New molecular structures based on phosphorus, boron, nitrogen or P-block elements

Keywords: P-heterocycles, pi-conjugated systems, fluorophores, optoelectronic devices

The research on P-containing π -conjugated has increased substantially thanks to the development of "plastic eclectronics". The P-atom can be involved in various bonding situations, which will strongly impacts the electronic delocalization. Furthermore, the specific reactivity of the σ³, λ³ P-atom affords an almost unlimited way of properties tuning. Embedding the P-center into an unsaturated ring is also an excellent way to modify the properties of the corresponding π -system. In this context, we developed variuos π -conjugated P-heterocycles phosphetenes (4 membered unsaturated P-ring), phospholes (5 membered P-ring), phosphinines (6 membered P-ring) or phosphenpines (7 membered P-ring). These compounds were successfully inserted into optoelectronic devices (OLED, OFETs etc).

Contacts : Muriel Hissler, Pierre-Antoine Bouit.

Keywords: liquid crystal, nonlinear optics, multifunctionality, stimulable systems, supramolecular organization.

Development of room temperature multiphotonic liquid crystalline thin films for high capacity 3D storage. This issue, in collaboration with Franck Camerel (MaCSE), will be adressed through the synthesis of multipolar chromophores flanked by chiral pro-mesogenic units able to organize as thin films. The writing process will be the result of a pin-pointed two photons absorption which will induce a local disorganization in the ordered thin films through photoisomerization. The reading process will be based on the second harmonic generation (SHG) contrast. The originality of this work resides on the association, within single molecule, several properties (absorption with two photons, generation of second harmonic, mesogenic properties and luminescence) to obtain new supramolecular photoactive materials which have a very high potential in the development of high density 3D data encoding devices.

Contact : Huriye Akdas-Kiliç.

Keywords: Chiral organic dyes, circularly polarized luminescence, exciton coupling chirality, optoelectronic devices.

In a complementary approach to the organometallic one (see axis 2), we investigate the development of innovative chiral organic molecular materials based on ℼ-extended helical architectures resulting from the combination of helicene units and achiral organic dyes (diketopyrrolopyrrole, naphthalimide). This molecular engineering notably allows us to obtain fundamental insights into the electronic and structural factors (nature of the optical transitions, chiral exciton coupling) that govern the CPL process, and tune the latter across the visible and the far-red region (600-800 nm) with intense glum values (up to 3 x 10-2) at the molecular level (Chem. Sci. 2018, 9, 735 ; Chem. Eur. J. 2018, 24, 14484, Chem. Sci. 2020, 11, 567 , Coll. J. Autschbach, M. Srebro-Hooper, B. Jamoussi, N. Vanthuyne). Our growing expertise on this specific chiroptical property, which was notably reinforced by the development of a home-made CPL instrument in close collabroation with JASCO^© company (AIS Rennes Métropole, 2017), allows us to investigate a diversity of chiral molecular systems either in solution (Coll. M. Stepien, J. Am. Chem. Soc. 2019, 141, 7421) or in solid state (films, powder). Finally, applications of these chiral molecular materials in optoelectronic devices such as OLEDs or in photovoltaics give us interesting opportunities to explore the potential of chirality in molecular electronics (Coll. C. Cabanetos, P. Blanchard, Chem. Eur. J. 2017, 23, 6277).

Contacts : Jeanne Crassous, Ludovic Favereau.

Keywords: Dithienylethenes, supramolecular interactions, photochromism, chirality.

This project aims to provide to the scientific community a single molecular system capable of Photo-activatable Near Infra-Red Circularly Polarized Luminescence response, in various environments (organic solvents, physiological media, surfaces, bulk). The original systems incorporating a photochromic backbone are designed to be light-activated and provide light as an output chiral signal. Conceptually, the photochromic property of the system will control the intra-molecular interaction between two chromophores leading to i) the photo-control of excimeric NIR emission derived from intra-molecular interactions, ii) the photo-control of chiroptical properties (CPL, CD) without racemization upon photochromism by involving a stable atropisomeric molecular system in its enantiopure version.

Contact : Julien Boixel.

Keywords: diazines, photoluminescence, white light emitters

White light-emitting diodes (WOLEDs) are an efficient alternative to conventional lighting sources. Nevertheless, approaches to obtain WOLEDs still require complex processes that lead to high costs. In this sense, the use of a single emitting material that can take two forms of complementary emitting colors has emerged as a new strategy for the fabrication of WOLEDs. Our approach is to study the luminescent behavior upon protonation of a series of D-π-A push-pull molecules based on a diazine acceptor unit. Protonation of some blue-emitting pyrimidine derivatives that exhibited white photoluminescence by controlled protonation both in solution and the solid state has been designed.

Contacts: Sylvain Achelle, Nolwenn Cabon, Sébastien Gauthier, Pascal Le Poul, Françoise Robin-Le Guen.

Keywords: Heterochemistry (B, Si, P…), heterocycles, photochromes, polymers

Photoresponsive scaffolds including P block elements are valuable molecular targets due to the tunability of their electronic properties conferred by the presence of the heteroatom and its modifiable valence shell. Heterosubstituted dithienylethene-based photochromes are in this prospect valuable candidates requiring new and efficient methodological approaches for their construction. By combining the chemistry of strained heterocycles, P block elements and dithienylethenes, new photochromic scaffolds have been recently prepared and are currently studied.

Contact : Gilles Alcaraz, Marc Devillard.