Two new Co(II) coordination polymers based on carboxylate-bridged di- and trinuclear clusters with a pyridinedicarboxylate ligand: synthesis, structures and magnetism

Two new Co(II) coordination polymers with a pyridinedicarboxylate ligand, {[Co(L)(H(2)O)]·H(2)O}(n) (1) and [Co(3)(HCOO)(2)(L)(2)(H(2)O)(2)](n) (2) (H(2)L = 5-(pyridin-4-yl)isophthalic acid), have been synthesized and structurally characterized by elemental analysis, IR, XRPD, and single-crystal X-ray diffraction. Structure analyses show that complex 1 has a two-dimensional (2D) double-layered structure with a (3,6)-connected kgd topology based on [Co(2)O(2)] units, while complex 2 takes a three-dimensional (3D) structure with (3,6)-connected rtl topology network based on linear [Co(3)(HCOO)(2)(CO(2))(4)] clusters with triple carboxylate bridges. Magnetic investigation indicates that besides strong spin-orbit coupling of Co(II) ions, ferromagnetic and weak ferromagnetic exchange interactions between Co(II) ions in the Co(2) and Co(3) clusters exist in 1 and 2, respectively. The FC/ZFC magnetization behaviors for both of them suggest the absence of any long-range magnetic ordering.