The main research area of the group is supramolecular chemistry. An important research topic is the development of synthetic anion receptors, most of which are based on cyclic peptides and pseudopeptides. Of particular interest is the recognition of anions in water and the understanding of the underlying principles. In addition to macrocyclic receptors, gold nanoparticles and polymeric materials have recently been used for anion binding. A completely different research topic, but also rooted in supramolecular chemistry, is the development of compounds that rapidly convert neurotoxic organophosphates into non-toxic metabolites under physiological conditions, allowing their use to treat poisoning with these nerve agents.
"Amino acid containing anion receptors" Chem. Soc. Rev. 2009, 38, 585-605; <doi>
My first cover I designed for a scientific journal. When I received the invitation, I wanted to show the 'nesting' of an anion within the environment of a protein and the amino acids involved in anion recognition. I knew I would need a graphics program with 3D modeling and rendering capabilities to create the image, so I purchased Cheetah 3D. Learning to draw and manipulate objects, as well as create the proper lighting, turned out to be more difficult than I expected. In the end, the best way I could find to illustrate the 'nest' was the purple bowl around which I distributed models of amino acid side chains. Labelling them was probably not a good idea. Ultimately, the image ended up being relatively simple, although I still like the reflections on the anion. The image was used for the inside cover of the Chem. Soc. Rev. issue and represents my first steps into graphic design.
"Side chain assisted nanotubular self-assembly of cyclic peptides at the air-water interface" Soft Matter 2010, 6, 4701-4709; <doi>
This is the only cover image that I did not create myself. It shows the results of my collaboration with the group of Kwanwoo Shin in Korea. The group found that one of our cyclopeptides forms tubular structures at the air-water interface, which are stabilized by hydrogen bonds between carboxylate groups in the side chains and amide groups along the cyclopeptide rings. The image created by Kwanwoo illustrates this behavior very nicely. Even though it may seem simple by today’s standards, it is far better than anything I could have created myself back then.
"Pathways for the reactions between neurotoxic organophorphorous compounds and oximes or hydroxamic acids" Eur. J. Org. Chem. 2016, 5831-5838; <doi>
This cover image illustrates a mechanistic study in which we elucidated the course of reactions between neurotoxic organophosphates, such as tabun, and certain α-nucleophiles. The image was intended to illustrate the conversion of highly toxic compounds into harmless ones, which the barrels and the arrow conveyed quite well. The structures ‐ both the line drawings and the models ‐ are probably not very clear, but the huge shadows look great. When I started creating the image, I still did not have much experience with the graphics program I was using. So it took me an entire afternoon just to design the barrel. When I was finally done, I realized that my barrel had a huge dent on one side because I had made a silly mistake while editing the mesh. Since undo was not possible, I had to start over from scratch, which was very annoying.
"Functionalisable acyclic cucurbiturils" Org. Chem. Front. 2019, 6, 1555-1560; <doi>
The publication to which this cover image belongs is one of the few papers by my group that contains a significant proportion of synthetic results. The image shows that, using our method, individual functional groups in the acyclic cucurbiturils developed by Lyle Isaacs can be modified and exchanged with relative ease. However, the magic wand should not be taken literally, as the synthetic steps are not as straightforward and 'magical' as the wand suggests. Nevertheless, the achievable structural diversity is substantial, as the flying stars nicely illustrate.
"Supramolecular Chemistry in Water" Wiley-VCH: Weinheim, 2019; <doi>
There are a few things about this cover image that don't look quite right. For example, the size of the waves and the life ring do not match, and the reflections in the water are too noisy. Nevertheless, superimposing the binding of a diamantane diammonium ion into the cucurbit[7]uril cavity and its incorporation into a life ring was a great way to illustrate the title of the book.
"Selective sensing of sulfate anions in water with cyclopeptide-decorated gold nanoparticles" Chem. Commun. 2020, 56, 10457-10460; <doi>
This rather futuristic image illustrates our work on the anion-induced aggregation of gold nanoparticles with surface-bound ligands that are terminated with one of our cyclopeptides. This cyclopeptide binds sulfate anions by sandwiching them between two rings. Thus, anions can link the nanoparticles, as illustrated by the structural model connecting the golden spheres on the bottom left and top right of the image. The other parts of the image tell the rest of the story. Upon self-assembly, the nanoparticles aggregate and ultimately precipitate as a black solid. The originally red solution becomes colorless, as shown by the color change in the background. Thus, the image shows more than is immediately apparent. In addition, it nicely demonstrates my progress from my initial feeble attempts at graphic modeling to this image.
"Supramolecular Chemistry – From Concepts to Applications" De Gruyter: Berlin, 2020; <doi>
When designing the cover of my book, I wanted to create something simple yet eye-catching that would be immediately associated with supramolecular chemistry. Using the structure of a crown ether–cation complex seemed like a logical choice. I chose the crystal structure of the potassium 18-crown-6 complex and depicted the ion and ring with metallic silver reflections. I created the reflections in the sphere using a photo of clouds that I had taken several years earlier. However, once the image was finished, it looked somewhat boring and dull. Therefore, I added the crown. When a colleague saw it, he remarked, "The molecule has a crown," to which I replied, "Well, it's a crown ether."
"When molecules meet in water – Recent contributions of supramolecular chemistry to the understanding of molecular recognition processes in water" ChemistryOpen 2022, 11, e202200028; <doi>
This is not a cover image, but rather a frontispiece that accompanies a review I wrote about molecular recognition in water. It is probably my favorite image. The title of the review is "When Molecules Meet in Water," which is exactly what this image is about. While not chemically accurate, the two "molecules" are recognizable as such. I created them with joints in the arms and legs so that I could move them like puppets. This allowed me to arrange them in an embrace, illustrating that they approach each other. The puddles and raindrops show that this meeting takes place in water. The gaslight, which appears to come straight out of a Charles Dickens novel, has no significance whatsoever. However, it adds to the gothic atmosphere of the image and allowed me to add nice reflections to the surface of the water. I hope the image motivated readers to check out the review.
"Supramolecular Chemistry – From Concepts to Applications", De Gruyter: Berlin, 2024; <doi>
"Sulfonatocalix[4]arene-based scavengers for V-type nerve agents with enhanced detoxification activity" Chem. Eur. J. 2025, 31, e202404321; <doi>