Functionalized porphyrins for visible-light photoredox catalysis

Abstract

Visible light photocatalysis, particularly in the context of its applications in organic synthesis, has undergone a remarkable development over the past decade. The design of innovative organophotocatalysts with optimized and well-planned properties, while reducing or eliminating the use of scarce and potentially toxic transition metals, is considered a key direction in this field for the coming years. Although free-base porphyrins have been identified as a promising class of easily accessible and tuneable organic photoredox catalysts, a systematic analysis of how the electronic nature and position of substituents influence the redox potentials of these compounds, both in the ground and excited states, is still lacking. In our research group, we recently synthesized a series of meso-tetraarylporphyrin derivatives functionalized with benzoyl groups in various positions and determined their redox potentials both in the ground state and the singlet excited state. These results demonstrated that the presence of a single benzoyl substituent at a meso position enhances the facility of reduction in both the ground and the excited state. Building on these findings, this bachelor’s Thesis aimed to study some meso-tetrabenzoylporphyrin derivatives to confirm the effect of these groups on both the ground-state and the excited-state redox properties of the porphyrins. After synthesizing these compounds, studies of their photophysical properties and redox potentials were conducted. These studies confirmed that the introduction of four benzoyl groups at the meso positions predictably and controllably modifies the redox behaviour of this promising class of organic photosensitizers. Finally, an initial analysis of their photocatalytic capacity was performed, validating the potential of these compounds as visible light-photoredox catalysts for future applications.