Synthesis, X-ray crystal structures, spectroscopic properties and magnetism of copper(II) compounds of formula trans-Cu(LL)2(anion)2, with N-(pyridin-2-yl)acetamide and N-(pyrimidin-2-yl)acetamide as ligands: Unexpected absence of hydrogen bonding to the

A coordination chemistry and lattice engineering study of 10 new Cu(II) compounds with the ligands N-(pyridin-2-yl)acetamide (Haap) and N-(pyrimidin-2-yl)acetamide (Haapm) with the general formula Cu(LL)2(anion)2 is described. The bidentate ligands bind in a N,O-chelating mode and the used anions are ClO4-, CF3SO3-, BF4-, NO3-, Cl−. For five of the compounds a 3D crystal and molecular structure analysis has been performed. All Cu(II) ions have a tetragonal-based geometry; the basal plane of each copper consists of a N and an O atom of two different bischelating N,O-donor ligands; Cu–N distances vary from 2.00 to 2.04 Å and Cu–O distances are between 1.93 and 1.96 Å, whereas the apical sites are occupied by an atom of the anions, thereby providing an elongated octahedral geometry (Cu–anion contacts are between 2.41 and 2.81 Å).The intermolecular interactions are all involving multiple H-bond systems, providing a 2D polymeric array for most of the compounds. The chloride compound forms a zigzag polymeric array of hydrogen bonds. Most surprisingly, the non-coordinating pyrimidine nitrogen atom, does not take part in any lattice hydrogen bonding.

Graphical abstractThe bifunctional ligands Haap and Haapm generate chains of coordination units, organized by hydrogen bonds between the semi-coordinating counter anions and the NH group of the amide.Figure optionsDownload full-size imageDownload as PowerPoint slide