Layered copper bromide coordination polymers from bis(pyridyl)piperazine-type precursors: Ligand dependent valence tuning and in situ hydrothermal reaction chemistry

Hydrothermal reaction of copper(II) bromide with either bis(4-pyridylmethyl)piperazine (bpmp) or bis(4-pyridylformyl)piperazine (bpfp) afforded layered coordination polymer solids. The racemic S,S and R,R stereochemistry dped ligands in [Cu2Br2(dped)]n (1, dped = 1,2-di(4-pyridyl)ethanediol) were formed by the in situ transformation of bpmp via putative 4-pyridylmethanol intermediates, along with concomitant reduction to monovalent copper. The structure of 1 contains [Cu2Br2]n chains comprising edge-shared [Cu3Br3] boat-conformation six-membered rings, linked into layer motifs by dped tethers with alternating stereochemistry. Lack of benzylic hydrogen atoms in bpfp causes that ligand to stay intact under the reaction conditions, generating the 2-D layered divalent copper phase [CuBr2(bpfp)]n (2).

Hydrothermal reaction of CuBr2 with bis(4-pyridylmethyl)piperazine resulted in in situ transformation to racemic S,S and R,R 1,2-di(4-pyridyl)ethanediol (dped) ligands in [Cu2Br2(dped)]n (1). The structure of 1 contains structurally unique [Cu2Br2]n chains with [Cu3Br3] boat-conformation rings.Figure optionsDownload as PowerPoint slideHighlights
► Conversion of bis(4-pyridylmethyl)piperazine into S,S and R,R 1,2-di(4-pyridyl)ethanediol.
► New aggregation of copper halide boat-conformation six-membered rings.
► Lack of benzylic hydrogen atoms in bis(4-pyridylformyl)piperazine prevents transformation.
► Layered monovalent and divalent copper coordination polymers.