Design, characterization, analytical, computational, antibacterial and mechanistic behavior of novel copper(II) Schiff base nano-complex

The Schiff base ligand (L1) 3-acetylcoumarin thiosemicarbazone was used to synthesize copper(II) complex. The ligand (L1), along with its copper(II) Schiff base nano-complex were characterized by Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), Ultraviolet-Visible spectroscopy (UV–Vis), and elemental analysis. The result of TEM illustrates that the size of Cu(II) lies in the nanoscale, while the result of FTIR spectrum indicates that the coordination between the metal ion and the ligand occurred through ketolate, azomethanem, and thiolate groups of the ligand. The Schiff base nano-complex [Cu(II)-(L1)] has been effectively separated by flotation technique using oleic acid (HOL) as an anionic surfactant. Flame atomic absorption spectrometry (FAAS) was utilized to quantify Cu(II) ion content in a range of pharmaceutical and environmental samples, including synthetic mixtures. Experimental variables affecting the flotation process were investigated such as pH, the concentration of metal ion, ligand, and HOL, temperature, sample volume, and interfering ions. The analytical detection limit of Cu(II) was found to be 0.052 mgL-1 with a pre-concentration factor of 125. The recovery (%) of the Cu(II) is almost 100% and the relative standard deviation (RSD %) was 0.3869 mgL-1. Mechanism of flotation was elucidated and found that the interactions between the Schiff base nano-complex and oleic acid were physical interactions. Moreover, the antimicrobial efficacy of the synthesized ligand (L1), along with its copper(II) Schiff base nano-complex was examined through controlled experiments in a laboratory environment. The findings demonstrated that both the ligand (L1), along with its copper(II) Schiff base nano-complex, demonstrated notable antimicrobial efficacy when tested against Escherichia coli and Staphylococcus aureus bacteria. Additionally, computational and theoretical investigations have been conducted on the geometric, electronic, and spectral characteristics of the synthesized ligand (L1), along with its copper(II) Schiff base nano-complex. These analyses encompassed quantum chemical evaluations of various properties, including the ELUMO-HOMO (Egap), chemical potential (μ), chemical hardness (η), ionization potential (IP), electron affinity (EA), electronegativity (EN), chemical softness (S), Optical softness (σ0), electrophilicity index (ω), electron-accepting capability (ω+), and electron-donating capability (ω-). The study also examined dipole moment, IR spectra, molecular electrostatic potential (MEP) profile, and natural bond orbital (NBO) characteristics. The Gaussian 09 program package was employed to perform the computational analyses for this investigation. Researchers utilized the hybrid B3LYP functional method in combination with the 6-311++G (d, p) basis set to conduct the necessary calculations.