The chemist with an unlimited imagination
“From Dendrimers to Macrocycles: Exploration of Covalent Templates in the Synthesis of Large Aromatic Structures” is the title of a project by dr Marcin Majewski from the Faculty of Chemistry, for which he received more than one million PLN in May from the National Science Centre (NCN), as part of the Sonata 18 competition.
Dr Marcin Majewski, an assistant professor working both as a researcher and a lecturer at the Faculty of Chemistry at the University of Wrocław, deals in his research work with, among other things, the synthesis and characterisation of new hydrocarbon systems.
Why is it so important for chemists to obtain new, unique molecules? Is it not enough what we already have and know?
Dr Marcin Majewski: – The essence of all science, including experimental fields, is to know (and explain!) what is still unknown. The progress of civilisation has always depended on those who ask themselves questions such as “what is it?” and “why is it so?” Currently, we know millions of unique chemical compounds, many of them described in detail, however, there is still an unexplored ocean of possibilities spreading before us. On the one hand, Nature has created many amazing substances over millions of years, many of which are still waiting to be isolated from living organisms. On the other hand, with the tools of modern chemical synthesis, we are able to create materials that do not naturally occur. We may be the first in the Universe to combine these atoms and molecules into a given system of interactions! In the context of fundamental research, anything new can be potentially interesting, possessing properties that cannot be found anywhere else. In theory, we are only limited by our imagination, although, of course, when planning specific projects, we usually have in mind the potential applications of our compounds in medicine or technology, or the elucidation of the fundamental processes occurring there.
Among the many chemical substances produced in the world each year, a significant fraction are organic compounds containing carbon as a major component. What is there about carbon that is not found in other elements?
– First and foremost, it stems from its very nature – carbon is capable of forming a multitude of bonds between itself and many other elements, and these bonds can be of varying strengths, forming spatially unique layouts. Even structures from pure carbon can be completely different from each other (think graphite and diamond – fundamentally composed of the same atoms). Any such structural change brings with it some change in material properties, whether chemical or physical. The other great area of interest is, of course, the biological sciences, as carbon is one of the basic building blocks of living organisms, found in every one of our cells, forming the backbone of everything from proteins over sugars and fats to enzymes.
You undoubtedly need specialised equipment for these types of experiments. What do you use in your research work?
– Organic synthesis itself mainly requires specialised laboratory glassware to work without oxygen and water, but testing the properties of our compounds is another story. Here, we make extensive use of equipment available within the Faculty Laboratories at the Faculty of Chemistry, as these instruments can often cost millions of PLN. One example is the study of the magnetic properties of molecules, which we perform using Nuclear Magnetic Resonance Spectroscopy. This is a specialised version of the Magnetic Resonance Imaging (MRI) equipment known from medicine. In our case, we “image” the structure of a molecule through the interaction of specific atoms, e.g. hydrogen, with a magnetic field. Other instruments and the knowledge of how to use them can be so unique that we also make extensive use of international collaborations.
Your project involves the creation of templates as dendrimers, i.e. branching structures formed by simple and reproducible procedures, quickly leading to compounds of significant size. What can this be compared to? To Lego?
– Indeed, the analogy with Lego bricks is perfectly valid, but our “building bricks” are specific chemical molecules with a size of a few nanometres at most, i.e. millionths of a metre. We need atomic precision to put them together properly, although we perform our actions on a macroscopic scale, usually in solution, combining millions of molecules at a time. Hence, the most important role is played by the so-called functional groups, appropriately selected and placed on the compounds, which, like indentations and protrusions in building bricks, allow individual fragments to be joined only in specific configurations. Another important parameter is the geometry of the building blocks (“shape of the bricks”), which favours the formation of certain spatial forms over others. Often, however, it is not easy to “control” the process of joining (and tearing) chemical bonds, resulting in materials with a variety of structures and, therefore, non-optimal properties for a given purpose. In my project, I assumed the creation of a series of dendrimers, which, due to their branched structure and appropriate selection of groups at their ends, would allow the assumed building blocks to be “cross-linked” in such positions that when they are joined together, preferentially large cyclic structures are formed. We can compare dendrimers to branches on a tree, where we have larger limbs from which smaller limbs branch off until they form a full crown. They are all structurally similar, but form a very complex structure as a whole. My further step is to create such networks in a reversible manner, so that the created macrocycles can be released at the final stage. We can imagine this like the use of a mould when baking a cake, the shape of which remains preserved in the baking itself even after the mould is removed.
According to experts, large polycyclic aromatic hydrocarbons (PAHs) and their heterocyclic analogues represent one of the fastest growing fields in materials chemistry. They can be considered as discrete models of graphene-like structures (nanographenes, graphene ribbons, carbon nanotubes), with well-defined geometries and possibilities for further functionalisation. Can you explain what can be achieved by changing their structure?
– Full control over the shape, size and type of bonds between individual aromatic fragments makes it possible to closely “tune” their properties, such as hardness, flexibility, electrical conductivity, but also the way they interact with electromagnetic radiation (absorbing and emitting light of a specific wavelength), or the ability to “catch” guest molecules in their structure. Such well-defined, discrete interactions are crucial, for example, in the design of materials in organic optoelectronics. For example, in obtaining new generations of flexible yet robust displays, where one specific compound is usually responsible for the emission of a given primary colour. Host-guest interactions, in turn, are the basis for the design of chemical sensors, e.g. for the detection of harmful gases in the air or heavy metals in water.
As part of your research, you have synthesised and characterised a wide variety of PAHs. What can/could they be used for?
– One of my favourite compounds I created was “oktulen”, with a large ring structure composed of PAH fragments. It provided a kind of effective and selective receptor for chloride ions. Although this compound worked mainly for non-polar (non-aqueous) solvents, we can imagine water-soluble analogues that could be used, for example, to monitor salinity in the Oder River, which, as we know, has recently become a pressing environmental problem. Another interesting compound was a stable derivative of diindenofluorene, which exhibited a biradical character, i.e. containing two unpaired (i.e. usually very reactive) electrons in its structure. The manipulation of electron spins is a relatively new and still developing field, and good control of these in conducting materials would open the way to the construction of unique types of logic gates, forming the basis of a new branch of electronics: spintronics.
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Dr Marcin Majewski has co-authored more than a dozen unique scientific articles in prestigious international journals. During his doctoral studies, he collaborated with scientists from Korea, India and the USA.
For part of his research, he obtained an internal grant from the funds of the Ministry of Science and Higher Education (MNiSW) and a PRELUDIUM grant of the National Science Centre (NCN), in which he acted as Project Manager. He was also employed as Project Contractor in SONATA BIS and FNP TEAM grants (Head: Prof. M. Stępień). For four years, he successfully taught organic synthesis laboratory classes for chemistry students and was the supervisor of a BA and MA thesis, which resulted in a joint scientific publication (JACS 2019). This year, he became a supervisor of two BA theses and prepared and gives a lecture on practical aspects of organic synthesis for 4th year students.
You can meet him at the Lower Silesian Science Festival (DFN), where he both explains the phenomena occurring around us and introduces the history of Wrocław chemistry and chemists.
During his master’s studies, he completed an internship in the laboratory of Prof. R. Leino (Åbo Akademi, Turku, Finland), where he conducted research on novel iron-catalysed arylation reactions. He also did a two-year postdoctoral fellowship in Prof. H. L. Anderson’s group at Oxford University, which resulted in the development of a new method for the formation of large porphyrin macrocycles by pre-organisation using covalent templates (Angew. Chem. Int. Ed. 2023). For this fellowship, he was awarded a Marie Skłodowska-Curie Individual Fellowship, the most prestigious travel grant for young researchers in Europe.
Currently, he has embarked on research on the exploration of covalent templates in the synthesis of large aromatic macrocycles, for which he was awarded an Excellence Initiative – Research University of the University of Wrocław (IDUB UWr), which is a preliminary research grant. And he was also fortunate to be among this year’s beneficiaries of the NCN Sonata competition, which will allow him to expand his research topics to new building blocks, reactivity types and future applications.
ATTENTION!!! He is looking for motivated students and young PhD students to accompany him on this new journey into the unknown ?
In his free time, he loves to travel, explore new places, immerse himself in the atmosphere of cities and nature, learn about interesting cultures and their cuisines. His ever-developing passion for architecture, art and local history is also a great break from the drudgery of working in the lab, and guiding tours and friends around Wrocław (licensed tour guide) is pure pleasure.
The winner of numerous awards, prizes and grants, incl.
2022 pro-quality one-off allowance for UWr researchers
2019 Rector’s team award for research
2017 START scholarship for outstanding young scientists, Foundation for Polish Science
2016/17 KNOW scholarship for the best doctoral students of the UWr Faculty of Chemistry
2015/16 P. L. Sosabowski scholarship for the best doctoral students of the Faculty of Chemistry UWr
2013/18 pro-quality scholarship for the best doctoral students of the Faculty of Chemistry UWr (five times)
2013/18 Rector’s scholarship for the best doctoral students of the Faculty of Chemistry UWr (five times)
Ed. Katarzyna Górowicz-Maćkiewicz
Translated by Kamil Sobierajski (student of English Studies at the University of Wrocław) as part of the translation practice.
