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The chiral resolving ability of the commercially available amylose (3,5-dimethylphenylcarbamate)-based chiral stationary phase (CSP) toward four chiral probes representative of four kinds of stereogenicity (central, axial, helical, and planar) was investigated. Besides chirality, the evident structural feature of selectands is an extremely limited conformational freedom. The chiral rigid analytes were analyzed by using pure short alcohols as mobile phases at different column temperatures. The enantioselectivity was found to be suitable for all compounds investigated. This evidence confirms that the use of the amylose-based CSP in HPLC is an effective strategy for obtaining the resolution of chiral compounds containing any kind of stereogenic element. In addition, the experimental retention and enantioselectivity behavior, as well as the established enantiomer elution order of the investigated chiral analytes, may be used as key information to track essential details on the enantiorecognition mechanism of the amylose-based chiral stationary phase. [ABSTRACT FROM AUTHOR]

This account summarizes the development of new biheteroaromatic chiral bisphosphine oxides. 3,3′-Bithiophene-based phosphine oxides (BITIOPOs) have been successfully used as organocatalysts to promote Lewis base catalyzed, Lewis acid mediated stereoselective transformations. These highly electron-rich compounds, in combination with trichorosilyl derivatives (allyltrichlorosilane and silicon tetrachloride), generate hypervalent silicon species that act as chiral Lewis acids in highly diastereo- and enantioselective organic reactions. Several relevant examples related to these applications are discussed in detail. 1 Introduction 2 The BITIOPO Family 3 Enantioselective Opening of Epoxides 4 Enantioselective Allylation of Aldehydes 5 Stereoselective Direct (Double) Aldol-Type Reaction with Ketones 6 Stereoselective Direct Aldol-Type Reaction with Ester Derivatives 7 Conclusions [ABSTRACT FROM AUTHOR]

In the present paper, the synthesis and characterization of 2,2′-bis{bi[2,2’-(3,4-ethylenedioxy)thiophen-5-yl]}-3,3′-bithianaphthene, nicknamed BT 2 E 4 , is reported. We show that electrooligomerization of BT 2 E 4 leads to electroactive films which are evaluated by cyclic voltammetry (CV), UV/vis spectroelectrochemistry and CV coupled with in-situ conductance measurements. Direct comparisons to the properties of the oligomers obtained from the atropisomeric all-thiophene analogue BT 2 T 4 show that the introduction of EDOT leads to a strong reduction of the band-gap, an overall red-shifted absorption spectrum and a rigidification of the structure. Finally, DFT and TD-DFT calculations were performed in parallel to investigate and to compare the electronic and molecular structures of neutral and charged monomer and oligomer species. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

'Inherently chiral' thiophene-based electroactive oligomer films have recently been shown to exhibit outstanding chirality manifestations. One of the most exciting among them is an unprecedented enantioselection ability as electrode surfaces. In fact, in preliminary chiral voltammetry experiments, the new electrodes have been shown to both discriminate the enantiomers of chiral probes (either enantiopure or in a mixture, in terms of large differences in peak potentials) and quantify them (in terms of linear dynamic ranges in peak currents), without the need for preliminary separation steps. Such ability has now been tested on a series of chiral DOPA-related molecules, from phenolic amino acid tyrosine (together with its methyl ester) to catecholic amino acid DOPA (together with its methyl ester), to catecholamine epinephrine (adrenaline). The wide-range enantioselectivity of the new inherently chiral electrode surfaces is fully confirmed, as large peak potential differences are obtained for probe enantiomers of the whole series working in common aqueous buffers. Moreover, interesting modulating effects on enantiodiscrimination can be observed as a function of both molecular structure and pH. [ABSTRACT FROM AUTHOR]

Unknown 1 H-2,7-dihydro-1-phenylphosphepine, containing a 2,2′,5,5′-tetramethyl-3,3′-bithiophene atropisomeric scaffold (Ph-tetraMe-Bithienine), and its oxide have been synthesized and structurally characterized by single-crystal X-ray diffraction analysis. The most evident structural feature is the very small dihedral angle. The electronic properties of the phosphane were quantitatively evaluated by cyclic voltammetry and compared with three other 2,7-dihydro-1-phenylphosphepines differing in the nature of the biaromatic scaffold (biphenyl, 1,1′-binaphthyl and 2,2′-dimethoxybiphenyl). The racemate of the phosphane oxide was resolved into antipodes, which were reduced to the enantiopure phosphanes and employed as ligands in Rh and Pt complexes in homogeneous stereoselective catalytic reactions. The enantioselective ability and catalytic activity of the new mediators were found to be quite modest in the hydrogenation reactions of olefinic double bonds, whereas good performances were achieved in specific C-C bond-forming reactions. The results are interpreted on the basis of the steric and electronic properties of the ligand. [ABSTRACT FROM AUTHOR]

A series of tris-aryl phosphanes, structurally designed to exist as residual enantiomers or diastereoisomers, bearing substituents differing in size and electronic properties on the aryl rings, were synthesized and characterized. Their electronic properties were evaluated on the basis of their electrochemical oxidation potential determined by voltammetry. The configurational stability of residual phosphanes, evaluated by dynamic HPLC on a chiral stationary phase or/and by dynamic 1H and 31P NMR spectroscopy, was found to be rather modest (barriers of about 18-20 kcal mol−1), much lower than that shown by the corresponding phosphane oxides (barriers of about 25-29 kcal mol−1). For the first time, the residual antipodes of a tris-aryl phosphane were isolated in enantiopure state and the absolute configuration assigned to them by single-crystal anomalous X-ray diffraction analysis. In this case, the racemization barrier could be calculated also by CD signal decay kinetics. A detailed computational investigation was carried out to clarify the helix reversal mechanism. Calculations indicated that the low configurational stability of tris-aryl phosphanes can be attributed to an unexpectedly easy phosphorus pyramidal inversion which, depending upon the substituents present on the blades, can occur even on the most stable of the four conformers constituting a single residual stereoisomer. [ABSTRACT FROM AUTHOR]

A series of tris-aryl phosphane oxides existing as residual enantiomers or diastereoisomers with substituents on the aryl rings differing in size and electronic properties were synthesized and characterized. Their electronic properties were evaluated on the basis of their electrochemical oxidation and reduction potentials together with those of the corresponding 'blade bromides' (i.e., the naphthalene derivatives displaying the same substitution pattern of the tris-naphthyl phosphane oxide blades, with a bromo substituent where the phosphorus atom is located) determined by CV. The residual stereoisomeric phosphane oxides were isolated in a stereochemically pure state and were found to be highly configurationally stable at room temperature (stereoisomerization barriers of about 27 kcal mol−1). The chiroptical properties of the residual stereoisomers and the assignments of absolute configuration are discussed. The configurational stability of residual tris-aryl phosphane oxides was found to be scarcely influenced by the electronic properties of the substituents present on the aromatic rings constituting the blades, while steric effects play the most relevant role. Detailed theoretical calculations are in agreement with the experimental results and also contribute to a rational interpretation of the stereodynamics of these systems. [ABSTRACT FROM AUTHOR]

The role played by the electronic properties and the steric features of bis(oxazoline) ligands in the Cu(I)-catalyzed cyclopropanation of styrene effected with ethyl diazoacetate was investigated. Two pairs of new bis(oxazolines) displaying flexible and atropisomeric 3,3′-bithiophene backbones were synthesized and structurally and electronically characterized. For the first time, the electrochemical oxidative potential was used as a reliable index of the electronic density on the nitrogen atom of the chelating groups of new and, for comparative purposes, of already known bis(oxazolines). The Cu(I) complexes of the new ligands were prepared, and their enantioselection ability and catalytic efficiency were tested. This investigation suggests that steric factors and catalyst geometrical features are clearly more important than any consideration of the electronic properties of the chiral ligands. [ABSTRACT FROM AUTHOR]

The 2,5-dimethyl-3,4-bis [(2R,5R)-2,5-dimethylphospholano]thiophene (UlluPHOS), a new thiophene-based analogue of (R,R)-1,2-bis(phospholano)benzene (Me-DuPHOS), was synthesized, geometrically and electronically characterized, and employed as ligand of Rh and Ru in some standard hydrogenation reactions of prostereogenic functionalized carbon-carbon and carbon-oxygen double bonds. The synthesis of UlluPHOS is much easier than that provided for Me-DuPHOS. UlluPHOS and Me-DuPHOS display very similar geometries, while the electronic availability of the former is higher than that exhibited by the latter. The Rh and Ru complexes of UlluPHOS produced excellent enantiomeric excesses (98.9-99.5%) in the hydrogenation of N-acetyl-α-enamino acids and reaction rates higher than those found when employing the analogous complexes of Me-DuPHOS. [ABSTRACT FROM AUTHOR]

The Pd(II) and Pt(II) complexes (perchlorates and hexafluoroantimoniates, respectively) of a series of C2 symmetric biheteroaromatic diphosphines differing in their electronic properties at phosphorus have been tested as catalysts in [4+2]-cycloaddition reactions of cyclopentadiene and N-2-alkenoyl-1,3-oxazolidine-2-ones. The best stereoselection results were obtained with the complexes produced from electron-rich ligands, which were found to give also the kinetically most active catalysts. [Copyright &y& Elsevier]

Provides evidence of the role played by the electronic properties of phosphorus in determining hydrogenation rate of the ketonic function of ethyl acetoacetate. Free energy linear correlation between the electrochemical oxidative potential of ligands exhibiting different electronic availability of phosphorus and the log of observed rate constant.

Describes the four-step straightforward synthesis of enantiopure(+)- and (-)-2,2',5,5'-tetramethyl-4,4'-bis(diphenylphosphino)-3,3'-bithiophene, A C2-symmetry chelating ligand for transition metals. Use of 2,5-dimethylthiophene as starting material; Application of the complexes of this electron-rich diphosphine with Ru(II) and Rh(I) as catalysts.

Among inherently chiral selectors of axial stereogenicity, usually resulting in very good enantiodiscrimination performances, the biindole‐based family has the additional advantage of very easy functionalization of the two nitrogen atoms with a variety of substituents with desirable properties. Aiming to evaluate the possibility of exploiting such feature to enhance the enantiodiscrimination ability of the archetype structure, a series of three inherently chiral monomers were designed and synthesized, characterised by a 2,2'‐biindole atropisomeric core conjugated to bithiophene wings enabling fast and regular electrooligomerization, and functionalised at the nitrogen atoms with an ethyl, a methoxyethyl, or a hydroxyethyl substituent. Nitrogen alkylation was also exploited to obtain for the first time the chemical resolution of the biindole selectors without employing chiral HPLC. The enantiodiscrimination ability of the selector series was comparatively evaluated in proof‐of‐concept chiral voltammetry experiments with a "benchmark" chiral ferrocenyl probe as well as with chiral non‐steroidal anti‐inflammatory drugs naproxen and ketoprofen. The large enantiomer potential differences for all probes increased in the ethyl < methoxyethyl ≪ hydroxyethyl sequence of selector substituents, supporting our assumption on the beneficial role of an additional coordination element. The powerful hydroxyethyl selector was also applied to ketoprofen in a commercial drug matrix. [ABSTRACT FROM AUTHOR]

An environmentally friendly and sustainable approach was adopted to produce a molecularly imprinted polymer (MIP) via electropolymerization, with remarkable electrochemical sensing properties, tested in tyrosine (tyr) detection. The 2,2′-bis(2,2′-bithiophene-5-yl)-3,3′-bithianaphtene (BT2-T4) was chosen as functional monomer and MIP electrosynthesis was carried out via cyclic voltammetry on low-volume (20 μL) screen-printed carbon electrodes (C-SPE) in ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ((BMIM) TFSI). An easy and rapid washing treatment allowed us to obtain the resulting MIP film, directly used for tyr electrochemical detection, carried out amperometrically. The sensor showed a linear response in the concentration range of 15–200 μM, with LOD of 1.04 µM, LOQ of 3.17 μM and good performance in selectivity, stability, and reproducibility. Tyrosine amperometric detection was also carried out in human plasma, resulting in a satisfactory recovery estimation. The work represents the first use of BT2-T4 as a functional monomer for the production of a molecularly imprinted polymer, with a green approach afforded by using a few microliters of a room temperature ionic liquid as an alternative to common organic solvents on screen-printed carbon electrodes, resulting in a valuable system that meets the green chemistry guidelines, which is today an essential criterion in both research and application field. [ABSTRACT FROM AUTHOR]

Describes the synthesis and application of three chiral (C2) atropisomeric diphosphines. Transition metal-catalyzed stereoselective reactions; Characterization; Advantages.

Examines the modular class of chiral diphosphine ligand for homogeneous stereoselective catalysis. Effectiveness of the chelating diphosphines; Comparison between C[sub 2]-symmetric diphosphino biheteroaryls and carbocyclic biaromatic systems; Influence of heterocyclic system on electronic properties at phosphorus.

In this paper it is experimentally demonstrated that the electron‐spin/molecular‐handedness interaction plays a fundamental role in the chiral recognition process. This conclusion is inferred comparing current versus potential (I–V) curves recorded using chiral electrode surfaces, which are obtained via chemisorption of an enantiopure thiophene derivative: 3,3′‐bibenzothiophene core functionalized with 2,2′‐bithiophene wings (BT2T4). The chiral recognition capability of these chiral‐electrodes is probed via cyclic voltammetry measurements, where, Ag nanoparticles (AgNPs) capped with enantiopure BT2T4 (BT2T4@AgNP) are used as the chiral redox probe. Then, the interface handedness is explored by recording spin‐polarized I–V curves in spin‐dependent electrochemistry (SDE) and magnetic‐conductive atomic force microscopy (mc‐AFM) experiments. The quality of the interfaces is thoroughly cross‐checked using X‐ray photoemission spectroscopy, Raman, electrodesorption measurements, which further substantiate the metal(electrode)‐sulfur(thiophene) central role in the chemisorption process. Spin‐polarization values of about 15% and 30% are obtained in the case of SDE and mc‐AFM experiments, respectively. [ABSTRACT FROM AUTHOR]

A correction to an article related to inherently chiral thiophene-based electrodes published in a previous issue of the journal is presented.

Preferential crystallization induced by chiral surfaces is an interesting alternative to isolate enantiopure antipodes. Herein, we take advantage of the outstanding enantiorecognition capabilities of inherently chiral oligomers to induce an enantioselective crystallization process. We exemplify this strategy with two amino acid model molecules, asparagine and glutamic acid, having a completely uncorrelated structure with respect to the template. This illustrates the versatility of the approach with potential applications in the resolution of pharmaceutical compounds. [ABSTRACT FROM AUTHOR]

The title ligand is synthesized and its utility for Rh-catalyzed asymmetric hydrogenations as well as for the alkoxycyclization of enyne (V) is demonstrated. [ABSTRACT FROM AUTHOR]

Microfluidic valves based on chemically responsive materials have gained considerable attention in recent years. Herein, a wireless enantio‐responsive valve triggered by bipolar electrochemistry combined with chiral recognition is reported. A conducting polymer actuator functionalized with the enantiomers of an inherently chiral oligomer was used as bipolar valve to cover a tube loaded with a dye and immersed in a solution containing chiral analytes. When an electric field is applied, the designed actuator shows a reversible cantilever‐type deflection, allowing the release of the dye from the reservoir. The tube can be opened and closed by simply switching the polarity of the system. Qualitative results show the successful release of the colorant, driven by chirality and redox reactions occurring at the bipolar valve. The device works well even in the presence of chemically different chiral analytes in the same solution. These systems open up new possibilities in the field of microfluidics, including also controlled drug delivery applications. [ABSTRACT FROM AUTHOR]

Two complementary Pd-catalyzed protocols enabling the ?- selective intermolecular allylic amination of but-3-enoic acid derivatives are reported. These transformations can be successfully achieved via either a direct Pd(II)-catalyzed protocol or by way of a one-pot Pd(II)/Pd(0)-catalyzed sequence, depending on the nature of the nitrogen nucleophile used. [ABSTRACT FROM AUTHOR]

The racemate of an inherently chiral 'spider-like' octathiophene monomer T83, in which chirality is generated by torsion in its backbone, was synthesized. The racemate was resolved into configurationally stable antipodes by HPLC on a chiral stationary phase. Electrooxidation of the enantiomers resulted in materials displaying high enantiorecognition ability towards the antipodes of some chiral probes. Moreover, the T83 racemate demonstrated great aptitude to stimulate formation of 3D rigid architectures if used as a cross-linking monomer for molecular imprinting. This feature was exploited to devise a molecularly imprinted polymer-based chemosensor selective for a thymine-adenine oligonucleotide. [ABSTRACT FROM AUTHOR]

The development of chiral catalysts plays a very important role in various areas of chemical science. Heterogeneous catalysts have the general advantage of allowing a more straightforward separation from the products. One specific case of heterogeneous catalysis is electrocatalysis, being potentially a green chemistry approach. However, a typical drawback is that the redox conversion of molecules occurs only at the electrode/electrolyte interface, and not in the bulk of the electrolyte. The second limitation is that the electrodes have to be physically connected to a power supply to induce the desired reactions. To circumvent these problems, we propose here a complementary approach by replacing macroscopic electrodes with an ensemble of self‐propelled redox active microswimmers. They move autonomously in solution while transforming simultaneously a prochiral starting compound into a specific enantiomer with a very high enantiomeric excess, accompanied by a significantly increased production rate of the favorite enantiomer. [ABSTRACT FROM AUTHOR]

The development of chiral catalysts plays a very important role in various areas of chemical science. Heterogeneous catalysts have the general advantage of allowing a more straightforward separation from the products. One specific case of heterogeneous catalysis is electrocatalysis, being potentially a green chemistry approach. However, a typical drawback is that the redox conversion of molecules occurs only at the electrode/electrolyte interface, and not in the bulk of the electrolyte. The second limitation is that the electrodes have to be physically connected to a power supply to induce the desired reactions. To circumvent these problems, we propose here a complementary approach by replacing macroscopic electrodes with an ensemble of self‐propelled redox active microswimmers. They move autonomously in solution while transforming simultaneously a prochiral starting compound into a specific enantiomer with a very high enantiomeric excess, accompanied by a significantly increased production rate of the favorite enantiomer. [ABSTRACT FROM AUTHOR]

The residual enantiomers of three tris-(3-indolyl)-phosphane oxides bearing different alkyl groups (methyl, ethyl or i-propyl) in position 2 of the indole rings constituting the blades were separated on the immobilized type Chiralpak IC column in polar organic and reversed-phase modes. The good and versatility of the IC CSP allowed easy isolation of the enantiomerically highly enriched samples suitable for configurational stability studies. The enantiomerization barriers of residual phosphane oxides were evaluated both by off-column techniques (CD signal and enantiomeric purity decay kinetics) and by dynamic high-performance (HPLC). Chirality 27:888-899, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Linear conjugated oligothiophenes of variable length and different substitution pattern are ubiquitous in technologically advanced optoelectronic devices, though limitations in application derive from insolubility, scarce processability and chain-end effects. This study describes an easy access to chiral cyclic oligothiophenes constituted by 12 and 18 fully conjugated thiophene units. Chemical oxidation of an 'inherently chiral' sexithiophene monomer, synthesized in two steps from commercially available materials, induces the formation of an elliptical dimer and a triangular trimer endowed with electrosensitive cavities of different tunable sizes. Combination of chirality with electroactivity makes these molecules unique in the current oligothiophenes literature. These macrocycles, which are stable and soluble in most organic solvents, show outstanding chiroptical properties, high circularly polarized luminescence effects and an exceptional enantiorecognition ability. [ABSTRACT FROM AUTHOR]

The typical design of chiral electroactive materials involves attaching chiral pendants to an electroactive polyconjugated backbone and generally results in modest chirality manifestations. Discussed herein are electroactive chiral poly-heterocycles, where chirality is not external to the electroactive backbone but inherent to it, and results from a torsion generated by the periodic presence of atropisomeric, conjugatively active biheteroaromatic scaffolds, (3,3′-bithianaphthene). As the stereogenic element coincides with the electroactive one, films of impressive chiroptical activity and outstanding enantiodiscrimination properties are obtained. Moreover, chirality manifestations can be finely and reversibly tuned by the electric potential, as progressive injection of holes forces the two thianaphthene rings to co-planarize to favor delocalization. Such deformations, revealed by CD spectroelectrochemistry, are elastic and reversible, thus suggesting a breathing system. [ABSTRACT FROM AUTHOR]

The typical design of chiral electroactive materials involves attaching chiral pendants to an electroactive polyconjugated backbone and generally results in modest chirality manifestations. Discussed herein are electroactive chiral poly-heterocycles, where chirality is not external to the electroactive backbone but inherent to it, and results from a torsion generated by the periodic presence of atropisomeric, conjugatively active biheteroaromatic scaffolds, (3,3′-bithianaphthene). As the stereogenic element coincides with the electroactive one, films of impressive chiroptical activity and outstanding enantiodiscrimination properties are obtained. Moreover, chirality manifestations can be finely and reversibly tuned by the electric potential, as progressive injection of holes forces the two thianaphthene rings to co-planarize to favor delocalization. Such deformations, revealed by CD spectroelectrochemistry, are elastic and reversible, thus suggesting a breathing system. [ABSTRACT FROM AUTHOR]

Bipolar electrochemistry has gained increasing attention in recent years as an attractive transduction concept in analytical chemistry in general and, more specifically, in the frame of chiral recognition. Herein, we use this concept of wireless electrochemistry, based on the combination of the enantioselective oxidation of a chiral probe with the emission of light from a light‐emitting diode (LED), as an alternative for an easy and straightforward readout of the presence of chiral molecules in solution. A hybrid polymer‐microelectronic device was designed, using an inherently chiral oligomer, that is, oligo‐(3,3′‐dibenzothiophene) and a polypyrrole strip as the anode and cathode of a miniaturized LED. The wireless induced redox reactions trigger light emission when the probe with the right chirality is present in solution, whereas no light emission is observed for the opposite enantiomer. The average light intensity shows a linear correlation with the analyte concentration, and the concept opens the possibility to quantify the enantiomeric excess in mixtures of the molecular antipodes. [ABSTRACT FROM AUTHOR]

Abstract: Novel thiophene-based oligomer, 2,2′-bis(2,2′-bithiophene-5-yl)-3,3′-bithianaphthene (TX), was designed and synthesized, and its electrochemical and spectral properties characterised. TX was readily polymerised electrochemically to form well organized conducting homopolymer films on various solid electrode substrates. Moreover, it was successfully used for deposition by electropolymerisation of electrochemically active thin films of co-polymers with three different monomers of functionalised bis(2,2′-bithienyl)methane derivatives. It appeared that TX was an effective crosslinker and 3D promoter in these electropolymerisations involving co-monomers intrinsically showing limited aptitude for the electropolymerisation or forming polymer films of low conductivity. This attractive TX ability stems from combination of its (i) high conjugation efficiency in each of the two planar moieties, (ii) intrinsic 3D structure on account of the presence of the central node, and (iii) intrinsic regioselectivity in electropolymerisation on account of the positions of the two available free α-thiophene sites. [ABSTRACT FROM AUTHOR]

A family of inherently chiral electroactive selectors based on the 2,2'‐biindole atropisomeric scaffold, of easy synthesis and modulable functional properties, is studied in cascade in two enantioselection contexts. They are at first investigated as probes in enantioselective HPLC, studying molecular structure and temperature effects, and achieving very efficient semipreparative enantioseparation. The enantiomers thus obtained, of remarkable chiroptical features (optical rotation as well as circular dichroism), are successfully applied as selectors in chiral voltammetry in different media for discrimination of the enantiomers of chiral electroactive probes, either by conversion into enantiopure electroactive electrode surfaces by electrooligomerization on glassy carbon substrate (the two monomers with shorter alkyl chains), or as chiral additive in achiral ionic liquid (the monomer with longest alkyl chains). Discrimination is conveniently and reproducibly achieved in terms of significant potential differences for the two enantiomers, specularly inverting either probe or selector configuration. In one case successful discrimination is also observed with the two probe enantiomers concurrently present, either as racemate or with enantiomeric excesses, neatly accounted for by the peak current ratios. [ABSTRACT FROM AUTHOR]

PHANE-TetraPHOS, a new D2 symmetric tetraphosphane based on the [2.2]paracyclophane scaffold, has been synthesized and characterized. The peculiarity of this system is the presence of four homotopic diphenylphosphane groups, exchangeable through C2 symmetry operations and consequently indistinguishable. Their spatial arrangement allows the simultaneous complexation of two metal atoms. Enantiomeric purity was attained at tetra-phosphane oxide level by fractional crystallization of the diastereomeric adducts obtained from the racemate with enantiopure dibenzoyltartaric acids. Alkaline treatment of diastereomerically pure adducts followed by exhaustive P-O groups reduction with HSiCl3 gave both PHANE-TetraPHOS antipodes in an enantiopure state. They were tested as rhodium ligands in the homogeneous enantioselective hydrogenation of some benchmark unsaturated compounds. Catalytic activity and enantiodiscrimination ability were found comparable to those exhibited by the complexes of the parent bidentate ligand PHANEPHOS, but only half a mole of precious chiral ligand was employed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The racemate of an inherently chiral “spider ‐ like” octathiophene monomer T83, in which chirality is generated by torsion in its backbone, was synthesized. In the cover image, the (S) ‐ T83 has woven a highly selective chiral web in which enantiomorphic insects (l ‐ and d ‐ DOPA, R ‐ and S ‐ FcA) are differently entrapped. More information can be found in the Full Paper by P. R. Mussini, T. Benincori, R. Martinazzo et al. on page 10839. [ABSTRACT FROM AUTHOR]

Invited for the cover of this issue are the groups of F. Sannicolò, P. R. Mussini and R. Martinazzo (University of Milan, Italy), T. Benincori (University of Insubria, Italy), and W. Kutner (Polish Academy of Sciences, Warsaw, Poland). The image depicts the spider ( S)-T83 in a highly selective chiral web, in which enantiomorphic insects ( l- and d-DOPA, R- and S-FcA) are differently entrapped. Read the full text of the article at . [ABSTRACT FROM AUTHOR]

Two diastereoisomeric pairs of bis-oxazolines, provided with a stereogenic center at carbon 4 and based on the 3,3′-bithiophene atropisomeric scaffold, were synthesized and structurally characterized. They differ in the substituents at positions 2 and 5 of the thiophene rings, which are functionalized with methyl (1) or phenyl (2) groups, respectively. In vibrational circular dichroism (VCD) spectra, recorded in CCl4 solutions, it is possible to distinctly recognize the characteristic features of axial and central stereogenic elements. In tandem with Density Functional Theory (DFT) calculations, the absolute configuration (AC) of the diastereoisomers was safely established. In this case, VCD was shown to be superior to ECD (electronic circular dichroism) in the assignment of AC. The normal modes, evaluated from DFT calculations, show that the VCD signals in correspondence with the stereogenic axis of the bithiophene unit are different for 1 and 2. The VCD spectra of a molecular analog of 1, the (S)-2,2′,5,5′-tetramethyl-4,4′-bis-(diphenylphosphino)-3,3′-bithiophene oxide (3), characterized by the same 3,3′-bithiophene scaffold, but devoid of stereogenic centers, exhibits signals similar to those observed in the case of diastereoisomer (aS,R,R)-1a, associated with almost identical normal modes. Chirality 28:686-695, 2016. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Efficient monitoring of chiral information of bioactive compounds has gained considerable attention, due to their involvement in different biochemical processes. In this work, we propose a novel dynamic system for the easy and straightforward recognition of chiral redox active molecules and its possible use for the efficient measurement of enantiomeric excess in solution. The approach is based on the synergy between the localized enantioselective oxidation of only one of the two antipodes of a chiral molecule and the produced charge-compensating asymmetric proton flux along a bipolar electrode. The resulting clockwise or anticlockwise rotation is triggered only when the probe with the right chirality is present in solution. The angle of rotation shows a linear correlation with the analyte concentration, enabling the quantification of enantiomeric ratios in mixtures where the two antipodes are present in solution. This device was successfully used to simultaneously measure different ratios of the enantiomers of 3,4-dihydroxyphenylalanine and tryptophan. The versatility of the proposed approach opens up the possibility to use such a dynamic system as a straightforward (bio)analytical tool for the qualitative and quantitative discrimination of different redox active chiral probes. [Display omitted] • Bipolar electrochemistry as transduction method for dynamic chiral recognition. • Enantiomeric excess quantification of amino acids with bipolar chiral electrochemistry. • Determination of chirality by a simple optical readout via the angle of rotation of a bipolar electrode. [ABSTRACT FROM AUTHOR]

• Bipolar electrochemistry as transduction method for chiral recognition. • Enantiomeric excess quantification of amino acids with bipolar chiral electrochemistry. • Determination of chirality in real samples through wireless light emission. Bipolar electrochemistry can be employed in the context of chiral recognition in order to obtain useful analytical readouts of enantiomeric analytes. Herein, we employ this concept for the simultaneous determination of two enantiomers present in solution, and its possible use as transduction mechanism for complex real matrices analysis. This approach is based on the combination of the enantioselective electrooxidation of only one of the two antipodes of a chiral analyte with the emission of light from light-emitting diodes (LEDs). A double hybrid device was designed, using the enantiomers of an inherently chiral oligomer and a bare gold wire as the anode and cathode of a green and red LED. By applying an appropriate voltage, the wirelessly induced redox reactions trigger light emission only when the probe with the right configuration is present in solution. This device was used to simultaneously measure the ratio between L- and D-Tryptophan, both present in solution and to quantify L-ascorbic acid in a commercial juice sample. The measurement correlates with the value reported on the sample specifications. These results illustrate the possible use of such light-emitting bipolar devices as analytical tools for qualitative and quantitative measurements of enantiomeric excess, even in real samples. [Display omitted] [ABSTRACT FROM AUTHOR]

With an established procedure of molecular imprinting, a synthetic polymer receptor for the neopterin cancer biomarker was devised and used as a recognition unit of a potentiometric chemosensor. For that, bis -bithiophene derivatized with cytosine and bithiophene derivatized with boronic acid were used as functional monomers. The open-circuit potential (OCP) based transduction under flow-injection analysis conditions (FIA) determined neopterin in the concentration range of 0.15–2.5 mM with the 22 µM limit of detection (LOD) and 7.01(±0.15) mV mM −1 sensitivity indicating its potential suitability in clinical analysis applications. The molecularly imprinted polymer (MIP) film showed an appreciable apparent imprinting factor of ~6. The chemosensor successfully discriminated the interferences including the 6-biopterin and pterin structural analogs of neopterin as well as glucose and creatinine. Moreover, it determined neopterin in synthetic serum samples. [ABSTRACT FROM AUTHOR]

A novel recognition unit of chemical sensor for selective determination of the inosine, renal disfunction biomarker, was devised and prepared. For that purpose, inosine-templated molecularly imprinted polymer (MIP) film was deposited on an extended-gate field-effect transistor (EG-FET) signal transducing unit. The MIP film was prepared by electrochemical polymerization of bis(bithiophene) derivatives bearing cytosine and boronic acid substituents, in the presence of the inosine template and a thiophene cross-linker. After MIP film deposition, the template was removed, and was confirmed by UV–visible spectroscopy. Subsequently, the film composition was characterized by spectroscopic techniques, and its morphology and thickness were determined by AFM. The finally MIP film-coated extended-gate field-effect transistor (EG-FET) was used for signal transduction. This combination is not widely studied in the literature, despite the fact that it allows for facile integration of electrodeposited MIP film with FET transducer. The linear dynamic concentration range of the chemosensor was 0.5–50 μM with inosine detectability of 0.62 μM. The obtained detectability compares well to the levels of the inosine in body fluids which are in the range 0–2.9 µM for patients with diagnosed diabetic nephropathy, gout or hyperuricemia, and can reach 25 µM in certain cases. The imprinting factor for inosine, determined from piezomicrogravimetric experiments with use of the MIP film-coated quartz crystal resonator, was found to be 5.5. Higher selectivity for inosine with respect to common interferents was also achieved with the present molecularly engineered sensing element. The obtained analytical parameters of the devised chemosensor allow for its use for practical sample measurements. [ABSTRACT FROM AUTHOR]

A molecularly imprinted polymer (MIP) was designed and synthesized to serve as a functional material for selective recognition of 6-thioguanine (6TG), an antitumor drug. For that, the newly synthesized functional monomer, cytosine-bis(2,2′-bithienyl)-(4-carboxyphenyl)methane ester (Cyt-S4), revealed Watson–Crick type nucleobase pairing of 6TG. Formation of the Cyt-S4 and 6TG complex of the 2:1 stoichiometry was postulated based on the DFT calculations at the B3LYP/3-21G( ⁎ ) level and experimentally confirmed by fluorescence titration. The molecularly imprinted polymer (MIP) film was deposited by potentiodynamic electropolymerization on a Pt disk electrode as well as on an Au-coated glass slide and on an Au-quartz crystal resonator. The statistical model of formation of this film was successfully simulated by molecular dynamics. Completeness of the subsequent 6TG template extraction from MIP was confirmed by the UV–visible spectroscopy. An imprinting factor of 2.9 for the MIP film was determined by piezoelectric microgravimetry using ECQM. The double-layer capacity and alternating current measurements under flow-injection analysis (FIA) conditions were selected to transduce the 6TG recognition signal into the change of the double-layer capacity dependence on the 6TG concentration in solution for different supporting electrolyte concentrations. Detectability of the resulting chemosensor was 10 µM 6TG for the 0.5 M KF carrier solution in FIA. Selectivity of the chemosensor with respect to common interferences was high, e.g., it exceeded 130 to 2-amino-6-methylmercaptopurine, a 6TG metabolite. [ABSTRACT FROM AUTHOR]

Invited for the cover of this issue is Francesco Sannicolò and co-workers at different Italian institutions, who all contributed to the different specific areas of this multidisciplinary work. The image depicts inherently chiral elliptical and triangular oligothiophene macrocycles and their symmetrical resemblance to mysterious crop circles. Read the full text of the article at . [ABSTRACT FROM AUTHOR]

When new topologically appealing molecules are formed, fantasy ‐ assisted cogitation tries to associate their shapes to objects of everyday life: knots, cylinders, pretzels, baskets, ladders, etc. Chirality adds a touch of intelligence to these molecules, which gain the ability to recognize enantiomorphic species. In their Communication on page 15298 ff., F. Sannicolò et al. describe some inherently chiral elliptical and triangular oligothiophene macrocycles which they associate with the pictograms of some more or less mysterious crop circles. Photograph courtesy of Mr. Steve Alexander, www.temporarytemples.co.uk. [ABSTRACT FROM AUTHOR]

The novel [Re2(μ-H)(μ-OOC-CPDT)(CO)6(μ-3-Me-pydz)] complex (1; OOC-CPDT = 4H-cyclopenta[2,1-b:3,4-b']dithiophene-4-carboxylate, 3-Mepydz = 3-methylpyridazine) has been prepared and characterized by single-crystal X-ray diffraction, density functional theory (DFT), and time-dependent DFT computations, UV-vis absorption and emission spectroscopy, and cyclic voltammetry (CV). The measured properties indicate the lack of electronic communication in the ground state between the CPDT and the rhenium diazine moieties. Oxidative electropolymerization of 1, achieved by repeated potential cycling (-0.4 to +1.0 V vs Fc+/Fc, in acetonitrile) with different supporting electrolytes, on different electrodes, afforded an electroactive and stable metallopolymer (poly-1). In situ measurements of the mass of the growing film (on a gold electrode, with an electrochemical quartz microbalance) confirmed the regularity of the polymerization process. The polymer exhibits two reversible oxidation peaks of the thiophene chain and a broad irreversible reduction peak (-1.4 V, quite close to that observed for the reduction of monomer 1), associated with a remarkably delayed sharp return peak, of comparable associated charge, appearing in close proximity (+0.3 V) to the first oxidation peak of the neutral polythiophene chain. This charge-trapping effect can be observed upon repeated cycles of p and n doping, and the negative charge is maintained even if the charged electrode is removed from the solution for many hours. Electrochemical impedance spectroscopy showed that the main CV oxidation peak corresponds to facile charge transfer, combined with very fast diffusion of both electrons and ions within the polymer. In summary, poly-1 provides a new example of a metallopolymer, in which the conductive properties of the π-conjugated system are added to the redox behavior of the pendant-isolated complexes. [ABSTRACT FROM AUTHOR]

Abstract: The electroreduction of bromothiophenes on Au and Ag provides a striking model of synergy in electrocatalysis, when a second group specifically interacting with the catalytic surface is present besides the reacting one, providing an auxiliary anchoring effect. The high catalytic activity of Ag for bromobenzene reduction is enhanced in the bromothiophene case. Moreover, Au, having for bromobenzene a much lower and less reproducible catalytic effect than Ag on account of the repulsive effect of its very negative surface charge in the working potential range, approaches Ag activity in the case of 2-bromothiophene, where the anchoring S group is adjacent to the Br group to be cleaved. The beneficial anchoring effect is lower when it has to be shared between two Br leaving groups adjacent to the S group, and becomes negligible in the case of a bromide leaving group in 3-position. [Copyright &y& Elsevier]