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

摘要

Two new Co ~II coordination polymers with a pyridinedicarboxylate ligand, {[Co(L)(H _2O)]·H _2O} n (1) and [Co 3(HCOO) _2(L) _2(H _2O) _2] _n (2) (H _2L = 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 _2O _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.