Synthesis of fully π-conjugated, pentagon-embedded non-alternant carbon nanobelts

Synthesis of carbon nanobelts (CNBs) with delocalized electronic structures and enhanced π-conjugation remains unclear but is fundamentally important. Herein, we present the first successful synthesis and characterization of fully π-conjugated, pentagon-embedded non-alternant CNBs, carefully designed with optimal strain and reactive site protection. These compounds were synthesized using an iterative Diels-Alder reaction followed by deoxygenative aromatization. Unlike all-benzenoid alternant CNBs, these CNBs exhibit smaller band gaps, stronger red emission, and more effective π-conjugation due to the incorporation of non-alternant moieties. One CNB can be oxidized into its dication, which exhibits an open-shell singlet ground state and intriguing global aromaticity, with theoretical calculations predicting two weakly coupled annulenes along the edges. This work opens new avenues for synthesizing complex carbon nanostructures with enhanced electronic properties.