Synthesis, spectroscopic, characterization, antimicrobial, DNA interaction, DFT and molecular docking studies of a new Cu(II)-Schiff base complex

Abstract A novel Schiff base (L) was synthesized via the condensation of folic acid with salicylaldehyde, and its copper (II) complex (Cu–L complex) was subsequently prepared, exhibiting notable biological activity. Comprehensive characterization of L and both bulk and nanoscale forms of Cu–L complex was conducted using elemental analysis, FT-IR, UV–Vis spectroscopy, magnetic susceptibility, mass spectrometry, gel permeation chromatography, 1H/13C NMR, thermogravimetric analysis, electron spin resonance, and transmission electron microscopy. DNA binding interactions were assessed using UV–Vis absorption, ethidium bromide displacement assay, and viscosity measurements, revealing significant binding affinity. The nano-sized Cu–L complex demonstrated enhanced antimicrobial activity and potent cytotoxic effects against MCF-7 breast cancer cells, comparable to the standard chemotherapeutic agent cisplatin. Density functional theory calculations were performed at the B3LYP/6-311G(d,p) level for L and B3LYP/6-311G(d,p)-LANL2DZ for the Cu–L complex. The theoretical results were consistent with experimental data. Nonlinear optical properties, including molecular polarizability (α) and hyperpolarizability (β), indicated improved optical responses in the synthesized compounds. Molecular docking studies revealed favorable binding of Schiff base ligand (L) and its Cu–L complex to the active sites of key bacterial protein targets, supporting their potential as therapeutic agents.