PhD defense: Mewenn Yvin

Title

Synthesis of new heptazines for photocatalysis, both for homogeneous use and grafter on solid support

Abstract

Heptazines are composed an aromatic core with alternating nitrogen and carbon atoms. This interesting structure is used at molecular level up to material scale in many fields. Many polymeric heptazines have been described in the literature for photocatalysis applications, but very few molecular heptazines. These molecules have been studied in optoelectronics, particularly in Organic Light-Emitting Diodes (OLED) devices. In this thesis, we sought to pave the way for the synthesis of molecular heptazines. We therefore began by optimising the synthesis of trisdiethylpyrazolylheptazine and its precursors. Molecular heptazines substituted with thiols were synthesized. Their photophysical and electrochemical properties were studied and these compounds were tested as photocatalysts.
In addition, the photophysical properties have proved interesting: by changing the nature of the substituent, it was possible to observe either TADF (Thermally Activated Delayed Fluorescence) properties or behaviour tending towards INVEST (Inverted Singlet Triplet Excited State). Grafting onto materials was another application targeted. To this end, a series of heptazines substituted with benzyl alcohols was synthesized and studied. In particular, this enabled us to obtain two heptazines functionalized with a benzyl alcohol bearing a tetrazine. An initial proof of concept demonstrated the reactivity of these molecules for inverse electron-demand Diels-Alder reaction with a strained alkyne. All this work has enabled to make progress in understanding the structure-property relationships of heptazines and to broaden the range of applications for this family of molecules.

 

PhD supervision

• Director: Pierre Audebert, Professor, PPSM, ENS Paris-Saclay
• Co-director: Clémence Allain, Research Director, PPSM, CNRS - ENS Paris-Saclay

Members of the jury

• Anthony D'Aléo, Research Director, CNRS - IPCMS Strasbourg (Rapporteur)

• Françoise Serein-Spirau, Professor, ENSCM Institut Charles Gerhardt Montpellier (Rapporteure)

• Philippe Blanchard, Research Director, CNRS - MOLTECH Anjou Angers (Examinateur)

• Géraldine Masson, Research Director, CNRS - ICSN Gif-sur-Yvette (Examinatrice)