Six TiIV complexes of branched diamine bis(phenolato) ligands that feature a pendant donor side arm with different aromatic and N-substitutions were synthesized and their hydrolytic stability and cytotoxicity were investigated as closely related analogues to the highly active and stable salan TiIV complexes [salan = N,Na′-bis(o-hydroxybenzyl)-1,2- diaminoethane]. Although the Cs-symmetrical complexes include binding of the side-arm N donor to the metal as analyzed crystallographically, thus making them highly similar in coordination features to the C2- symmetrical salan complexes, they exhibit poor hydrolytic stability, presumably due to higher flexibility in binding of the side arm in solution. Complexes of alkyl aromatic substituents, both N-methylated and N-ethylated, with varying steric constraints demonstrated poor cytotoxicity. In contrast, ortho-halogenation, although it does not affect hydrolytic stability, substantially enhances the cytotoxicity towards colon HT-29 and ovarian OVCAR-1 cells. The cytotoxicity and hydrolysis of TiIV complexes of branched diamine bis(phenolato) ligands are reported. Alkylated complexes exhibit poor stability presumably due to weaker binding of the side arm, with negligible cytotoxicity. In contrast, ortho-halogenated complexes, although hydrolytically unstable, demonstrate marked cytotoxicity.
- Antitumor agents
- Phenolato ligands