Application of Exciton Coupling for Characterization of Nanographene Edge

The structural characterization of nonstoichiometric nanographene (NG)‐organic hybrid materials is usually difficult. The number of substituents on the edge and their arrangements are frequently questioned but are difficult to answer. Since the number of functional groups is closely related to the distance between the nearest neighbors (dISD), the extraction of dISD from spectroscopic data could provide important information on their structural characterization. We show that exciton coupling, which is a theoretical prediction of the absolute structures of discrete molecules, is a possible candidate to address this issue. The comparison of the calculated CD spectra of the chiral chromophores extracted from the model NG edge with the observed edge spectra indicated a dISD of ca. 8 Å; this corresponded to substitution on every other armchair edge. Furthermore, an up‐up‐down‐down alternate orientation was found to be a possible edge structure. Although the procedure was limited to NGs carrying chiral substituents, our method could facilitate the detailed structural characterization of NG‐organic hybrid materials. The number of organic functional groups on the edge of nanographenes (NGs) and their arrangement are frequently questioned, although the nonstoichiometry of NGs causes difficulty in their structural characterization. The exciton coupling with the help of density functional theory calculations provides a possible procedure for the structural characterization of NGs.