A High-Frequency and High-Field EPR Study of New Azide and Fluoride Mononuclear Mn(III) Complexes.

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)]

Références

Titre
A High-Frequency and High-Field EPR Study of New Azide and Fluoride Mononuclear Mn(III) Complexes.
Type de publication
Article de revue
Année de publication
2003
Revue
J. Am. Chem. Soc.
Volume
125
Pagination
12337–12344
ISSN
0002-7863
Soumis le 15 juin 2018