The first coordination co
mpounds of 1,2,3,4-butanetetracarboxylate anion (butca
4-) of the for
mula [M
2(butca)(H
2O)
5]
n·2
nH
2O [M = Mn(II) (
1), Co(II) (
2), and Ni(II) (
3)] were prepared and their X-ray crystal structures and
magnetic properties investigated. The three co
mplexes have a very si
milar two-di
mensional structure which consistsof (4,4) networks,
1 and
2 being isostructural. The tetracarboxylate ligand acts as a 4-fold connector leading totwo-di
mensional (4,4) networks of
metal ato
ms, this topology being possible because of its planar confor
mation.The nodes of these networks are for
med by dinuclear
motifs which exhibit the unusual (
![](/i<font color=)
mages/entities/
mgr.gif">-aqua)bis(
![](/i<font color=)
mages/entities/
mgr.gif">-carboxylate)bridging unit which is analogous to that observed in so
me
molecules of biological interest. The variable-te
mperature
magnetic susceptibility
measure
ments of
1-
3 show that
1 and
2 are antiferro
magnetically coupled syste
ms whereas
3 exhibits a ferro
magnetic behavior. The analysis of the
magnetic data of
1-
3 through a si
mple dinuclear
modelallowed the deter
mination of the values of the
magnetic coupling (
J) -3.6 (
1), -1.2 (
2), and +1.47 c
m-1 (
3) withthe Ha
miltonian being defined as
H = -
JSA·
SB. The counterco
mple
mentarity between the two bridges (aqua andsyn-syn carboxylate) accounts for the trend exhibited by the values of the
magnetic coupling in this fa
mily.