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Chiroptical spectroscopy exploring the interaction of matter with polarized light provides many tools for molecular structure and interaction studies. Here, some recent discoveries are reviewed, primarily in the field of vibrational optical activity. Technological advances results in the development of more sensitive vibrational circular dichroism (VCD), Raman optical activity (ROA) or circular polarized luminescence (CPL) spectrometers. Significant contributions to the field also come from the light scattering and electronic structure theories, and their implementation in computer systems. Finally, new chiroptical phenomena have been observed, such as enhanced circular dichroism of biopolymers (protein fibrils, nucleic acids), plasmonic and resonance chirality‐transfer ROA experiments. Some of them are not yet understood or attributed to instrumental artifacts so far. Nevertheless, these unknown territories also indicate the vast potential of the chiroptical spectroscopy, and their investigation is even more challenging. Chiroptical spectroscopy: Chiroptical spectroscopy and vibrational optical activity developed into many branches. The figure displays one example which is the investigation of complex‐solute chirality transfer. In the review, some selected recent discoveries are listed that are sought to provide an historical context along with a future outlook.

Amyloid fibrils are supramolecular systems showing distinct chirality at different levels of their complex multilayered architectures. Due to the regular long‐range chiral organization, amyloid fibrils exhibit the most intense Vibrational Optical Activity (VOA) signal observed up to now, making VOA techniques: Vibrational Circular Dichroism (VCD) and Raman Optical Activity (ROA) very promising tools to explore their structures, handedness and intricate polymorphism. This concept article reviews up‐to‐date experimental studies on VOA applications to investigate amyloid fibrils highlighting its future potential in analyzing of these unique supramolecular systems, in particular in the context of biomedicine and nanotechnology. Exceptional enhancement of Vibrational Optical Activity (VOA) for amyloid fibrils makes it a highly promising tool for research on the structure, polymorphism, and chirality of their multi‐layered architectures. This concept paper discusses current applications of VOA in the analysis of proteinaceous fibrils and outlines future possibilities of VOA for fibril characteristics, particularly in the fields of biomedicine and nanomaterials.

We experimentally investigated remotely excited Raman optical activity (ROA) using propagating surface plasmons in chiral Ag nanowires. Using chiral fmoc-glycyl-glycine-OH (FGGO) molecules, we first studied the local surface plasmon-enhanced ROA. We found that the Raman intensity can be excited by left- and right-circularly polarized lights and that the circular intensity difference (CID) can be significantly enhanced. Second, by selecting vibrational modes with large Raman and ROA intensities that are not influenced by chemical enhancements, we studied remotely excited ROA imaging and the CID of FGGO molecules by propagating a plasmonic waveguide using Ag chiral nanostructures. When laser light was radiated on one of the Ag terminals, the measured CID of the FGG at the other terminal showed little change compared to the local excited CID. Meanwhile, when the laser light was radiated on the Ag nanowires (not on the terminals) and was coupled to the nearby nanoantenna, the CID of the ROA could be manipulated by altering the coupling angle between the Ag nanowires. To directly demonstrate the propagation of ROA along the nanowire and its remote detection, we also measured the remotely excited ROA spectra. Our experimental method has the potential to remotely determine the chirality of molecular structures and the absolute configuration or conformation of a chiral live cell. Chiral studies: Plasmonic enhancement Researchers in China have developed an optical technique for probing the chirality of molecular structures. Mengtao Sun and co-workers enhanced the strength of Raman measurements by using silver chiral nanowires as plasmonic waveguides. Such measurements, which determine the differences in Raman spectra excited by left- and right-handed circularly polarized light, can then be used to ascertain the chirality and conformation of the sample. A further benefit of this approach is that the use of nanowires allows the excitation and detection to be performed remotely. In their initial studies, the researchers studied a sample of chiral fmoc-glycyl-glycine-OH molecules, but say that the approach also suits use with living cells.

The concept of chirality dates back to 1848, when Pasteur manually separated left-handed from right-handed sodium ammonium tartrate crystals 1 . Crystallization is still an important means for separating chiral molecules into their two different mirror-image isomers (enantiomers) 2 , yet remains poorly understood 3 . For example, there are no firm rules to predict whether a particular pair of chiral partners will follow the behaviour of the vast majority of chiral molecules and crystallize together as racemic crystals 4 , or as separate enantiomers. A somewhat simpler and more tractable version of this phenomenon is crystallization in two dimensions, such as the formation of surface structures by adsorbed molecules. The relatively simple spatial molecular arrangement of these systems makes it easier to study the effects of specific chiral interactions 5 ; moreover, chiral assembly and recognition processes can be observed directly and with molecular resolution using scanning tunnelling microscopy 6 , 7 , 8 , 9 . The enantioseparation of chiral molecules in two dimensions is expected to occur more readily because planar confinement excludes some bulk crystal symmetry elements and enhances chiral interactions 10 , 11 ; however, many surface structures have been found to be racemic 12 , 13 , 14 , 15 , 16 , 17 , 18 . Here we show that the chiral hydrocarbon heptahelicene on a Cu(111) surface does not undergo two-dimensional spontaneous resolution into enantiomers 19 , but still shows enantiomorphism on a mesoscopic length scale that is readily amplified. That is, we observe formation of racemic heptahelicene domains with non-superimposable mirror-like lattice structures, with a small excess of one of the heptahelicene enantiomers suppressing the formation of one domain type. Similar to the induction of homochirality in achiral enantiomorphous monolayers 20 by a chiral modifier, a small enantiomeric excess suffices to ensure that the entire molecular monolayer consists of domains having only one of two possible, non-superimposable, mirror-like lattice structures.

The cover feature image shows measurement of Raman optical activity spectra, which provide extended information about molecular behavior in solutions. If coupled with multi‐scale density functional theory and molecular dynamics computations, whole potential energy maps can be deduced from the spectra. The maps can serve, for example, to verify or improve common force fields. For glutathione, a limited effect of pH on the backbone conformation was found. More information can be found in the Research Article by Petr Bouř and co‐workers.

The optical purity of a chiral sample is of particular importance to the analytical chemistry and pharmaceutical industries. In recent years, the vibrational optical activity (VOA) has become established as a sensitive and nondestructive technique for the analysis of chiral molecules in solution. However, the relatively limited accuracy in the range of about 1–2% reported in published papers and the relatively small spread of experimental facilities to date have meant that vibrational spectroscopy has not been considered a common method for determining enantiomeric excess. In this paper, we attempt to describe, in detail, a methodology for the determination of enantiomeric excess using Raman optical activity (ROA). This method achieved an accuracy of 0.05% for neat α-pinene and 0.22% for alanine aqueous solution, after less than 6 h of signal accumulation for each enantiomeric mixture, which we believe is the best result achieved to date using vibrational optical activity techniques. An algorithm for the elimination of systematic errors (polarization artifacts) is proposed, and the importance of normalizing ROA spectra to correct for fluctuations in excitation power is established. Results comparable to those obtained with routinely used chemometric analysis by the partial least squares (PLS) method were obtained. These findings show the great potential of ROA spectroscopy for the quantitative analysis of enantiomeric mixtures.

Chirality plays a crucial role in drug discovery and development. As a result, a significant number of commercially available drugs are structurally dissymmetric and enantiomerically pure. The determination of the exact 3D structure of drug candidates is, consequently, of paramount importance for the pharmaceutical industry in different stages of the discovery pipeline. Traditionally the assignment of the absolute configuration of druggable molecules has been carried out by means of X-ray crystallography. Nevertheless, not all molecules are suitable for single-crystal growing. Additionally, valuable information about the conformational dynamics of drug candidates is lost in the solid state. As an alternative, vibrational optical activity (VOA) methods have emerged as powerful tools to assess the stereochemistry of drug molecules directly in solution. These methods include vibrational circular dichroism (VCD) and Raman optical activity (ROA). Despite their potential, VCD and ROA are still unheard of to many organic and medicinal chemists. Therefore, the present review aims at highlighting the recent use of VOA methods for the assignment of the absolute configuration of chiral small-molecule drugs, as well as for the structural analysis of biologics of pharmaceutical interest. A brief introduction on VCD and ROA theory and the best experimental practices for using these methods will be provided along with selected representative examples over the last five years. As VCD and ROA are commonly used in combination with quantum calculations, some guidelines will also be presented for the reliable simulation of chiroptical spectra. Special attention will be paid to the complementarity of VCD and ROA to unambiguously assess the stereochemical properties of pharmaceuticals.

Cellulose Nanocrystals The cover page illustrates cellulose nanocrystals extracted from trees, symbolizing nature's contribution to advanced materials. These nanocrystals align to form stratified thin films of varying thickness, each displaying vibrant, tunable colors. The artwork visually conveys the study's focus on environmentally friendly, optically active coatings, emphasizing the elegance and scalability of cellulose‐based materials for innovative applications. More details can be found in article 2400608 by Youssef Habibi and co‐workers.

Nature's most brilliant hues arise from the interaction of light with multilayered‐ structures of aligned building blocks. Mimicking this hierarchical organization in highly‐ordered thin films of liquid crystalline species has attracted increasing attention for potential applications in sensors and optical switching displays. Due to its intriguing ability to organize into optically active materials, cellulose nanocrystals (CNCs) are attracting a strong interest in the scientific community. This study demonstrates that the shear‐driven convective assembly technique can be used to stratify in a controlled fashion highly ordered multilayers of rod‐like CNC embedded in a protective hydrophobic polymer matrix leading to optically active thin films. The films remain fully transparent even after stratifying 50 layers. Atomic force microscopy analysis reveals that over 87% of the CNCs in the upper layer aligned within ±20° of the withdrawal direction. Notably, the stratification does not disrupt the organization of the underlying layers. The films exhibit strong selective reflections with uniform and intense colors, dependent on the number of stratified layers. This scalable appraoch enables precise control over the optical characteristics of CNC‐polymer composite films, presenting opportunities for environmentally friendly applications in pigment‐free coatings, security papers, and optical devices. Explore shear‐driven convective assembly's role in creating optically active thin films. Highly ordered multilayers of cellulose nanocrystals (CNCs) in a hydrophobic polymer matrix are achieved, offering precise control. The resulting films' optical activity, modulated by layer count, presents possibilities for pigment‐free coatings, security papers, and optical devices in this scalable, green technology.

We discuss optical chirality in different types of gyrotropic media. Our analysis is based on the formalism of nongeometric symmetries of Maxwell's equations in vacuum generalized to material media with given constituent relations. This approach enables us to directly derive conservation laws related to nongeometric symmetries. For isotropic chiral media, we demonstrate that like a free electromagnetic field, both duality and helicity generators belong to the basis set of nongeometric symmetries that guarantees the conservation of optical chirality. In gyrotropic crystals, which exhibit natural optical activity, the situation is quite different from the case of isotropic media. For light propagating along a certain crystallographic direction, there arises two distinct cases: (1) the duality is broken but the helicity is preserved, or (2) only the duality symmetry survives. We show that the existence of one of these symmetries (duality or helicity) is enough to define optical chirality. In addition, we present examples of low-symmetry media, where optical chirality cannot be defined.