Möbius Aromaticity in N-Fused [24]Pentaphyrin upn Rh(I) Metalation

Abstract

N-fused pentaphyrins (NFP5), stable forms of meso-aryl pentaphyrins, are interesting platforms to realize Huckel aromaticity, nonaromaticity and Mobius aromaticity depending upon the number of pi-electrons, meso-substituent, and metalation. Remarkably, Rh(1) complex of pentakis(pentafluorophenyl) substituted [24]NFPS has been characterized as a Mobius aromatic macrocycle by the crystal structure, H-1 NMR spectrum, NICS calculation, and two-photon absorption (TPA) cross section. This system is, to the best of our knowledge, the smallest Mobius aromatic molecule with a distinct diatropic ring current characterized so far. This work demonstrates the great potential of our synthetic strategy toward Mobius aromatic molecules as well as the possible use of TPA value as a quantitative measure of aromaticity.