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1. Metal Halide Perovskite Nanocrystals for Near-Infrared Circularly Polarized Luminescence with High Photoluminescence Quantum Yield via Chiral Ligand Exchange

   https://doi.org/10.1021/acs.jpclett.3c01184  

   Wei, Jianwu; Luo, Qiulian; Liang, Sengui; Zhou, Liya; Chen, Peican; Pang, Qi; Zhang, Jin Zhong (June 2023, The Journal of Physical Chemistry Letters)

   Using ligand exchange on FAPbI3 perovskite nanocrystals (PNCs) surface with chiral tridentate L-cysteine (Lcys) ligand, we successfully prepared chiral FAPbI3 PNCs that show circularly polarized luminescence (CPL) (dissymmetry factor; glum = 2.1 × 10−3) in the near-infrared (NIR) region from 700 to 850 nm and a photoluminescence quantum yield (PLQY) of 81%. The chiral characteristics of FAPbI3 PNCs are ascribed to induction by chiral L/D-cys, and the high PLQY is attributed to the passivation of the PNCs defects with L-cys. Also, effective passivation of defects on the surface of FAPbI3 PNCs by L-cys results in excellent stability toward atmospheric water and oxygen. The conductivity of the L-cys treated FAPbI3 NC films is improved, which is attributed to the partial substitution of L-cys for the insulating long oleyl ligand. The CPL of the L-cys ligand treated FAPbI3 PNCs film retains a glum of −2.7 × 10−4. This study demonstrates a facile yet effective approach to generating chiral PNCs with CPL for NIR photonics applications. 

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2. 2D Ising Model for Enantiomer Adsorption on Achiral Surfaces: L- and D-Aspartic Acid on Cu(111)

   https://doi.org/10.3390/e24040565  

   Dutta, Soham; Gellman, Andrew J. (April 2022, Entropy)

   The 2D Ising model is well-formulated to address problems in adsorption thermodynamics. It is particularly well-suited to describing the adsorption isotherms predicting the surface enantiomeric excess, ees, observed during competitive co-adsorption of enantiomers onto achiral surfaces. Herein, we make the direct one-to-one correspondence between the 2D Ising model Hamiltonian and the Hamiltonian used to describe competitive enantiomer adsorption on achiral surfaces. We then demonstrate that adsorption from racemic mixtures of enantiomers and adsorption of prochiral molecules are directly analogous to the Ising model with no applied magnetic field, i.e., the enantiomeric excess on chiral surfaces can be predicted using Onsager’s solution to the 2D Ising model. The implication is that enantiomeric purity on the surface can be achieved during equilibrium exposure of prochiral compounds or racemic mixtures of enantiomers to achiral surfaces. 

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3. Multilayer electrodeposition of Pt onto 1–2 nm Au nanoparticles using a hydride-termination approach

   https://doi.org/10.1039/d0nr02929g  

   Lapp, Aliya S.; Crooks, Richard M. (May 2020, Nanoscale)

   Here we report on hydride-terminated (HT) electrodeposition of Pt multilayers onto ∼1.6 nm Au nanoparticles (NPs). The results build on our earlier findings regarding electrodeposition of a single monolayer of Pt onto Au NPs and reports relating to HT Pt electrodeposition onto bulk Au. In the latter case, it was found that electrodeposition of Pt from a solution containing PtCl 4 2− can be limited to a single monolayer of Pt atoms if it is immediately followed by adsorption of a monolayer of H atoms. The H-atom capping layer prevents deposition of Pt multilayers. In the present report we are interested in comparing the structure of NPs after multiple HT Pt electrodeposition cycles to the bulk analog. The results indicate that a greater number of HT Pt cycles are required to electrodeposit both a single Pt monolayer and Pt multilayers onto these Au NPs compared to bulk Au. Additionally, detailed structural analysis shows that there are fundamental differences in the structures of the AuPt materials depending on whether they are prepared on Au NPs or bulk Au. The resulting structures have a profound impact on formic acid oxidation electrocatalysis. 

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4. Chemoselective and enantioselective fluorescent identification of specific amino acid enantiomers

   https://doi.org/10.1039/D2CC02363F  

   Pu, Lin (July 2022, Chemical Communications)

   The enantiomers of chiral amino acids play versatile roles in biological systems including humans. They are also very useful in the asymmetric synthesis of diverse chiral organic compounds. Therefore, identifying a specific amino acid and distinguishing it from its enantiomer are of great importance. Although significant progress has been made in the development of fluorescent probes for amino acids, most of them are not capable of conducting simultaneous chemoselective and enantioselective detection of a specific amino acid enantiomer. In this article, several fluorescent probes have been designed and synthesized for chemoselective as well as enantioselective recognition of certain amino acid enantiomers. ( S )-1 shows greatly enhanced fluorescence in the presence of l -glutamic acid and l -aspartic acid, but produces no or little fluorescence response toward their opposite enantiomers and other amino acids. ( R )-4 in combination with Zn 2+ shows greatly enhanced fluorescence in the presence of l -serine. ( S )-6 is designed for the selective recognition of histidine. Micelles made of an amphiphilic diblock copolymer are used to encapsulate the water-insoluble compound ( S )-8 which shows chemoselective as well as enantioselective fluorescence enhancement with l -lysine in the presence of Zn 2+ in aqueous solution. The same micelles are also used to encapsulate several ( S )-1,1′-binaphthyl-based monoaldehydes ( S )-10 for the chemoselective and enantioselective fluorescence recognition of l -tryptophan in the presence of Zn 2+ in aqueous solution. These findings have demonstrated that highly selective fluorescence identification of a specific amino acid enantiomer can be achieved by incorporating certain functional groups at the designated locations of the 1,1′-binaphthyls. The binaphthyl core structure of these probes provides both a chirality source and highly tunable fluorescence properties. Matching the structure and chirality of these probes with those of the specific amino acid enantiomers can generate structurally rigid reaction products and give rise to greatly enhanced fluorescence. The strategies of this work can be further expanded to develop fluorescent probes for the specific identification of many amino acids of interest. This should facilitate the analysis of chiral amino acids in various applications. The outlook of this research and its comparison with other methods are also discussed. 

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5. Asymmetric reactions induced by electron spin polarization

   https://doi.org/10.1039/d0cp03129a  

   Bloom, B. P.; Lu, Y.; Metzger, Tzuriel; Yochelis, Shira; Paltiel, Yossi; Fontanesi, Claudio; Mishra, Suryakant; Tassinari, Francesco; Naaman, Ron; Waldeck, D. H. (January 2020, Physical Chemistry Chemical Physics)

   Essential aspects of the chiral induced spin selectivity (CISS) effect and their implications for spin-controlled chemistry and asymmetric electrochemical reactions are described. The generation of oxygen through electrolysis is discussed as an example in which chirality-based spin-filtering and spin selection rules can be used to improve the reaction's efficiency and selectivity. Next the discussion shifts to illustrate how the spin selectivity of chiral molecules (CISS properties) allows one to use the electron spin as a chiral bias for inducing asymmetric reactions and promoting enantiospecific processes. Two enantioselective electrochemical reactions that have used polarized electron spins as a chiral reagent are described; enantioselective electroreduction to resolve an enantiomer from a racemic mixture and an oxidative electropolymerization to generate a chiral polymer from achiral monomers. A complementary approach that has used spin-polarized, but otherwise achiral, molecular films to enantiospecifically associate with one enantiomer from a racemic mixture is also discussed. Each of these reaction types use magnetized films to generate the spin polarized electrons and the enantiospecificity can be selected by choice of the magnetization direction, North pole versus South pole. Possible paths for future research in this area and its compatibility with existing methods based on chiral electrodes are discussed. 

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