Synthesis and structure of 2-acetylpyridine-salicyloylhydrazone and its copper(ii) and zinc(ii) complexes. The effect of the metal coordination on the weak intermolecular interactions

We have studied the crystal and molecular structure of 2-acetylpyridine-salicyloylhydrazone (H2L) and its copper and zinc complexes. The crystal structure of H2L is mainly dominated by the intermolecular moderate hydrogen bonding O(2)–H⋯O(1) whereas the intramolecular interaction N(1)–H⋯O(2) is responsible for the almost planar molecular structure. Reaction with copper and zinc acetates afford the complexes [CuBr(HL)] and [Zn(HL)2]. The ligand undergoes deprotonation [at the N(1) atom] and is coordinated in a tridentate manner in both complexes. Furthermore, the intramolecular hydrogen bond is retained but involves the O(2)–H⋯N(1) groups. In the absence of intermolecular hydrogen bonding, the molecules of the complexes are associated by weak interactions such as π–π stacking as effectively as in the free ligand.