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Recently, the control of dynamic chirality has emerged as a powerful strategy to design chiral functional materials. In this context, we describe herein a molecular design in which a tethered configurationally stable binaphthyl chiral unit efficiently controls the dynamic chirality of donor‐acceptor fluorophores, involving diverse indolocarbazoles as electron donors and terephthalonitrile as an electron acceptor. The high conformational discrimination in such a molecular system suggested by density functional theory calculations is experimentally probed using electronic and vibrational circular dichroism and confirmed by the crystallization of these chiral molecules in gel and their single crystal X‐ray diffraction analysis. This work also highlights the positive effect of the configurationally stable chiral unit on the magnitude of the dissymmetry factors of the active dynamically chiral fluorophores, both in ground and excited states, through chiral perturbation. [ABSTRACT FROM AUTHOR]

Chirality is a curious phenomenon that appears in various forms. While the concept of molecular (RS‐)chirality is ubiquitous in chemistry, there are also more intricate forms of structural chirality. One of them is the enantiomorphism of crystals, especially molecular crystals, that describes the lack of mirror symmetry in the unit cell. Its relation to molecular chirality is not obvious, but still an open question, which can be addressed with chiroptical tools. Vibrational circular dichroism (VCD) denotes chiral infrared (IR) spectroscopy that is susceptible to both, the molecular as well as the intermolecular space by means of vibrational transitions. When carried out in the solid state, VCD delivers a very rich set of non‐local contributions that are determined by crystal packing and collective motion. Since its discovery in the 1970s, VCD has become the method of choice for the determination of absolute configurations, but its applicability reaches beyond towards the study of different crystal forms and polymorphism. This brief review summarises the theoretical concepts of crystal chirality and how computations of solid‐state VCD can shed light into the intimate connection of chiral structure and vibrational optical activity. [ABSTRACT FROM AUTHOR]

Solid‐State Vibrational Circular Dichroism (VCD) can be used to determine the absolute structure of chiral crystals, but its interpretation remains a challenge in modern spectroscopy. In this work, we investigate the effect of a twofold screw axis on the solid‐state VCD spectrum in a combined experimental and theoretical analysis of P21 crystals of (S)‐(+)‐1‐indanol. Even though the space group is achiral, a single proper symmetry operation has an important impact on the VCD spectrum, which reflects the supramolecular chirality of the crystal. Distinguishing between contributions originating from molecular chirality and from chiral crystal packing, we find that while IR absorption hardly depends on the symmetry of the space group, the situation is different for VCD, where completely new non‐local patterns emerge. Understanding the two underlying mechanisms, namely gauge transport and direct coupling, will help to use VCD to distinguish polymorphic forms. [ABSTRACT FROM AUTHOR]

The structure of in situ generated chiral aryl‐λ3‐iodanes obtained under oxidative reaction conditions was not yet observable with experimental techniques and their proposed structures are purely based on DFT calculations. Herein, we establish vibrational circular dichroism (VCD) spectroscopy as an experimental technique to verify DFT‐calculated chiral iodane structures. Based on a chiral triazole‐substituted iodoarene catalyst, we were able to elucidate a yet undescribed cationic chiral iodane as the most populated intermediate under oxidative conditions with a significant intramolecular N−I‐interaction and no significant interactions with tosylate or m‐chlorobenzoic acid as potential anionic ligands. Instead, aggregation of these substrates was found, which resulted in the formation of a non‐coordinating anionic hydrogen bonded complex. The importance of VCD as a crucial experimental observable is further highlighted by the fact that our initial structural proposal, that was purely based on DFT calculations, could be falsified. [ABSTRACT FROM AUTHOR]

Cyanido‐bridged dimetallic complexes are attracting attention due to their varied structures and properties. However, homochiral cyanido‐bridged dimetallic complexes are rare, and making them ferroelectric is a great challenge. Introducing C−F⋅⋅⋅K interactions between the guest chiral cations and the host [KFe(CN)6]2− framework, gives three‐dimensional cyanido‐bridged dimetallic multiferroics, [R‐ and S‐3‐fluoropyrrolidinium]2[KFe(CN)6] (R‐ and S‐3‐FPC). The mirror‐symmetric vibrational circular dichroism (VCD) signal shows their enantiomeric nature. R‐ and S‐3‐FPC crystallize in the same chiral‐polar space group P21 at 298 K. Piezoresponse force microscopy (PFM), polarizing optical microscopy, and temperature‐dependent second‐harmonic generation (SHG) measurements show their multiferroic properties (the coexistence of ferroelectricity and ferroelasticity), in line with the Aizu notation of 222F2. R‐3‐FPC shows excellent ferroelectricity with saturated polarization up to 9.4 μC cm−2. [ABSTRACT FROM AUTHOR]

Chiral perovskites have emerged as a significant class of materials showing promising optoelectronic and spintronic applications. Reports of chiral perovskite ferroelectrics, however, have been scarce. In this work, we have successfully synthesized homochiral lead–iodide perovskite ferroelectrics [(R)‐N‐(1‐phenylethyl)ethane‐1,2‐diaminium]PbI4 and [(S)‐N‐(1‐phenylethyl)ethane‐1,2‐diaminium]PbI4 by introducing a methyl group into the organic cation of the parent (N‐benzylethane‐1,2‐diaminium)PbI4. Vibrational circular dichroism spectra identify the chiral mirroring relationship. They both undergo 222F2‐type paraelectric–ferroelectric behavior at around 378 K coupled with clear ferroelastic domain "ON/OFF" switching. Besides, they exhibit an evident thermochromism with color change from orange–yellow to orange–red. To our knowledge, the discovery of integrated ferroelectricity, ferroelasticity, and reversible thermochromism in chiral perovskites is unprecedented. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate that molecular vibrations with originally low or zero intensity in a vibrational circular dichroism (VCD) spectrum attain chirality in molecular crystals by coordinated motion of the atoms. Ab initio molecular dynamics simulations of anharmonic solid‐state VCD spectra of l‐alanine crystals reveal how coherent vibrational modes exploit the space group's chirality, leading to non‐local, enhanced VCD features, most significantly in the carbonyl region of the spectrum. The VCD‐enhanced signal is ascribed to a helical arrangement of the oscillators in the crystal layers. No structural irregularities need to be considered to explain the amplification, but a crucial point lies in the polarization of charge, which requires an accurate description of the electronic structure. Delivering a quantitative atomic conception of supramolecular chirality induction, our ab initio scheme is applicable well beyond molecular crystals, for example, to address VCD in proteins and related compounds. [ABSTRACT FROM AUTHOR]

Characterizing the stereochemistry of transient photoisomerization products remains a big challenge for the design of molecular machines, such as unidirectional molecular motors. Often these states are not stable long enough to be characterized in detail using conventional spectroscopic tools. The structurally simple camphorquinone imine 1 serves to illustrate the advantage of combining the matrix-isolation technique with vibrational circular dichroism (VCD) spectroscopy for the investigation of photoisomerizations of chiral molecules. In particular, it is shown that both ( E)- and ( Z)- 1 can be generated photochemically at cryogenic temperatures in an argon matrix, and more importantly, that the stereochemistry of both switching states can be characterized reliably. [ABSTRACT FROM AUTHOR]

Cover Picture: Structure Elucidation of In Situ Generated Chiral Hypervalent Iodine Complexes via Vibrational Circular Dichroism (VCD) (Angew. Keywords: Asymmetric Catalysis; Computational Chemistry; Hypervalent Iodine; Stereochemistry; Vibrational Spectroscopy EN Asymmetric Catalysis Computational Chemistry Hypervalent Iodine Stereochemistry Vibrational Spectroscopy 1 1 1 12/07/22 20221212 NES 221212 B Vibrational circular dichroism b (VCD) spectroscopy was used by Boris J. Nachtsheim, Christian Merten et al. in their Communication (e202204624) to verify DFT-calculated chiral iodane structures. Asymmetric Catalysis, Computational Chemistry, Hypervalent Iodine, Stereochemistry, Vibrational Spectroscopy. [Extracted from the article]

The determination of the absolute configuration of chiral molecules is at the heart of asymmetric synthesis. Here we probe the spectroscopic limits for chiral discrimination with NMR spectroscopy in chiral aligned media and with vibrational circular dichroism spectroscopy of the sixfold-deuterated chiral neopentane. The study of this compound presents formidable challenges since its stereogenicity is only due to small mass differences. For this purpose, we selectively prepared both enantiomers of 2H6- 1 through a concise synthesis utilizing multifunctional intermediates. While NMR spectroscopy in chiral aligned media could be used to characterize the precursors to 2H6- 1, the final assignment could only be accomplished with VCD spectroscopy, despite the fleetingly small dichroic properties of 1. Both enantiomers were assigned by matching the VCD spectra with those computed with density functional theory. [ABSTRACT FROM AUTHOR]

Ionic interactions are increasingly appreciated as a key, asymmetry-inducing factor in enantioselective catalytic transformations, including those involving Brønsted acid or base catalysis, phase-transfer catalysis, and related processes. However, a detailed understanding of these interactions is often lacking. Herein, we show how an enantiopure anion enforces a chiral conformation onto a catalytically relevant achiral cation. Specifically, we use vibrational circular dichroism (VCD) spectroscopy to monitor the transmission of stereochemical information from a chiral phosphate anion to a flexible manganese(III)-salen cation. We show that VCD can be used to study solvent effects and that the obtained chiroptical data directly and quantitatively correlate with the experimentally observed enantioselectivity in an asymmetric olefin epoxidation reaction. [ABSTRACT FROM AUTHOR]

IR and vibrational circular dichroism (VCD) spectra of a chiral amine-borane in solution are investigated. By comparison of experimental and calculated spectra, unique VCD spectral signatures, which can be attributed to the formation of dihydrogen-bonded dimers in solution, are identified for the first time. These VCD features are highly sensitive to the specific dihydrogen-bonding topologies utilized by the chiral amine-borane subunits and thus provide direct structural information of these dihydrogen-bonded species in solution. Differences in the dihydrogen binding arrangements in solution and in solid state are also revealed. [ABSTRACT FROM AUTHOR]

Hand‐me‐down chirality: Chirality transfer from methyl lactate to ammonia has been investigated and the mirror‐imaged vibrational circular dichroism (VCD) spectra of a pair of enantiomers of a flexible chiral molecular complex are presented. The distinct VCD spectral pattern provides decisive evidence for the existence of two dominant and subtly different conformers of the complex. [ABSTRACT FROM AUTHOR]

A correction regarding the configuration of maximiscin under the experimental conditions employed for vibrational circular dichroism (VCD) spectroscopy is presented.

Chirality transfer from chiral to achiral molecules can occur through hydrogen‐bonding interactions. In their Communication on page 2073 ff., Y. Xu and C. Merten use matrix‐isolation vibrational circular dichroism spectroscopy to measure the spectral signatures of chirality transfer from methyl lactate to ammonia, data which cannot be obtained in solution owing to the immediate protonation of ammonia (graphic by W. Jäger). [ABSTRACT FROM AUTHOR]