Investigation of structural, spectral, theoretical, and antimicrobial properties of Iron(III) complexes with thiosemicarbazide ligands

Different thiosemicarbazide ligands, (H2PAPS), (H2PAPT), (H2PABT), have been utilized to synthesize a series of Fe(III) complexes. These complexes were characterized using conventional techniques, and their chemical formulas were determined as [Fe(H2PAPS)Cl3], [Fe(H2PAPT)Cl3(H2O)], and [Fe(HPABT)Cl2(H2O)], respectively. The spectral analysis of the Fe(III) complexes showed that H2PAPS coordinate as a neutral tridentate, while H2PAPT suggests its coordination as a neutral bidentate but in the case of H2PABT, it acts as a mononegative tridentate. The proposed structures of all complexes were found to be octahedral. Confirmation of the geometries of the ligands and their Fe(III) complexes, various parameters were calculated using DFT (density functional theory) with the Materials Studio program. Thermal degradation studies of the complexes were conducted. Additionally, the antibacterial activities of the ligands and their Fe(III) complexes were evaluated. The results showed that Fe(III) complexes exhibited greater antibacterial effects compared to their the free ligands, except for [Fe(H2PAPT)Cl3(H2O)], which demonstrated lower activity than its corresponding ligand. Interestingly, the ligands demonstrated higher cytotoxicity compared to fluorouracil (5-FU), a known anticancer drug. However, the Fe(III) complexes showed lower activity compared to their corresponding ligands in the tested cell lines.