Toward Long Rylene Ribbons and Quinoidal Rylene Diradicaloids

Rylenes are peri-fused naphthalene oligomers and possess a unique electronic structure, which makes them attractive materials as organic dyes and semiconductors. In particular, rylenes beyond terrylene are promising near-infrared dyes with high molar extinction coefficients. Recent studies have demonstrated an unusual open-shell diradical character for long rylene molecules and potential half-metallic properties of polyrylene ribbon. However, the synthesis of long rylenes and polyrylene is a very challenging task, with various strategies directed towards solving the critical molecular aggregation and stability problems having been developed since 1910. In addition, recent research has also shown that quinoidal rylenes have an irresistible tendency to become diradical, and so they constitute a new type of open-shell singlet diradicaloids with magnetic activity. This microreview mainly summarizes the synthesis of long rylene ribbons and quinoidal rylene diradicaloids, together with their unique electronic structures and physical properties.