PhotoCORMs based on zinc(ii)-flavonol derivatives with superior biological properties for use in living organisms

CO is an important gas signal molecule and plays an indispensable role in the maintenance of cell homeostasis. Herein, photoinduced CO-releasing molecules (photoCORMs), that combine the effects of zinc(ii) and different ligands including flavonol derivatives and tripod pyridyl compounds, are reported. The photoCORMs can release about one equivalent of CO, and the solid samples are stabile for more than 90 days in air. Cytotoxicity tests suggest that photoCORMs possess low toxicity and have the potential to be used in organisms. The intracellular uptake and photoreactivity of photoCORM 3a, with low toxicity and a rapid CO-release rate, were studied in HeLa cells. The results indicate that 3a could successfully penetrate the cell membrane and enter the cytoplasm. More importantly, it is further demonstrated that 3a can successfully release CO in HeLa cells, which is detected using intracellular CO sensors. Based on the cell study, the same result was found when the photoinduced CO release of 3a in Kunming mice was studied utilizing a carboxyhemoglobin kit. This study is of great significance for the development of new valuable CO donors that can be applied to organisms to exert their biological effects.