Active Cytotoxic Reagents Based on Non-metallocene Non-diketonato Well-Defined <i>C</i>₂-Symmetrical Titanium Complexes of Tetradentate Bis(phenolato) Ligands

A new family of non-Cp-based non-diketonato-based C2-symmetrical octahedral Ti(IV) complexes of dianionic diamine bis(phenolato) ligands, which are conveniently obtained as single isomers in quantitative yields, leads to appreciable cytotoxicity against colon and ovarian cells with a non-transferrin-dependent cell penetration mechanism. The ligand structural features including steric demands, symmetry, and aromaticity strongly influence activity, supporting its role in the biological mechanism of action.