Département de chimie moléculaire

The isolation, structural characterization and electronic properties of three new six-coordinated Mn(III) complexes, [Mn(bpea)(F)3] (1), [Mn(bpea)(N3)3] (2), and [Mn(terpy)(F)3] (3) are reported (bpea = N,N-bis(2-pyridylmethyl)ethylamine; terpy = 2,2':6',2''-terpyridine). As for [Mn(terpy)(N3)3] (4) (previously described by Limburg J.; et al., 2001), all these complexes exhibit a Jahn-Teller distortion of the octahedron characteristic of high-spin Mn(III) (S = 2). The anal. of the crystallog. data shows an elongation along the tetragonal axis of the octahedron for complexes 1 and 3, while complex 2 presents an unexpected compression. The electronic properties were studied using a high-field and high-frequency EPR study performed between 5 and 15 K (190-575 GHz). The spin Hamiltonian parameters detd. in solid state are in agreement with the geometry of the complexes obsd. in the crystal structures. A neg. D value found for 1 and 3 is related to the elongated tetragonal distortion, whereas the pos. D value detd. for 2 is in accordance with a compressed octahedron. The high E/D values, at 0.103-0.230 for all complexes, are correlated with the highly distorted geometry present around the Mn(III) ion. HF-EPR expts. were also performed on complex 1 in soln. and show that the D value is the only spin Hamiltonian parameter which is slightly modified compared to the solid state (D = -3.67 cm-1 in solid state; D = -3.95 cm-1 in soln.). [on SciFinder(R)]