Benziporphyrins: Exploring arene chemistry in a macrocyclic environment

Benziporphyrins are synthetic porphyrin analogues, in which one of the pyrroles is replaced with a benzenoid ring. The arene can be incorporated into the macrocycle in several ways leading to molecules with distinct physical and chemical properties. By appropriately changing the structure of benziporphyrins, it is possible to affect their aromaticity, tautomeric equilibria, and reactivity. Benziporphyrins are versatile ligands, which offer a means to study the metal-arene couple in a macrocyclic environment. The coordination brings the metal ion into the vicinity of the arene fragment leading to activation of C-H bonds or weak interactions, which can be observed spectroscopically.