Synthesis and characterization of a new N4-Schiff base its zinc halide/pseudohalide complexes with thermal, antimicrobial, antioxidant, anticancer, DNA cleavage and wound healing properties

A novel Schiff base ligand, N¹,N²-bis(2-(((1E,2E)-3-(2-methoxyphenyl)allylidene)amino)ethyl)ethane-1,2-diamine (L), was synthesized from triethylenetetramine and o-methoxycinnamaldehyde, and its six new zinc halide/pseudohalide complexes were prepared and characterized using molar conductance measurements, melting point analysis and spectroscopic techniques. Thermogravimetric and differential thermal analyses (TG/DTG/DTA) coupled with the Coats–Redfern method provided key thermo-kinetic activation parameters (A*, E*, ΔH* , ΔG*, ΔS* ) for the synthesized complexes. In vitro, zinc(II) complexes with Cl⁻, N₃⁻, and NO₃⁻ exhibited superior antimicrobial activity against Gram-positive ( B. subtilis and S. aureus ), Gram-negative ( E. coli and P. aeruginosa ) bacteria, and fungi ( C. albicans and A. oryzae ) compared to the free ligand. In DPPH and FRAP assays, zinc complexes, especially ZnL(N₃)₂ and ZnLI₂, exhibited superior antioxidant activity compared to the SB-ligand. In the MTT assay, ZnLI₂ and ZnL(NCS)₂ showed the highest anticancer activity against MCF-7 and PC3 cells, respectively. ZnLBr₂, ZnL(NCS)₂, ZnL(NO₃)₂, and ZnL(N₃)₂ completely cleaved E. coli DNA via a non-oxidative hydrolytic mechanism. Finally, the wound-healing potential of the SB-ligand and its ZnLI 2 (zinc iodide complex) was evaluated in a rat model of second-degree burns, demonstrating a wound closure percentage of 100% at day 21, which promises its therapeutic efficacy.