Synthetic routes to porphyrins bearing fused rings

The synthetic routes to porphyrins bearing fused rings, which can effect porphyrins by alternating their optical properties, both ground state and excited state, coordination chemistry and redox behavior , are discussed. Porphyrines with fused rings can be formed via several routes such as intramolecular cyclizations including metal-mediated cyclization and acid and base-catalyzed cyclization, or via intermolecular reactions, which includes Diels-Alder reactions, cycloaddition reactions or Bergman cyclization of porphyrine diynes. Fused porphyrine macrocycles are of great interest as potential molecular wires. These can be used to assemble heterodyads, in which a porphyrin and another chromophore are fused two neighboring β-carbons. It can give rise to the extended conjugation of the aromatic π-system and led to the development of many new products.