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1. Supramolecular polymerization of chiral molecules devoid of chiral centers

   https://doi.org/10.1002/pi.6111  

   Henderson, Will_R; Castellano, Ronald_K (September 2020, Polymer International)

   Abstract The iterative association of monomer units through noncovalent interactions often leads to chiral supramolecular polymers. Monomers comprising these materials can be further divided into those with chiral centers and those without. The latter class is often less studied but attractive since it features monomer designs with chirality at the core rather than the periphery of the molecules. In this mini‐review, we summarize the existing strategies to construct supramolecular polymers from chiral molecules with no chiral centers and offer perspectives on fundamental trends and differences between them and their counterparts with chiral centers. © 2020 Society of Industrial Chemistry 

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2. Observation of a Giant Nonlinear Chiro‐Optical Response in Planar Plasmonic–Photonic Metasurfaces

   https://doi.org/10.1002/adom.201900744  

   Wang, Feng; Harutyunyan, Hayk (June 2019, Advanced Optical Materials)

   Abstract Plasmonic nanosystems and metamaterials have recently attracted considerable attention because of their ability to enhance the light–matter interactions. One of such optical phenomena is the chiral‐ or handedness‐dependent response which typically requires 3D samples. Planar structures that can exhibit chiral response are highly desirable because of their facile fabrication, however fundamental challenges arising from the 2D nature of these systems prevent the generation of strong chiro‐optical effects. In this work, giant enhancement of the handedness‐dependent optical response in planar metallic nanostructures is shown by exploring the hybridization of plasmonic–photonic modes in a chiral metasurface. The resulting planar hybrid metasurface exhibits over an order of magnitude difference in nonlinear optical response when illuminated with excitation light of opposite circular polarizations. The unique properties of the hybridized plasmonic–photonic modes are shown to be responsible for the giant chiral nonlinear response. This platform allows to study the fundamental framework of chiral optical effects that arise from the combination of planar chirality and collective interaction of discrete nanosystems. 

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3. Chiral Metallopolymers for Redox‐Mediated Enantioselective Interactions

   https://doi.org/10.1002/adfm.202301545  

   Jeon, Jemin; Elbert, Johannes; Chung, Ching‐Hsiu; Chae, Junice; Su, Xiao (April 2023, Advanced Functional Materials)

   Abstract Synthetic chiral platforms can be a powerful platform for enantioselective interactions, especially when coupled with redox‐mediated electrochemical processes. While metallopolymers are versatile platforms for molecularly selective binding, their application for chiral applications is limited. In particular, the recognition and separation of biologically relevant chiral molecules can be key for biomanufacturing and diagnostics. Here, the design of chiral redox‐polymers enables electrochemically‐controlled enantioselective interactions, and supramolecular chirality is leveraged for enhancing recognition towards target enantiomers. Chiral redox‐metallopolymers are synthesized based on Ugi's amine‐inspired chiral monomers, and their enantioselective recognition toward ionic enantiomers such as tryptophan and naproxen is demonstrated, with higher enanhcement provided by the chiral redox‐polymer over the single‐site, chiral building bloack itelf. 2D nuclear magnetic resonance spectroscopy and solid‐state circular dichroism support the emergence of supramolecular chirality resulting from the intramolecular interaction between the ferrocene and the alkyl group in the backbone. The half potential shift of the redox‐polymers behaves linearly from 0% to 100%eel‐tryptophan to enable enantiomer quantification. Investigation on solvent polarity and pH effect reveal that the enantioselective mechanism is attributed to the subtle balance between hydrogen bonding and π–π interaction. This study highlights the potential of chiral redox‐metallopolymers as platforms for electrochemically‐modulated enantioselective interactions towards a range of amino acids and pharmaceutical carboxylates. 

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4. Synthesis of enantiopure 1,2,3-triazolylidene-type mesoionic carbene (MIC) conjugate acids featuring a rigid bicyclic scaffold

   https://doi.org/10.1039/d4qo00269e  

   Dočekal, Vojtěch; Melaimi, Mohand; Petrželová, Simona; Veselý, Jan; Yan, Xiaoyu; Bertrand, Guy (April 2024, Organic Chemistry Frontiers)

   Chiral NHCs have found numerous applications as ligands for transition metals and in their own right for asymmetric catalysis. We report a synthetic route froml-malic acid to enantiopure 1,2,3-triazoliums with the chiral center in a fused ring. 

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5. Observation of Chiral Surface Excitons in a Topological Insulator Bi_2Se_3

   Kung, H; Goyal, A; Maslov, D; Wang, X; Lee, A; Kemper, A; Cheong, S; Blumberg, G (January 2019, Proceedings of the National Academy of Sciences of the United States of America)

   We observe novel composite particles -- chiral excitons -- residing on the surface of a topological insulator (TI), Bi_2Se_3. Unlike other known excitons composed of massive quasiparticles, chiral excitons are the bound states of surface massless electrons and surface massive holes, both subject to strong spin-orbit coupling which locks their spins and momenta into chiral textures. Due to this unusual feature, chiral excitons emit circularly polarized secondary light (photoluminescence) that conserves the polarization of incident light. This means that the out-of-plane angular momentum of a chiral excitonis preserved against scattering events during thermalization, thus enabling optical orientation of carriers even at room temperature. The discovery of chiral excitons adds to the potential of TIs as a platform for photonics and optoelectronics devices. 

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