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Generating antiaromatic moieties on surfaces


bandgap opening

On-surface generation of antiaromatic subunits in a molecular precursor after its deposition on top of a hot metal surface. Image credit: Patricia Bondía.

  • Researchers at IMDEA Nanociencia have designed a new route to synthesize elusive antiaromatic moieties on surfaces.
  • Their novel synthetic route includes depositing specific molecular precursors on a hot surface that enables new skeletal rearrangements.


Madrid, December 7th, 2023Antiaromatic polycyclic conjugated hydrocarbons are interesting materials because their unique structural, electronic and magnetic properties with prospects in molecular optoelectronics. Antiaromaticity is a chemical property of a cyclic molecule with an electron system that has higher energy, hence the molecule is less stable due to the presence of delocalised electrons in it, as opposed to aromaticity. Unlike aromatic compounds, the synthesis of antiaromatic compounds is demanding because of their high reactivity, thus proving the synthesis of these special materials very challenging.

In the last decade, on-surface synthesis has emerged as a promising strategy for the development and design of new materials at the nanoscale, complementary to solution synthesis. It is based on the deposition of molecular precursors on top of a surface, and annealing to create new bonds, thus new nanomaterials. The chemical structure of the final products depends on the reaction mechanism followed by the initial molecular precursor. For instance, ring-rearrangement reactions are recently gaining increasing attention as a possible alternative toward the generation of novel nanostructures. However, controlling such reaction mechanism remains challenging due to the countless skeletal rearrangements.

In their research, researchers at Nanoarchitectonics on Surfaces group at IMDEA Nanociencia, led by Prof. David Écija in collaboration with the group of Nanocarbons and Organic Photovoltaics, led by Prof. Nazario Martín, have successfully developed a new strategy to synthesize polycyclic conjugated hydrocarbons featuring antiaromatic moieties by on-surface synthesis. They showed that the deposition of specific molecular precursors on a hot gold substrate resulted in novel intra- and inter-molecular reactions affording a skeletal ring-rearrangement. Such reaction pathways differred from the covalent polymerization of the same initial species upon deposition on top of the surface at room temperature followed by subsequent annealing. Combining different advanced microscopy techniques, researchers unveiled the chemical structures of the obtained compounds showing the formation of antiaromatic subunits within the molecular backbones.

The results, published in Nature Synthesis, prove that a new strategy to create these special nanomaterials is now possible. “Based on the power of organic synthetic protocols, the rational design and synthesis of suitably functionalized precursors paves the way to an unlimited new scenario” says Nazario Martín. The use of a hot metal surface during the sublimation of the molecular precursor to afford antiaromatic units represents a departure from traditional on-surface synthesis, marking a significant advancement in the field. This innovation opens up new avenues for designing molecular structures with tailored properties. “On-surface synthesis now introduces a unique paradigm to unlock new possibilities in chemistry that could impact the materials and technologies that surround us”, David Écija says. Their findings consolidate a new method for the development and design of organic materials at the nanoscale, affording the incorporation of antiaromatic subunits in their backbones. The control of ring-rearrangement reactions of carbon-based compounds on surfaces is envisaged to open new routes towards the design of low dimensional organic materials with prospects in molecular optoelectronics.

This work is an outcome of the Nanoarchitectonics on Surfaces Group at IMDEA Nanociencia, and has been partially funded by the ERC grant ELECNANO (GA number 766555), the grants QUIMTRONIC-CM, MAD2D and NANOMAGCOST from Comunidad de Madrid, and the Severo Ochoa Centre of Excellence distinction to IMDEA Nanociencia.


Pérez-Elvira, E., Barragán, A., Chen, Q. et al. Generating antiaromaticity in polycyclic conjugated hydrocarbons by thermally selective skeletal rearrangements at interfaces. Nat. Synth (2023). https://doi.org/10.1038/s44160-023-00390-8 (preprint at https://www.researchsquare.com/article/rs-2371634/v1)




Prof. David Écija
Group webpage: https://nanociencia.imdea.org/nanoarchitectonics-on-surfaces/group-home

IMDEA Nanociencia Dissemination and Communication Office
divulgacion.nanociencia [at]imdea.org
Twitter: @imdea_nano
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Source: IMDEA Nanociencia.