Two-dimensional organic (bio)layers on surfaces

Abstract

Surface-assisted cyclodehydrogenation and de hydrogenative polymerisation of polycyclic (hetero)aromatic hydrocarbons (PAH) are among the most important strategies for bottom-up assembly of new nanostructures from their mo lecular building blocks. Although diverse compounds have been formed in recent year s using this methodology, a limited knowledge on the molecular machinery operating at the nanoscale has prevented a rational control of the reaction outcome. By controlling surface diffusion of N-heteroaromatic precursors, the on- surface dehydrogenation can either lead to monomolecular triazafullerenes and diazahexabenzocoronenes (N-doped nanographe ne), to N-doped oligomeric or polymeric networks, or to carbonaceous monolayers. G overning the on-surface dehydrogenation process is a step forward towards the tailored fabrication of molecular 2D nanoarchitectures distinct to graphene and exhibiting new properties of fundamental a nd technological interest. We combined advanced in-situ surface techniques as STM and NEXAFS with theoretical ab- initio calculations to achieve a complete unders tanding of the self-assembling of molecular precursors on surfaces. Herein, by merging info rmation from these techniques and different single-crystal metal substrates, we report on the diffusion control of competitive intramolecular and intermolecular dehydrogenative processes respectively called cyclodehydrogenation and dehydrogenative polym erisation, which operate in the on-surface synthesis of N-doped fullerene, nanographene, polyaromatic netw ork, membrane or graphene.