MgTPPS/block copolymers complexes for enhanced stability and photoactivity

Inspired by the chlorophyll–protein complex in photosynthesis, two types of micelles were formed by the noncovalent complexes between magnesium porphyrins and block copolymers. A series of electrostatic micelles were prepared from magnesium tetrakis(4-sulfonatophenyl) porphyrin (MgTPPS) and poly(ethylene glycol)-block-poly(L-lysine). Meanwhile, the coordination micelles were fabricated from MgTPPS and poly(ethylene glycol)-block-poly(4-vinylpyridine). Here, we aim to analyze the origin of the enhanced stability of MgTPPS, particularly focusing on the photoactivity of MgTPPS in the micelles. The electrostatic micelles had better hydrolytic stability due to the electrostatic repulsion interaction and the coordination micelles showed high photostability, benefiting from axial coordination. The electrostatic micelles can promote the generation of singlet oxygen due to their swollen micellar cores. While the coordination micelles displayed better electron transfer ability owing to the lower HOMO of MgTPPS induced by axial coordination. These results may provide a novel approach to understand the amazing properties of the natural chlorophyll–protein complex and also have important implications, such as, in artificial photosynthetic reactions and photodynamic therapy.