Photocyclization of Cationic <i>Bay</i> ‐Substituted Perylene Diimide Derivatives to Corronene Analogs Used as Lysosome Targeted Type‐II Photosensitizer

ABSTRACT Two bioactive, water‐soluble cationic perylene diimide (PDI) derivatives have been rationally designed and successfully developed to investigate their unique photochromic behavior in a polar protic medium. Spectroscopic and structural analyses have confirmed that a photocyclization reaction occurs upon light irradiation, converting the PDI backbones concurrently to annulated coronene diimide (CDI) moieties. Aggregation studies before and after photocyclization, supported by energetic and structural analysis from molecular dynamic simulations, have provided insights at the molecular level. Both derivatives exhibit high singlet oxygen ( 1 O 2 ) generation efficiencies, as measured using 9,10‐anthracenediyl‐bis(methylene)dimalonic acid (ABDA) and 1,3‐diphenylisobenzofuran (DPBF) probe with Rose Bengal as a reference. Cell uptake studies have confirmed their non‐toxic nature and efficient lysosomal localization. Intracellular ROS generation observed under visible light irradiation results in cytotoxicity. These results highlight the potential of these CDI derivatives as promising photosensitizers for photodynamic therapy applications in a biological environment.