Integrating a fluorescent coumarin core into Schiff base half-sandwich Ir(III) or Ru(II) complexes for...

To merge the intrinsic fluorescence and bioactivity of coumarin with the anticancer efficacy of Schiff base metal complexes, a series of half-sandwich Ir(III) and Ru(II) complexes bearing coumarin-salicylaldimine (N^{^}O) ligands were designed and synthesized. The structures of the complexes were fully characterized, and their photoluminescent and biological properties were systematically investigated. These complexes exhibited adequate stability with slow hydrolysis and cytotoxicity comparable to that of cisplatin. The introduction of the coumarin group endowed the complexes with favorable photoluminescence, which facilitated the further investigation of their anticancer mechanism. Confocal microscopy revealed that the complexes enter cells via an energy-dependent pathway and preferentially accumulate in mitochondria. Consequently, they induce apoptosis by disrupting the mitochondrial membrane potential and generating excessive reactive oxygen species (ROS). In addition, the complexes interfere with the cell cycle, arresting cancer cells at the S or G0/G1 phase, and effectively inhibit cell migration in vitro.