Picolinamides with β-Thiophosphorylated Amine Residues as a Useful Scaffold to Generate Biologically Active Pd(II) Pincer Complexes

The creation of new potential metal-based therapeutics largely relies on the development of useful ligand scaffolds. In recent years, our research group has introduced thiophosphoryl-functionalized carboxamides as a convenient framework for obtaining biologically active cyclopalladated derivatives. In continuation of these studies, β-(aminoalkyl)phosphine sulfides bearing additional substituents in the ethylene backbone were synthesized for the first time and reacted with picolinic acid to afford a series of new functionalized amide ligands. The latter readily underwent direct cyclopalladation under the action of PdCl2(NCPh)2 under mild reaction conditions. The resulting S,N,N-complexes were studied for in vitro cytotoxicity against several solid and hematopoietic cancer cell lines, as well apoptosis induction and DNA damage ability, which showed their promising anticancer properties. In addition, moderate antibacterial activity was observed for a representative palladocycle of the β-thiophosphorylated derivatives.