Core-modified N-confused pentaphyrin variants with adaptive (anti)aromaticity

Abstract

The retrosynthetic design and syntheses of three unprecedented core-modified N-confused pentaphyrins (sapphyrins) possessing an E-ethylene bithiophene moiety with tunable Hückel (anti)aromaticity are reported. Solution-state spectroscopic analyses reveal the sustained E-conformation for the ethylene moiety. All three N-confused pentaphyrins exhibited vis-NIR absorption. All possible stereoisomers of the S₂N₃ hybrid N-confused pentaphyrins 14–16 have been unravelled via thorough DFT studies. DFT studies support the Hückel π aromaticity of pentaphyrins 14 and 16 but π-antiaromaticity for 15.