Intermolecular Watson–Crick-like ligand pairing in two Cu(II) compounds with the ligand bis(pyrimidin-2-yl)amine forming 2D chain-type compounds

Two unusual copper(II) compounds with formule [Cu(dipm)(HCOO)2(H2O)] (1) and [Cu(dipm)(C2O4)(H2O)] (2) (in which dipm = bis(pyrimidin-2-yl)amine) have been synthesized and characterised by X-ray crystallography, spectroscopy and EPR. The geometry around the Cu(II) ion in compound 1 is distorted octahedral with the basal plane formed by two nitrogen atoms of a ligand molecule with Cu–N distances of 1.992(2), 2.040(2) Å and two oxygen atoms of two formato anions with Cu–O distances of 1.948(2), 1.984(2) Å. The axial positions are occupied by an oxygen atom of the water molecule (Cu–O distance 2.195(2) Å) and by the second oxygen atom of one of the formato molecules at a semi-coordinating distance of 2.711(2) Å. The geometry around the Cu(II) in compound 2 is square pyramidal with the basal plane occupied by two nitrogen atoms of a ligand molecule (Cu–N distances of 2.007(3), 2.015(3) Å) and two oxygen atoms of the oxalato anion (Cu–O distances of 1.955(3), 1.956(2) Å). The fifth position is occupied by an oxygen atom of the water molecule with a Cu–O distance of 2.246(3) Å.The 2D chain of H-bonds consists of intermolecular built hydrogen bonds between 2 dipm ligands of the Watson–Crick-type and H-bonds between the water molecules and the formato (compound 1), or oxalato anions (compound 2). In addition, stacking interactions between dipm ligands are present in both compounds (ring–ring distances 3.6–3.8 Å).

Graphical abstractTwo unusual copper(II) compounds with formula [Cu(dipm)(HCOO)2(H2O)] and [Cu(dipm)(C2O4)(H2O)] (in which dipm = bis(pyrimidin-2-yl)amine) have been synthesized and characterised by X-ray crystallography, spectroscopy and EPR. A 2D chain of H-bonds is formed by intermolecular hydrogen bonds between 2 dipm ligands of the Watson–Crick-type and H-bonds between the water molecules and the formato, or oxalato anions.Figure optionsDownload full-size imageDownload as PowerPoint slide