Macrocyclic aromaticity in Huckel and Mobius conformers of porphyrinoids

Macrocyclic aromaticity is one of the key concepts in porphyrin chemistry. The degree of macrocyclic aromaticity and the associated main macrocyclic conjugation pathway in Huckel- and Mobius-type porphyrinoids were determined using our recently proposed procedure based on bond resonance energy (BRE). All porphyrinoids with diatropic and paratropic macrocycles were found to have positive and negative superaromatic stabilization energies (SSEs), respectively. Main macrocyclic conjugation pathways predicted for various porphyrinoids were exactly the same as those predicted from the annulene model for porphyrinoids. Thus, macrocyclic aromaticity of Huckel and Mobius porphyrinoids has been rationalized successfully using an energetic criterion of aromaticity.