A new C2-symmetric atropisomeric thiophene-based monomer for inherently chiral electroactive materials: synthesis, HPLC resolution, and absolute configuration assignment

Herein, we report on the synthesis and high-performance liquid chromatography (HPLC) resolution of a new atropisomeric C2-symmetry chiral monomer based on the 3,3′-bithiophene core, which was developed to produce novel, inherently oligomeric chiral electroactive materials. The analytical enantioseparation was optimized using the cellulose-type Chiralpak IB-3 column and a mixture of n-hexane–methanol–dichloromethane 90:5:5 (v/v/v) as the mobile phase. During the scale-up of the enantioseparation analytical conditions to a semipreparative level, remarkable deformations in the HPLC profile, such as peak splitting and plateau zones between enantiomeric peaks, were observed. We demonstrate the effects of sample diluent as they relate to distorted peak profiles, as well as provide experimental solutions to prevent the disturbing phenomenon. The optimized chromatographic conditions were exploited to collect milligram amounts of the enantiopure sample, which was submitted to chiroptical and stereochemical characterization studies

Incidence and risk factors of hospitalization for bronchiolitis in preterm children: a retrospective longitudinal study in Italy

<p>Abstract</p> <p>Background</p> <p>Bronchiolitis is a distressing, potentially life-threatening respiratory condition that affects infants. We evaluated the incidence and risk factors of hospitalization for broncholitis in preterm infants (i.e., a gestational age of <36 weeks) born between 2000 and 2006, and the use and impact of Palivizumab, a monoclonal antibody that in randomized clinical trials has been shown to lessen the severity of RSV-related bronchiolitis.</p> <p>Methods</p> <p>Retrospective cohort study that linked data from four health administrative databases in the Lazio region (a region of central Italy): the birth register, the hospital discharge register, and two ad-hoc databases that record the doses of Palivizumab administered at two local health units.</p> <p>Results</p> <p>Among 2407 preterm infants, 137 had at least one hospitalization for bronchiolitis in the first 18 months of life, an overall incidence rate of 4.70 per 100 person-years (95%CI: 3.98-5.56); similar incidence rates were observed by calendar year. A multiple Poisson model showed that the following characteristics were associated with higher incidence: younger age of the infant, the period between October-April, male gender, low Apgar score at birth, low birth weight, and low maternal educational level. At least one dose of Palivizumab was administered to 324 (13.5%) children; a dramatic increase from 2000 (2.8%) to 2006 (19.1%) (p < 0.01) was observed. Other factors independently associated with more frequent Palivizumab use were older maternal age, Italian-born mothers, female gender, low Apgar score, low birth weight, shorter gestational age, a diagnosis of broncho-dysplasia, and the month of birth. It is of note that none of the 34 children with congenital heart disease were prescribed Palivizumab. Performing several multiple Poisson models that also considered Palivizumab use as covariate, although the point estimates were in agreement with previous clinical trial results, we did not find in most of them a significant reduction for immunized children to be hospitalized for bronchiolitis.</p> <p>Conclusion</p> <p>In Italy the incidence of hospitalization for bronchiolitis, and its associated risk factors, are similar to that found in other countries. Although Palivizumab use is associated with the most important characteristics of severe prematurity, other aspects of its non-use in children with congenital heart disease, the age and the birth country of the mother suggest the need for public health measures that can reduce these health disparities. Finally, the estimated effectiveness of Palivizumab in routine practice, although not significant, confirms the results of previous clinical trials, but its impact on modifying the temporal trend in this population is still negligible.</p

Enantiomer discrimination in absorption spectroscopy and in voltammetry: highlighting fascinating similarities and connections

Absorption spectroscopy and voltammetry, of known analogies and connections, share even more fascinating similarities and connections at a higher complexity level, when "upgrading" them with the ability to discriminate between enantiomers by chiral selector implementation. In both techniques either "molecular" selectors or "electromagnetic" ones (L- versus Rcircularly polarized light components for spectroscopy, ccversus b-spin electrons for voltammetry) can be considered; moreover, external magnetic field application can replace a truly chiral actor. A tentative schematization is provided. Analogies and connections also concern molecular features of the enantiodiscrimination actors. In both techniques outstanding performances are obtained with inherently chiral molecules, in which a conjugated backbone with tailored torsion is source of chirality as well as spectroscopic and electrochemical activity, in an attractive three-fold interconnection. Their outstanding effects can be justified by a combination of chemical and electromagnetic properties (excellent potential molecular spin filters), a fascinating challenge for future developments

TetraPh-Tol-BITIOPO: a new atropisomeric 3,3’-bithiophene based phosphine oxide as organocatalyst in Lewis Base-catalyzed Lewis Acid mediated reactions

A new chiral phosphine oxide based on 3,3’-bithiophene scaffold (tetraPh-Tol-BITIOPO) was synthesized, fully characterized and separated into antipodes through chiral HPLC. This new compound was successfully employed as organocatalyst in Lewis base-catalyzed Lewis acid mediated reactions involving trichlorosilyl compounds. The new atropisomeric catalyst was able to promote the allylation of aldehydes with allyltrichlorosilane in up to 98% yield and up to 96% enantiomeric excess (ee), and the direct aldol reaction to afford β-hydroxy ketones and β-hydroxy thioesters, with good chemical yields and modest stereochemical efficiency. Computational studies helped to elucidate and to rationalize the stereochemical outcome of the reactions catalyzed by TetraPh-Tol-BITIOPO, that was found to favour the formation of the isomer with the opposite absolute configuration in comparison with the products obtained with the previously reported 3,3’-bithiophene-based catalyst

In Situ Electrochemical Investigations of Inherently Chiral 2,2′-Biindole Architectures with Oligothiophene Terminals

AbstractThe synthesis and characterization of three new inherently chiral N,N′‐dipropyl‐3,3′‐diheteroaryl‐2,2′‐biindole monomers, nicknamed Ind2T4, Ind2T6 and Ind2Ph2T4, which differ in the number of thiophenes as terminals, are reported. In addition to a full monomer characterization, stable electroactive oligomeric films were obtained by electro‐oxidation upon cycling to potentials which activate the thiophene terminals. Cyclic voltammetry, UV‐Vis‐NIR spectroelectrochemistry and in situ conductance measurements show that oligomeric films of Ind2T6 present the best stability and electrochromic switching performance. Enantioselective tests with a chiral ferrocene amine clearly show the potential as chiral selectors for analytical and sensing purposes

"Solid state charge trapping": Examples of polymer systems showing memory effect

The paper reports on a characteristic property of electroactive materials bearing an electron-rich and an electron-poor moiety, known as charge trapping. As examples of materials that exhibit this phenomenon, films of poly(4,4"-dipentoxy-4\u27-(2,2\u27-dicyano)ethenyl-2,2\u27:5\u27,2"-terthiophene), poly(2,3-dihexylthieno[3,4-b]pyrazine) and a blend between a fulleropyrrolidine derivative and poly(3-hexylthiophene) were investigated by cyclic voltammetry, spectroelectrochemistry and electrochemical quartz crystal microbalance. In the cyclic voltammetry, the reduction processes show the reverse oxidation potential about 1 V higher than the expected value, indicating a strong stabilization of the corresponding anion species. The mechanism leading to the stabilisation of the anions is discussed and the results indicate that the investigated materials exhibit a remarkable and quite stable memory effect

Chiral Recognition: A Spin-Driven Process in Chiral Oligothiophene. A Chiral-Induced Spin Selectivity (CISS) Effect Manifestation

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 &amp; PRIME;-bibenzothiophene core functionalized with 2,2 &amp; PRIME;-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.It is demonstrated that probing the handedness of a chiral system (here a chiral-electrode-surface/solution interface) by using a spin-polarized current, allows for chiral recognition. This conclusion is inferred by tight comparison with cyclic voltammetry results, where the handedness of the "chiral-electrode-surface/solution interface" is recognized by using an enantiopure chiral redox couple.imag

Electrocatalytic reduction of bromothiophenes on gold and silver electrodes: An example of synergy in electrocatalysis

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. Keywords: Molecular electrocatalysis, Dissociative electron transfer, Anchoring groups, Bromothiophenes, Gold electrodes, Silver electrode

Metal-Free Alpha Trifluoromethylselenolation of Carbonyl Derivatives under Batch and Flow Conditions

Trifluoromethylselenolated carbonyl compounds represent an emerging class with potential applications in several fields; however, a widespread use of such compound is hampered by the very limited number of strategies for their preparation. In this study we developed a method for the preparation of alpha-SeCF3 substituted carbonyl derivatives using an in situ generated electrophilic ClSeCF3 species. We also implemented an in-flow protocol to improve the safety features of the process