A combined experimental and theoretical study on bis(Iμ-alkoxo) diiron(III) complexes with hydroxybenzylaminoethanol [O,N,O] donor ligands: Syntheses, structures and magnetic properties

摘要

Three new neutral bis(Iμ-alkoxo)diiron(III) complexes were prepared from N(R),N-(2-methylene-4,6-di-tert-butylphenol)aminoethan-1-ol ligands (H_ 2L1, R = Me and H_2L2, R = H). In these complexes, the ligand wraps around the metal center exhibiting a tridentate facial coordination mode with alkoxo-bridging oxygen, amine nitrogen and phenoxo oxygen donor atoms. In the complex [Fe(acac)L1]_2·MeCN (1) acetylacetonato coligand complete the distorted octahedral coordination spheres of the iron(III) ions, whereas in the five-coordinate iron(III) chloride complexes [FeClL1] _2 (2) and [FeClL2]_2 (3) the ligands induce a geometry that is intermediate between square pyramidal and trigonal bipyramidal. Magnetic studies carried out on these dinuclear complexes showed that J values vary from -16.1 to -29.6 cm~(-1). Both experimental and theoretical DFT studies address a strong magneto-structural correlation between the exchange coupling constant and the Fe-O-Fe angle of the complexes. The crossover point from antiferromagnetic to ferromagnetic coupling is predicted to be 100.4° for this family of N(R),N-(2-methylene-4,6-di-tert-butylphenol)aminoethan-1-ol ligands.