Synthesis, Spectroscopic, SQUEEZE method/XRD interactions, linear and Nonlinear Optical properties, and antibacterial effect of the ligand/copper(II) complex tetradentate Schiff base: Experimental and Theoretical Studies

Abstract This study focuses on the synthesis, characterization, and biological evaluation of a novel N2O2 donor Schiff base ligand: N,N'-bis(2-hydroxypropiophenone)-1,2-ethanediamine L and its’ copper(II) complex CuL Extensive spectroscopic methods including 1H and 13C NMR, FT-IR, Raman and UV-Vis spectroscopy were employed for the detailed characterization of these compounds. The structure of the CuL complex was elucidated using single-crystal X-ray crystallography, employing the SQUEEZE procedure in PLATON to resolve refinement issues. The antibacterial efficacy of the synthesized compounds was assessed using the disc-diffusion method against a range of bacteria: Staphylococcus aureus, Bacillus cereus (Gram-positive), and Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae (Gram-negative). Additionally, the study extends to the computational realm, where Density Functional Theory (DFT) and Time-Dependent-DFT (TD-DFT) methods were utilized to analyze the structural optimization, optical properties, and both static and dynamic hyperpolarizabilities of CuL and its analogues with nickel (NiL) and zinc (ZnL). The findings contribute valuable insights into the spectral properties, crystal structure, and biological activities of these Schiff base complexes.