Triindenoolympicenyl Radical with High Reduction Potential

Spin-1/2 open-shell polycyclic aromatic hydrocarbons (PAHs) typically exhibit pronounced redox amphotericity; however, accessing species with high reduction potentials (>-0.5 V) remains challenging. Herein, we report the synthesis and crystalline-state isolation of a stable triindenoolympicenyl radical (TIOR). Density functional theory (DFT) calculations and electrochemical analyses reveal that incorporation of three indeno units shifts the first reduction potential of TIOR by approximately 1.0 V toward more positive values relative to the triisopropylsilylethynyl (TIPSE)-substituted olympicenyl radical (OR1). These findings demonstrate that indeno annulation can serve as an effective strategy for fine-tuning the redox behavior of open-shell PAHs.