HL 3 )(N 3 ) 4 ] ( 3 ) and [Fe 2 (HL 4 )(N 3 ) 4 ] ( 4 ), were synthesized with a similar procedure by the reaction of H 2 L 1–4 , Fe(NO 3 ) 3 ·9H 2 O and NaN 3 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 -FeN 4 O 2 ) in all of 1 – 4 which can be described as distorted octahedral geometry. The 1,3-oxazolidine ligands act as mononegative tridentate N 2 O-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 A. 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 ( S 1 S 2 ).