Group VA Aromatic Thiosemicarbazone Complexes: Synthesis, Characterization, Biological Activity, and Topological Studies

The antiproliferative and antibacterial activities of thiosemicarbazones increase markedly with the presence of metal ions. One of the factors determining the activity of metal thiosemicarbazone complexes is the coordination structure. In this study, the biological effects of new antimony (III) and bismuth (III) thiosemicarbazone complexes with different binding modes and geometrical structures were demonstrated. Three new complexes, with the formulae {[SbCl₃(µ₂-S-Hacptsc)(η¹-S-Hacptsc)], 2/3H₂O,1/3CH₂Cl₂}, {[SbCl₃(κ²-S,N-Hacpmtsc)(η¹-S-Hacpmtsc)₂CH₂Cl₂]}, and{[BiCl₃(η¹-S-Hbzmtsc)₃]·C₂H₅OH}, where Hacptsc: acetophenone thiosemicarbazone, Hacpmtsc: acetophenone-N-methyl thiosemicarbazone, Hbzmtsc: benzaldehyde-N-methyl thiosemicarbazone) were elucidated by different methods and deeply analyzed in accordance with their structure by X-ray structure analysis and Atoms-In-Molecules topological analysis. This analysis provided a deeper understanding of the coordination spheres of the Sb/Bi complexes. For instance, the first reported two binding modes of the same ligand are observed in a single crystal structure of antimony (III) halide complexes. Additionally, in one of the complexes, a solid-to-solid phase transition was detected and analyzed in detail. Those complexes, very unique in terms of their geometry, have also been tested for their in vitro cytotoxic activity against human adenocarcinoma cervical cancer (HeLa) cells, whereas antimony (III) complex 1is the most active complex of this study. Further, the antibacterial activity of the complexes has been screened against two Gram-negative (<i>Pseudomonas aeruginosa</i> and <i>Escherichia coli</i>) and two Gram-positive (<i>Staphylococcus epidermidis</i> and <i>Staphylococcus aureus</i>) pathogenic bacteria. From the results, it is found that all the complexes exhibited significant activity against the Gram-negative pathogenic bacteria.