2,3,17,18-Tetraethylsulfanyl [30]hexaphyrin(1.1.1.1.1.1) as the first aromatic isophlorin-type free-base

Abstract

β-Tetraethylsulfanyl-substituted [28]hexaphyrin 5 was prepared and converted to the corresponding β-tetraethylsulfonyl [28]hexaphyrin 6 and tetraethylsulfanyl [26]hexaphyrin 7. Both 5 and 6 are antiaromatic molecules with figure-of-eight structures while the major conformer of 7 is an aromatic species with a rectangular shape. Thorough reduction of 5 with NaBH₄ produced tetraethylsulfanyl [30]hexaphyrin 8 as the first example of expanded isophlorin free-base with distinct 30π aromaticity.