Two new CoII coordination polymers based on carboxylate-bridged di- and trinuclear clusters with a pyridinedicarboxylateligand: synthesis, structures and magnetism

Abstract

Two new Co^II coordination polymers with a pyridinedicarboxylate ligand, {[Co(L)(H₂O)]·H₂O}_n (1) and [Co₃(HCOO)₂(L)₂(H₂O)₂]_n (2) (H₂L = 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 [Co₂O₂] units, while complex 2 takes a three-dimensional (3D) structure with (3,6)-connected rtl topology network based on linear [Co₃(HCOO)₂(CO₂)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 Co₂ and Co₃ 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.