Stable cationic nanobelts synthesized by chemical oxidation of methylene-bridged [6]cycloparaphenylene

Nanobelts are cyclic arenes that only consist of annulated structures. Recently, various types of nanobelts have been synthesized and their unique properties have been unveiled. However, cationic nanobelts without heteroatoms have been rarely synthesized, and their properties are of significant interest from both fundamental and application perspectives. Herein, we report the synthesis of radical cationic and dicationic hydrocarbon nanobelts by chemical oxidation of methylene-bridged [6]cycloparaphenylene ([6]MCPP). These cationic species are remarkably stable in air, which made it possible to measure and uncover their structural and electronic properties. Notably, the [6]MCPP dicationic salt has sharp absorption and fluorescence bands at longer wavelengths than those of neutral [6]MCPP, close to the near-infrared region. From both experimental and theoretical investigation, the existence of a strong diatropic belt current in [6]MCPP dication was indicated. In addition, a longer lifetime was observed for the hexamethyl[6]MCPP dicationic salt than for the [6]MCPP dicationic salt in solution.