Perylenemonoimide-based superstable radical anions and dianions with solid-state emission properties

Abstract

The generation of ambient stable radical anions has always been a challenging task owing to their intrinsic reactivity. Electron-deficient molecules with an extended π-conjugation are popular choices for developing such stable radical species. In this report, we developed a strategy for the efficient generation of an ultrastable radical anion from the oxidized products of tetra thiophenol-substituted perylenemonoimide (TT-PMI). We isolated and thoroughly characterized four oxidized sulfoxide and sulfone derivatives: TT-PMI-2O (1), TT-PMI-2IO (2), TT-PMI-4O (3), and TT-PMI-8O (4). Subsequently, the effectiveness of radical anion generation was investigated using UV-vis-NIR absorption spectroscopy in different solvents in the presence of an external electron donor under both dark and visible light conditions. Cyclic voltammetry measurements underscored a notable electron accepting behaviour, following the oxidation of sulfur within the TT-PMI core. Electron paramagnetic resonance, spectroelectrochemistry, and chemical reversibility experiments were carried out to confirm the formation of radical anions. The radical anions and dianions of compound 4 display remarkable stability even under ambient conditions. We have successfully demonstrated the potential generation of radical anions from compound 4 in solid-state thin films. We also achieved perfect white light emission from the dianion of compound 4 in solution. Moreover, the origin of the solid-state emission was assessed from the intermolecular interactions obtained from the single-crystal X-ray structure. Furthermore, we performed density functional theory (DFT) calculations to understand the thermodynamic stability of various plausible isomers and determined their LUMO energy levels. We believe such ambient stable radical anions from PMI will be potentially useful for molecular magnetism, catalysis, and photovoltaic applications.