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

The synthesis of carbon nanobelts (CNBs) with novel structures remains a significant challenge in organic chemistry. Herein, we report the synthesis and characterization of fully π-conjugated, pentagon-embedded non-alternant CNBs, marking a significant advancement in nanocarbon chemistry. These CNBs were designed by considering their strain and protection of reactive sites and synthesized through a deoxygenative aromatization pathway. This represents a significant breakthrough since the first attempt to synthesize this type of non-alternant CNB almost 20 years ago by Schlüter and co-workers. Their ground state, aromaticity, and optical, electronic, and electrochemical properties were studied through both experiments and theoretical calculations. Unlike previously reported all-benzenoid alternant CNBs, these novel CNBs exhibit a smaller band gap, more effective π-conjugation, and unique electronic properties due to the incorporation of non-alternant moieties. They show intense red emission with good fluorescence quantum yields. One CNB can be chemically oxidized into its dication, which exhibits an open-shell singlet ground state and interesting global aromaticity with two weakly coupled annulenes along the edges. This work opens new avenues for synthesizing complex carbon nanostructures with enhanced electronic properties.