Fe(III), Co(II), Ni(II) and Ga(III) innovative complexes with thiosemicarbazones: a biological insight.

In this work we propose innovative coordination compounds involving four thiosemicarbazone ligands (L1, L2, L3 and L4), and four different metal centres. On one hand this category of chelators is well-known for its biological applications and for its versatility to bind various metals[1–2]; on the other hand the set of cations we chose (Fe(III), Co(II), Ni(II) and Ga(III)) spans different coordination affinities, geometries, diverse redox properties and biological effects[3–7]. Moreover, usually Ga(III) therapeutic effects are due to its ability to stop iron metabolic routes, therefore the comparison between Fe(III) and Ga(III) complexes may be even more interesting[8]. On this basis, we firstly characterised the coordination compounds via NMR, IR, ESI-MS, UV, EA and XRD to understand their structure and chemical properties. In addition, we employed UV titration to study their stability in solution, their interactions and affinity with biological macromolecules such as DNA and BSA, and their capacity to consume radicals and oxidants (such as DPPH, OH·, H2O2 and O2-·). These studies are combined with tests in vivo (i. e. toxicity tests on Galleria mellonella larvae) and in vitro (cytotoxicity against lung cancer cells), to eventually compare how these different metals, complexed with the same ligands, influence biological activity.