Syntheses, crystal structures, and magnetic properties of Mn-Nb and Co-Nb cyanido-bridged bimetallic assemblies

Cyanido-bridged Mn-Nb and Co-Nb bimetal assemblies, MnII2[NbIV(CN)8]·(L)2·nH2O (1: L = 5-aminopyrimidine, n = 5; 2: L = 5-methylpyrimidine, n = 4), and CoII2[NbIV(CN)8]·(4-pyridinealdoxime)8·2H2O (3) are synthesized. 1 and 2 have isomorphic three-dimensional (3D) cyanido-bridged network composed of a square antiprism Nb sites, showing ferrimagnetism with Curie temperatures (TC) of 32 and 34 K, respectively, due to the antiferromagnetic coupling between MnII (S = 5/2) and NbIV (S = 1/2) through the CN groups. 3 has a 3D cyanido-bridged network composed of a dodecahedral Nb site and axially distorted Co site, exhibiting ferromagnetism with a TC of 18 K. Magnetization versus rotation angle of single crystal reveals that 3 has a large coercive field of 15 000 Oe as crystal is oriented to a-axis, which is due to the strong magnetic anisotropy on distorted CoII.