Stabilizing Delocalized Charge-Transfer State in Anthraquinone-Centered TADF Emitters for Enhanced Reactive Oxygen Species Production.

This study explores the physical mechanism underlying thermally activated delayed fluorescence (TADF) emitters as metal-free photosensitizers for reactive oxygen species (ROS) production. Through a comparative investigation of anthraquinone-based D-A-type emitter, , with D-A-D-type emitter, , we demonstrate that the multidonor architecture markedly enhances TADF properties and ROS generation efficiency. Combined theoretical and transient spectroscopic analyses reveal that possesses a more stabilized charge-transfer state with suppressed conformational relaxation relative to its D-A counterpart, leading to improved performance, including a higher delayed fluorescence quantum yield, an increased radiative transition rate, and inhibited nonradiative decay of triplet states. When incorporated into water-dispersible nanoparticles, both anthraquinone-based D-A-type emitters predominantly generate superoxide radicals (O), but shows superior ROS production capability relative to that of . These findings establish symmetric multidonor molecular design as an effective strategy for developing efficient type-I photosensitizers with potential applications in hypoxia-tolerant cancer therapy.