Hückel‐ and Baird‐Type Global Aromaticity in a 3D Fully Conjugated Molecular Cage

Abstract

AbstractGlobal aromaticity in 3D π‐conjugated molecular cages remains largely unexplored. Herein, we report the facile synthesis of a fully conjugated molecular cage (1) containing two bridged triphenylamine units and three quinoidal bithiophene arms. X‐ray crystallographic analysis, NMR/ESR measurements and theoretical calculations reveal that: 1) its dication (12+) has an open‐shell singlet ground state and is 3D globally aromatic, with individual macrocycles being 2D Hückel aromatic; 2) its tetracation (14+) has a triplet ground state and is also 3D globally aromatic, with individual macrocycles being 2D Baird aromatic; and 3) its hexacation (16+) has a closed‐shell nature and shows local aromaticity. The study demonstrated a close relationship between 2D Hückel/Baird aromaticity and 3D global π‐aromaticity.