The synthesis, structural characterization, magnetochemistry and Mossbauer spectroscopy of [Fe(3)LnO(2)(CCl3COO)(8)H2O(THF)(3)] (Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Lu and Y)

摘要

The new tetranuclear complexes [Fe(3)Ln(mu(3)-O)(2)(CCl3COO)(8)(H2O)(THF)(3)]center dot THF (Ln = Ce-III (1), Pr-III (2), Nd-III (3)) and [Fe(3)Ln(mu(3)-O)(2)(CCl3COO)(8)(H2O)(THF)(3)]center dot THF center dot C7H16 (Ln = Sm-III (4), Eu-III (5), Gd-III (6), Tb-III (7), Dy-III (8), Ho-III (9), Lu-III (10) and Y-III (11)) have been prepared. All compounds were prepared by the reaction between [Fe2BaO(CCl3COO)(6)(THF)(6)] and the corresponding Ln(III) nitrate salt. The crystal structures of 1-4, 8 and 9 have been determined; these isostructural molecules have a non-planar {Fe(3)Ln(mu(3)-O)(2)} "butterfly" core. Magnetic susceptibility measurements show dominant intramolecular antiferromagnetic exchange interactions for all the complexes. Fe-57 Mossbauer spectroscopy shows three different environments for the Fe-III metal ions, all in their high-spin state S = 5/2 (confirming that no electron transfer from Ce-III to Fe-III occurs in 1). At the time scale of the Mossbauer spectroscopy (about 10(-7) s), evidence of magnetization blocking, i.e. slow relaxation of the magnetization, is observed below 3 K for 7, which was confirmed by ac susceptibility measurements.