Controlled Photooxidation via Singlet Oxygen Generation by Triplet Harvesting in a Heavy Atom Free Pure Organic Dithienylethene‐Naphthalene Diimide

Noninvasive control over the reversible generation of singlet oxygen ( 1 O 2 ) has found the enormous practical implications in the field of biomedical science. However, metal‐free pure organic emitters, connected with a photoswitch, capable of generating “on‐demand” 1 O 2 via triplet harvesting remain exceedingly rare; therefore, the utilization of these organic materials for the reversible control of singlet oxygen production remains at its infancy. Herein, an ambient triplet mediated emission in quinoline‐dithienylethene (DTE)‐core‐substituted naphthalene diimide (cNDI) derivative is unveiled via delayed fluorescence. The quinoline‐DTE‐cNDI triad displayed enhanced photoswitching efficiency via double FRET mechanism. It was found to have direct utilization in controlled photosensitized organic transformations via efficient generation of singlet oxygen (yield Φ Δ ~0.55 in DCM and 0.73 in methanol). The designed molecule exhibits a long‐lived emission (τ∼1.1 μs) and very small singlet‐triplet splitting (ΔE ST ) of 0.13 eV empowering it to display delayed fluorescence. Comprehensive steady state and time‐resolved emission spectroscopy (TRES) analyses along with DFT calculations offer detailed understandings into the excited‐state manifolds of organic compound and energy transfer (ET) pathways involved in 1 O 2 generation.