An official website of the United States government
Metal‐halide perovskites are known for their strong and tunable luminescence. However, the synthesis of perovskite‐based particles with circularly polarized light emission (CPLE) remains challenging due to the complex interplay of metal‐ligand chemistries, crystallization patterns, and chirality transfer mechanisms. Achiral perovskites can be deposited on chiral “hedgehog” particles (CHIPs) with twisted spikes, producing chiroptically active materials with spectroscopic bands specific to the perovskite and chirality specific to the template CHIPs. Left‐ and right‐handed CPLE is engineered into complex particles comprised of a layer of perovskite deposited onto CHIPs coated with an intermediate silica layer. The spectral position of chiroptical bands, the optical asymmetryg‐factors, and single‐particle circularly polarized microscopy indicate that the observed CPLE is dominated by the post‐emission scattering from the twisted spikes of the parent particle. Templating luminescent nanofilms on CHIPs provides a simple pathway to a wide range of complex chiroptical materials; the dispersibility of the CHIPs in various solvents and the tunability of their chiral geometry enable their applications as single‐particle emitters with strong and controllable polarization rotation.
more »
« less
Optical Enantiodifferentiation of Chiral Nitriles
Chiroptical sensing of nitriles is achieved with excellent functional group tolerance by hydrozirconation and subsequent transmetalation of the corresponding iminate to a chromophoric palladium complex. A one-pot workflow that uses the Schwartz’ reagent and [(η3-1-tert-butylindenyl)(μ-Cl)Pd]2 as sensor generates a palladium complex displaying red-shifted CD inductions and characteristic UV changes. These chiroptical responses are accurately correlated to the enantiomeric ratio and total concentration, respectively, of the original nitrile.
more »
« less
- Award ID(s):
- 2246747
- PAR ID:
- 10597979
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- Organic Letters
- Volume:
- 26
- Issue:
- 36
- ISSN:
- 1523-7060
- Page Range / eLocation ID:
- 7644 to 7649
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Wei, Mengjie (Ed.)In two-dimensional chiral metal-halide perovskites, chiral organic spacers endow structural and optical chirality to the metal-halide sublattice, enabling exquisite control of light, charge, and electron spin. The chiroptical properties of metal-halide perovskites have been measured by transmissive circular dichroism spectroscopy, which necessitates thin-film samples. Here, by developing a reflection-based approach, we characterize the intrinsic, circular polarization-dependent complex refractive index for a prototypical two-dimensional chiral lead-bromide perovskite and report large circular dichroism for single crystals. Comparison with ab initio theory reveals the large circular dichroism arises from the inorganic sublattice rather than the chiral ligand and is an excitonic phenomenon driven by electron-hole exchange interactions, which breaks the degeneracy of transitions between Rashba-Dresselhaus-split bands, resulting in a Cotton effect. Our study suggests that previous data for spin-coated films largely underestimate the optical chirality and provides quantitative insights into the intrinsic optical properties of chiral perovskites for chiroptical and spintronic applications.more » « less
-
null (Ed.)A new biaryl phosphine-containing ligand from an active palladium catalyst for ppm level Suzuki–Miyaura couplings, enabled by an aqueous micellar reaction medium. A wide array of functionalized substrates including aryl/heteroaryl bromides are amenable, as are, notably, chlorides. The catalytic system is both general and highly effective at low palladium loadings (1000–2500 ppm or 0.10–0.25 mol%). Density functional theory calculations suggest that greater steric congestion in N 2 Phos induces increased steric crowding around the Pd center, helping to destabilize the 2 : 1 ligand–Pd(0) complex more for N 2 Phos than for EvanPhos (and less bulky ligands), and thereby favoring formation of the 1 : 1 ligand–Pd o complex that is more reactive in oxidative addition to aryl chlorides.more » « less
-
Perovskite materials passivated by chiral ligands have recently shown unique chiroptical activity with promising optoelectronic applications. However, the ligands have been limited to chiral amines. Here, chiral phosphate molecules have been exploited to synthesize CsPbBr 3 nanoplatelets. The nanoplatelets showed a distinct circular dichroism signal and maintained their chiroptical properties after purification with anti-solvent.more » « less
-
Fey, Natalie; Chirik, Paul (Ed.)The palladium-catalyzed sp-sp2 C−C bond forming the Sonogashira reaction has been both extensively studied mechanistically and widely used in organic synthesis. Herein, we describe an investigation into how a palladium(II) complex with arylazoformamide (AAF) ligands mediates these transformations. When mixed, two AAFs coordinate in a κ1-fashion with an equivalent of PdCl2, creating complexes of the form PdCl2(AAF)2. Under typical and optimized copper(I)-cocatalyzed Sonogashira conditions, using phenylacetylene and iodobenzene as reagents, these complexes (precatalysts) reduce to Pd(0) and afford the coupled diphenylacetylene product in high yields (i.e., 99%). A substrate scope explored the substitution on both rings, yielding 18 examples with yields varying from 38 to 99%. Mechanistically, from DFT studies, a formal Pd(I) open-shell singlet complex is suggested, along with an explanation of the need for DBU when employing CuI in toluene. Further DFT exploration provides insight into the copper-free Sonogashira reaction when utilizing Pd(AAF)2 complexes.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1021/acs.orglett.4c02758
