On-surface synthesis of nitrogen-doped nanographenes assisted by self-assembly

Despite the vast literature on in-solution synthesized heterocycle-based nanographenes, examples of their on-surface synthesized counterparts remain remarkably scarce. A major limitation is related to the stability of heterogroups throughout the thermal reaction steps. In this study, we show how the supramolecular steric hindrance arising from densely packed, saturated monolayers of the molecular precursor, suppresses Ullmann polymerization and significantly reduces the temperature required for internal cyclodehydrogenation from 300 °C down to 140 °C. This alternative route leads to the formation of self-assembled islands of a prochiral chloro-substituted nitrogen-doped ovalene derivative, offering a promising strategy for the synthesis of doped nanographenes under mild thermal conditions. Such conditions are crucial for preserving sensitive functional groups or heteroatoms and enable the integration of these reactions into more complex synthetic sequences.