Three new Mn-[Mo(CN)] molecular magnets constructed from chiral bidentate chelating ligands.

Three new cyanide-bridged compounds {[Mn((,)-Dpen)][Mn((,)-Dpen)(HO)][Mo(CN)]·4HO·4CHN} (1-SS), {[Mn((,)-Dpen)][Mn((,)-Dpen)(HO)][Mo(CN)]·4.5HO·4CHN} (1-RR), and {[Mn(Chxn)][Mn(Chxn)(HO)][Mo(CN)]·HO·4CHN} (2) (/-Dpen = (,)/(,)-1,2-diphenylethylenediamine and Chxn = 1,2-cyclohexanediamine) have been successfully synthesized from the self-assembly reaction of the [Mo(CN)] unit, the Mn ions, and two chiral bidentate chelating ligands. Single-crystal structure determinations show that compounds 1-SS and 1-RR containing ligands /-Dpen are enantiomers and crystallize in the chiral space group 2. On the other hand, compound 2 crystallizes in the achiral centrosymmetric space group 1̄ due to the racemization of the /-Chxn ligands during the growth of the crystals. Despite their different space groups and ligands, all three compounds exhibit similar framework structures consisting of cyano-bridged Mn-Mo two-dimensional layers separated by the bidentate ligands. The circular dichroism (CD) spectra have further demonstrated the enantiopure character of compounds 1-SS and 1-RR. Magnetic measurements revealed that all three compounds display ferrimagnetic ordering with similar critical temperatures of about 40 K. The chiral enantiomers 1-SS and 1-RR exhibit the magnetic hysteresis loop with a coercive field of about 8000 Oe at 2 K, which is by far the highest for all known Mn-[Mo(CN)] magnets. Analyses of their structures and magnetic properties indicated that their magnetic properties depend on the anisotropic magnetic interactions between the Mn and Mo centers, which are closely related to the C-N-M bond angles.