Protonation‐Triggered Conformational Changes to Möbius Aromatic [32]Heptaphyrins(1.1.1.1.1.1.1)

Abstract

Switching Aromaticity: Conformations of [32]heptaphyrins(1.1.1.1.1.1.1) are dependent upon meso‐aryl substituents, solvents, temperature, and protonation. Particularly, protonation of meso‐pentafluorophenyl‐substituted [32]heptaphyrin triggers conformational changes to form twisted aromatic Möbius structures (see picture), even at room temperature.

[32]π Fused Core‐Modified Heptaphyrin with Möbius Aromaticity

“…Heptaphyrins are expanded porphyrins, in which seven heterocyclic units are linked through multiple meso ‐carbon bridges. A series of non‐fused heptaphyrins are reported by Sessler, Osuka– and Kim, Imahori, and our group . We have demonstrated the synthesis of core‐modified heptaphyrins with four, five, and six ( 3 ) meso ‐carbon bridges .…”

Evaluation of the nonlinear optical properties for an expanded porphyrin Hückel-Möbius aromaticity switch

“…The conformational flexibility, the number and the nature of substituents on the pyrrolic and meso positions, and the metallation of the porphyrins allow them to achieve different topologies with distinct aromaticities, magnetic, and electric properties. 4 In the last five years several Hückel and Möbius topological systems have been prepared through replacement of the solvent and protonation, [5][6][7] temperature control, 8,9 metal coordination, 10 and functional group modifications. 11 As one can see, the synthesis of aromatic systems with Möbius topology has just started and there are still a lot of aspects and applications to be analyzed.…”

Regioselective Palladation of a Möbius Aromatic [28]Hexaphyrin(1.1.1.1.1.1) PdII Complex

“…2 Among the increasing number of Möbius aromatic molecules reported,3–5 we have demonstrated that meso ‐aryl‐substituted expanded porphyrins are remarkably effective platform to realize stable Möbius aromatic systems by means of metal coordination,5a,b temperature control,5c,d protonation,5e,f and intramolecular fusion reactions 5g. h The large two‐photon absorption properties and unique excited‐state dynamics of Möbius aromatic expanded porphyrins have been revealed 5a,b,e–g. 6 In addition, [28]hexaphyrin(1.1.1.1.1.1) Pd II , Ni II , and Pt II complexes have been enantiomerically separated by chiral HPLC, which opened possibilities to utilize Möbius twisted molecules as chiral sensors or ligands 7.…”