Synthesis, spectroscopic characterization, density functional theory calculations and biological evaluation of novel Cu(II) and Zn(II) Schiff base complexes as antimicrobial agents

The advancement of Schiff base ligands represented a significant breakthrough in the field of bioinorganic chemistry. The current work involved the synthesis of a novel class of Schiff base ligands from benzoyl chloride and diamines with varying chain lengths, together with the matching copper(II) and zinc(II) complexes. Utilizing several physicochemical and spectroscopic approaches, such as FTIR, ¹H-NMR, ¹³C-NMR, Mass, PXRD investigations, and UV–Visible, all of the synthesized ligands and complexes were characterized. The octahedral geometry of the Cu(II) and Zn(II) complexes was determined by analysing the spectral data of the synthesized complexes, which validated their chemical structures. In addition, quantum chemical parameters were also calculated using DFT (density functional theory calculations). The recently synthesized ligands (1E,1'E)-N',N''-(ethane-1,2-diyl)dibenzimidoyl chloride (L₁), (1E,1'E)-N',N''-(propane-1,3-diyl)dibenzimidoyl chloride (L₂), and their complexes Cu(L₁)₂Cl₂, Zn(L₁)₂Cl₂, Cu(L₂)₂Cl₂, Zn(L₂)₂Cl₂ were assessed for their biological properties, including antibacterial and antifungal activities, against E. coli (ATTC code 25922), B. cereus (ATTC code 14579), S. aureus (ATTC code 25923), C. albicans (ATTC code 10231), and A. flavus (ATTC code 22546) by disc diffusion method. The results revealed favourable outcomes. Good antibacterial and antifungal qualities were demonstrated by all of the synthesized compounds. In contrast to their parent ligands, metal complexes are discovered to be more effective antibacterial agents.