Three new Mn II -[Mo III (CN) 7 ] 4- molecular magnets constructed from chiral bidentate chelating ligands.

Three new cyanide-bridged compounds {[Mn(( S , S )-Dpen)] 3 [Mn(( S , S )-Dpen)(H 2 O)][Mo(CN) 7 ] 2 ·4H 2 O·4C 2 H 3 N} n (1-SS), {[Mn(( R , R )-Dpen)] 3 [Mn(( R , R )-Dpen)(H 2 O)][Mo(CN) 7 ] 2 ·4.5H 2 O·4C 2 H 3 N} n (1-RR), and {[Mn(Chxn)][Mn(Chxn)(H 2 O) 0.8 ][Mo(CN) 7 ]·H 2 O·4C 2 H 3 N} n (2) ( SS / RR -Dpen = ( S , S )/( R , R )-1,2-diphenylethylenediamine and Chxn = 1,2-cyclohexanediamine) have been successfully synthesized from the self-assembly reaction of the [Mo III (CN) 7 ] 4- unit, the Mn II ions, and two chiral bidentate chelating ligands. Single-crystal structure determinations show that compounds 1-SS and 1-RR containing ligands SS / RR -Dpen are enantiomers and crystallize in the chiral space group P 2 1 . On the other hand, compound 2 crystallizes in the achiral centrosymmetric space group P 1̄ due to the racemization of the SS / RR -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 II -Mo III 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 II -[Mo III (CN) 7 ] 4- magnets. Analyses of their structures and magnetic properties indicated that their magnetic properties depend on the anisotropic magnetic interactions between the Mn II and Mo III centers, which are closely related to the C-N-M bond angles.