Grégory Nocton awarded by the Société Chimique de France
Two lines lie at the bottom of the periodic table, the famous classification of chemical elements introduced by Mendeleev. They represent the lanthanide and actinide families. Grégory Nocton knows those two lines well. He did his PhD thesis on the chemistry of uranium, an actinide. Today, at the Molecular Chemistry Laboratory (LCM*), the lanthanides are at the heart of the work of this researcher, who was already awarded the CNRS bronze medal. Dysprosium, erbium, thulium... these metals are also known as rare-earth elements. “These are so-called f elements," he explains. That's chemist's jargon for how the electrons arrange themselves around the nucleus in different layers designated by the letters s, p, d, f." The f elements fill the layer of the same name, which explains their chemical properties.
Organometallic assemblies
However, as the name of his laboratory suggests, Grégory Nocton is not as much interested in materials as in the more fundamental scale of molecules. More specifically, 'organometallics', i.e. molecules that combine metals, such as lanthanides, with chemical species known as organic because they form the basis of life, such as carbon, oxygen, nitrogen, etc. The way in which the elements fit together with their environment is the subject of coordination chemistry, a speciality of Grégory Nocton. “In the haemoglobin molecule, he illustrates, an iron atom is surrounded by organic elements in such a way that an oxygen atom can coordinate, i.e. binds to the iron atom, and thus be transported into the human body.”
The spectrum of research in f-element coordination chemistry is broad. Much of the work in Nocton’s group is driven by curiosity, not by applications. "We're looking to do better. If chemists haven't managed to synthesise a molecule, we'll try to do it. It's a scientific challenge," he emphasises. Thus, in a paper published in 2018, his team showed how to synthesise 'sandwich' organometallic molecules, lanthanidocenes, which chemists had been trying to make for over 50 years.
Sustainable chemistry and quantum technologies
Although he takes pride in this fundamental research, Grégory Nocton does not lose sight of the other end of the chain, that of applications. One of these consists of designing organometallic molecules that can catalyse, i.e. promote, a chemical reaction that transforms other molecules. For example, the aim is to produce methanol from methane or carbon monoxide, using as little energy as possible. In the context of a collaboration, notably with Grégory Danoun, also a researcher at the LCM, the aim is to obtain hydrogen from food or plastic waste. This process would be more environmentally friendly than the steam methane reforming, which is currently the main method used.
Lanthanide-based organometallics not only form catalysts, but also molecular magnets. "Usually, the magnetisation arises from a set of atoms. We now know how to make molecules in which a single metal atom behaves like a magnet at low temperatures," explains the chemist. Thulium-based molecules have such properties. The ability to switch the magnetisation on and off could make one of these molecules a bit carrier, with a '0' and a '1' state. With a considerable miniaturisation advantage for a possible molecular computer.
We are talking about a 'classical' computer here, but lanthanide organometallics can also be placed in 'both 0 and 1' superposition states that could become building blocks for a quantum computer. This area of research is now gaining momentum and a PhD will soon be starting in his team on this subject. However, even if applications are on the horizon, Grégory Nocton has not lost sight of what drives him: "Above all, these are beautiful molecules !”
These works are funded by the ERC Starting Grant "LanAsCat", the ANR grants "RelaxMax" and "ReDivaLan", as well as by an AID agreement led by Grégory Danoun.
*LCM: a joint research unit CNRS, École Polytechnique - Institut Polytechnique de Paris