Transition metal complexes with 2-acetylpyridine-ethylcarbazate: noncovalent interactions in their structures and antimicrobial studies

The 2-acetylpyridine-ethylcarbazate ligand (HL) formed four metal complexes, [Cu(HL)Cl-2].H2O (1), [Cu(HL)Br-2].H2O (2), [Zn(HL)Cl-2] (3) and [Ni(L)(2)].H2O (4). The carbazate and their metal complexes have been investigated by single crystal X-ray analysis, physicochemical, and spectroscopic methods. The Schiff base is coordinated to the metal ions as an anionic bi or tridentate ligand with theZconfiguration about the imine C = N at the carbazate. Interactions in the crystal structures were analyzed using Hirshfeld surfaces and the 2D-fingerprint plots. Complexes1,2, and3present pi...pi stacking between the pyridyl rings with inter-centroid separations of 3.664(3)-3.887(2) angstrom. The water solvent molecules and the halogens allow the formation of intramolecular hydrogen bonds which close supramolecular structures in the molecular packing of the complexes. Free HL and1-4have been evaluated for antibacterial and antifungal activity against several multi-resistant bacteria and fungi. Significant antimicrobial activity of the complexes was observed; however, the free ligand and its complexes did not reveal any activity against some of the tested organisms.