  We report on the synthesis and magnetic properties of Mn12-based single
molecular magnets (SMMs) with benzene and pentafluorobenzene carboxylate
ligands. The changes in ligand structure are shown to have a decisive effect on
magnetic properties of produced complexes. The compound with benzene
demonstrates unusual magnetic behaviour, namely, temperature dependencies of
magnetization taken under the zero field cooled and field cooled conditions are
split below 10 K and furthermore remnant magnetization and coercive force
remain nonzero in this temperature range. In contrast, compound with
pentafluorobenzene displays the customary signatures of a blocking temperature
at 3K. The effect of ligand substitution was theoretically studied within local
density approximation taking into account on-site Coloumb repulsion.
Calculation results confirm that the electronic structure and the magnetic
exchange interactions between different Mn atoms strongly depend on the type of
ligands.
