Structures and magnetism of cyano-bridged grid-like two-dimensional 4f-3d arrays

With the introduction of 4,4'-bipyridine N, N'-dioxide (bpdo) ligands, six novel cyano/bpdo mixed-bridged heterometallic 4f - 3d compounds {{Ln(III)( bpdo)(H2O)(2)M( III)(CN)(6)}center dot 2H(2)O}(n) (Ln = Nd( 1), Sm( 2), Gd( 3), Tb( 4) with M = Fe; Ln = Nd( 5), Sm( 6) with M = Co) have been prepared. X-Ray crystallography revealed that they have the same two-dimensional molecular structures, where each [M(CN)(6)](3-) unit uses four co-planar cyanide groups to connect with four square anti-prism Ln(3+) ions and, accordingly, each Ln(3+) ion links four [M(CN)(6)](3-) units, giving a corrugated grid-like layer and, simultaneously, the next nearest Ln(3+) ions are bridged by bpdo in the diagonal direction. Magnetic studies showed that the Ln(3+) - Fe3+ interaction is ferromagnetic for NdFe ( 1), antiferromagnetic for SmFe ( 2) and GdFe ( 3), while negligible for TbFe ( 4). Especially, 2 and 3 exhibited ferrimagnetic orderings below 2.9 and 1.9 K, respectively, with a coercive field of 40 Oe at 1.8 K for 2. Additionally, 5 showed an unusual field-induced magnetization relaxation.