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

Abstract

The 2-acetylpyridine-ethylcarbazate ligand (HL) formed four metal complexes, [Cu(HL)Cl₂]⋅H₂O (1), [Cu(HL)Br₂]⋅H₂O (2), [Zn(HL)Cl₂] (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 the Z configuration about the imine C = N at the carbazate. Interactions in the crystal structures were analyzed using Hirshfeld surfaces and the 2D-fingerprint plots. Complexes 1, 2, and 3 present π⋅⋅⋅π stacking between the pyridyl rings with inter-centroid separations of 3.664(3)–3.887(2) Å. 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 and 1–4 have 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.

Graphical Abstract

Keywords:

• Noncovalent interactions
• metal complexes
• carbazates
• crystal structure
• antimicrobial activity

Acknowledgment

All funding agencies are acknowledged for partial financial support.

Disclosure statement

There are no conflicts of interest to declare.

Additional information

Funding

The authors wish to thank FAPDF (process number 0193.001545/2017). This work has been partially supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001, FINEP/CTINFRA, CNPq and UnB.