  The structure and magnetic properties of oligonuclear manganese complex
[Mn(hfa)2cpo]2 (where hfa is hexafluoroacetylacetonate dehydrate and cpo is
4-cyanopyridine-N-oxide) are presented. In the unit cell, the dinuclear
molecules are well isolated from each other. The non-monotonous dependence of
magnetic susceptibility is explained in terms of the hierarchy of exchange
parameters by using exact diagonalization. The thermodynamic behavior of pure
cpo and [Mn(hfa)2(cpo)]2 is simulated numerically in a dimer approximation by
an extrapolation to spin S = 5/2. The Mn-Mn exchange integral is evaluated.
