A CONCEPT FOR THE SYNTHESIS OF 3-DIMENSIONAL HOMOMETALLIC AND BIMETALLIC OXALATE-BRIDGED NETWORKS [M(2)(OX)(3)](N) - STRUCTURAL, MOSSBAUER,AND MAGNETIC STUDIES IN THE FIELD OF MOLECULAR-BASED MAGNETS
S. Decurtins et al., A CONCEPT FOR THE SYNTHESIS OF 3-DIMENSIONAL HOMOMETALLIC AND BIMETALLIC OXALATE-BRIDGED NETWORKS [M(2)(OX)(3)](N) - STRUCTURAL, MOSSBAUER,AND MAGNETIC STUDIES IN THE FIELD OF MOLECULAR-BASED MAGNETS, Journal of the American Chemical Society, 116(21), 1994, pp. 9521-9528
The tris-chelated [M(II)(bpy)(3)](2+) cations, where M(II) is a divale
nt transition metal and bpy is 2,2'-bipyridine, cause a remarkable cry
stallization of anionic three-dimensional (3D) coordination polymers o
f oxalate-bridged metal complexes [M(2)(ox)(3)](2n-)(n). With these ca
tions, which are appropriate in charge, size, and symmetry, two types
of stoichiometric units of the anionic 3D networks, with metals in dif
ferent valence states, can be distinguished: [M(2)(II)(ox)(3)](2-) and
[M(I)M(III)(ox)(3)](2-). Results of a structural analysis of compound
s within each of the two isomorphous series are discussed: [Ni-II(bpy)
(3)][Mn-2(II)(ox)(3)] (3), cubic, merohedrically twinned, P4(1)32/P4(3
)32, a = 15.579(2) Angstrom, Z = 4; [Fe-II(bpy)(3)] [NaFeIII(ox)(3)] (
4), cubic, P2(1)3, a = 15.507(3) Angstrom, Z = 4; [Fe-II(bpy)(3)][LiCr
III(ox)(3)] (5), cubic, P2(1)3, a = 15.262(4) Angstrom, Z = 4. The Mos
sbauer spectra of the iron-containing compounds [Fe-II(bpy)(3)][Fe-2(I
I)(ox)(3)] (1) and [Fe-II(bpy)(3)][Mn-2(II)(ox)(3)] (2) and type 4 but
LiFeIII are consistent with the stoichiometric formula and the corres
ponding iron valence states. The straightforward synthetic approach an
d easy crystallization behavior, as well as the variety of metal combi
nations within the 3D networks, fender these systems valuable candidat
es for studies in the field of molecular-based magnets. They fulfill t
he requirements of three-dimensional connectivity as well as accessibi
lity to detailed structural characterization. The magnetic susceptibil
ity data in the temperature range 2-300 K of 1, 2 and type 4 but LiFeI
II are presented and the results should be taken as a starting point f
or more extended systematical studies. 1 and 2 reveal antiferromagneti
c ordering behavior, indicated by a negative Weiss constant theta of -
28 and -33 K, whereas the LiFeIII compound exhibits the expected behav
ior of single iron(III) ions. Further extensions to possible networks
of the types [M(II)M(III)(ox)(3)](1n-)(n) and [M(I)M(II)(ox)(3)](3n-)(
n) are discussed.