Computational Investigation of Meso‐Substituted, Heavy Atom‐Free BODIPY Derivatives asPhotosensitizers: Insights from TDDFT and Dynamics Studies

This study investigates the structural and electronic properties of BODIPY (BDP) derivatives featuring meso‐substituted donors arranged orthogonally, leveraging Time‐Dependent Density Functional Theory (TD‐DFT). These deriva‐ tives, selected based on experimental evidence of their quantum yield towards singlet oxygen generation, exhibit intricate excited‐state dynamics, transitioning from fluorescence to intersystem crossing (ISC), thereby presenting a promising avenue for applications in photodynamic therapy. Emphasizing heavy‐atom‐free organic triplet photosensitizers, with BDP dyes highlighted for their exceptional adaptability in photophysical characteristics, our analysis contributes to a deeper understanding of the fundamental design principles governing such photosen‐ sitizers. Through a combined approach of static and dynamic calculations, we elucidate the mechanisms underlying the population transfer from singlet to triplet states, thereby providing valuable insights for the development of efficient photodynamic therapy agents.