Covalent Bond Regulation in Nanographene: En Route to Precise Aggregation State Modification

ABSTRACT The aggregation state modification of graphene, including nanographene molecules, is essential for optimizing their performance in various applications. However, the current understanding of how to regulate the structures and features of nanographene aggregates primarily relies on non‐covalent bonding interactions, while achieving exact control remains a significant challenge. Herein, we describe unique occurrence in which a σ‐bond is reversibly constructed and subsequently broken to produce dimeric nanographene and monomeric analogues. These molecules are fused with azulene unit(s) at the edge. The acid‐driven transformation occurs with a radical mechanism. Moreover, the manipulation of the chemical employed to terminate the reaction can regulate the selective creation of dimer and monomer. As compared to the monomer, the dimer with a helical structure exhibited a substantial rise in the molar absorbance coefficient ( ɛ ), fluorescence emission, a greater range of electrochemical characteristics, and much enhanced chirality stability. This study presents an unprecedented strategy that can precisely control and modulate the structures of aggregation state and characteristics of nanographene by regulating covalent bond cleavage and formation.