Inorganic Chemistry, Vol.45, No.20, 8239-8250, 2006
Synthesis, crystal structure, and magnetic studies of one-dimensional cyano-bridged Ln(3+)-Cr3+ complexes with bpy as a blocking ligand
The reaction of Ln(NO3)(3)center dot aq with K-3[Cr(CN)(6)] and 2,2'-bipyridine (bpy) in a water/ethanol solution led to two families of complexes: 4 one-dimensional (1D) complexes of the formula trans-[Cr(CN)(4)(mu-CN)(2)Ln(H2O)(3)(bpy)(2)](n)center dot 4nH(2)O, 3.5nbpy (Ln(3+) = La, Ce, Pr, and Nd) and 10 1D complexes of the formula trans-[Cr(CN)(4)(mu-CN)(2)Ln(H2O)(4)(bpy)](n)center dot 3.5nH(2)O center dot 1.5nbpy (Ln(3+) = Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu). The structures for the fourteen complexes [LaCr](n) (1), [CeCr](n) (2), [PrCr](n) (3), [NdCr](n) (4), [NdCr](n) (4'), [SmCr](n) (5), [EuCr](n) (6), [TbCr](n) (7), [DyCr](n) (8), [HoCr](n) (9), [ErCr](n) (10), [TmCr](n) (11), [YbCr](n) (12), and [LuCr](n) (13) have been solved. Complexes 1-4 crystallize in the orthorhombic space group Pbam and are isomorphous; complexes 4'-13 crystallize in the triclinic space group P (I) over bar and are isomorphous. The X-ray structural characterization of complexes 1-4 shows the presence of a discrete decameric water cluster built around a cyclic hexameric core stabilized by the solid-state structure, which represents another new mode of association of water molecules. The Ln(3+)-Cr3+ magnetic interaction is negligible in 6 and 12, antiferromagnetic in 2, 4', 7, 8, 9, 10, and 11, and unresolved for 3. The complex 5 is a ferrimagnet because its magnetic studies suggest the onset of a very weak ferromagnetic three-dimensional ordering.