Syntheses, structures and magnetic properties of dinuclear oxo-bridged iron(III) complexes

Abstract The reaction of tris(2-pyridylmethyl)amine (TPyA)/ N , N -bis(2-pyridylmethyl)-2-aminoethanol (bpaeOH), H 2 DHBN/Na 2 C 2 O 4 /NaN 3 and Fe(II/III) ions in MeOH leads to the isolation of three iron(III) dimeric complexes, namely [(TPyA)(DHBN)Fe III OFe III (TPyA)(DHBN)]·2H 2 O ( 1 ), [(bpaeOH)(C 2 O 4 )Fe III OFe III (C 2 O 4 )(bpaeOH)]·2H 2 O ( 2 ) and [(TPyA)(N 3 )Fe III OFe III (N 3 )(TPyA)](ClO 4 ) 2 ( 3 ) (H 2 DHBN = 3,4-dihydroxybenzonitrile). These complexes have been investigated by single crystal X-ray diffractometry and magnetochemistry. Complexes 1 – 3 show dimeric structures with a bridging oxo (O 2− ) ion, and all the iron(III) ions have a distorted octahedral geometry. Complexes 1 and 3 have offset face-to-face π–π interactions between the dimers and possess a supramolecular structure, while 2 has O–H···O hydrogen bonding interactions between the dimers, which gives rise to a 1-D chain structure. These ( μ -oxo)diiron(III) complexes exhibit antiferromagnetic interactions [ 1 : g  = 2.0, J / k B  = −112 K (−78 cm −1 ), θ  = −0.29 K, ρ  = 0.035; 2 : g  = 2.0, J / k B  = −141 K (−98 cm −1 ), θ  = −0.3 K, ρ  = 0.01; 3 : g  = 2.0, J / k B  = −130 K (−90 cm −1 ), θ  = −0.5 K, ρ  = 0.009]. These indicate that very strong antiferromagnetic interactions occur via the oxo bridge within the iron(III) dimer and weak antiferromagnetic interactions exist between the dimers.