Synthesis of a Selena‐Hybrid [5]Radialene Derivative and Exploration of Polycyclic Heteroterphenoquinones as Ambipolar Charge Carriers

para ‐Terphenoquinone ( p TPQ) in which a benzenoid ring has been replaced with a heterocycle is known as heteroterphenoquinone (HTPQ). While (H)TPQs are typically non‐emissive and potentially open‐shell species, it is recently reported that fully fused polycyclic HTPQs (or PHTPQs) bearing a sulfur heteroatom can either exhibit fluorescence or antiaromaticity depending on the π‐conjugation arrangement in the core. Since the synthesis of PHTPQs is rare, until now limited to the reported compound containing a sulfur atom, a selenium‐containing fluorescent PHTPQ is now synthesized while attempting the isolation of elusive dinaphtho‐dicyclopenta[ b , d ]selenophene. The fluorescent PHTPQ is further dehydrogenated to synthesize the first PHTPQ with an embedded selenophenoradialene (selena‐hybrid [5]radialene), which is found to exhibit antiaromatic properties. The narrow optical highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gap, short intermolecular interactions in the solid state, and redox amphoterism prompt the investigation of its ambipolar charge transport properties alongside the thia‐analogue. The electron mobilities for PHTPQs comprising selenaradialene (1.96 × 10 −3 cm 2 V −1 s −1 ) and thiaradialene (1.58 × 10 −3 cm 2 V −1 s −1 ) cores are found to be one order of magnitude higher than that of the holes due to low‐lying LUMO energy levels.