Polypyridyl CoII‐Curcumin Complexes as Photoactivated Anticancer and Antibacterial Agents

Four new CoII complexes, [Co(bpy)2(acac)]Cl (1), [Co(phen)2(acac)]Cl (2), [Co(bpy)2(cur)]Cl (3), [Co(phen)2(cur)]Cl (4), where bpy=2,2’‐bipyridine (1 and 3), phen=1,10‐phenanthroline (2 and 4), acac=acetylacetonate (1 and 2), cur=curcumin monoanion (3 and 4) have been designed, synthesized and fully characterized. The X‐ray crystal structures of 1 and 2 indicated that the CoN4O2 core has a distorted octahedral geometry. The photoactivity of these complexes was tuned by varying the π conjugation in the ligands. Curcumin complexes 3 and 4 had an intense absorption band near 435 nm, which made them useful as visible‐light photodynamic therapy agents; they also showed fluorescence with λem≈565 nm. This fluorescence was useful for studying their intracellular uptake and localization in MCF‐7 breast cancer cells. The acetylacetonate complexes (1 and 2) were used as control complexes to understand the role of curcumin. The white‐light‐triggered anticancer profiles of the cytosol targeting complexes 3 and 4 were investigated in detail. These non‐dark toxic complexes displayed significant apoptotic photo‐cytotoxicity (under visible light) against MCF‐7 cells through ROS generation. The control complexes 1 and 2 did not induce significant cell death in the light or dark. Interestingly, 1‐4 produced a remarkable antibacterial response upon light exposure. Overall, the reported results here can increase the boundary of the CoII‐based anticancer and antibacterial drug development. The spice of cell death: Cytosol‐targeting polypyridyl‐CoII complexes of curcumin have shown remarkable apoptotic anticancer activity through in‐cell ROS production triggered by visible light. These complexes also presented significant antibacterial response on visible light exposure. These reported results have the potential to deliver new CoII‐based anticancer and antibacterial drugs.