Metal and ligand binding mode dependent topologies in phthalate coordination polymers with bis(4-pyridylformyl)piperazine co-ligands

Abstract

Hydrothermal reaction of divalent metal salts, phthalic acid (H₂pht), and bis(4-pyridylformyl)piperazine (bpfp) has afforded two-dimensional (2-D) and three-dimensional (3-D) dual-ligand coordination polymers. Their topologies are influenced by the coordination environment of the metal, binding mode of the pht ligands, and ligation of bpfp formyl groups. {[Co(pht)(bpfp)(H₂O)₂]·H₂O}_n (1) displays acentric (4,4) grid layers. [Cu₂(pht)₂(bpfp)(H₂O)₂]_n (2) exhibits binding of bpfp formyl oxygen atoms and a simple but previously unreported 4,4-connected binodal layer structure with (4.6⁴8)₂(4²6⁴) topology. [Cd₂(pht)₂(bpfp)(H₂O)₂]_n (3) manifests a 3-D structure built from the bpfp pillaring of [Cd(pht)(H₂O)]_n layer motifs. A 4,5-connected binodal net with rare (4⁴6²)(4⁴6⁶) tcs topology can be invoked for 3. Employment of the bpfp ligand affords topologies very different from those seen in many other divalent metal phthalate coordination polymers, including the heretofore unrecognized uninodal 6-connected 3-D self-penetrated 5¹⁰6⁴7 topology in [Co(Hpht)₂(bpy)]_n (bpy = 4,4′-bipyridine). Dehydration and thermal properties of 1–3 are also discussed, along with the luminescent behavior of 3.