Asymmetric modification of particles with various patches of different composition and size at predefined positions is an important challenge in contemporary surface chemistry, as such particles have numerous potential applications, ranging from materials science and (photo)catalysis to self-assembly and drug delivery. However, approaches allowing the synthesis of this kind of complex objects in the bulk of a solution in a straightforward way are currently lacking. In this context, bipolar electrochemistry (BE) is a powerful technique for the asymmetric modification of conducting objects. Herein, this approach is used for the highly controlled modification of particles with different metal patches, generated at specific locations of isotropic objects. The synthesis is carried out in the bulk of the solution and leads to predefined patterns of increasing complexity, including even a specific chiral arrangement of the patches.

Chemoresponsive microgels functionalized with enantiomeric D- or K-[Ru(bpy)3] 2+ showed tunable chiroptical properties upon swelling and shrinking. The tuning is triggered by a modulation of the local mobility of [Ru(bpy)3]2+ upon addition of fructose, controlling inter- actions and distances between [Ru(bpy)3]2+ and phenylboronic acid. DOI: 10.1039/D3CC04391F

Who ? Dr. Narcis AVARVARI du Laboratoire MOLTECH Anjou  (Université d'Angers).
Where ? salle de conférences de l'ISM (3e étage)
When ? 22 dec. 2023, 10h30-11h30
Keywords: CISS effect, eMChA effect, Helicene, Conductivity, TTF
Abstract and references on  : https://www.ism.u-bordeaux.fr/actualites/dr-narcis-avarvari

Le PEPR LUMA invite les chercheurs travaillant dans les axes de recherche sur la chiralité listés sur : https://www.pepr-luma.fr/axes/chiralite/ de déposer des lettres d'intention (<3 pages) avant le 15 sept. 2023 afin de construire lors de workshops en visioconférence (dates prévisionnelles 27-28 sept. 2023) des consortia (typiquement 10 équipe de recherche travaillant ensemble) qui répondront aux AMI-appel à manifestation d'intérêts- auprès de l'ANR-PEPR-LUMA en automne 2023. Le template de la lettre d'intention et les dates clefs sont consultables sur : https://www.pepr-luma.fr/appels/appel-a-manifestations-dinteret-recherche-thematique/ NB : les AMI sont des financements sur 5 ans n'incluant pas de l'équipement >50 keuros.

Chirality is a property of asymmetry resulting, for an object, from the non-superposition of its image in a mirror. The notion of symmetry breaking, inherent in the organization of matter, the formation of new structural edifices, and, more fundamentally, weak interactions, is omnipresent. From the physics of elementary particles to molecules of the living world and functional organisms, to climatic phenomena inducing vortices of forces, chirality often plays a crucial role. It is also a conception of geometry exploited in design fields and man-made constructions for its functionality and uniqueness. In this chapter, we will focus on the chirality observed in solid state matter, that is, chirality based on the solid state organization of atoms or molecules. While there can be an important overlap with inorganic chiral nanostructures or nanoparticles for which there are a number of reviews, the solid state matters treated in this chapter can include crystals as well as amorphous solids of both organic and inorganic molecules. As we will discuss below, the study of the chirality of solid materials has mainly been focused on asymmetric ordered and periodic structures. When atoms are considered as a repeating unit, chiral crystals of achiral molecules can be classified as 3D asymmetric periodic structures. Chiral crystal faces of centric crystals and chiral 2D patterns of achiral molecules can be classified as 2D asymmetric periodic structures. Individual helical polymeric chains, chiral carbon nanotubes, and nanoparticles can be classified as 1D asymmetric periodic structures. We should also mention that chiral quasicrystals do not have mirror symmetry or translational symmetry, but have rotational symmetry, showing beautiful chiral ordered structures. We will also describe how chirality can be enhanced by the 2D or 3D organization of building components of solid materials. We will close with a discussion of spectroscopic methods to characterize chiral objects and assemblies. Reiko Oda, Peizhao Liu, Elizabeth Hillard, Patrick Rosa, Sylvain Nlate, Yutaka Okazaki, Emilie Pouget, Yann Battie and Thierry Buffeteau
https://doi.org/10.1142/9789811259227_0006
 

The synthesis and characterization of diketopyrrolopyrroles and perylenemonoimidodiesters linked to a substituted benzoic acid in the ortho, meta, and para positions, are reported. Grafting of these dyes on the surface of chiral silica nanohelices is used to probe how the morphology of the platform at the mesoscopic level affects the induction of chiroptical properties onto achiral molecular chromophores. The grafted structures are weakly (diketopyrrolopyrroles) or strongly (perylenemonoimidodiesters) emissive, exhibiting both locally-excited state emission and a broad, structureless emission assigned to excimers. The dissymmetry factors obtained using circular dichroism highlight optimized supramolecular organization between the chromophores for enhancing the chiroptical properties of the system. In the ortho- derivatives, poor organization due to steric hindrance is reflected in a low density of chromophores on walls of the silica-nanostructures (<0.1 vs. >0.3 and up to 0.6 molecules/nm² for the ortho and meta or para derivatives, respectively) and lower g_abs values than in the other derivatives (g_abs<2×10⁻⁵ vs 6×10⁻⁵ for the ortho and para derivatives, respectively). The para derivatives presented a better organization and increased values of g_abs. All grafted chromophores evidence varying degrees of excimer emission which was not found to directly correlate to their grafting density.
Maria João Álvaro-Martins, José Garcés-Garcés, Antoine Scalabre, Peizhao Liu, Fernando Fernández-Lázaro, Ángela Sastre-Santos, Dario M. Bassani, Reiko Oda ChemPhysChem 2023, 24, e202200573

Helical perovskite nanocrystals (H-PNCs) were prepared using nanometric silica helical ribbons as platforms for the in-situ growth of the crystals using supersaturated recrystallization method. The H-PNCs grow inside nanometric helical porous silica, their handedness are determined by the handedness of porous silica templates. They show strong induced circular dichroism (CD) and induced circularly polarized luminescence (CPL) signals, with very high dissymetric g-factors. Right-handed and left-handed PNCs show respectively positive and negative CD and CPL signals, with dissymmetric g-factor (abs and lum) of ~ +/- 2*10-2. Simulations based on the boundary element method demonstrate that the circular dichroism comes from the chiral shape of H-PNCs.
Peizhao Liu, Yann Battie, Takaki Kimura, Yutaka Okazaki, Piyanan Pranee, Hao Wang, Emilie Pouget, Sylvain Nlate, Takashi Sagawa, and Reiko Oda
https://doi.org/10.1021/acs.nanolett.2c04823

The Research Federation "Chirality in Nouvelle Aquitaine" (Ki-NOA) is organizing its 2nd day of scientific meetings and exchanges on the 25th of April at the IECB (2 rue Robert Escarpit, Pessac). This event will take place from 8h50-17h15, and the program is available at https://kinoa.cnrs.fr/2nd-kinoa-meeting/ Registration mandatory before the 7th of April on the framaform sent by email.

Nous avons eu 10 propositions de visite de labo sur le campus bordelais pour échanger autour de la chiralité. Ces visites se sont tenues entre décembre 2022 et février 2023, avec des échanges scientifiques très constructifs. Merci à tous ceux qui ont donné de leur temps et curiosité 🙂

Alexander Kuhn, membre très actif de la fédération kinoa, professeur à l’École nationale supérieure de matériaux, d’agroalimentaire et de chimie et chercheur à l’Institut des Sciences Moléculaires a recu l'une des 24 médailles d'argent du CNRS octroyée en 2023. Félicitation de tous à l'équipe NSYSA (NanoSystèmes Analytiques) https://www.cnrs.fr/fr/personne/alexander-kuhn
https://nsysa.ism-bordeaux.cnrs.fr/staff/permanent/22-staff/288-contact-alexander-kuhn-2.html

Conglomerate formation, where enantiomers within a racemic mixture self-segregate upon crystallization, is an advantageous property for obtaining chirally pure crystals and allows large-scale chiral resolution. However, the prevalence of conglomerates is low and difficult to predict. In this report, we describe our attempts to engineer conglomerates from racemate-forming compounds by integrating them into a conglomerate-forming matrix. In this regard, we found that Ni(II) and Fe(II) form molecular alloys with Zn(II) in [M_xZn_(1−x)(bpy)₃](PF₆)₂ (where bpy = 2,2′-bipyridyl). Powder X-ray Diffraction (PXRD) and Energy-Dispersive X-ray spectroscopy (EDX) evidenced conglomerate crystallization with Ni(II) concentrations up to about 25%, while it was observed only for much lower concentrations of Fe(II). This can be attributed to the ability of [Ni(bpy)₃](PF₆)₂ to access a metastable conglomerate phase, while no such phase has been detected in [Fe(bpy)₃](PF₆)₂. Furthermore, the chiral phase appears to be favored in fast-growing precipitates, while the racemic phase is favored in slow re-crystallizations for both Ni(II) and Fe(II) molecular alloys. X-ray natural circular dichroism (XNCD) measurements on [Ni_0.13Zn_0.87(bpy)₃](PF₆)₂ demonstrate the chirality of the nickel molecules within the zinc molecular matrix.
U. Serdan, L. Robin, M. Marchivie, M. Gonidec, P. Rosa, E. Duverger-Nédellec, E. Pouget, P. Sainctavit, M.-A. Arrio, A. Juhin, A. Rogalev, F. Wilhelm and E. A. Hillard Chemistry. 5(1) (2023) 255-268
fig :Molecular alloy of conglomerate [Ni@Zn(bpy)3](PF6)2

The development of chiral catalysts plays a very important role in various areas of chemical science. Heterogeneous catalysts have the general advantage of allowing a more straightforward separation from the products. One specific case of heterogeneous catalysis is electrocatalysis, being potentially a green chemistry approach. However, a typical drawback is that the redox conversion of molecules occurs only at the electrode/electrolyte interface, and not in the bulk of the electrolyte. The second limitation is that the electrodes have to be physically connected to a power supply to induce the desired reactions. To circumvent these problems, we propose here a complementary approach by replacing macroscopic electrodes with an ensemble of self-propelled redox active microswimmers. They move autonomously in solution while transforming simultaneously a prochiral starting compound into a specific enantiomer with a very high enantiomeric excess, accompanied by a significantly increased production rate of the favorite enantiomer.
S. Arnaboldi, G. Salinas, G. Bonetti, P. Garrigue, R. Cirilli, T. Benincori, A. Kuhn
Angew.Chem.Int.Ed. 61 (2022) e202209098

Chiral-imprinted mesoporous Pt-Ir alloy surfaces were combined in a synergetic way with electrochemiluminescence (ECL) to detect the two enantiomers of phenylalanine (PA) as a model compound, acting simultaneously as a chiral target and as a co-reactant to generate significant differences in ECL signals. The chiral features of the metal surfaces are converted into an enantioselective electrogeneration of the excited state of the [Ru(bpy)3]2+ dye, which in fine produces the differentiating light emission with up to 20-fold differences in intensity for the two enantiomers. These findings open up the possibility of developing new ECL-based bioassays and microscopy of chiral environments.
S. Butcha, J. Yu, Z. Pasom, B. Goudeau, C. Wattanakit, N. Sojic, A. Kuhn
ChemComm 58 (2022) 10707-10710

Efficient monitoring of chiral information of bioactive compounds has gained considerable attention, due to their involvement in different biochemical processes. In this work, we propose a novel dynamic system for the easy and straightforward recognition of chiral redox active molecules and its possible use for the efficient measurement of enantiomeric excess in solution. The approach is based on the synergy between the localized enantioselective oxidation of only one of the two antipodes of a chiral molecule and the produced charge-compensating asymmetric proton flux along a bipolar electrode. The resulting clockwise or anticlockwise rotation is triggered only when the probe with the right chirality is present in solution. The angle of rotation shows a linear correlation with the analyte concentration, enabling the quantification of enantiomeric ratios in mixtures where the two antipodes are present in solution. This device was successfully used to simultaneously measure different ratios of the enantiomers of 3,4-dihydroxyphenylalanine and tryptophan. The versatility of the proposed approach opens up the possibility to use such a dynamic system as a straightforward (bio)analytical tool for the qualitative and quantitative discrimination of different redox-active chiral probes.
S. Arnaboldi, G. Salinas, G. Bonetti, R. Cirilli, T. Benincori, A. Kuhn
Biosens. Bioelectron. 218 (2022) 114740

Microfluidic valves based on chemically responsive materials have gained considerable attention in recent years. Herein a wireless enantio-responsive valve triggered by bipolar electrochemistry combined with chiral recognition is reported. A conducting polymer actuator functionalized with the enantiomers of an inherently chiral oligomer was used as bipolar valve to cover a tube loaded with a dye, and immersed in a solution containing chiral analytes. When an electric field is applied, the designed actuator shows a reversible cantilever-type deflection, allowing the release of the dye from the reservoir. The tube can be opened and closed by simply switching the polarity of the system. Qualitative results show the successful release of the colorant, driven by chirality and redox reactions occurring at the bipolar valve. The device works well even in the presence of chemically different chiral analytes in the same solution. These systems open up new possibilities in the field of microfluidics, including also controlled drug delivery applications.
G. Salinas, F. Malacarne, G. Bonetti, R. Cirilli, T. Benincori, S. Arnaboldi, A. Kuhn
Chirality (2022) in press