New Palladium Complexes with 8‐Hydroxyquinolines Prepared by a Ligand Exchange During NMR Experiments

Palladium(II) complexes with derivatives of 8‐hydroxyquinoline (HXQ) of composition NH2(CH3)2[PdCl2(XQ)], where HXQ is 5‐nitro‐7‐iodo‐8‐hydroxyquinoline (HNIQ) (1a), 5‐nitro‐7‐bromo‐8‐hydroxyquinoline (HNBrQ) (2a), 5‐iodo‐7‐bromo‐8‐hydroxyquinoline (HIBrQ) (3a), and 5‐chloro‐7‐bromo‐8‐hydroxyquinoline (HClBrQ) (4a), were prepared. Upon their dissolution in DMSO, a series of [PdCl(DMSO)(XQ)] (1b‐4b) and [Pd(XQ)2] (1c‐4c) complexes is prepared as a consequence of a ligand exchange. The composition of the complexes is elucidated by infrared and NMR spectroscopy and elemental and single‐crystal X‐ray structure analysis. Moreover, crystal structures of the ligands HClBrQ and HIBrQ are solved. A bidentate coordination mode of HXQ ligands to palladium atoms is consistently observed, resulting in a square planar coordination geometry of the central atom, across all complexes. The molecular packing within all crystal structures is analyzed, distinguished by the presence of hydrogen bonds and π–π interactions, and has been described. The negative influence of complexes 1b‐4b on the growth and metabolism of the cells is studied on seven cancer cell lines, with the highest activity observed for complexes 3b and 4b. Accordingly, the selectivity of complexes on the human dermal fibroblast cells is investigated. The highest selectivity indexes are observed for complexes 3b and 4b on the Jurkat cell line, where the values reach 1.73 and 1.87, respectively.