ABSTRACT Strategic substitution of the 5 and 12 positions in pentacene with an electron‐donating nitrogen and electron‐accepting phosphine oxide, sulfone and carbonyl groups results in highly polarized para ‐quinodimethane (pQDM) derivatives with large dipole moments exceeding 10 D. These push‐pull systems feature narrow HOMO‐LUMO gaps (1.0–1.7 eV), reversible redox properties and near‐infrared (NIR) absorption and emission with maxima between 800 and 1100 nm. Remarkably, the polarization induces aromaticity switching: unlike their non‐aromatic double–donor and double–acceptor counterparts, the donor–acceptor analogues develop weak aromatic character in the central quinoidal ring, which is further enhanced in polar solvents, as confirmed by theoretical calculations, NMR spectroscopy and X‐ray crystallography. These findings demonstrate how molecular polarization can modulate aromaticity and electronic structure, providing a design platform for functional quinoidal π‐systems with tunable optical and redox properties.
Nowak et al. (2026) studied this question.