A wide-range of redox states of core-modified expanded porphyrinoids

Core-modified hexaphyrin and octaphyrin display four- and six-electron reversible redox reactions respectively, to alternate between aromatic and anti-aromatic states of a given macrocycle. We have identified and isolated a hexaphyrin in three discrete states with 26π, 28π and 30π electrons that are inter-convertible with each other. Its higher congener, octaphyrin, can exist as four discrete species with 34, 36, 38 and 40 electrons. A difference of two-electrons between each stable redox state is reflected by the significant variation in their electronic and structural properties as characterized in both solution and solid states. The observed redox inter-conversions were achieved by a combination of both proton coupled electron-transfer (PCET) and electron-transfer (ET) processes respectively. Core-modified hexaphyrin and octaphyrin display four- and six-electron reversible redox reactions respectively, to alternate between aromatic and anti-aromatic states of a given macrocycle.