Synthesis, characterization, biological properties, and molecular docking studies of new phosphoramide-based Ag(i) complexes

Abstract

Two new Ag(I) complexes of N-(n-pyridinyl)diphenylphosphinic amide (n = 2 and 3) (L_o and L_m) with formulae Ag(L_o)NO₃ (C_o) and Ag(L_m)NO₃·H₂O (C_m) were synthesized. Infrared, NMR, and elemental analyses were applied to fully characterize them. The crystal structure of C_m was also assessed using single-crystal X-ray diffraction and the monoclinic nature of the silver complex was illustrated. The organization of four coordinated dinuclear Ag(I) complexes and intermolecular interactions were also studied. The supramolecule was formed by the cooperation of various intermolecular interactions, hydrogen bonds, M⋯π, π⋯π contacts, and CH⋯π synthons. Antibacterial studies of Ag(I) complexes and the corresponding ligands against Gram-negative (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus) were carried out by MIC, MBC, and DDA methods and C_m showed more bactericidal activity than C_o against both bacteria (E. coli; MIC = 9.7 μg mL⁻¹ and S. aureus; MIC = 78 μg mL⁻¹). The potential antitumor activity of C_o and C_m was also evaluated for human colon cancer cell lines (SW480) through anticancer (MTT and apoptosis) experiments, and it was revealed that C_m has the most toxicity (IC₅₀ = 39.6 μg mL⁻¹) by an MTT assay. An initial evaluation of the mechanism of cell death induced by C_o and C_m was performed. Cell death was mainly from the activation of apoptosis processes. The results were further examined by docking studies to confirm that C_m has the potency to be a good candidate for biological applications.