Intrinsic Advantage of Singlet Photosensitization in Electronic Coupling for Singlet Oxygen Generation

Photosensitization to generate singlet oxygen is of significant research interest due to its various roles in photochemistry, phototherapy, and physiological processes. This study introduces a quantitative comparison of electronic couplings in singlet and triplet photosensitization, revealing that singlet photosensitization offers superior coupling strength. By leveraging both of singlet and triplet photosensitizations, we propose a novel photosensitization circle that can yield two singlet oxygens from one photoexcitation. The photoexcited sensitizer is converted from 1PS* to 3PS* in the first step, and then from 3PS* to 1PS in the second step, enhancing the excitation energy efficiency and bypassing the requirement of high triplet yield from intersystem crossing.