A large variety of studies have proved manganese to be the site of binding
and oxidation substrate. Nowadays special attention is focused on studying

the cooperative action of binuclear or multinuclear Mn(II) compounds. Indeed,
binuclear dimanganese(II) metal complexes are present in several enzymes, such
as arginase, catalase, thiosulfate-oxidizing enzyme and glycohydrolase. Due to
these facts, carboxylate-bridged bi- or polymanganese centers have attracted
growing interest in both systematic modelling and physical characterization.
Here we report on the magnetic investigation of [Mn2(μ-H2O)(μ-CCl3COO)2
(CCl3COO)2 (H2O)4]H2O, synthesised earlier.1 The magnetic susceptibility (χ, χT)
of powdered samples has been measured from 2 to 300K with use of a SQUID
magnetometer. At 297.8 K, the magnetic moment value, 8.39 BM, corresponds
to two uncoupled high spin (S=5/2) manganese(II) ions. The μeff value decreases
upon cooling and reaches a value of 5.15 BM at 1.97 K, which is characteristic
of an antiferromagnetic interaction between the two metal ions. The magnetic
data of complex were fitted with help of the Heisenberg Dirac Van Vleck HDVV
spin-exchange operator. The least-squares fit of the experimental data gave the
following set of parameters: g=2.002(6), θ=-1.28(2)K Nα=0,002(6) J=-0.499(5)
cm-1 The θ value has been obtained from the Curie-Weiss law [C=2.49(2)
cm3·K·mol-1 θ =-1.28(2) K] and suggests the presence of second-order effects
(such as intermolecular interactions, zero- field splitting, etc.). The obtained J
value(-0.5 cm-1), similar to the ones given in early published works, corresponds
to the disymmetric manganese(II) (μ-aqua) dimmer compound.
1. S.G. Shova, L.G. Turyatke, Gh.V. Novitchi, M.D. Mazus, A.P. Gulea
Russ. J. Coord. Chem. 1996, 22, 485-487.