A Thiophenoradialene-Embedded Polycyclic Heteroterphenoquinone Exhibiting Dominant Antiaromatic Traits.

A thiophenoradialene-embedded polycyclic heteroterphenoquinone (PHTPQ) derivative of diindeno[1,2- b :2',1'- d ]thiophene-2,8-dione, with antiaromatic characteristics, was synthesized by dehydrogenating its fluorescent dihydro PHTPQ precursor. The antiaromatic character was evidenced by the visible absorption band with a weakly intense tail extending to 800 nm in the near-infrared region (forbidden HOMO → LUMO transition) and non-emissive and amphoteric redox properties. Single-crystal and (anti)aromaticity analyses found a non-aromatic thiophene core while suggesting antiaromaticity/paratropicity of the pentafulvene subunits dominating the overall ground state properties.