First Access to Tetraazadiindenopyrenes via Selective Pyrrole Cyclization of Phenyl-Substituted Tetraazapyrene Derivatives on Au(111).

In stark contrast to cyclodehydrogenation (CDH) for constructing graphene nanoribbons through C─C or C─N bond formation, selective pyrrole cyclization via on-surface chemistry remains exceptionally rare and largely unexplored. To the best of our knowledge, this study reports the first demonstration of the sequential CDH of phenyl-substituted tetraazapyrene (TAP) derivatives on an Au(111) surface, providing the first access to tetraazadiindenopyrenes via selective pyrrole cyclization followed by C-C coupling. By varying the number and position of the phenyl substituents, we reveal how molecular geometry and aromaticity dictate the cyclization pathway, promoting C─N bond formation over the well-established C-C coupling embedded within the TAP framework. Low-temperature noncontact atomic force microscopy (nc-AFM) and differential conductance spectroscopy, complemented by density functional theory (DFT) calculations, not only provide an unambiguous structural assignment of the final products but also offer mechanistic insight into the sequential C-N and C-C cyclization processes.