1,721,555 research outputs found
Approach to inherently chiralionic liquids
No full textIonic Liquids (ILs) constitute a class of solvents which got an increasing importance in the last ten years on account of some peculiar properties (low vapor pressure, chemical and thermal stability, solvating ability, non-flammability). Chiral ionic liquids (CILs) are used as solvents in asymmetric synthesis and in stereoselective polymerization, as chiral phases for gas chromatography, as chiral shift reagents in NMR spectroscopy and, in some cases, as promoters of cholesteric liquid crystals. Most of known CILs, are onium salts bearing chiral substituents characterized by one or several stereocenters. The research is focused to the design, synthesis, characterizetion and test in electrochemical oxo-reduction processes of a new family of CILs in which the stereogenic element (a stereogenic axis) coincides with the function responsible for the IL properties. Using the successful strategy recently employed for designing “inherently chiral” oligotiophenes,1 some “inherently chiral” CILs have been prepared based on bis-imidazolium and bi-piridinium atropisomeric scaffolds. The general structures and some specific examples are reported in the following scheme. The synthetic accessibility, the chromatographic behaviour of the precursors and the configurational stability of the new compounds is discussed.
This work is supported by Fondazione Cariplo (reg. No 2011-1851) and C.N.R.
(PM.P03.002.002).
1 Sannicolò, F.; Arnaboldi, S.; Benincori, T.; Bonometti, V.; Cirilli, R.; Dunsch, L.;
Kutner, W.; Longhi, G.; Mussini, P.R.; Panigati, M.; Pierini, M.; Rizzo, S. Angew.
Chem. Int. Ed. 2014, 53, 2623
Electronic and Spectroscopic Properties of Thiophene-based Organic Polyconjugated Semiconductors Built from Inherently Chiral Monomers
No full textThe availability of materials which could couple electroactivity properties and enantiorecognition capability is an ambitious objective of the modern chemical research. Chirality is generally introduced in these materials by attaching chiral pendants to an electroactive polyconjugated backbone through suitable linkers and a great variety of substituents have been employed either chosen from the chiral pool, like sugar and amino-acids, or man-made, designed and synthesized for specific applications. We have developed a new strategy for preparing electroactive chiral polymers, consisting in the oxidative polymerization of chiral oligothiophene monomers in which chirality results from a tailored torsion produced along the oligothiophene backbone by an atropisomeric bithiophene or bipyrrole scaffold (Scheme 1).1 The structural design of the monomers requires that the biheteroaromatic core could take part in the conjugative communication between the bithiophene termini. Furthermore, the polymerization sites of the monomers should be homotopic, thus granting the perfect constitutional regularity of the polymers. The 2,2’-bis(2,2’-bithiophene-5-yl)-3,3’-bithianaphthene and the 1,1’-dimethyl-3,3’-bis(2,2’-bithiophene-5-yl)- 2,2’-biindole are the first examples of this strategy. The antipodes have been obtained in an enantiopure state and submitted to the electropolymerization process yielding materials exhibiting outstanding chirality manifestations.
References
1) F. Sannicolò, S. Rizzo, T. Benincori, W. Kutner, K. Noworyta, J. W. Sobczak, V. Bonometti, L. Falciola, P. R. Mussini, M. Pierini, Electrochimica Acta, in press
C2-Symmetric Oligothiophene Monomers as Precursors of Inherently Chiral Semiconductors
No full textThe introduction of chirality in organic conjugated polymers displaying electroconductive properties has been considered for a wide variety of purposes: 1) the ordered spontaneous chain assembling induced by chirality; 2) the noncentrosymmety associated to chiral materials, which is a prerequisite for second-order nonlinear optical applications; 3) the ability of chiral enantiomerically enriched molecules to discriminate between antipodes, as required in sensors designed for the detection of chiral analytes; 4) chiral electroconductive polymers could be used to modify the surface of electrodes to be employed in asymmetric redox reactions.
Chirality is generally introduced in the polymer by attaching chiral pendants to the electroactive conjugated backbone through suitable linkers, and a great variety of chiral substituents have been employed either chosen from the chiral pool, like sugar and amino-acids, or man-made, designed and synthesized for specific applications. We have developed a new strategy for preparing electroactive chiral polymers, consisting in the oxidative polymerization of chiral oligothiophene monomers in which chirality results from a tailored torsion produced along the oligothiophene backbone by an atropisomeric bithiophene1 or bipyrrole scaffold (Scheme 1).
The structural design of the monomers requires that the biheteroaromatic core would take part in the conjugative communication between the bithiophene termini. Furthermore, the polymerization sites of the monomers should be homotopic, thus granting the perfect constitutional regularity of the polymers. are reported The first examples of monomers designed according to this strategy (Scheme 1) and their electropolymerization to yield materials exhibiting outstanding chirality manifestations are discussed.
References: 1) F. Sannicolò, S. Rizzo, T. Benincori, W. Kutner, K. Noworyta, J. W. Sobczak, V. Bonometti, L. Falciola, P. R. Mussini, M. Pierini, Electrochimica Acta, 2010,55, 8352; A. Pietrzyk, W. Kutner, R. Chitta, M. E. Zandler, F. D’Souza, F. Sannicolò, P. R. Mussini, Anal. Chem. 2009, 81, 10061
Approach to inerently chiral Ionic Liquids
No full textChiral Ionic Liquids (CILs) constitute a class of solvents which got an increasing importance in the last ten years on account of some peculiar properties (low vapor pressure, chemical and thermal stability, solvating ability, nonflammability). CILs are used as solvents in asymmetric synthesis and in stereoselective polymerization, as chiral phases for gas chromatography, as chiral shift reagents in NMR spectroscopy and, in some cases, to generate cholesteric liquid crystals. Most of known CILs, are onium salts characterized by chiral substituents having one or several stereocenters. The aim of the research is to design, synthesize, characterize and test in electrochemical oxo-reduction processes a new family of CILs in which the stereogenic element (a stereogenic axis) coincides
with the function responsible for the IL properties. Using the successful strategy recently employed for designing “inherently chiral” oligotiophenes,1 some “inherently chiral”
CILs have been prepared based on bis-imidazolium atropisomeric scaffolds (Fig. 1).
Fig. 1
In the series of the 1,1’-bisbenzimidazoles precursors of CILs carrying progressively longer R’ groups (Fig. 1) a surprising inversion in the elution times of
the enantiomers on the amylose tris(3,5-dimethylphenyl carbamate) chiral stationary phase (Chiralpak AD-3) under normal phase mode was investigated.
This work was supported by Fondazione Cariplo (reg. No 2011-1851) and C.N.R. (PM.P03.002.002).
1 Sannicolò, F.; Arnaboldi, S.; Benincori, T.; Bonometti, V.; Cirilli, R.; Dunsch, L.;
Kutner, W.; Longhi, G.; Mussini, P.R.; Panigati, M.; Pierini, M.; Rizzo, S. Angew.
Chem. Int. Ed. 2014, 53, 2623
SCHEDE STORICO-CRITICHE SULLE SEGUENTI OPERE: Mario Ceroli, Cassa Sistina, 1966; Fabio Novembre, Vassoio 100 Piazze (Roma), 2007; Henry Moore, Omaggio a Michelangelo, 1975; Eduardo Paolozzi, Omaggio a Michelangelo, 1975; Alberto Giacometti, Tête de l’esclave enchaînée par la mort d’après Michel-Ange, 1958 ca.; Le Corbusier, Studi sul Campidoglio dai documenti della Fondation Le Corbusier, 1911-1915; Giovanna Sgrilli, Giovanni Michelucci nella casa di Fiesole davanti al calco della Pietà Rondanini, 1986; Manifesto della mostra Vitalità del negativo nell’arte italiana 1960-70, 1970; Aldo Rossi, Disegno di studio per la Schutzenstrasse a Berlino, 1992-1995; Vassilij Kandinskij, Rot in Spitzform, 1925
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Synthesis of a basket-resorc[4]arene via metathesis reaction and encapsulation studies of fullerenes C60 and C70
No full textCoco Rebecca Edogamhe: A Very Ordinary Girl
Full text linkThe work of Coco Rebecca Edogamhe (born 2001) is unique and relevant case study due to three interdependent factors: her young age and short acting experience, which allow us to observe the construction of professional narratives and practices from scratch; her debut in a leading role without prior acting training, which led her to interpret the set as a school; her identity as an Italian of Afro-descent, which places her at the centre of the debate on diversity and representation. While acknowledging her exceptional profile, she also makes a constant shift towards the notion of 'ordinary', proposing a nuanced and everyday model of celebrity, suitable for both television and digital media. Crucial to all this was the casting process, the debut during the Covid-19 pandemic, and her mirroring in the part of summer in 'Summertime' (Netflix 2020-2022). In this essay, press interviews and an in-depth dialogue between the author and the actress will interact diachronically to capture the main trajectories through which Edogamhe negotiated her public identity and began to build her professional culture
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
