A coumarin Schiff base and its Ag(i) and Cu(ii) complexes: synthesis, characterization, DFT calculations and biological applications

Abstract

8-Acetyl-7-hydroxy-4-methyl coumarin and 3-amion-1,2,4-triazole were used to prepare a Schiff base (Sbat). The [Ag(Sbat)(NO₃)]·H₂O and [Cu(Sbat)(OH)(H₂O)₂]·3H₂O complexes were separated by the reaction of the Schiff base with Ag(I) and Cu(II) metal ions. All the prepared compounds were subjected to elemental and spectral analyses (IR, UV-vis, ¹H NMR, and mass spectroscopy). Moreover, the complexes were also subjected to TG analysis, molar conductance measurements, magnetic moment analysis, and XRD measurements. The value of the molar conductance designates their non-electrolytic character. The local minimum structure, global properties and nonlinear optical parameters of the Schiff base were calculated at the B3LYP/6-31++(d,p) level of theory and those of its complexes were calculated at the B3LYP/GENECP level. The electronic spectra in the UV-visible region of the Schiff base (Sbat) and [Ag(Sbat)(NO₃)]·H₂O and [Cu(Sbat)(OH)(H₂O)₂]·3H₂O complexes in DMSO as a solvent were investigated experimentally and theoretically using the time dependent density functional theory (TD-DFT) method at the CAM-B3LYP/6-311++G(d,p) level of theory. The studied compounds were screened for their in vitro antibacterial activity against three Gram-positive (B. subtilis, S. aureus and S. faecalis) and three Gram-negative bacteria (E. coli, N. gonorrhoeae and P. auregenosa). An antifungal assay was performed against two fungal (C. albicans and A. flavus) species. The Ag-Sbat complex showed the highest antimicrobial activity. The cytotoxic activity of the Schiff base and its silver complex was tested in vitro against the MCF-7 (breast cancer) and HCT-116 (colon cancer) cell lines.