Copper(ii) metal–organic networks derived from bis(pyridylformyl)piperazineligands and aromatic polycarboxylates: 2D layered structures and a novel 3,5-connected binodal 3D topology

Abstract

Three novel coordination polymers [Cu₂(3-bpfp)(BDC)₂(H₂O)₂]·4H₂O (1), [Cu(3-bpfp)(HBTC)]·0.5H₂O (2) and [Cu(4-bpfp)_0.5(HBTC)(H₂O)] (3) have been hydrothermally synthesized by self-assembly of aromatic polycarboxylate ligands H₂BDC (H₂BDC = 1,3-benzenedicarboxylate acid) or H₃BTC (H₃BTC = 1,3,5-benzenetricarboxylate acid), bridging ligands 3-bpfp/or 4-bpfp [3-bpfp = bis(3-pyridylformyl)piperazine, 4-bpfp = bis(4-pyridylformyl)piperazine], and copper chloride. X-Ray diffraction analysis reveals that each Cu^II ion is connected by BDC/or HBTC and 3-bpfp/or 4-bpfp ligands to form two dimensional (2D) layer structures in compounds 1 and 3. Ligands 3-bpfp and 4-bpfp both display μ₄-bridging coordination mode in 1 and 3 (via ligation of pyridyl nitrogen and carbonyl oxygen atoms). In compound 2, each Cu^II ion is connected by HBTC to construct 2D polymeric layers, which are further linked into a novel 3,5-connected 3D coordination polymeric framework with (4·6²)(4·6⁶·8³) topology by 3-bpfp ligand in μ₂-bridging mode (via ligation of pyridyl nitrogen atoms). Compound 2 is the first 3D example of coordination polymer constructed from 3-bpfp and aromatic polycarboxylate ligands. Moreover, the electrochemical properties of the three copper compounds bulk modified carbon paste electrodes have been studied.