Five new heterotetranuclear complexes of type [Fe3LnO2(CCl3COO)8
(H2O)(THF)3] ⋅ THF, where Ln = La, Ce, Pr, Nd, Sm were synthesized by
using the method described in [1]. All complexes present butterfly structure
with FeO6 coordination core, with the oxygen related to different molecules or
ions, as follows: Fe1Oc(Ocarb)3OaqOTHF; Fe2Oc (Ocarb)4OTHF; Fe3Oc
2(Ocarb)4. The
57Fe Mossbauer spectra (MS) of the complexes, both at room temperature
and 15 K, consist of two asymmetrical wide peaks, which were least square
fitted via two doublets. The Mossbauer parameters of the two doublets with
isomer shift and quadrupole splitting ranging between 0.22 and 0.52 mm.s-
1 and, respectively, between 0.94 and 1.72 mm.s-1 indicate that all Fe(III)
ions are in high spin state (S = 5/2) and that the electronic structures of two
iron configurations are very similar. The relative areas of the two Mossbauer
components are in the ratio ~ 2:1. The doublet with lower relative intensity was
assigned to Fe1 containing water molecule in his environment. The MS of the
analyzed complexes do not evidence any magnetic ordering around the iron
nucleus, down to 15 K.
According to QS values at 15 K, the symmetry of the electronic environment
around the Fе1 nuclei is higher than around the other two iron nuclei (Fe2 and
Fe3). The nature of lanthanide ion in the complex has an insignificant effect on
the electronic interaction of the iron ions. However, the QS (Doublet 1) of the Ce
containing complex at 15 K is higher with about 0.18 mm.s-1 as compared with
the corresponding QS of the rest of compounds. This fact needs supplementary
investigations.
[1] Turta, C.I., Prodius, D.N., Mereacre, V.M., Shova, S.G., Gdaniec, M.,
Simonov, Yu. A., Kuncser, V., Filoti, G., Caneschi, A., Sorace, L. Inorg. Chem.
Commun. (2004): 7, № 4, 576-579.