  A new high symmetry Mn12 oxocarboxylate cluster
[Mn12O12(CN-o-C6H4CO2)12(CH3CO2)4(H2O)4]*8CH2Cl2 (1) with mixed carboxylate
ligands is reported. It was synthesized by the standard carboxylate
substitution method. 1 crystallizes in the tetragonal space group I41/a.
Complex 1 contains a [Mn12O12] core with eight CN-o-C6H4CO2 ligands in the
axial positions, four CH3CO2 and four CN-o-C6H4CO2 those in equatorial
positions. Four H2O molecules are bonded to four Mn atoms in an alternating up,
down, up, down arrangement indicating 1:1:1:1 isomer. The Mn12 molecules in 1
are self-assembled by complementary hydrogen C-H...N bonds formed with
participation of the axial o-cyanobenzoate ligands of the adjacent Mn12
clusters. The lattice solvent molecules (CH2Cl2) are weakly interacted with
Mn12 units that results in solvent loss immediately after removal of the
crystals from the mother liquor. The electronic structure and the
intramolecular exchange parameters have been calculated. Mn 3d bands of 1 are
rather broad and center of gravity of the bands shifts down from Fermi level.
The overlap between Mn 3d bands and 2p ones of the oxygen atoms from
carboxylate bridges is higher than in the parent Mn12-acetate cluster. These
changes in electronic structure provide significant difference in the exchange
interactions in comparison to Mn12-acetate. The magnetic properties have been
studied on a dried (solvent-free) polycrystalline sample of 1. The dc magnetic
susceptibility measurements in the 2-300 K temperature range support a
high-spin ground state (S = 10).
