摘要:
The tridentate unsymmetrical ligand N-(2-hydroxymethylphenyl) salicylideneimine H2L, derived from salicylaldehyde and 2-aminobenzylalcohol, with [ONO] donor atoms yields [(L2Fe2Cl2)-Cl-III] (1) and [L6Fe4III] (2) complexes containing alkoxide bridges, which have been structurally characterized by X-ray diffraction. In complex 1, each ferric ion is five-coordinated with a distorted square-pyramidal geometry, the basal planes of which are symmetrically bridged by two alkoxide oxygen atoms. Analysis of the susceptibility data reveals antiferromagnetic interactions with an exchange parameter J = -15.8 cm(-1) between the high-spin d(5) ferric centers. The structure of 2 can be considered as "linear (2,2,2)'' to specify the number of enolate oxygen atoms between four iron atoms. Variable-temperature magnetic susceptibility data are fitted to a "three-J'' model, yielding pairwise antiferromagnetic exchange interactions, J(12) = J(34) = -13.4 cm(-1),J(13) = J(24) = -7.1 cm(-1),J(23) = -14.9 cm(-1), between the neighboring ferric centers; J(14) is assumed to be negligible. Complex 2 has a complicated low-lying magnetic structure with a non-diamagnetic ground state. In addition, the Fe-O-Fe angles at the bridging ligands seem to be determinant for the strength of the antiferromagnetic interactions. (C) 2011 Elsevier B.V. All rights reserved.