A Three-Dimensional Coordination Framework with a Ferromagnetic Coupled Ni(II)-CrO(4) Layer: Synthesis, Structure, and Magnetic Studies

We report herein on the crystal structure and magnetic studies of a three-dimensional (3D) Ni(II)-chromate coordination polymer, [Ni(CrO(4))(bpym)(H(2)O)](n) (1; bpym = 5,5′-bipyrimidin), prepared by self-assembly of Ni(II) and chromate ions with a multi-N donor auxiliary ligands, bpym, through hydrothermal processes. The structure of 1 is composed of Ni(II)-CrO(4) layers with [Ni(3)(μ(3)-CrO(4))] triangular motifs, in which the Ni(II) centers are bridged by O′:O′:O′:μ(3)-CrO(4)(2−) anions, and the resulting layers are further connected by twisted trans-μ(2)-N,N′-bpym auxiliary ligands to form a 3D pillar-layered network with an hms topology. The magnetic properties of compound 1 were illustrated by variable field and temperature magnetic susceptibility measurements. The findings reveal that compound 1 shows intralayer ferromagnetic interactions within Ni(II)-CrO(4) layers, and furthers the 3D antiferromagnetic ordering in the resulting of interlayer antiferromagnetic couplings with a Néel temperature (T(N)) of 5.6 K. In addition, compound 1 shows the field-induced metamagnetic behavior at temperature below the T(N).