Researchers from the SNI network have shown that copies of a single molecular building block can spontaneously form a complex supramolecular structure on surfaces. Writing in the journal Communications Chemistry, the researchers describe how the studied porphyrin derivate arranges itself as individual molecules, in short chains or as a complex Kagome network on a silver surface. In each of these three roles, the molecule adopts a different conformation. The results are an example of how — and in what conditions —self-assembled molecular structures can use a small number of components to form complex structures at interfaces. Even in the primordial atmosphere, adaptable structures of this kind may have contributed to the origin and development of biochemical processes.

The self-assembly of molecules on surfaces is one of the most fascinating phenomena in the nanoworld. With no outside intervention, various interactions cause different molecules to arrange themselves into specific patterns and structures. Professor Thomas Jung, who carries out research at the Department of Physics of the University of Basel and at the Paul Scherrer Institute, has been working with his team for many years to investigate the basic principles of this supramolecular chemistry at interfaces.

Diversity of shapes
Now, Dr. Fatemeh Mousavi and Dr. Aisha Ahsan from Jung’s team (University of Basel, Department of Physics) have used scanning tunneling microscopy to investigate the self-assembly of a flexible porphyrin derivate (5,10,15,20-Tetrakis(3,4,5-trimethoxyphenyl)porphyrin, TTMPP). These molecules were designed “on the drawing board” in collaboration with Dr. Jonathan Hill before being synthesized by Hill at the National Institute of Materials Science in Tsukuba (Japan). The researchers then identified three different conformations of the molecules existing alongside one another on a silver surface — isolated as a single molecule, in short chains and in the form of a complex Kagome network. This network featured an alternating pattern of triangles and hexagons made up of the molecules.

The Kagome structure occurs due to an interplay between many different interactions. Although the molecules are bound to one another by very weak hydrogen bonds, these bonds are strong enough as a whole to produce conformational changes in the molecules. Other key factors include interactions between the molecule and the surface.

“We were surprised that we could achieve such complex network structures using a single, relatively simple molecule. This can be explained by the flexibility of the molecular structure, which changes shape based on whether and how bonding partners are available in its environment,” explain the two physicists, Mousavi and Ahsan.

TTMPP also assembles itself into complex patterns on gold, confirming that the molecular properties are responsible for the pattern’s formation at interfaces.

“Flexible molecules and their ability to adapt to their environment are also key to our understanding of a phenomenon known as prebiotic self-assembly at interfaces,” explains Jung. “When life emerged from self-replicating structures at interfaces, similar processes may have been involved.”

Original publication:
Emergence of conformational diversity and complexity of supramolecular structure by the interaction of a simple molecule with a uniform surface
S. Fatemeh Mousavi, Aisha Ahsan, Aaron Oechsle, Narmadha Devi, Yoshitaka Matsushita, Luiza Buimaga-Iarinca, Cristian Morari, Waka Nakanishi, Katsuhiko Ariga, Yutaka Wakayama, Yusuke Yamauchi, Thomas A. Jung & Jonathan P. Hill 
Communications Chemistry Vol 8, Article number: 214 (2025), doi: https://doi.org/10.1038/s42004-025-01607-x

Further information:
Research gropuorschungsgruppe Prof. Thomas Jung, Department of Physics, University of Basel