Exploration of Push-Pull Type Hypervalent Group 15 Porphyrins
Porphyrins are highly conjugated aromatic systems with four pyrroles connected by
methylene bridges, able to accept functional groups in their meso- and beta-pyrrolic positions. These porphyrins are highly tunable, allowing us to change their properties accordingly, and capable of capturing a wide range of visible light. Push-pull porphyrins are studied because of their intramolecular charge transfer (ICT) character and their ability to capture light. It is possible to insert hypervalent atoms, such as P(V) and Sb(V), in the central cavity of the ring to allow two axial bonds to form on this central atom, leading to a positively charged center, making them good candidates for push-pull porphyrins. By attaching functional groups with high electron donating potential, such as triphenylamine (TPA), the system’s ICT becomes stronger. When such porphyrins are excited, it prompts the outer ring groups to donate their electrons towards the electron-deficient center. These systems are easier to synthesize relative to other artificial photosynthetic systems because these do not consist of multiple individual molecular entities that are covalently joined, such as polyads.