A new amino functionalized thio-modified β-cyclodextrin based ligand and its Fe(III) complex with physico‑chemical and antibacterial activity: an integrated experimental and computational investigation

Abstract

β-Cyclodextrin plays a crucial role in augmenting the activity of metal complexes by ameliorating their solubility, stability, and reactivity, therefore the thio-functionalized β-cyclodextrin based amino ligand mono-6-deoxy-(o-aminobenzylthio)-β-cyclodextrin (4) was synthesized and analyzed by elemental analyses, AAS, UV–visible, FTIR, and ¹H NMR spectroscopy. The newly synthesized Fe III) complex was soluble in water. The Fe(III) complex's spectral analysis using FTIR confirmed that the ligand aided the metal ion coordinate by way of the sulfur atom of the β-cyclodextrin moiety and the nitrogen atoms of the two ligand molecules, with two H₂O occupying the fifth and sixth coordination sites. Additionally, the mass spectrometry verifies that the intended Fe(III) complex has synthesized. Density functional theory (DFT) was used to calculate different electronic parameters of the optimized structure of Fe(III) complex to reveal its stability. Antimicrobial metal complexes that are suitable for therapeutic application are known to be more stable and bioavailable when β-cyclodextrin is introduced, therefore studies have been done to inquire into the possible comparative in vitro antibacterial activity of the Fe(III) complex and free ligand against two gram positive (Bacillus subtilis, and Staphylococcus aureus) and two gram negative bacteria (Escherichia coli, Klebsiella pneumoniae) strains. Molecular docking was used to further corroborate these capabilities.