Magnetic Investigation of a Double-Helix Chain Framework Based on Dinuclear Cobalt(II) SBUs

A coordination polymer [Co(dpa)pyz0.5] n (1) with double-helix chains has been constructed hydrothermally using H2dpa (H2dpa = diphenic acid), pyz (pyz = pyrazine) and Co(NO3)2· 6H2O. Its structure and magnetic properties were investigated. The compound crystallizes in the triclinic space group P -1. Each Co atom is five-coordinated and takes a distorted tetragonal pyramid geometry. Two carboxylates of the H2dpa ligands bridge four Co(II) ions to form infinite right-handed or left-handed helical ─C─O─Co─ chains. The two types of helical chains are interconnected to each other through the Co(II) centers to produce double-helix chains. The chains form a 2D sheet through the coordination interaction of pyz molecules between adjacent chains. Magnetic studies for complex 1 show stronger antiferromagnetic coupling between the Co(II) ions.