Synthesis, Crystal Structure, DFT Studies, and Antimicrobial Evaluation of a Square Planar Nickel(II) Schiff Base Complex

Abstract

We report the synthesis, structural elucidation, and physicochemical evaluation of a bis{2‐methoxy‐6‐[(butylimino)methyl]phenolato}nickel (II) complex. Single‐crystal x‐ray diffraction (SCXRD) revealed that the complex crystallizes in the monoclinic space group P 2 1 / c with a square planar geometry. Spectroscopic techniques (UV–vis, FT–IR, NMR) and mass spectrometry confirmed its monomeric nature ( m/z  = 471.17) and validated the azomethine (C═N) linkage at 1612 cm −1 . Thermogravimetric analysis (TGA) showed high thermal stability up to 215°C. Density functional theory (DFT) calculations indicated remarkable kinetic stability via a wide HOMO−LUMO energy gap (ΔE = 3.43 eV). Hirshfeld surface analysis (HSA) and noncovalent interaction (NCI) plots showed crystal packing stabilized by H···H (65.6%), C···H (23%), and O···H (7.9%) van der Waals and weak hydrogen‐bonding interactions. Antimicrobial screenings demonstrated significant efficacy against bacterial and fungal strains (MIC > 30 µg/mL). Molecular docking against microbial receptors ( Escherichia coli 6F86, Staphylococcus aureus 2W9H, Candida albicans 2Y7L, and Candida tropicalis 8BH9) revealed high binding affinities driven by hydrogen bonding, electrostatic, and hydrophobic interactions, yielding sub‐micromolar to nanomolar inhibition constants ( K i ) against fungal targets 2Y7L and 8BH9. These findings highlight its usefulness for biomedical applications.