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International audience; Straightforward enantioselective analytical methods are very important for drug safety, considering that in certain cases one of the two enantiomers of a chiral molecule might be harmful for humans. In this work, we propose a simple system for the direct and easy read-out of the enantiomeric excess of 3,4-dihydroxyphenylalanine (DOPA) as a model analyte. A conducting oligomer, i.e. oligo-(3,3′-dibenzothiophene), bearing inherently chiral features, is electrogenerated on a polypyrrole film. The resulting freestanding hybrid material is used as a wireless enantioselective actuator in a bipolar electrochemical cell. Combining in a single setup two individual actuators with opposite chiral features allows a direct visual read-out of enantiomeric excess, as the bending amplitude of each of the two actuators is directly correlated with the concentration of the corresponding stereoisomer of the analyte. Optimization of the experimental parameters results in efficient bending, giving access to the percentage values of the enantiomeric excess in mixtures containing different ratios of the antipodes, thus opening the way to potential applications for chiral in situ analysis.

β-Cyclodextrin (β-CD) modified silver nanoparticles (AgNPs), denoted as β-CD/AgNPs, were prepared by a simple one-pot method. Due to the inherent chirality of β-CD, the developed β-CD/AgNPs exhibited higher affinity toward l-tyrosine (l-Tyr) than d-tyrosine (d-Tyr), leading to serious aggregation of AgNPs in the presence of l-Tyr. Consequently, the l-Tyr induced aggregation of AgNPs can result in signal amplification in the differential pulse voltammograms (DPVs) of l-Tyr, which can be applied for the electrochemical chiral discrimination of the Tyr enantiomers. Other chiral amino acids including tryptophan and phenylalanine can also be successfully discriminated with the β-CD/AgNPs, suggesting high universality of the developed chiral sensor.

In this work, we proposed one simple and effective chiral-sensing method for the discrimination of carnitine enantiomers. The gold nanorods (AuNRs) were used as colorimetric probes to recognize carnitine enantiomers in this method. l-Carnitine can induce rapidly the blue-to-gray change of AuNR solution color, whereas d-carnitine cannot induce the obvious change of the color. Based on this distinct difference of color, a visual method for recognition of carnitine enantiomers was suggested. This method has been applied to detect the enantiometric excess of l-carnitine in the range of − 100~100%. The presented chiral measurement can be performed with a simple ultraviolet-visible spectrometer and even the naked eyes. In this method, AuNRs need no modification with chiral molecule, and the chiral recognition is based on the inherent chirality of AuNRs. This new method opens up possibility for fast and easy assay of carnitine enantiomers.

Chiral organic-inorganic perovskites (COIPs) have recently attracted increasing interest due to their unique inherent chirality and potential applications in next-generation optoelectronic and spintronic devices. However, COIP ferroelectrics are very sparse. In this work, for the first time, we present the nickel-nitrite ABX3 COIP ferroelectrics, [(R and S)-N-fluoromethyl-3-quinuclidinol]Ni(NO2)3 ([(R and S)-FMQ]Ni(NO2)3), where the X-site is the rarely seen NO2- bridging ligand. [(R and S)-FMQ]Ni(NO2)3 display mirror-relationship in the crystal structure and vibrational circular dichroism signal. It is emphasized that [(R and S)-FMQ]Ni(NO2)3 show splendid ferroelectricity with both an extremely high phase-transition point of 405 K and a spontaneous polarization of 12 μC/cm2. To our knowledge, [(R and S)-FMQ]Ni(NO2)3 are the first examples of nickel-nitrite based COIP ferroelectrics. This finding expands the COIP family and throws light on exploration of high-performance COIP ferroelectrics.

This tutorial provides a comprehensive description of the origin of chiroptical properties of supramolecular and plasmonic assemblies in the UV–visible region of the electromagnetic spectrum. The photophysical concepts essential for understanding chiroptical signatures are presented in the first section. Just as the oscillator strength (a positive quantity) is related to absorption, the rotational strength (either a positive or a negative quantity) defines the emergence of chiroptical signatures in molecular/plasmonic systems. In supramolecular systems, induced circular dichroism (ICD) originates through the off-resonance coupling of transition dipoles in chiral inclusion complexes, while exciton coupled circular dichroism (ECD) originates through the on-resonance exciton coupling of transition dipoles in chiral assemblies resulting in the formation of a bisignated CD signal. In bisignated ECD spectra, the sign of the couplet is determined not only by the handedness of chiral supramolecular assemblies, but also by the sign of the interaction energy between transition dipoles. Plasmonic chirality is briefly addressed in the last section, focusing on inherent chirality, induced chirality, and surface plasmon-coupled circular dichroism (SP-CD). The oscillator strength is of the order of 1 in molecular systems, while it becomes very large (104–105) in plasmonic systems due to the collective plasmonic excitations, resulting in intense CD signals, which can be exploited for the design of plasmonic metamaterial platforms for chiral sensing applications.

An evidence for the formation of a rare meta-metalated inherently chiral calix[4]arene is described. Our strategy involved using a mesoionic carbene to direct C–H activation, but proved to form an unexpectedly unstable intermediate that was identified through high-resolution mass spectrometry. On route to our target, a new optimized method to mononitrocalix[4]arenes was developed, including optimized and high yielding transformations to azide and 1,2,3-triazole derivatives which may have application in other areas of research.

Nitroso-ene (NE) reactions have been adapted in the construction of nitrogen-containing motifs in many biologically interesting compounds. The transient and highly reactive “nitroso” species remains a challenge for designing stereocontrolled syntheses. Although chiral auxiliary-based method has been developed to achieve high diastereoselectivity, the use of the inherent chirality of the nitroso compound for stereochemical control remains underdeveloped. We chose the formation of a γ-lactam via a NE cyclization as a basis to study the applicable principles for future asymmetric syntheses. The selected examples presented herein reveal that the intramolecular hydrogen bond would provide conformational restraint to facilitate excellent facial selectivity in the NE reaction via a chair-like transition state. The sterically bulky amino group also provides excellent stereochemical control possibly through steric repulsion. The following transformations led to a key intermediate (Ohfune's lactone) in the preparation of manzacidins A and C and thus constitutes a formal synthesis.

The coupling between molecular conformation and chirality is a cornerstone in the construction of supramolecular helical structures of small molecules across various length scales. Inspired by biological systems, conformational preselection and control in artificial helical molecules, polymers, and aggregates has guided various applications in optics, photonics, and chiral sorting among others, which are frequently based on an inherent chirality amplification through processes such as templating and self-assembly. The so-called B4 nano- or microfilament phase formed by some bent-shaped molecules is an exemplary case for such chirality amplification across length scales, best illustrated by the formation of distinct nano- or microscopic chiral morphologies controlled by molecular conformation. Introduction of one or more chiral centers in the aliphatic side chains led to the discovery of homochiral helical nanofilament, helical microfilament, and heliconical-layered nanocylinder morphologies. Herein, we demonstrate how a priori calculations of the molecular conformation affected by chiral side chains are used to design bent-shaped molecules that self-assemble into chiral nano- and microfilament as well as nanocylinder conglomerates despite the homochiral nature of the molecules. Furthermore, relocation of the chiral center leads to formation of helical as well as flat nanoribbons. Self-consistent data sets from polarized optical as well as scanning and transmission electron microscopy, thin-film and solution circular dichroism spectropolarimetry, and synchrotron-based X-ray diffraction experiments support the progressive and predictable change in morphology controlled by structural changes in the chiral side chains. The formation of these morphologies is discussed in light of the diminishing effects of molecular chirality as the chain length increases or as the chiral center is moved away from the core-chain juncture. The type of phase (B1-columnar or B4) and morphology of the nano- or microfilaments generated can further be controlled by sample treatment conditions such as by the cooling rate from the isotropic melt or by the presence of an organic solvent in the ensuing colloidal dispersions. We show that these nanoscale morphologies can then organize into a wealth of two- and three-dimensional shapes and structures ranging from flower blossoms to fiber mats formed by intersecting flat nanoribbons.

Cyclodextrins (CD) are cyclic oligosaccharides consisting of ?-D-glucopyranosyl units linked through 1,4-linkages, which are obtained from enzymatic degradation of starch. The co-existence of hydrophilic and hydrophobic regions in the same structure makes these macrocycles extremely versatile as complexing host with application in food, cosmetics, environmental, agriculture, textile, pharmaceutical and chemical industries. Due to their inherent chirality, CDs have been also successfully used as chiral selectors in enantioseparation science, in particular for capillary electrophoresis (CE) enantioseparations. In the last decades, multidisciplinary approaches based on CE, NMR spectroscopy, X-ray crystallography, microcalorimetry, and molecular modeling have shed light on some aspects of recognition mechanisms underlying enantiodiscrimination. With the ever growing improvement of computer facilities, hardware and software, computational techniques have become a useful tool to model at molecular level the dynamics of diastereomeric associate formation to sample low-energy conformations, the binding energies between the enantiomer and the CD, and to profile noncovalent interactions contributing to the stability of CD/enantiomer association. On this basis, the aim of this review is to provide the reader with a critical overview on the applications of CDs in CE. In particular, the contemporary theory of the electrophoretic technique and the main structural features of CDs are described, with a specific focus on techniques, methods and approaches to model CE enantioseparations promoted by native and substituted CDs. A systematic compilation of all published literature has not been attempted.

As the highest form of molecular recognition, the chiral molecular recognition is the most difficult measurements. Herein, a disposable dual-signal enantioselective platform was fabricated based on stereoscopic porous chiral carbon nanotubes hydrogel modified screen printed electrode. This kind of chiral hydrogel was prepared by a simple heating method with l-cysteine and chiral single-walled carbon nanotubes of chirality (6,5), and its dispersion and morphology were characterized by several techniques including scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The stereogenic chiral interface was successfully employed to discriminate mandelic acid enantiomers via both oxidation peak intensity and peak potential value of cyclic voltammetry. The chiral recognition mechanism was discussed specifically, which resulted from the formation of an efficient three-dimensional chiral nanospace. The inherent chirality of chiral carbon nanotubes hydrogel, together with their orderly spatial arrangement, can significantly improve the efficiency of chiral recognition compared with traditional electrochemical chiral sensors. As a novel chiral sensing interface, such chiral carbon nanotubes hydrogel was simple to prepare, fast to operate, with good sensitivity and excellent stability for the construction of efficient and practical electrochemical chiral sensors.

2,2'-Bis[2-(5,2'-bithienyl)]-3,3'-bithianaphthene (1) is the progenitor of a class of C2 symmetric thiophene-based electroactive monomers that, when electrooxidized in the enantiomerically pure form, produce inherently chiral films endowed with outstanding electrochemical enantiorecognition properties. The enantioselective high-performance liquid chromatography (HPLC) is the only approach used so far to resolve the racemic form of 1 into enantiomers. In this work, an improved HPLC method for multimilligram enantiomer production is presented. Key factors controlling the enantioseparation, such as mobile phase composition and column temperature, were identified using a 100 × 4.6 mm i.d. Chiralpak IB-3 column and subsequently scaled up to a 250 × 10.0 mm i.d. Chiralpak IB column. In the optimized semipreparative conditions, about 34 mg of pure (P) and (M) enantiomers per hour could be produced.

Enantioselective electroanalysis, which aims to discriminate the enantiomers of electroactive chiral probes in terms of potential difference, is a very attractive goal. To achieve this, its implementation is being studied for various "inherently chiral" selectors, either at the electrode surface or in the medium, yielding outstanding performance. In this context, the new inherently chiral monomer Naph2T4 is introduced, based on a biaromatic atropisomeric core, which is advantageously obtainable in enantiopure form without HPLC separation steps by a synthetic route hinging on enantiopure 2,2&rsquo, dibromo-1,1&rsquo, binaphthalenes. The antipodes of the new inherently chiral monomer can be easily electrooligomerized, yielding inherently chiral electrode surfaces that perform well in both cyclic voltammetry (CV) enantiodiscrimination tests with pharmaceutically interesting molecules and in magnetoelectrochemistry experiments.

Biological systems usually respond differently to enantiomers of a chiral molecule due to the inherent chirality of the active receptor sites of enzymes in nature [...]

Shikimic acid is a natural product of industrial importance utilized as a precursor of the antiviral Tamiflu. It is nowadays produced in multihundred ton amounts from the extraction of star anise ( Illicium verum) or by fermentation processes. Apart from the production of Tamiflu, shikimic acid has gathered particular notoriety as its useful carbon backbone and inherent chirality provide extensive use as a versatile chiral precursor in organic synthesis. This review provides an overview of the main synthetic and microbial methods for production of shikimic acid and highlights selected methods for isolation from available plant sources. Furthermore, we have attempted to demonstrate the synthetic utility of shikimic acid by covering the most important synthetic modifications and related applications, namely, synthesis of Tamiflu and derivatives, synthetic manipulations of the main functional groups, and its use as biorenewable material and in total synthesis. Given its rich chemistry and availability, shikimic acid is undoubtedly a promising platform molecule for further exploration. Therefore, in the end, we outline some challenges and promising future directions.

Two new inherently chiral oligothiophenes characterized by the atropisomeric 3,3'-bithianaphtene scaffold functionalized with fused ring bithiophene derivatives, namely 4H-cyclopenta[2,1-b3:4b']dithiophene (CPDT) and dithieno[3,3-b:2',3'-d]pyrrole (DTP), were synthesized. The racemates were fully characterized and resolved into antipodes by enantioselective HPLC. The enantiomers were analyzed through different chiroptical techniques: electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) were employed to attribute the absolute configuration (AC). Comparison of experimental and calculated VCD spectra confirmed the DFT calculated conformational characteristics. The compound functionalized with two CPDT units was oxidized with FeCl3 , and ECD and CPL of the resulting material were measured. Circularly polarized luminescence (CPL) was measured to verify if inherently chiral oligothiophenes could be promising systems for chiral photonics applications.

2,3-bis(diphenylphosphino)butane enantiomers (chiraphos, L) used as chiral auxiliaries results in the preferential formation of an unprecedented Au24 framework with inherent chirality. The crystal structure of [Au24 L6 Cl4 ]2+ (1) has a square antiprism-like octagold core twinned by two helicene-like hexagold motifs, where the inherent chirality is associated with the helical arrangement. The clusters carrying (R,R)- and (S,S)- diphosphines had right- and left-handed strands, respectively. Circular dichroism spectra showed peaks in the visible to near-IR region, some of which did not coincide with absorption bands, suggesting the enantiomeric Au24 frameworks possess unique chiroptical properties. The Au24 frameworks were thermally robust, which could be attributed to the superatomic concept (18 e- system) and the steric constraint effects of the bridging ligand units.

A dialkyl-1,1′-bibenzimidazolium salt, consisting of an atropisomeric dication (i.e. featuring a stereogenic axis and thus “inherently chiral”) and an achiral counteranion, is employed as a chiral additive in three commercial ionic liquids, providing successful enantiodiscrimination in voltammetry experiments on screen-printed electrodes (SPEs) with the enantiomers of N,N′-dimethyl-1-ferrocenyl-ethylamine as model chiral probes. Significant differences in redox potentials are observed for the probe enantiomers despite the low concentration (0.01 M) of the chiral additive. The nature of the achiral ionic liquid in which the additive is employed significantly affects the peak potentials and potential differences, but does not alter the enantiomer sequence. Keywords: Chiral electrochemistry and electroanalysis, Ionic liquids, Chiral additives, Inherent chirality, Enantiorecognition

Robust atomic-to-meso-scale chirality is now observed in the one-dimensional form of tellurium. This enables a large and counter-intuitive circular-polarization dependent second harmonic generation response above 0.2 which is not present in two-dimensional tellurium. Orientation variations in 1D tellurium nanowires obtained by four-dimensional scanning transmission electron microscopy (4D-STEM) and their correlation with unconventional non-linear optical properties by second harmonic generation circular dichroism (SHG-CD) uncovers an unexpected circular-polarization dependent SHG response from 1D nanowire bundles – an order-of-magnitude higher than in single-crystal two-dimensional tellurium structures – suggesting the atomic- and meso-scale crystalline structure of the 1D material possesses an inherent chirality not present in its 2D form; and which is strong enough to manifest even in the aggregate non-linear optical (NLO) properties of aggregates.

Herein we report a peculiar organocatalyzed domino-reaction on the carbapenem core structure. As previously reported, 30 mol% of proline yields diazabicyclo[4.2.1]nonane analogues, while we currently report the formation of novel 1,4-diazepin-5-ones from the same starting material in the presence of 100 mol% proline. The inherent chirality of the starting material led to the stereochemical preference of the products with excellent diastereoselectivity (>99 : 1). The diazepinone products were confirmed using X-ray diffraction and 2D-NMR structure elucidation. A plausible mechanism of the re-arrangement, involving an unactivated retro-Dieckmann condensation, is also presented.

Summary Electronically conducting polymer (ECP) and oligomer films are one of the most popular classes of artificial materials for electrode surface modification and nanostructured electroactive film preparation for use as active layers in advanced sensing electrochemical devices. They can act as both receptors and transducers on account of their electroactivity and easy derivatization in a virtually unlimited structure range, and typically have low cost and easy processability. The tailoring possibilities of ECP films also make them attractive selector candidates to achieve the superior level of molecular recognition represented by enantioselective electroanalysis, implying to discriminate between specular images of a chiral molecule. This superior recognition level requires to endow them with chirality and to employ them as enantiopure films, which can be made along different strategies, with different implications in terms of enantioselectivity, kind of transduction of the recognition event, specificity vs general applicability, preparation difficulty, robustness, etc. In this context an outstanding tool is provided by the “inherent chirality” strategy.

This article looks at the chemistry surrounding the concept of inherently chiral calixarenes (ICCs), whose synthesis and application have only recently being realised. One challenge in the area of ICC chemistry is the sheer breadth and scope for installing different aspects of inherent chirality. The aim of this article is not to cover every known method, but rather to give the reader an overview of the main themes that have emerged in this area, including more recent additions to the literature. This overview will also touch on the very limited reports on the applications of ICCs which give a glimpse into the potential these compounds may have in future studies.

In pursuit of nonracemic, inherently chiral calix[4]arenes, we describe herein the application of a chiral tert-butyl sulfoxide in asymmetrically directing ortholithiation on a calix[4]arene. We demonstrate good diastereoselectivity (dr = 95:5) in the reaction, and also provide proof of the major diastereomer through single-crystal X-ray diffraction.

A linearly linked triscalix[4]arene, in which each calix[4]arene unit possesses both axial chirality and inherent chirality, was synthesized by repeated use of two stereoselective Williamson etherification on calix[4]arene. In the crystal lattice of the biscalix[4]arene intermediate, there are interesting alternate layers of biscalixarene molecules and solvent molecules in the ab plane.

Hybrid materials resulting from the combination of Deep Eutectic Systems (DES) with well-known encapsulating agents like β-cyclodextrin (βCD) can open up new possibilities in the design of novel drug delivery systems or chiral-recognizing platforms. Here, 1:1 inclusion complexes of βCD and the tricyclic drugs amitriptyline (AMT) and cyclobenzaprine (CBZ) are studied in DES choline chloride:urea (reline) using a combination of NMR experiments. 1H complexation-induced chemical shift and intermolecular host-guest NOEs in the rotating frame (ROESY) confirm genuine drug encapsulation, and diffusion and relaxation measurements are used to study the dynamics of the guest-host inclusion complexes at the molecular level. Given the inherent chirality of AMT and CBZ, 13C NMR spectra unambiguously indicate the formation of diastereomeric inclusion complexes, demonstrating for the first time the retained enantiorecognition ability of βCD in DES. The proposed supramolecular systems combine then effectively the properties of DES and CDs.

The synthesis of a new type of chiral and dynamic nonplanar aromatics containing a combination of fused perylene‐based coronenes and helicenes is reported. Either one or two helicene moieties were fused to the bay regions of an extended perylene core. The target compounds contain either identical or two different helicene building blocks. The combination with two helicene units leads to six different isomers, including two pairs of enantiomers and two meso forms. The experimental determination of the isomerization barriers the corresponding double [5]‐helicenes revealed activation energies of E a=24.81 and 25.38 kcal mol−1, which is slightly above the barrier of the parent [5]‐helicene. Resolution of all possible regio‐ and stereoisomers allowed for the systematic investigation of the chiroptical properties. They revealed remarkable dissymmetry factors Ig abs I of up to 1.2×10−2, which mirror the synergy between the strong absorbing perylenes and the inherent chirality of helicenes., Dynamic helicenes: Double helicenes with a coronene core were synthesized. Temperature‐dependent NMR experiments and DFT calculations shine light on the inversion process of the helicenes and revealed a two‐step isomerization pathway. The isolated enantiomers exhibit remarkable optical and chiroptical properties.

Solubilized fullerene derivatives have revolutionized the development of organic photovoltaic devices, acting as excellent electron acceptors. The addition of solubilizing addends to the fullerene cage results in a large number of isomers, which are generally employed as isomeric mixtures. Moreover, a significant number of these isomers are chiral, which further adds to the isomeric complexity. The opportunities presented by single-isomer, and particularly single-enantiomer, fullerenes in organic electronic materials and devices are poorly understood however. Here, ten pairs of enantiomers are separated from the 19 structural isomers of bis[60]phenyl-C61-butyric acid methyl ester, using them to elucidate important chiroptical relationships and demonstrating their application to a circularly polarized light (CPL)-detecting device. Larger chiroptical responses are found, occurring through the inherent chirality of the fullerene. When used in a single-enantiomer organic field-effect transistor, the potential to discriminate CPL with a fast light response time and with a very high photocurrent dissymmetry factor (gph = 1.27 ± 0.06) is demonstrated. This study thus provides key strategies to design fullerenes with large chiroptical responses for use as chiral components of organic electronic devices. It is anticipated that this data will position chiral fullerenes as an exciting material class for the growing field of chiral electronic technologies.

As the first of a series of molecular solenoids, two classes of dithia[7]helicenes (coil-shaped molecules with sulfur atoms integrated within a helical conjugated system) have been devised and synthesized to be used in molecular electronics. We used a modular assembly of fragments using Pd catalyzed coupling reactions and a final photocyclization step for the syntheses; this strategy gave us straightforward access to helicenes bearing thiophene end rings with either exo or endo topologies. Unequivocal structural characterization was carried out by X-ray crystallography. In the solid state, their crystal architectures show little similarities; both can be considered an ensemble of heterochiral dimers (P/M) that are themselves very different in nature in light of their main pairing interactions. On a gold surface, the effect of the sulfur atom is to strengthen their binding to the electrodes, as manifested by scanning tunneling microscopy (STM) performed at room temperature. Different coating patterns were observed for each class of molecule, although the most prominent finding is that we could see resolved STM images of a single molecule, with a full display of its inherent chirality under room temperature conditions. Financial support by the Spanish Ministry of Economy and Competitiveness (MAT2016-78625-C2-1-P and MAT2016-78625-C2-2-P), the Generalitat Valenciana (PROMETEO/2017/139 and CDEIGENT/2018/028), and finally the University of Alicante (VIGROB-285 and 188) is gratefully acknowledged.

Dirhodium complexes bearing N-substituted chiral amino acid ligands are investigated. These complexes have an unusual twisted paddlewheel structure, showing inherent chirality. We would like to demonstrate that parallel application of chiroptical spectroscopic methods (ECD and VCD) and NMR spectroscopy combined with quantum chemical calculations constitutes a powerful tool to determine the configuration of the complexes unequivocally. Two chiroptical methods are needed to determine the absolute configuration: ECD for the coordinated nitrogen atom and VCD for the rhodium core. A quick to use NMR method is also presented: Upon the coordination of small molecules in the axial position, the relative configuration of both the rhodium core and the nitrogen atom can be determined simultaneously by studying spatial proximities provided by 1D NOE spectra.

Aminomethylation reactions between chiral amino compounds (S)-(-)-1-phenylethylamine and l-proline with tetranonylresorcinarene and tetra-(4-hydroxyphenyl)resorcinarene in presence of formaldehyde were studied. The reaction between l-proline and resorcinarenes generated regioselectively chiral tetra-Mannich bases, due to the molecular incorporation of the fragment of the chiral amino acid. On the other hand, tetranonylresorcinarene and (S)-(-)-1-phenylethylamine formed regio- and diasteroselectively chiral tetrabenzoxazines, both by chiral auxiliary functionalization and by the transformation of the molecular structure that confers inherent chirality. The products obtained were characterized using IR, 1H-NMR, 13C-NMR, COSY, HMQC, and HMBC techniques. The reaction of (S)-(-)-1-phenylethylamine with tetra-(4-hydroxyphenyl)resorcinarene did not proceed under the experimental conditions. Once the chiral aminomethylated tetra-(4-hydroxyphenyl)resorcinarene was obtained, the chemical modification of poly(GMA&ndash, co&ndash, EDMA) was studied, and the results showed an efficient incorporation of the aminomethylated compound. For the physical modification, chiral aminomethylated tetranonylresorcinarenes were employed, finding that the incorporation of modified resorcinarenes occurs, but with less efficiency than that observed using chemical modification. The modified polymers were characterized via FT-IR, scanning electron microscopy imaging, and elemental analysis. Finally, polymers modified with chiral resorcinarenes were used as sorbents in norepinephrine microextraction, for practical purposes, artificial urine was prepared and used. To perform the microextraction, the decision was made to use the modern rotating-disk sorptive extraction technique (RDSE), because of its analytical attributes as a green, or eco-friendly, technique. According to the results, the method preliminarily validated for the determination of norepinephrine in artificial urine shows that the modified polymer with chiral derivative of tetra-(4-hydroxyphenyl)resorcinarene worked effectively as a new sorbent phase for the quantitative microextraction of norepinephrine, exhibiting high stability and homogeneity of composition and structure within the working range.

A simple and reliable colorimetric method for visual differentiation between the S-citalopram and R-citalopram enantiomers in aqueous solution based on the inherent chirality of silver nanoparticles as a colorimetric probe was presented. Upon addition of (RS)-citalopram to a solution of silver nanoparticles, a color change from yellow to red can be seen and quantified by spectrophotometry, while no color change is found upon addition of S-CIT. Citalopram enantiomers were determined over a concentration range of 7.6 × 10−9 to 1.7 × 10−4 M with a detection limit of 3.0 × 10−9 M. The developed method showed good repeatability and linearity, as well as advantages such as low cost, simplicity, sensitivity, and high feasibility. More importantly silver nanoparticles selectively interacted with R-CIT from a solution of (RS)-CIT.

© 2016 American Chemical Society. We report the first hyperpolarizability of the [Au 20 (PP 3 ) 4 ]Cl 4 cluster (PP 3 : tris(2-(diphenylphosphino)ethyl)phosphine) using the Hyper-Rayleigh Scattering technique. This is the first determination of nonlinear optical properties of a phosphine-protected "superatomic" gold cluster. Weak contributions of multiphoton-excited fluorescence were observed in the spectral dispersion of the generated light upon excitation at 1300 and 1064 nm. The first hyperpolarizability of the intrinsically chiral cluster is weaker than that of thiolate-protected gold clusters of similar size and inherent chirality. ispartof: Industrial & Engineering Chemistry Research vol:55 issue:39 pages:10500-10506 status: published

Palladium–bis(oxazoline) complexes (Pd-BOX-A and Pd-BOX-B) were synthesized and characterized by 1H, 13C NMR, IR and elemental analysis. The molecular structures of the complexes were confirmed by single-crystal X-ray analysis. In both cases, the palladium center is coordinated by the nitrogen atoms of the two oxazoline rings and two chloride ligands in a distorted square planar geometry. Despite the fact that the bis(oxazoline) ligand is achiral, the asymmetrical substitution on the phenyl spacer and the rigid backbone of the complex Pd-BOX-A induce inherent chirality and the compound crystallizes as a racemic mixture. Both complexes were found to be highly effective catalysts for Suzuki–Miyaura, Mizoroki–Heck and Sonogashira cross-coupling reactions. They also show excellent catalytic activities toward carbonylative coupling reactions.

Five-membered thiazole-annelated subphthalocyanine derivatives have been prepared for the first time. Both regioisomers with C3 and C1 molecular symmetry have been isolated and optical resolution of C3 enantiomers was achieved. Heterocycle annelation resulted in red shifted long wave Q-band with regard to the unsubstituted subphthalocyanines, in the case of linear annelated compounds it is more red shifted (603, 615 nm) than the corresponding band in angular annelated derivatives (590, 594 nm). Analysis of fluorescence quantum yields revealed the heavy atom effect of bromine. Irrespective of the present bromine atom, all complexes were characterized by high singlet oxygen production with quantum yields ranging from 0.62 to 0.80. The HOMO and LUMO energy levels (DFT calculated and electrochemically determined) showed that frontier orbital energies can be effectively tuned by different type of annelation.

Triply periodic constant mean curvature surface structures have been discovered in a variety of biological and self-assembly systems. Among them, the single gyroid is of significant interest, because of its unique geometry, inherent chirality, and corresponding spectacular optical properties. Despite theoretical and experimental efforts on this structure, so far, limited progress has been made regarding the formation of the single-network structures and the structural relationships with the thermodynamically stable double networks. Herein, we report the electron microscopic observation and analysis on the interconversion between the single gyroid and double diamond structure in an amphiphilic ABC triblock terpolymer templated macroporous silica synthesis system with a solvent mixture of tetrahydrofuran and water. The two structures were interconnected by a “side-by-side” epitaxial relationship with rescaling of the unit cell. The single-network structure was formed via a new type of alternating gyroid und...

Since the first homochiral ferroelectric crystal Rochelle salt (NaKC4H4O6•4H2O) was discovered in 1921 by Valasek, the single-component homochiral organic molecular ferroelectrics still remain unexplored although a number of molecular ferroelectrics were discovered in the past decade. Here we present the first example of homochiral single component organic ferroelectric, nopinic acid, (2-hydroxy-6, 6-dimethyl bicycle [ 3 , 1 , 1 ] heptane-2-carboxylic acid), 1, which experiences a unique ferroelectric to ferroelectric phase transition around 161 K from space group C2 to P1. The heat anomaly, switchable dielectric and varied SHG responses dependence on temperatures directly confirm its reversible phase transition behavior. The further X-ray single crystal diffraction analysis indicates that with the temperature changes the relative displacement motions of H-proton caused the collective shift along the direction of double helical nopinic acid chains, and results the reversible phase transition. The piezo-response force microscopy (PFM) measurements on thin films of 1 probed and switched the local ferroelectric polarization at the nanoscale, and directly proved its ferroelectricity. Because of its inherent chirality, flexibility, environment-friendly, easy process ability, and room-temperature polarization switching, we believe these finding affords a new venue to explore for high performance ferroelectrics.

The new inherently chiral material shows outstanding chirality manifestations with chiral probes, as well as with circularly polarized light components and electron spins., Chiral oligothiophene monomers with C2 symmetry, based on 3,3′-bithiophene atropisomeric cores with high racemization barriers, have recently been shown to provide excellent chiral starting materials with high electroactivity for the easy preparation of enantiopure electroactive films endowed with powerful chirality manifestations. We now introduce an inherently chiral monomer based on a 2,2′-biindole core, as the prototype of a new inherently chiral monomer family, whose properties could be modulable through functionalization of the pyrrolic N atoms. By fast, regular electrooligomerization the new monomer yields inherently chiral films with high, reversible electroactivity and, above all, impressive enantioselectivity towards very different chiral probes, some of pharmaceutical interest, as general-scope electrode surfaces. Such results, while opening the way to a new, attractive inherently chiral selector class, nicely confirm the general validity of the inherent chirality strategy for chiral electrochemistry. Furthermore, the enantioselectivity of the new selectors not only holds with electroactive chiral probes, but also with circularly polarized light components as well as electron spins, resulting in good chiroptical and spin filter performances, which suggests fascinating correlations between the three contexts.

International audience; Cyclobis[n]helicenes (n = 3 or 5) are chiral D2-symmetric p-conjugated macrocycles with stable lemniscular, or figure-eight, shapes. The conformational analysis of five different cyclobis[n]helicenes revealed that these molecules can only exist as their lemniscular conformers with high barriers to enantiomerization (>200 kJ.mol-1). The enantiomers of a cyclobis[5]helicene were resolved by HPLC and their unusual chiroptical properties were attributed to the inherent chirality of their macrocyclic figure-eight.

In spite of the increasing fundamental and practical interest of electrochemistry in ionic liquids (ILs), exploration of chiral ionic liquids (CILs) in view of enantioselective electrochemistry and electroanalysis is surprisingly overdue. In this study a family of chiral ionic liquids (CILs) based on natural chiral building blocks, of easy synthesis, is detailedly characterized in terms of thermal and electrochemical properties, achieving valuable information about structure−property relationships on account of the systematicity of available family terms. Moreover, they are submitted to a series of chiral electroanalysis tests. Cyclic voltammetry in bulk CILs or with CIL as additives in a bulk achiral ionic liquid IL, shows small but statistically significant potential differences for the enantiomers of two quite different chiral probes, an interesting result since enantiodiscrimination in terms of potential differences in chiral voltammetry (more desirable respect to current differences) has been only seldom obtained so far. The present first example of enantioselective voltammetry in CIL media with stereocenters as localized chirality sources also offers an important and so far missing confirmation of the intrinsically superior level of the inherent chirality strategy, recently resulting in larger potential differences with the same protocols implemented in "inherently chiral" ionic liquid media. Furthermore, an alternative transduction mode, based on electrochemical impedance spectroscopy EIS, is proposed to effectively highlight the enantiodiscrimination ability of CIL media in analytical experiments.

Enzymes generally display strict stereospecificity and regioselectivity for their substrates. Here by using FAD-dependent human acetylpolyamine oxidase (APAO), human spermine (Spm) oxidase (SMOX) and yeast polyamine oxidase (Fms1), we demonstrate that these fundamental properties of the enzymes may be regulated using simple guide molecules, being either covalently attached to polyamines or used as a supplement to the substrate mixtures. APAO, which naturally metabolizes achiral N1-acetylated polyamines, displays aldehyde-controllable stereospecificity with chiral 1-methylated polyamines, like (R)- and (S)-1-methylspermidine (1,8-diamino-5-azanonane) (1-MeSpd). Among the novel N1-acyl derivatives of MeSpd, isonicotinic acid (P4) or benzoic acid (Bz) with (R)-MeSpd had Km of 3.6 ± 0.6/1.2 ± 0.7 µM and kcat of 5.2 ± 0.6/4.6 ± 0.7 s−1 respectively, while N1-AcSpd had Km 8.2 ± 0.4 µM and kcat 2.7 ± 0.0 s−1. On the contrary, corresponding (S)-MeSpd amides were practically inactive (kcat < 0.03 s−1) but they retained micromole level Km for APAO. SMOX did not metabolize any of the tested compounds (kcat < 0.05 s−1) that acted as non-competitive inhibitors having Ki ≥ 155 µM for SMOX. In addition, we tested (R,R)-1,12-bis-methylspermine (2,13-diamino-5,10-diazatetradecane) (R,R)-(Me2Spm) and (S,S)-Me2Spm as substrates for Fms1. Fms1 preferred (S,S)- to (R,R)-diastereoisomer, but with notably lower kcat in comparison with spermine. Interestingly, Fms1 was prone to aldehyde supplementation in its regioselectivity, i.e. the cleavage site of spermidine. Thus, aldehyde supplementation to generate aldimines or N-terminal substituents in polyamines, i.e. attachment of guide molecule, generates novel ligands with altered charge distribution changing the binding and catalytic properties with polyamine oxidases. This provides means for exploiting hidden capabilities of polyamine oxidases for controlling their regioselectivity and stereospecificity.

The helical stereomutation in the kinetically controlled coassembly of the reported carbonyl-bridged triarylamines (CBTs) is described. The copolymerization of chiral CBTs (S)-1 or (R)-1 with achiral 2 in sergeants-and-soldiers (SaS) experiments results in a tunable helicity conditioned by the percentage of the chiral sergeant and by the cooling rate. The dissimilar inherent chirality of the extended monomeric (M) and intramolecularly H-bonded metastable (M*) species, as well as the different stability of the kinetic trap of the chiral CBTs (S)-1/(R)-1 and the achiral CBT 2, condition the chirality transfer and afford J-aggregates of inverse handedness.

Chirality plays a key role in modern science and technology. Here, we report a simple and effective sensing platform for visual chiral recognition of enantiomers. In this sensing platform, gold nanorods (AuNRs) prepared through a common synthesis route are used as colorimetric probes for visual recognition of glutamine (Gln) enantiomers. D-Gln could rapidly induce the aggregation of AuNRs, thereby resulting in appreciable blue-to-gray color change of AuNRs solution; however, L-Gln could not induce color change of AuNRs. This distinct color change can be easily distinguished by the naked eyes; as a result, a visual method of chiral recognition was suggested. The method was applied to determine the enantiometric excess of D-Gln through the whole range of −100% ~ 100%. The chiral assay can be performed with a simple UV-vis spectrometer or the naked eyes. Notably, the AuNRs do not need any chiral labeling or modification, and the chiral recognition is based on the inherent chirality of AuNRs. This chiral assay method is simple, sensitive, cheap and easy to operate. This study is the first example using AuNRs for direct visual recognition of enantiomers, and will open new opportunity to construct more chiral recognition methods for some important compounds.

The facile method of generating internal chirality into the calixarene with two hydroxy groups at the lower rim via an attached chiral substituent has been proposed. The reaction with acylisocyanates, catalyzed by a small amount of triethylamine, proceeds forming predominantly one of the two possible calixarene carbamates. The best diastereomeric excess (60 %) has been achieved in the reaction of trichloroacyl isocyanates with 1,3-hydroxycalixarene substituted with the chiral phenylethyl amide moiety. The individual diastereomers of trichloroacetyl-carbamoylcalix[4]arenas were isolated by crystallization, and their absolute configuration was determined by X-ray diffraction study. The most favored conformations predicted for 1,3-dihydroxy calixarene structures by quantum chemical calculations possess very similar stability. However, the triethylamine molecule preferably connects to the one hydroxyl group of the two available ones, providing the most favorable adduct, which predominantly participates in the reaction with acylisocyanates. This gives rise to the observed diastereomeric excess. The subsequent treatment of the formed carbamoyl with n-propyl bromide in presence of NaH and hydrolysis of the product of alkylation easily provide a persistent internally chiral calixarene.

Helicenes have attracted great attention due to their inherent chirality and distinctive optical features. Moreover, the intrinsic chirality of helicene can meet non-centrosymmetric electronic structure requirements of second-order optical materials. Thiophene or polythiophene plays an important role in organic photoelectric materials. For organic molecular materials, several electronic behaviors could be combined into a single molecular entity. By utilizing density functional theory calculations, we here for the first time investigated the electronic structures and optical properties of thiophene-based double helicenes. The calculated electronic excitation energies are in good agreement with the experimental ones. The simulated ECD spectra nicely reproduce the experimental ECD spectra in both excitation energy and rotational strength, which can be used to assign the absolute configurations of thiophene-based double helicenes with high confidence. The electronic transition properties and chiroptical origins have been assigned and analyzed. The studied compounds possess remarkably large molecular first hyperpolarizabilities, especially compound a-5 which has a value of 29.09 × 10−30 esu, which is about 300 times larger than the first hyperpolarizabilities of an organic urea molecule and 7 times larger than that measured for a highly π-delocalized phenyliminomethyl ferrocene complex. The effect of single/double helicenes on first hyperpolarizabilities is compared and discussed. We also probed the intramolecular charge transfer cooperativity, which is important for further experimental investigation. Based on the intrinsic non-centrosymmetric electronic structures, high transparency, and the larger first hyperpolarizability values, the studied compounds are expected to be excellent second-order nonlinear optical materials.

Biomacromolecules including protein and nucleic acids are considered as promising chiral selectors in the fields of enantioselective separation, owing to their inherent chirality, polymorphous structures, stable physicochemical properties, good biocompatibility as well as susceptible modification and regulation. In this review, firstly, enantioselective recognition mechanism of proteins and nucleic acids toward different enantiomers is discussed, as well as their potential applications on the chiral separation of racemic compounds. Secondly, preparative enantioseparation adopting biomolecule-modified hybrid materials including porous microspheres, magnetic nanoparticles and affinity membranes, are introduced respectively. Finally, novel chiroptical materials constructed on the basis of chiral induction, transfer, amplification and transcription, are recognized as promising candidates in future applications.

Macrocycles consisting of naphthalene units connected via methylene bridges offer certain advantages as macrocylic scaffolds as compared with parent calixarenes. These advantages originate from their electron rich and enlarged cavities. Additionally, macrocycles containing 1,3-bridged naphthalene units are dissymmetric and therefore they present interesting stereochemical features, including inherent chirality. We describe here a facile, one-step synthesis of two new calix[4]naphthalenes, by the condensation of 1,6-dimethoxynaphthalene with formaldehyde catalyzed by Bronsted acid (TFA). Additionally, we show the first example of hybrid[n]arene containing a 1,6-dimethoxynaphthalene unit and 1,3-dimethoxybenzene units obtained by a simple, one-pot condensation. The conformational and complexation properties were also studied for the resulting hybrid macrocycles.

International audience; A facile method for the preparation of enantiomerically pure inherently chiral calix[4]arene phosphonic acid (cR,pR)-7 in four steps starting from the readily available and previously synthesized (cS)-enantiomer of calix[4]arene acetic acid 1 or its methyl ester 2 was developed. The first tests of this unique calixarene Brönsted acid with inherent chirality in organocatalysis of the aza-Diels–Alder reaction of imines with Danishefsky’s diene and epoxide ring opening by benzoic acid were performed. The calixarene phosphonic acid (cR,pR)-7 shows good catalytic activities but with low enantioselectivities in these reactions.

The properties of two inherently chiral cavitands in enantioselective recognition of N-methyl-leucine was studied in solution, through 1H and 31P NMR experiments, and in the solid state, through co-crystallisation experiments. The inherent chirality of the receptors was obtained through the desymmetrization of the rigid concave cavity by introducing three different bridging groups at the upper rim: two inward P=O groups, one inward P=S moiety and one methylene bridge in the AABC mode. For the solution studies, N-methyl-L-leucine was used as pure enantiomer and partial enantioselectivity was observed in the presence of an excess of a racemic mixture of cavitand receptor. Centrosymmetric crystals consisting of the complexes cR-cav1·N-methyl-D-leucine and cS-cav1·N-methyl-L-leucine were obtained from co-crystallisation of the racemic mixture of cR-cav/cS-cav 1 and N-methyl-D/L-leucine. Differently to the solution case, in the solid state the enantioselectivity of the chiral cavitand is complete and only the two enantiopure mirror complexes were obtained.

Buckybowls are polynuclear aromatic hydrocarbons that have a curved aromatic surface and are considered fragments of buckminsterfullerenes. The curved aromatic surface led to the loss of planar symmetry of the normal aromatic plane and may cause unique inherent chirality, so-called bowl chirality, which it is possible to thermally racemize through a bowl-to-bowl inversion process. In this short review, we summarize the studies concerning the special field of bowl chirality, focusing on recent practical aspects of attaining diastereo/enantioenriched chiral buckybowls through asymmetric synthesis, chiral optical resolution, selective chiral metal complexation, and chiral assembly formation.

A cubic nanocage (O symmetry) that exhibits inherent chirality and has a covalent, rigid skeleton with molecule-sized entrance portals was obtained by means of dynamic covalent chemistry using a reaction between aldehyde-functionalized resorcin[4]arene and hydrazine.