Enhancement of the photostability and photoactivity of metallo-meso-5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrins by polymeric micelles

Metallo-meso-5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrins (metallo-TPPSs), such as ZnTPPS, have been widely used as photosensitizers. However, their vulnerability to photodegradation significantly limits their applications. In this contribution, we demonstrate a method to enhance the photostability of metallo-TPPSs while retaining photoactivity via encapsulation inside cores of complex micelles. Poly(ethylene glycol)-b-poly(4-vinylpyridine) (PEG-b-P4VP) and metallo-TPPSs can form complex micelles in acidic solution through electrostatic interactions and then undergo axial coordination with the pyridine moieties of PEG-b-P4VP when the pH is adjusted to 7.4. In this way, metallo-TPPSs are entrapped in the hydrophobic, compact micellar cores, which effectively prevents photodegradation of the metallo-TPPSs that would otherwise occur in aqueous solution. In addition, the photodebromination of 2,3-dibromo-3-phenylpropionic acid (DPP) sensitized with ZnTPPS has been used as a model reaction to study the photosensitive activity of ZnTPPS entrapped in complex micelles. The entrapped ZnTPPSs exhibit pronounced activity and have much higher efficiency and faster photosensitive reaction rates than free ZnTPPS.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (219 K)Download as PowerPoint slideHighlights► Complex micelles, with a hydrophilic shell and an enriched metallo-porphyrin core, were fabricated. ► Photostability of metallo-porphyrins is enhanced by polymeric micelles while still exhibiting high photoactivity. ► Metallo-porphyrin containing polymeric micelles can effectively catalyze certain reactions in aqueous media.