Synthesis, spectroscopic characterization, DFT studies, and preliminary antimicrobial evaluation of new antimony(III) and bismuth(III) complexes derived from 1,3,5-triazine

Abstract

Herein, we describe the synthesis and characterizations of 2,4,6-tris(thiomorpholine)-1,3,5-triazine, 2,4,6-tris(piperazine)-1,3,5-triazine and their new Sb(III) and Bi(III) complexes. Characterizations of the ligands and complexes were carried out by elemental analysis, thermogravimetric analysis (TGA), and spectroscopic methods such as infrared (IR), 1H and 13C nuclear magnetic resonance (NMR), and single crystal X-ray. Theoretical vibrational frequencies and 1H and13C NMR chemical shifts of free ligands as well as their Sb(III) and Bi(III) complexes have been calculated using density functional theory (DFT/B3LYP and M06-2X) methods. Our theoretical results matched the corresponding experimental data and helped with the interpretation of the IR and 1H and 13C NMR spectra. The antimicrobial in vitro studies were carried out against bacterial species Staphylococcus aureus and fungal species Candida albicans, Candida tropicalis, and Candida krusei by the microdilution method. The preliminary antimicrobial evaluations indicated that Sb(III) complexes showed moderate activities against all tested strains of bacterial and fungal with minimum inhibitory concentration (MIC) in range of 512–1024 μg mL−1.