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.