Enantioresolution of a Series of Chiral Benzyl Alcohols by HPLC on a Dinitrobenzoylphenylglycine Stationary Phase after Achiral Pre-Column Derivatization

High performance liquid chromatography method for the separation of a series of chiral benzyl alcohols on N-(3,5-dinitrobenzoyl)-D-phenylglycine stationary phase (Macherey Nagel, Chiral-2) after pre-column achiral derivatization was developed. Cheap and easy available aromatic acid chlorides were used as derivatization agents. Good to excellent separations of the enantiomers were achieved in all cases in relatively short analytical runs. It was shown that the enantiorecognition depends on the substituents both in the starting alcohol and in the acid chloride. The method presents an efficient alternative to the direct analyses on polysaccharide and cyclodextrine-derived stationary phases.

Enumeration of Stereoisomers of Chiral and Achiral Derivatives of Monocyclic Cycloalkanes Having Heteromorphous Alkyl Substituents with Distinct Length <i>k</i>

A combinatorial method based on the determination of the averaged weight of permutations controlling the chirality/achirality fittingness of 2n substitution sites of the monocyclic cycloalkane allows to obtain generalized functional equations for direct enumeration of enantiomers pairs and achiral skeletons of any derivatives of monocyclic cycloalkanes having heteromorphic alkyl substituents with the distinct length k with the empirical formula , wherein at least two alkyl groups??of the distinct size ?each. ?is the number of alkyl radicals ?of the system??verifying the relation . The integer sequences of enantiomer pairs and achiral skeletons are given for substituted derivatives of monocyclic cycloalkane for n = 3, 4 and k = 3, 4, 5. The composite stereoisomerism of this particular compound is also highlighted.

Recognition and chirality sensing of guanosine-containing nucleotides by an achiral tetraphenylethene-based octacationic cage in water

The development of molecular probes or systems with the ability of multiple orthogonal responses is an effective approach to precisely detect biomolecules with similar chemical structures.Herein,we report the synthesis of a water-soluble TPE-based octacationic cage(1)with the compressed TPE-containing bilayer,which endows it with good fluorescence properties and potential conformation chirality.As a result,1 exhibits molecular recognition for anionic nucleotides within its two“claw”-like cavities to form 1:2 host-guest complexes in water,companying with selective turn-off fluorescence and turn-on CD responses to G/GTP over other nucleotides.

Theoretical study of tunable chirality from graphene integrated achiral metasurfaces

Control of chirality using metamaterials plays a critical role in a diverse set of advanced photonics applications,such as polarization control, bio-sensing, and polarization-sensitive imaging devices. However, this poses a major challenge, as it primarily involves the geometrical reconfiguration of metamolecules that cannot be adjusted dynamically. Real-world applications require active tuning of the chirality, which can easily manipulate the magnitude, handedness, and spectral range of chiroptical response. Here, enabled by graphene, we theoretically reveal a tunable/switchable achiral metasurface in the near-infrared region. In the model, the achiral metasurface consists of an array of circular holes embedded through a metal/dielectric/metal trilayer incorporated with the graphene sheet, where holes occupy the sites of a rectangular lattice. Circular conversion dichroism(CCD) originates from the mutual orientation between the achiral metasurface and oblique incident wave.The achiral metasurface possesses dual-band sharp features in the CCD spectra, which are tuned over a broad bandwidth by electrically modulating the graphene's Fermi level. By selecting aluminium as the metal materials,we numerically achieved strong CCD and considerably reduced materials costs with our nanostructures compared with the typically used noble metals such as gold and silver.

Strict Achirality of Prime Links up to 11-Crossing

In this paper we determine all strictly achiral prime links up to 11 crossings. There are exactly four strictly achiral non-trivial prime links up to 11 crossings.

Self-twisting for macrochirality from an achiral asterisk molecule with fluorescence-phosphorescence dual emission

Understanding of the role of supramolecular chirality for tuning material optoelectronic properties has been restricted by the limited number of cases. A particular challenge is to impose supramolecular chirality onto multicolor luminescent systems that can emit in aggregation state. Here we present a self- assembly strategy from a well-selected asterisk molecule for generating supramolecular chirality with fluorescence-phosphorescence dual emission. The work takes advantages of （1） achiral chemical structure dependent peculiar self-assembly that can spontaneously undergo symmetry breaking to produce macrochirality, and （2） the assembly process can be monitored by time which due to the crystallization-driven self-assembly by self-twisting, allowing a self-progressing chiral amplification. A multicolor luminescence induced by the fluorescence-phosphorescence dual emission along with such a self-assembly behavior was also observed at a single solution system versus the time. The self-twisting chiral self-assembly fashion provides new prospects for understanding the establishment of nanochirality from achiral molecular building blocks.

Topological chirality and achirality of the closed circular DNAs

THE study of the relations between the topological structure and its function is one of the focus-es in modern chemistry and life science. In this note we set up a topological model to de-scribe the ccDNAs on the basis of Seifert construction in knot theory. Our model for theccDNAs helps to determine whether a structure is topologically chiral or achiral. This is one ofthe fundamental biological problems.

Spontaneous resolution and absolute chiral induction of 3d-4f heterometal-organic frameworks from achiral precursors

The asymmetric assembly and spontaneous resolution of chiral heterometal-organic frameworks from achiral precursors remain a great challenge. Herein, we report the formation and spontaneous resolution of three-dimensional(3 D) chiral 3 d-4 f heterometal-organic frameworks from achiral ligands in the presence of lactic acid enantiomers as chiral inducers. In the absence of a chiral inducer, the reactants randomly generated both enantiopure crystals in equal measure. However, enantiopure lactic acid induced asymmetric resolution to achieve single chiral crystallization. DFT theoretical calculations showed that the absolute chiral resolution of the enantiomers is due to the difference in the interactions between the two enantiomeric Λ/Δ-[Fe L_(3)]^(3-)units and the chiral inducer.

Molecular Chirality and Chiral Superlattice in Crystal of Tetrakis[(pyrrol-1-yl)methyl]methane

The crystal structure of tetrakis[(pyrrol-1-yl)methyl]methane was determined by X-ray diffraction measurement, and the result shows that it belongs to monoclinic crystal system, space group is P2 1/n, with a=0.9284(3) nm, b=1.0950(6) nm, c=1.8749(8) nm; α=γ= 90.00(4)°, β=103.63(3)°, V=1.8523(14) nm 3, Z=4, ρ calcd. =1.192 kg/m 3, μ=0.072 nm -1 , F(000)=712, R 1=0.0854, wR 2=0.1884. It has been found that the molecules exist in two enantiomeric states. Enantioselective self-assemblies such as one-dimensional molecular stacks in a single handedness, homochiral monolayers and a chiral superlattice are specified in this racemic crystal. In addition, a simple technique is advocated to distinguish chiral states from tetrahedral molecules in the solid state. The present R/S nomenclature of the tetracooradinated carbon centers is used solely for its convenience to distinguish the two enantiomeric states, but not used to determine the absolute configurations.

Superchiral fields generated by nanostructures and their applications for chiral sensing

Chirality is ubiquitous in natural world.Although with similar physical and chemical properties,chiral enantiomers could play different roles in biochemical processes.Discrimination of chiral enantiomers is extremely important in biochemical,analytical chemistry,and pharmaceutical industries.Conventional chiroptical spectroscopic methods are disadvantageous at a limited detection sensitivity because of the weak signals of natural chiral molecules.Recently,superchiral fields were proposed to effectively enhance the interaction between light and molecules,allowing for ultrasensitive chiral detection.Intensive theoretical and experimental works have been devoted to generation of superchiral fields based on artificial nanostructures and their application in ultrasensitive chiral sensing.In this review,we present a survey on these works.We begin with the introduction of chiral properties of electromagnetic fields.Then,the optical chirality enhancement and ultrasensitive chiral detection based on chiral and achiral nanostructures are discussed respectively.Finally,we give a short summary and a perspective for the future ultrasensitive chiral sensing.

Mixed-cation chiral perovskites displaying warm-white circularly polarized luminescence

Chiral perovskites with exceptional structural flexibility and optoelectrical properties are regarded as promising materials for optoelectronic and spintronic devices.However,the effects of achiral organic ligands on the chiroptical activity of chiral perovskites have been rarely explored.Here,we present four one-dimensional lead bromide perovskites R-/S-(AMP)_(2)Pb_(3)Br_(10)(1-R and 1-S)with mono-cation and R-/S-AMP(DMA)Pb Br_(5)(2-R and 2-S)with mixed-cation templated by chiral R-/S-2-aminomethylpyrrolidine(R-/S-AMP)and achiral dimethylammonium(DMA).All four compounds demonstrate broadband emissions from self-trapped excitons(STEs).Derived from the stronger chirality transfer synergistically induced by achiral DMA,amplified bathochromically-shifted circular dichroism signals and strong warm-white circularly polarized emissions have been observed in 2-R and 2-S.This mixed-cation structural engineering provides a new route toward developing chiral perovskites for optoelectronic applications.

Memorable full-color circularly polarized luminescence from chiral co-assembled polymer films enabled by multipath transfer

The modulation of circularly polarized luminescence(CPL)is of importance for display and asymmetric chemical synthesis.However,the underlying mechanism of CPL transfer remains rarely studied.Herein,we rationally design a multipath transfer system including multistep chirality transfer(MCT)and sequential fluorescence resonance energy transfer(SFRET),and we are the first to fabricate memorable full-color CPL-active films with a high dissymmetry factor(~10^(-2)).Specifically,(P/M)-helical nanofibers are constructed by co-assembly between an achiral polymer,poly(9,9-di-n-octylfluorene)(PF8),and easy-to-remove R/S-limonene.When matching achiral emitters are added,the PF8 mediates MCT and simultaneously triggers the SFRET process.Furthermore,full-color CPL memory is realized after removing the chiral source.Molecular simulation and structure analysis indicate that the robust helical superstructure of PF8 provides chiral sites to accommodate emitters,which is essential for CPL transfer and memory.This work provides a novel strategy for constructing CPL-active materials in an aggregated state and insights into CPL transfer and memory.

Construction of Supramolecular Chirality in Polymer Systems:Chiral Induction, Transfer and Application

Chirality,commonly found in organisms,biomolecules and nature such as L-amino acids and D-sugars,has been extensively studied in chemistry and biomedical science.Hence,the demand for simple and efficient construction of chiral structures,especially chiral polymers,has been rapidly growing due to their potential applications in chemosensors,asymmetric catalysis and biological materials.However,most chiral polymers reported are prepared directly from chiral monomers/chiral catalysts,the corresponding strategies usually involve tedious and expensive design and synthesis.Fortunately,chirality induction strategies(such as circularly polarized light,chiral solvation and chiral gelation etc.)have been known to be highly versatile and efficient in producing chirality from achiral polymers.In this feature article,the current research on chirality induction,transfer and application in achiral polymer systems is summarized.Furthermore,this article discusses some basic concepts,seminal studies,recent advances,the structural design principles,as well as perspectives in the construction and applications of chiral polymers derived from achiral monomers,with the hope to attract more interest from researchers and further advance the development of chiral chemistry.

Absolute Asymmetric Synthesis Using A Cocrystal Approach

1 Results Absolute asymmetric synthesis by means of solid-state reaction of chiral crystals self-assembled from achiral molecules is an attractive and promising methodology for asymmetric synthesis because it is not necessary to employ any external chiral source like a chiral catalyst.In order to design reliably absolute asymmetric syntheses in the solid state,it is inevitable to prepare and predict the formation of chiral crystals from achiral compounds.We have prepared a number of chiral cocrystals co...