On-surface synthesis of cyclic organic molecules.

Creating or connecting together large organic molecules, as polycyclic aromatic hydrocarbons (PAH), by chemical reactions readily on surfaces is the first step to a true advance in the field of molecular electronics. On-surface synthesis can be regarded as an efficient means to build new molecular species by using bottom-up strategies. Recently, a collection of different reactions leading to large tailor-made organic molecules on single-crystal metal surfaces has been reported. The fundamental mechanisms controlling these reactions can be investigated from a surface science perspective. This discipline skillfully combines the use of characterization techniques at the nanoscale, with single-crystal metallic surfaces able to catalyse these reactions. We present a tutorial review that highlights the relevance of the new bottom up strategies and classifies most of the different molecular on-surface reactions involving aromatic organic molecules that have been published up to date.

Tailored formation of N-doped nanoarchitectures by diffusion-controlled on-surface (cyclo)dehydrogenation of heteroaromatics.

Surface-assisted cyclodehydrogenation and dehydrogenative polymerization of polycyclic (hetero)aromatic hydrocarbons (PAH) are among the most important strategies for bottom-up assembly of new nanostructures from their molecular building blocks. Although diverse compounds have been formed in recent years using this methodology, a limited knowledge on the molecular machinery operating at the nanoscale has prevented a rational control of the reaction outcome. We show that the strength of the PAH-substrate interaction rules the competitive reaction pathways (cyclodehydrogenation versus dehydrogenative polymerization). By controlling the diffusion of N-heteroaromatic precursors, the on-surface dehydrogenation can lead to monomolecular triazafullerenes and diazahexabenzocoronenes (N-doped nanographene), to N-doped oligomeric or polymeric networks, or to carbonaceous monolayers. Governing the on-surface dehydrogenation process is a step forward toward the tailored fabrication of molecular 2D nanoarchitectures distinct from graphene and exhibiting new properties of fundamental and technological interest.