Self-Assembly Regulated Singlet Oxygen Generation of Heavy-Atom-Free Organic Chromophores

Assembly of organic dyes is an effective way to achieve novel properties that are drastically distinctive from those of monomers. However, achieving well-organized nanostructures through controllable assembly with desired performance remains a challenge. Herein, we present the first example of modulation of singlet oxygen generation through controlling the self-assembly behaviors of heavy-atom-free BODIPY derivatives (1–4) by incorporating different TEG chains on the BODIPY core. Different assembly behaviors remarkably alter the structures and ISC efficiencies of the nanoassemblies, thus leading to a remarkable distinction in singlet oxygen (1O2) generation efficiency. Experimental and theoretical studies suggest these different behaviors are attributed to their different molecular stacking modes, which affect the energy splitting of optically allowed transitions. Significantly, the 1O2 generation rate of assembly 1 is 13.4-fold higher than that of iodo-BODIPY (a traditional heavy-atom effect based photosensitizer), which allows application for photodynamic therapy with excellent phototherapeutic efficacy. This work not only deepens the understanding of the self-assembly effects of organic dyes on the ISC process but also provides a feasible strategy to construct materials with tunable ISC rates through rational selection of the assembly of dyes instead of molecule design and synthesis.