Structures and properties of trans-dichloro{tetrakis (5-chloro-2(1H)-pyridone-O)}M(II) [M=Mn, Fe, Co, Ni, Cu]; formation of quasi-macrocyclic metal complexes through hydrogen bonding

The reaction of 5-chloro-2(1H)-pyridone (HL) with M(II)Cl2 (M=Mn, Fe, Co, Ni, Cu) in ethanol solution results in the formation of octahedral complexes represented as [M(II)(HL)4Cl2], X-ray structure determination of the Mn(II) and Ni(II) complexes revealed that the four ketone ligands are O bonded in the equatorial positions, which are arranged in a quasi-macrocyclic fashion through NH⋯O hydrogen bonds. The packing arrangements of the complexes are symmetrical and show three-dimensional (3-D) π–π stacking structures, though these complexes are paramagnetic with negligible intermolecular interactions.