Synthesis, structure and the Hirshfeld surface analysis of three novel metal-tiron coordination complexes

Three novel metal-tiron (4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt) and other pillared ligand bpy (4,4′-bipyridyl)-centered coordination polymers of the formulae [Cd(tiron)(bpy)(2)(H(2)O)(2)]·0.5(H(2)O), 1, [Co(3)(tiron-bpy)(2)(bpy)(H(2)O)(8)]·(H(2)O)(2), 2, and [Ba(2)(tiron-bpy)(2)(H(2)O)(4)][solvent], 3, were successfully synthesized under hydrothermal conditions. The as-synthesized materials were well characterized by complimentary techniques such as single-crystal X-ray diffraction, powder X-ray diffraction, Fourier-transform infrared spectroscopy and thermogravimetric analysis techniques. The as-synthesized coordination polymers of 1 and 2 featured 1D chains, while 3 shows a layered structure. Co-based 2 shows linear trinuclear Co(ii) ions and these Co(ii) ions have antiferromagnetic interactions among themselves. The structure of 1 features a zig-zag chain formed by the linkage between monodentate tiron ligands and octahedral Cd(ii) ions, interconnected by a twisted bpy ligand, 2 shows a linear chain constructed from corner-sharing trinuclear octahedral Co(ii) ions and coordinated with a tridentate tiron-bpy adduct ligand, whereas 3 shows nona-coordinated Ba(ii) ions sharing edges with other Ba(ii) ions and connected by hexadentate tiron-bridged structures resulting in a layered structure. In 2 and 3, the bpy nitrogen attacks at the ortho position of the tiron ligand and forms an in situ ligand adduct. The central metal ions show an octahedral geometry in 1 (Cd(ii) ions) and 2 (Co(ii) ions), but nona-coordination of Ba(ii) ions in 3. The short interatomic interactions in the crystal structures were evaluated by mapping the Hirshfeld surface process using pseudo-mirrored 2D fingerprint plots. The major short interatomic interactions H⋯H, O⋯H and C⋯H cover the Hirshfeld surfaces.