To path indicator Subpages of “Research“ To navigation by target groups To navigation by topic To quick access To footer with other services
To content
The head of a football playing robot. © Nikolas Golsch​​/​​TU Dort­mund
PUBLICATION IN THE JOURNAL OF THE AMERICAN CHEMICAL SOCIETY

Research Team From TU Dortmund University Stabilizes Nanocages With Light

-
in
  • Research
  • Top News
There is a graphic with different molecules on a white background. © ACS Publications ​/​ CC
Through irradiation with UV light, the structure of a self-assembled nanocage based on diazocine photoswitches is modified in such a way that it can accommodate a guest molecule in its cavity. This host-guest complex is not located in the thermodynamic minimum and can only be maintained under dissipative conditions as long as energy in the form of light is continuously supplied.
A team headed by Professor Guido Clever from the Department of Chemistry and Chemical Biology at TU Dortmund University has published its latest research results in the prestigious Journal of the American Chemical Society (JACS). For the first time, the group was able to stabilize hollow molecular structures, which assemble themselves from a handful of components, beyond thermodynamic equilibrium by means of light.

The team of chemists led by Professor Clever is investigating the principle of metal-mediated self-assembly, with which it is possible to build complex three-dimensional nanostructures out of customized organic molecules and suitable metal ions in a simple way. The result is compounds with accessible cavities. These “supramolecular cages” can act as hosts and accommodate smaller guest molecules inside their cavities. This property makes them an interesting starting point for the development of new selective receptors, enzyme-like catalysts and smart materials.

In particular, the group is looking at the integration of photoswitchable components with which the system’s chemical properties can be reversibly modified through external impulses. This enables, for example, the targeted control of guest binding or structural transformation processes. In the study recently published, the chemists from TU Dortmund University have now shown for the first time that it is possible – through continuous energy input in the form of light – to keep such host-guest complexes in a state beyond thermodynamic equilibrium, while they reconstitute back into their initial components when the light source is switched off.

Che­mical sys­te­ms that operate in a state beyond thermodynamic equilibrium form the basis for all of life’s metabolic processes – and are thus interesting for research. However, they only remain in that state as long as energy is supplied and dissipated in the form of heat and waste products. An especially attractive method for supplying energy to such a system is light because it does not produce any material waste. To do this, chromophores (= dyes) must be able to absorb and convert the light’s energy, like green plants do, for example, in order to boost metabolism and growth.

Creation of an artificial host-guest complex

Chemists are developing model systems to imitate and understand such processes and further develop them into useful applications.

Graphic: Light-switchable structural change of the self-assembled host compound.
The light-triggered structural modification of the self-assembled host compound leads to a change of color (a), can be repeated several times (b) and can be thermally reversed (c). Continuous irradiation makes it possible to keep the system in a photostationary state beyond thermal equilibrium; switching off the light source leads to a thermal backswitching process.

The JACS publication describes the dissipative formation of an artificial host-guest complex beyond the thermodynamic equilibrium. For this purpose, first author Dr. Haeri Lee incorporated so-called diazocine photoswitches into coordination cages, which undergo a structural change when irradiated with UV light and only in this form can bind smaller molecules as guests inside them.

Picture collage of four people © Prof. Guido Clever
First author of the study, Dr. Haeri Lee (1st from the left), conducted the work at TU Dort-mund University and is now assistant professor at Hannam University, South Korea. Dr. Jacopo Tessarolo (2nd from the left) and Dr. Ananya Baksi (3rd from the left) are postdoctoral researchers in the group led by Professor Guido Clever (right), Chair of Bioinorganic Chemistry.

“The important thing is that the host-guest complexes we created only survive as long as energy in the form of light is supplied. If this energy source runs out, the system seeks a lower energetic state, whereby the photoswitches convert back to their original form under thermal conditions, and the guest molecules are released,” explains Professor Clever. “The process is fully reversible and serves as the basis for developing innovative chemical systems and materials, which only display special functions, structures or properties when continuously exposed to light.”

Potential areas of application are light-powered transport and separation processes, photoswitchable catalysis and smart coatings exposed to sunlight.

The research was conducted in collaboration with the group led by Professor Rainer Herges, Kiel University, and funded by the European Research Council (ERC Consolidator pro­ject “RAMSES”), the National Research Foun­da­tion of Korea and the German Research Foundation. The Journal of the American Chemical Society additionally recognized the work by printing a “Supplementary Cover” illustration.

Original Publication

Contact for further information:

Back

To top of page