Fulvalene Embedded Perylene Diimide and Its Stable Radical Anion

The first example of a two-state (neutral and reduced), stable electron-accepting material and its radical anion is presented. FV-PDI, generated from cyclocarbonylation and then a carbonyl coupling reaction, shows a largely degenerate LUMO of -4.38 eV based on the delocalization of pi-electrons across the whole molecular skeleton through a fulvalene bridge. The stability and electron affinity allow spontaneous electron transfer to afford a stable radical anion. Spectroscopic characterization and structural elucidation showed that the radical anion [FV-PDI](.-) has remarkable stability and near-infrared absorptions extending to 1200 nm. Single-crystal X-ray diffraction analyses revealed significant changes in the molecular shape and packing arrangement of the formed radical anion. The central C-C bond linking the two PDI halves is lengthened from approximately 1.33 to 1.43 angstrom, and the alternating arrangement of positively and negatively charged units favor the stable charge-transfer complex.