Céline Dorval, awarded for her work on cobalt catalysis
Catalysis plays a very important role in chemistry as it promotes and accelerates reactions. In particular, organometallic catalysis, which uses metal-based catalysts, is now widely deployed. However, the metals still most commonly used - palladium, rhodium or ruthenium - are rare, expensive and their extraction poses environmental problems. "Cobalt is a more abundant metal and, while it is not a miracle metal, it does help to overcome some of these problems," explains Céline Dorval, who carried out her thesis at the Molecular Chemistry Laboratory (LCM*) in the group of Corinne Gosmini, one of the specialists in cobalt catalysis.
Céline Dorval studied the implementation of cobalt-catalysed coupling reactions, which consist of assembling two molecules together by creating a bond between two carbon atoms. These coupling reactions involve electrophilic molecules, i.e. those that are poor in electrons. The electrophilic molecules that are still mainly used for these coupling reactions include at least one bond between a carbon atom and a halogen atom such as bromine or iodine. However, these species are not very abundant in nature," explains Céline Dorval, "they have to be synthesised, sometimes under drastic reaction conditions, which limits the diversity of usable molecules.
To get around this problem, the junior researcher focused on the use of two types of electrophiles. Firstly, species with amide functions, which are very common in proteins, for example. She has shown that cobalt can 'activate' this bond under specific conditions, enabling these amide compounds to be used in a coupling reaction to create a carbon-carbon bond. On the other hand, Céline Dorval studied electrophiles of the "nitrile" type. This led to the first ever demonstration of a cobalt-catalysed reaction capable of forming a carbon-carbon bond from this type of electrophile.
Intrigued by this reaction, the chemist tried to understand the process in more detail. "Unfortunately, in chemistry, you can't take a magnifying glass and look at what's going on in the reaction medium! Céline Dorval therefore carried out theoretical calculations in support of a multitude of experimental studies, in collaboration with Vincent Gandon, in order to lift the veil in particular on the nature of the cobalt complexes capable of activating these nitrile electrophiles. All of this doctoral work was rewarded with an organic chemistry thesis prize awarded at the Journée des Jeunes Talents de la Chimie en Ile-de-France 2021 organised by the Île-de-France section of Société Chimique de France. The researcher now plans to continue her work as a post-doctoral fellow in the United States in the field of photochemical catalysis.
*LCM: a joint research unit CNRS, École Polytechnique - Institut Polytechnique de Paris