CuAAC-enabled Ferrocenyl TitaniumIV Salan complexes as mitochondria-enriched photosensitizers for ROS-mediated ferroptosis

Copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) was employed to functionalize dipicolinic acid-stabilized titanium salan complexes, yielding four derivatives with high efficiency under microwave-assisted conditions (up to 91% yield). Among them, the ferrocene-containing complex, [L 1 Ti IV L 2 -Fer] , exhibited potent photodynamic anticancer activity against Hep G2 cells while sparing normal AML12 cells. Mechanistic studies revealed that [L 1 Ti IV L 2 -Fer] rapidly accumulates in mitochondria and generates ROS upon light irradiation, while the ferrocenyl moiety further enhances •OH accumulation through Fenton chemistry. This induces mitochondrial dysfunction, oxidative stress, lipid peroxidation, glutathione depletion, and SOD inhibition. Light-activated [L 1 Ti IV L 2 -Fer] induces oxidative stress-associated ferroptotic responses, accompanied by decreased expression of SLC7A11 and GPX4, whereas the roles of apoptosis, autophagy and necroptosis are negligible. These findings demonstrate that [L 1 Ti IV L 2 -Fer] acts as a mitochondria-enriched ROS-generating photoactive agent, inducing ferroptosis through oxidative stress. The study highlights CuAAC as a versatile strategy for Ti IV complex functionalization and provides mechanistic insights into ROS-driven ferroptotic cell death, offering a promising platform for next-generation photodynamic anticancer agents.