Deprotection of a benzyl unit induces a 22π aromatic macrocycle of 3-oxypyripentaphyrin(0.1.1.1.0) with strong NIR absorption

We report aromaticity switching from a 6 pi pyridine ring to a 22 pi macrocyclic ring of 3-oxypyripentaphyrin(0.1.1.1.0). This system has potential applications in photodynamic therapy owing to macrocyclic aromaticity being selectively induced by protecting group removal and strong absorption bands produced in the NIR region especially in methanol.