Mixed-Valence Dimeric Olympicenyl Radical Cation With Improved Electrical Conductivity

p-Type doping is an effective strategy for modulating molecular packing arrangement of organic compounds, thus improving their electrical conductivity. In this work, the first example of a mixed-valence radical cation dimer based on an odd alternant hydrocarbon, [OR5]₂ ^+•[FeCl₄]^- (OR5-MV), was successfully prepared by the oxidation of olympicenyl radical (OR) derivative OR5 using FeCl₃. X-ray crystallographic analysis revealed that cation-radical dimer [OR5]₂ ^+•, acting as a fundamental building block, forms [OR5]₄ ²⁺ tetramer via a multi-center-two-electron bond, which further aggregates into a one-dimensional chain in the solid state. SQUID measurement reveals that the magnetic susceptibility is dominated by the FeCl₄ ^- anions with no detectable OR5 moiety contribution. Theoretical calculations disclosed an open-shell singlet ground state for [OR5]₄ ²⁺ tetramer and demonstrated that the pancake-bond formation between OR5 cation-radical dimers confers significant energetic stabilization. Compared to the neutral compound, more uniform molecular packing and reduced intermolecular distance in the one-dimensional columnar architecture of OR5-MV facilitate effective intermolecular orbital overlap, leading to broader band dispersion along the molecular stacking direction. A substantially improved electrical conductivity of up to 10^{- 3} S cm^{- 1} is achieved compared to neutral radical (10^{- 9} S cm^{- 1}), representing the highest value reported for monomeric odd alternant hydrocarbons.