Large Aromatic Hydrocarbon Radical Cation with Global Aromaticity and State-Associated Magnetic Activity
Jing Guo, Cong Zhou, Sheng Xie, Shenglian Luo, Tullimilli Y. Gopalakrishna, Zhe Sun, Jabrane Jouha, Jishan Wu, Zebing Zeng
Abstract
The stable radical cation of large aromatic hydrocarbons remains a challenge, due to the recessive aromatic character and high reactivity. Here we report the design, synthesis, and characterization of new aromatic π-radical cations from one π-electron oxidation of bay-twisted dibenzoperopyrene derivatives. Experimental observations and theoretical calculations revealed that these π-radical cations had significant resonance hybrid structures, advantageous to the spin- and charge-delocalizations over the molecular backbones and emerging global aromaticity in the distorted π-system. Therefore, they are thermodynamically stable even without fully steric protection of all C–H bonds on the carbon skeleton and can be well characterized and studied routinely at ambient conditions. Moreover, the π-radical cation materials demonstrated readily formed magnetic molecule aggregates in the solution phase, while in powder states cationic monoradical characters were manifested and in the crystalline state intermolecular through-space interactions were popular. The phenomenon of varied magnetic activity in different states is experimentally investigated by various spectral means and X-ray crystallographic analysis, assisted by DFT calculations. Our study provides an insight into the resonance hybrid effects in the design of stable large aromatic hydrocarbon radical cations and demonstrates state-associated magnetic activities for π-radical cations, which are necessary in applications as magnetic materials.