Periodic Reporting for period 4 - SURFINK (Functional materials from on-surface linkage of molecular precursors)
Reporting period: 2020-03-01 to 2020-08-31
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."
Along different lines, a variety of reactants and functional groups have been used to render different porous structures. Whereas in some of them the functional grops were keto and enol groups whose tautomerization reaction determines the molecular self-assembly , in others we used thiol groups. For the latter, the porous structures are held together by Au-thiolate links. We have studied the influence of those metal-organic linkers on surface-supported alkyne coupling reactions. The metal-organic centers have been shown to have a remarkable influence on the reactions, reducing the activation temperature and modifying its outcome . Furthermore, the attractive interactions between the metal centers and the alkyne coupling motifs allows for the selective decoration of the metal-organic structures by periodically arranged molecular systems.
During the project’s progress, several side topics more focused on a further development of the on-surface synthesis toolbox and its improved understanding than on the synthesis of particular functional structures have also been addressed. Examples thereof are the development of new chemical reaction schemes, chirality transfer along surface-supported reactions , a better understanding of hierarchic chemical processes , the assessment of the catalytic action of the substrates and their leveraging for aligning the molecular structures atop , or the performance of reactions processes on non-metallic surfaces .
Altogether, the project has generated to date 24 peer-reviewed publications in internationally renowned journals. Each of the involved team members has actively contributed to the dissemination of the results at national and international conferences that have been chosen to cover both a broader range of attendants as well as a highly specialized audience. For the latter we have furthermore contributed organizing and establishing the “On-surface synthesis international workshop” as the reference forum for dissemination of results, exchange of ideas and launching collaborations within this growing field.