Polycyclic Aromatic Hydrocarbon‐/Heterocycle‐Embedded Porphyrinoids

Abstract

AbstractPorphyrinoids in which one or two pyrrole rings are replaced with polycyclic aromatic hydrocarbons/heterocycles such as naphthalene, phenanthrene, biphenyl, bipyridine, or phenanthroline are a new class of porphyrinoids represented as polycyclic aromatic hydrocarbon (PAH)‐/heterocycle‐embedded porphyrinoids. These macrocycles possess the structural features of both polycyclic aromatic hydrocarbons/heterocycles and cyclic polypyrrolic porphyrinoids. The PAH‐embedded porphyrinoids have drawn significant interest in recent times because of the following: (1) these macrocycles exhibit different π‐conjugation pathways unlike porphyrinoids, which exhibit circular conjugation pathways in their macrocyclic rings with various molecular structures; (2) the PAHs embedded macrocycles show variable degree of aromaticity which varies from weak aromaticity to antiaromaticity and (3) the PAHs embedded porphyrinoids provide unique ligand environment to form stable coordination and organometallic complexes in which metals may show uncommon oxidation states and unusual reactivity. All these above‐listed features depend on polycyclic aromatic hydrocarbon/heterocycle moiety present as a part of porphyrinoid macrocyclic framework. This Minireview focuses on the synthesis of different polycyclic aromatic hydrocarbon‐/heterocycle‐embedded porphyrins, contracted porphyrins and expanded porphyrins and briefly discusses their structural, spectral, aromatic and coordination properties.