Synthesis, Characterization, and Magnetic Properties of Two New Co(II) Coordination Polymers with a Carboxylate- and Benzimidazolyl-containing Ligand

The hydrothermal reaction of cobalt(II) nitrate hexahydrate with 5-(benzimidazol-1-ylmethyl)isophthalic acid (H₂L) leads to the formation of a complex [Co(L)] (1). In the presence of 2-(pyridin-2-yl)-1H-benzimidazole (pybim) as an auxiliary ligand, a complex [Co(L)(pybim)]·H₂O (2) was obtained. The complexes 1 and 2 have been characterized by single-crystal and powder X-ray diffraction, IR spectroscopy, and elemental and thermogravimetric analyses. Complex 1 shows a binodal (3,6)-connected 2D kgd network with (4³)₂(4⁶.6⁶.8³) topology; 2 shows a chain structure, further linked together by hydrogen bonding and π–π interactions to give rise to a 3D supramolecular framework. Complexes 1 and 2 are examples of auxiliary ligand-assisted structural diversity. The frameworks of 1 and 2 display high thermal stability up to 400 °C. The magnetic properties of 1 were investigated.