After 13 years of training at the Weizmann Institute of Science in Israel, Professor Rafal Klajn is now moving to the Austrian Institute of Science and Technology (ISTA). His group focuses on supramolecular and colloidal chemistry. The chemistry department at ISTA in Klosterneuburg continues to grow: with the start of Klajn, there are now six chemistry research groups. At first, the new research group immediately published a significant result: the specialized journal Science recently published the group’s latest discoveries about molecules that can be transformed into other states using colored light.
Chemistry and nature are often considered opposites. But nature has long impressed chemists with its ability to create complex structures and exquisite nanomaterials with unparalleled precision and efficiency. For example, nature consistently uses so-called nanoconfinement – limitation in the nano range. Nanoconfinement is fundamentally different from the way chemists currently carry out reactions. “This idea has fascinated me for a long time: as scientists, of course we deepen our understanding of nature,” says Klajn, “but we can also use this understanding in a targeted way.” There are three main questions.
Nanoconfinement and self-assembly
With his research group, Klajn investigates various aspects of supramolecular chemistry – a field that deals with connecting molecules into larger “superstructures” with new and “emerging” properties. Emergence refers to the properties or behaviors that a complex structure exhibits only through the interaction of its individual parts within a larger whole.
The first pillar of the Klajn Group is chemistry, which works with the fact that substances are spatially confined, namely in the nanometric range. The team designs and develops new molecular assemblies and materials containing such nanoscale limitations and explores their properties. “This approach has the potential to show us innovative ways to carry out chemical reactions,” says Klajn, “and ultimately paves the way for the synthesis of unique nanostructures and materials.”
The second focus is on the self-organization of particles 1 to 100 nanometers in size – smaller than 1/1000th the width of a human hair. The group studies how nanoparticles interact with each other to gain precise control over self-assembly. They want to use this to create complex materials with innovative functionality.
The third research focus addresses the question of how highly developed self-organized structures—think of the complex supramolecular architectures that make up living organisms—remain stable far from thermodynamic equilibrium. The group investigates design principles for such structures, particularly for systems assembled under the influence of light, magnetic fields or chemical fuels.
The new paper in Science addresses two of these pillars: Introduces a new approach based on nanoconfinement that expands the spectrum of light that can be used to “switch” a molecule. What does this mean exactly?
broadband photoswitch
Azobenzenes are the simplest and best-studied molecules whose state can be changed with light. When they are irradiated with ultraviolet (UV) light, their configuration changes from the stable E form (“opposite”) to the metastable, high-energy Z form (“together”). This process, called “photoisomerization,” is reversible: the “retroisomerization” of Z to E occurs spontaneously over periods of time ranging from milliseconds to centuries, depending on the molecule. The highly reversible nature between E and Z has led to applications of azobenzenes in energy storage systems, switchable catalysis, and photopharmacology. The fact that you could only use ultraviolet light significantly limited its practicality.
Now the Klajn Group has overcome this limitation based on inspiration from nature. Over the course of evolution, some species of deep-sea fish have developed an intelligent way of expanding the absorption range of their visual pigments. Fish retinas apply a visual pigment called “retinal”. The retina can use another molecule to detect red light, almost like a kind of “antenna” that captures red light. This causes the retinal to change its configuration, which ultimately leads to vision. The Klajn Group’s new method uses a combination that resembles the natural antenna-retinal doublet. It is composed of an azobenzene and a visible dye that acts as a light sensitizer. By applying nanoconfinement to this dye together with an azobenzene, each “dye antenna” can convert hundreds of E-azobenzene molecules into the metastable Z form, converting visible light energy into chemical energy. Depending on the choice of dye, the desired color of visible light – not just UV but also the opposite red – can be used to control the process.
“The process is, in principle, also applicable to other classes of photosensitive compounds”, says Klajn, commenting on the possible effects of his results. “We hope our method will be a powerful tool for controlling chemical reactivity through a combination of light and nanoconfinement.”
Klajn’s path to ISTA
Born in Poland, Klajn received his early education in chemistry in his hometown of Wrocław (Breslau) and later at Uniwersytet Warszawski (University of Warsaw). In 2009, he obtained his PhD in chemical and biological engineering from Northwestern University (Illinois, USA), where he worked under the supervision of Prof. Bartosz A. Grzybowski. He then moved to the Department of Organic Chemistry at the Weizmann Institute of Science in Israel, where he received several prizes and prizes. His work has been recognized by awards from the American Chemical Society (ACS) and chemical societies in the Netherlands, Germany, Japan and Israel. He has received two grants from the European Research Council (ERC Starting Grant 2013 and ERC Consolidator Grant 2018). He co-founded the Gordon Research Conference (GRC) series on artificial molecular switches and motors in 2015 and recently led GRCs on self-assembly and supramolecular chemistry and systems chemistry.
Starting at ISTA in 2023, Klajn will be the sixth leader of the institute’s chemistry group. “The conditions and opportunities offered here are simply excellent. I am confident that ISTA, with its rapidly growing chemical division, will soon be recognized for its chemical research and I am excited to be part of this journey. I’m also looking forward to exploring possible collaborations with my fantastic new colleagues.”
Publication and financing of projects:
J. Gemen et al., Imbalancing azobenzenes by visible light sensitization under confinement, Science 2023, 381, 1357–1363. DOI: 10.1126/science.adh9059
This project was supported by funding from the Horizon 2020 Framework Program (812868 and 101022777), the Engineering and Physical Sciences Research Council (EP/R00188X/1), the European Research Council (820008 and 101045223) and the Academy of Finland (346107, 32016, 340103).
About ISTA
The Austrian Institute of Science and Technology (ISTA) is a research institute with its own right to award doctorates. It employs tenure-track faculty, postdoctoral researchers and doctoral students. The ISTA Graduate School offers fully funded doctoral positions for highly qualified students with bachelor’s or master’s degrees in biology, mathematics, computer science, physics, chemistry and related fields. In addition to the commitment to the principle of basic research, which is driven purely by scientific curiosity, ISTA focuses on bringing scientific discoveries to society through technology and knowledge transfer. The current president is Martin Hetzer, a renowned molecular biologist and former senior vice president of the Salk Institute for Biological Studies in California, USA. www.ista.ac.at
Information: Andreas Rothe [email protected] +43 664 8832 6510