Synthesis, spectral characterization, crystal structure determination and antimicrobial activity of Ni(II), Cu(II) and Zn(II) complexes with the Schiff base ligand derived from 3,5-dibromosalicylaldehyde

Three new mononuclear metal complexes of the type ML, (M = Ni, Cu and Zn), with salen type tetradentate (ONNO) Schiff base, N,N'-bis(3,5-dibromosalicylidene)-1,3-diaminopropane (H2L), have been prepared and characterized using FT-IR, H-1 NMR and elemental (CHN) analyses. In addition, the crystal structures of all complexes were analyzed by single crystal X-ray diffraction (SC-XRD) technique. The SC-XRD data explored that in the nickel and copper complexes a monoclinic crystal system was present and the coordination sphere around the metal centers consists of two oxygen atoms and two nitrogen atoms from chelating ligands to give a square planar geometry, while the zinc complex has orthorhombic crystal system and in addition to the atoms from chelating ligand, two O-atoms from the water molecules also coordinate to Zn atom to give distorted octahedral geometry. The in vitro antibacterial activities of the ligand and complexes were elaborated by screening them against Gram (+ve) (Staphylococcus aureus and Bacillus cereus) Gram (-ve) (Escherichia coli and Pseudomonas aeruginosa). All the synthesized compounds showed significant activity against the tested bacterial strains. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Three new mononuclear metal complexes with Salen-type tetradentate Schiff base ligand have been synthesized and characterized, showing significant antibacterial activities against various bacterial strains. Nickel and copper complexes have monoclinic crystal system, while zinc complex has orthorhombic crystal system, all with specific coordination geometries.