3D Coumarin Systems Based on [2.2]Paracyclophane Synthesis, Spectroscopic Characterization, and Chiroptical Properties

International audienceIn this article, we report the preparation of a series of [2.2]paracyclophane-fused coumarin systems through a simple and general procedure involving a transition-metal-catalyzed cyclization of aryl alkynoates as the key step. We also highlight the influence of the [2.2]paracyclophane (pCp) motif and its "phane" interactions on the spectroscopic properties of the newly synthesized fluorophores, which emit in the blue-green region of the visible spectrum (lambda(em), up to 560 nm) and show extremely large Stokes shifts (up to 230 nm). Finally, we demonstrate that our straightforward approach can easily be used to access optically active planar chiral 3D coumarins. Compared to previously described fluorescent paracyclophanes and other organic dyes, our compact heteroaromatic derivatives show promising chiroptical properties, both in term of circular dichroism (g(abs) similar to 8 x 10(-3)) and circularly polarized luminescence (g(lum) similar to 5 x 10(-3)), thus demonstrating a practical application of our synthetic method

Helically chiral NHC‐gold(I) complexes: synthesis, chiroptical properties and electronic features of the [5]helicene‐imidazolylidene ligand

The golden twist: Monodentate [5]helicene-imidazolylidene gold(I) complexes were prepared in good yields and structurally characterized. Benefiting from the presence of the configurationally stable [5]helicenic unit, they exhibit appealing chiroptical features, such as strong circular dichroism, moderate circularly polarized phosphorescence and dual emission with phosphorescence lifetimes up to the millisecond range

Modulation of chiroptical and photophysical properties in helicenic rhenium(I) systems: the use of an N‐(aza[6]helicenyl)‐NHC ligand

The photophysical and chiroptical properties of a novel, chiral helicene-NHC−Re(I) complex bearing an N-(aza[6]helicenyl)-benzimidazolylidene ligand are described, showing its ability to emit yellow circularly polarized luminescence. A comparative analysis of this new system with other helicene-Re(I) complexes reported to date illustrates the impact of structural modifications on the emissive and absorptive properties

Circularly polarized-thermally activated delayed fluorescent materials based on chiral bicarbazole donors

G. P. thanks the SCBM, the “PTC du CEA” (POLEM) and the ANR (iChiralight, ANR-19-CE07-0040) for funding and David Buisson, Amélie Goudet and Sabrina Lebrequier. J. C. and L. Fa. acknowledge the Ministère de l’Education Nationale, de la Recherche et de la Technologie, the CNRS and the Spectroscopies-CDTP core facility is also acknowledged. The St. Andrews team thanks the China Scholarship Council, 201906250199 to W. S. and 202006250026 to J. W., E. Z.-C. is a Royal Society Leverhulme Trust Senior Research fellow (SRF\R1\201089). We thank the EPSRC (EP/R035164/1) for funding.We describe herein a molecular design to generate circularly polarized thermally activated delayed fluorescence emitters in which chiral bicarbazole donors are connected to acceptor units via a rigid 8-membered cycle and how the nature of the donor and acceptor units affect the photophysical and chiroptical properties.Publisher PDFPeer reviewe

A novel carbazolophane : a comparison of the performance of two planar chiral CP-TADF emitters

Jürgen Manchot Foundation Deutsche Forschungsgemeinschaft. Grant Number: EXC-2082/1–390761711 China Scholarship Council. Grant Number: 202106310038 Engineering and Physical Sciences Research Council. Grant Numbers: EP/R035164/1, EP/W015137/1, EP/W524505/1 Helmholtz Association Program Ministère de l’Enseignement Supérieur et de la Recherche Centre National de la Recherche ScientifiqueThe prototypical example of a (cyclo)phane, [2.2]paracyclophane (PCP), has proven to be a versatile stereogenic moiety within the design of circularly polarized thermally activated delayed fluorescence (CP-TADF) emitters; however, the exploration of other cyclophanes within CP-TADF emitter design has been largely neglected. Here, a comparative study of the photophysical and optoelectronic properties of two cyclophane emitters, (1,7)tBuCzpPhTrz and its isomer (1,4)tBuCzpPhTrz, is presented. The carbazolophane-triazine compound (1,7)tBuCzpPhTrz, obtained via an unprecedented intramolecular rearrangement, is the first example of a planar chiral TADF emitter deviating from the PCP scaffold. Significant geometrical change of the enclosed carbazole in (1,7)tBuCzp results in an attenuation of the donor strength, while the merits of rigidity and steric bulk remain. In particular, the full width at half maximum (FWHM) of the photoluminescence spectrum in toluene of (1,7)tBuCzpPhTrz is reduced by 34% and blue-shifted by 20 nm compared to that of (1,4)tBuCzpPhTrz. In doped films, the compounds reach high photoluminescence quantum yields (ΦPL) of 91 and 81%, respectively. The chiroptical properties reveal dissymmetry factors |gPL| of up to 5 ? 10?4. These results demonstrate the impact of the cyclophane for the development of CP-TADF materials and add to the currently limited scope of available planar chiral donors.Peer reviewe

Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

International audienceIn this review, we discuss the rich chemistry of helicenes and helicenoids containing main-group elements. Enantioenriched helicenic derivatives containing main-group elements B, Si, N and P, either incorporated within the helical backbone or grafted to it, will be thoroughly presented. We will describe their synthesis, resolution, and asymmetric synthesis, their structural features, electronic and chiroptical properties, emission, together with other photochemical properties and applications

Recent advances in room temperature phosphorescence of chiral organic materials

International audienceRoom temperature phosphorescence (RTP) in purely organic materials is an uncommon phenomenon of emission, which can be characterized by a long persistent luminescence after removal of the excitation source. In the recent years, RTP organic materials have received a considerable attention due to their high application potential in various advancing technologies, ranging from optoelectronic to biomedical applications. In parallel, many progresses have been achieved on the rationalization of this process and led to the emergence of innovative strategies aiming to achieve highest performances both in terms of phosphorescence efficiency and lifetime. While the topic is still on an ascendant development, the generation of circularly polarized phosphorescent (CPP) emission from purely organic molecules is by far much less explored and remains an impressive challenge. Still, the perspective of CPP materials appears as an interesting opportunity to answer several comprehensives issues existing in the field. In this article, we define, in a straightforward way, basic principles and key notions for the generation of RTP and CP luminescence (CPL) guiding the design toward CPP materials. After this brief insight, recent advances in the field of chiral organic RTP materials are discussed with an emphasis on their CP-RTP properties. Based on this development, the conclusion drawn allows establishing the next challenges and future opportunities standing in the field

La chiralité à la lumière des matériaux moléculaires, une nouvelle direction pour l'électronique organique

National audienceUbiquitous in our world, the property of chirality at the molecular level is a crucial element in drug discovery and development, owing to its fundamental role in biological processes. More recently, this molecular dissymmetry[1] has been extended to the research domain of molecular materials, providing them with innovative properties such as a specific interaction with a circularly polarized light. Given the potential of the latter in several research domains including display applications, cryptography, bio-imaging and spintronics, chiral molecular materials have recently attracted considerable attention as innovative CPL emitters. This latter aspect is notably illustrated in this article with selected examples of -conjugated helical architectures, investigated within the 'Organométalliques : Matériaux Moléculaires et Catalyse' team (OMC) at the Institut des Sciences Chimiques de Rennes (UMR 6226 CNRS - Université de Rennes), opening new opportunities in “chiral” organic electronics.Omniprésente dans notre monde, la propriété de chiralité à l'échelle moléculaire est un élément majeur dans la découverte et le développement de médicaments du fait de son effet sur l'activité biologique. Plus récemment, cette dissymétrie moléculaire [1] s'est étendue au domaine des matériaux organiques en leur conférant des propriétés inédites, telles qu'une interaction spécifique avec une lumière dite circulairement polarisée. Du fait du potentiel de cette dernière dans différents domaines d'applications incluant les technologies d'affichage, la cryptographie, l'imagerie biologique ou encore la spintronique, un intérêt grandissant est porté sur les matériaux chiraux luminescents en tant qu'émetteurs de lumière circulairement polarisée. Cette dernière particularité est discutée dans cet article au travers d'exemples d'architectures moléculaires hélicoïdales développées ces dernières années au sein de l'équipe 'Organométalliques : Matériaux Moléculaires et Catalyse' (OMC) à l'Institut des Sciences Chimiques de Rennes (UMR 6226 CNRS-Université de Rennes), laissant entrevoir de nouvelles perspectives en électronique organique « chirale »

Why is the Energy of the Singly Occupied Orbital in Some Radicals below the Highest Occupied Orbital Energy?

International audienceOrganic (mono)radicals where the singly occupied molecular orbital (SOMO) is energetically below the highest occupied molecular orbital (HOMO) level have recently attracted much interest. A clear understanding of the electronic factors that lead to this energetic SOMO/HOMO inversion (SHI) would be desirable to aid the rational design of SHI radicals with high stability and other desired properties. The electronic factors that govern SHI in known SHI radicals are studied computationally. Then, the findings are applied to design potential SHI candidates 'in silico'. The electrostatic repulsion among the frontier orbitals and the repulsion between the alpha and beta spin components of the orbitals in a closed-shell 'parent' compound are key to understanding the occurrence of SHI in a radical

Designs and Applications of Circularly Polarized Thermally Activated Delayed Fluorescence Molecules

International audienceThe design of fluorophores merging circularly polarized (CP) luminescence and thermally activated delayed fluorescence (TADF) properties has recently emerged as a promising direction for the development of efficient CP-Organic Light-Emitting Diodes (CP-OLEDs). This progress report gives an overview of the molecular designs explored to obtain CP-TADF properties, of their performances as chiral emitters in CP-OLEDs, and discusses future challenges for this burgeoning field of research