Major impact of N-methylation on cytotoxicity and hydrolysis of salan Ti(IV) complexes: sterics and electronics are intertwined?

Dalton Transactions Pub Date: 2011-08-26 DOI: 10.1039/C1DT11108F

Abstract

A series of Ti(IV) complexes containing diamino bis(phenolato) “salan” type ligands with NH coordination were prepared, and their hydrolysis and cytotoxicity were analyzed and compared to the N-methylated analogues. Substituting methyl groups on the coordinative nitrogen donor of highly active and stable Ti(IV) salan complexes with H atoms has two main consequences: the hydrolysis rate increases and the cytotoxic activity diminishes. In addition, the small modification of a single replacement of Me with H leads to a different major hydrolysis product, where a dinuclear Ti(IV) complex with two bridging oxo ligands is obtained, as characterized by X-ray crystallography, rather than a trinuclear cluster. A partial hydrolysis product containing a single oxo bridge was also crystallographically analyzed. Investigation of a series of complexes with NH donors of different steric and electronic effects revealed that cytotoxicity may be restored by fine tuning these parameters even for complexes of low stability.

Graphical abstract: Major impact of N-methylation on cytotoxicity and hydrolysis of salan Ti(IV) complexes: sterics and electronics are intertwined
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