Light-Frozen Dynamic Covalent Synthesis of Organic Semiconducting Materials

Project Information

PhotoFreeze

Grant agreement ID: 101116355

DOI

10.3030/101116355

EC signature date 12 September 2023

Start date 1 January 2024

End date 31 December 2028

Funded under

• European Research Council (ERC)

Total cost

€ 1 500 000,00

EU contribution

€ 1 500 000,00

Coordinated by

UNIVERSITE D'ANGERS
France

Periodic Reporting for period 1 - PhotoFreeze (Light-Frozen Dynamic Covalent Synthesis of Organic Semiconducting Materials)

Reporting period: 2024-01-01 to 2026-06-30

Summary of the context and overall objectives of the project

The PhotoFreeze methodology addresses key limitations of dynamic covalent chemistry by exploiting a recently discovered irreversible, visible-light-induced reaction to “freeze” imine-based dynamic combinatorial libraries. This light-locking step kinetically stabilizes the selected products while preserving and enhancing electronic conjugation between the building blocks. As a result, complex conjugated architectures that are typically difficult or impossible to isolate using conventional dynamic or stepwise synthetic approaches become readily accessible.
By combining the thermodynamic control of dynamic covalent chemistry with the kinetic robustness of classical covalent synthesis, PhotoFreeze enables precise programming of molecular size, composition, and geometry through rational adjustment of building block stoichiometry and structure. The photochemical locking step promotes the formation of strong carbon–carbon bonds, facilitating purification, characterization, and reliable integration into functional devices.
This unique strategy opens a conceptually new route to electron-deficient conjugated materials. It provides access to imide-functionalized graphene nanoribbons, conjugated macrocycles, and covalent organic frameworks with tailored optoelectronic properties, thereby significantly advancing the state of the art in organic electronics, photocatalysis, and bio-imaging.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The project has reached a significant operational milestone with a team of six active members as of October 2025, which has notably accelerated research momentum. Efforts in WP1 have led to the successful development of a light-locked dynamic covalent polymerization methodology for conjugated polymers, a major achievement published in JACS in 2025. While synthetic challenges and intermediate instability have required a strategic pivot away from the original size-controlled ribbons, this redirection has yielded high-impact results regarding rare intermolecular mixed-valence anion species in ortho-fused diimides, documented in Angewandte Chemie in 2024. This discovery has opened a promising new research avenue into through-space electron delocalization and supramolecular self-assembly, with several papers currently in preparation. Simultaneously, WP2 has delivered on its expected milestones by utilizing the light-frozen dynamic methodology to synthesize complex macrocycles and cyclophanes in a single step. We have recently achieved a critical breakthrough toward conjugated nanohoops through the isolation of cyclic precursors, with final aromatization studies ongoing. Although WP3 remains in the preliminary stages, the overall project is demonstrating strong productivity and technical agility, successfully integrating advanced electrochemical deconvolution and spectroelectrochemistry to characterize the unique electronic behaviors of these new materials.

Achievments and outcomes:

1. The successful implementation of the “light-frozen dynamic covalent strategy” represents a significant achievement for our group. This proof of concept validates the overall premise of the project and allows us to confidently move toward more complex systems, knowing that we now have a robust and reliable methodology at our disposal.
Two key publications related to the light-frozen strategy and to the detection of unprecedented anionic intermolecular mixed-valence species have been published in two of the most prestigious international chemistry journals.
2. Intermolecular Anionic Mixed‐Valence and π‐Dimer Complexes of Ortho‐Pentannulated BisAzaCoroneneDiimides. David, A. H. G.; Roger, M.; Alévêque, O.; Melnychenko, H.; Le Bras, L.;* Allain, M.; Gapin, A.; Canevet, D.; Ségut, O.; Levillain, E.;* Goujon, A.* Angew. Chem. Int. Ed. 2025, e202413616.
3. Synthesis of Electron-Deficient BisAzaCoroneneDiimide-Conjugated Polymers by Light-Locking Dynamic Covalent Bonds. Gapin, A.; Chatir, E.; Alévêque, O.; Pasgrimaud, C.; David, A. H. G.; H.; De Maria, A.; Legros, M.; Le Bras, L.;* Levillain, E.;* Goujon, A.* J. Am. Chem. Soc. 2025, 147, 12218-12227.
4. We succesfuly applied the lock to another systems through collaboration with another group of the laboratory, as a first step toward proving that it can be generalized to other electron-deficient motifs.
David, A. H. G.;* Puchán Sánchez, D.; Kassem, A.; Roger, M.; Allain, M.; Le Bahers, T.; Monnereau, C.; Goujon, A.*; Cabanetos,* C. Exploring the Azabenzannulation of Benzothioxanthene Imide. J. Org. Chem. 2025, 90, 14479–14486.
5. In addition, several communication, science outreach, and public engagement activities have been carried out in connection with the ERC project
-Press release from the Université d’Angers for the obtention of the ERC Starting Grant Funding 2023 PhotoFreeze: https://www.univ-angers.fr/fr/recherche/actualites/actus-2023/bourse-erc-antoine-goujon-laureat.html
-Invitation to the Alumni Days of the Faculty of Chemistry to the Université de Strasbourg (21 Mars 2025). Participation to a conference about the future of studying chemistry, and discussions with small group of students about following a career in academia. It was associated to the recording of a podcast, “Portraits Croisés”: (https://savoirs.unistra.fr/talents/podcast-portraits-croises/des-atomes-crochus-avec-la-chimie).
-Portrait from Echoscience: https://www.echosciences-paysdelaloire.fr/articles/antoine-goujon-ouvrir-les-possibilites-en-chimie-organique

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Our new light-locked dynamic covalent methodology marks a significant departure from the state of the art, as recognized by the reviewers of our 2025 JACS paper. While traditional dynamic covalent chemistry often struggles with material instability, our approach provides access to kinetically stable organic semiconductors, offering a robust new strategy for the field of organic electronics. Furthermore, the unexpected discovery of strong intermolecular mixed-valence anion species in dissociative solvents—published in Angewandte Chemie in 2025—represents a fundamental breakthrough. This finding has established a new research direction focused on stabilizing free electrons within supramolecular architectures, a challenging goal with high potential for developing self-assembled conductive materials in thin films and liquid-crystalline phases.