The project has aimed at boosting a newly developing type of chemistry typically termed "on-surface synthesis". It is closely related to heterogeneous catalysis, which addresses the favorable effect of particular supports in reaction processes. On-surface synthesis maintains the reaction support of heterogeneous catalysis, normally using atomically well defined surfaces. However, in contrast to the catalysis case, here the product structures remain on the surface. The main goal is complementing conventional organic chemistry by extending its capabilities thanks to the surface confinement of the reactants, since molecules behave and react differently if they float in three-dimensional space (as in the solutions of conventional wet chemistry) or if they are confined to a two dimensional plane. In fact, the dimensionality can be reduced even further to one- or zero-dimensional reaction space by the use of appropriately tailored substrates. Apart from the implicit surface support, the rest of the environment can be a solution, controlled atmospheres or vacuum. This project focuses on the latter. Altogether, the reduced dimensionality and completely disparate vacuum environment thus cause the molecules to behave and react in strikingly different ways from what is typically known in conventional organic chemistry. On-surface synthesis can thus be seen as a new methodology or branch within the wider field of organic chemistry.
Furthermore, also the characterization techniques used in on-surface synthesis are different from those commonly applied in wet-chemistry. One important difference is that the two-dimensional space allows for scanned probe techniques to be applied for characterization, which in turn offer sufficient resolution to perform single-molecule studies. Whereas a statistical analysis of many molecules allows comparison with conventional ensemble averaging techniques, the single-molecule information provides unique insight into reaction processes and allows for a better characterization of minority products. Finally, the vacuum environment also allows generating and characterizing molecular structures that would be unstable under conventional conditions.
Advancing this new type of chemistry has allowed the development of new materials not achievable by conventional means. On the longer term, this may have an important impact in society, given the irrevocable and continuously increasing presence that synthetic materials have gained in our daily lives. In fact, beyond conventional "cheap" plastic use in packaging or as purely structural materials, the variety of their applications is continuously growing, including highly refined functionalities as for example in optoelectronic devices, catalysts, filters or batteries. Molecular materials are even being considered as strong candidates to become an important technological platform for future quantum technologies.
Within this project, the ultimate goal has been to bring this new type of chemistry a big step further, closer to applications. Going beyond the state-of-the-art, we have actually used this new type of chemistry to synthesize functional materials like atomically precise graphene nanoribbons, porous networks or organic semiconductors with predefined n-type or p-type behaviors.
