Simona Rizzo - Academia.edu (original) (raw)
Papers by Simona Rizzo
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
![Research paper thumbnail of A Raman and SERS study on the interactions of aza[5]helicene and aza[6]helicene with a nanostructured gold surface](https://attachments.academia-assets.com/105212636/thumbnails/1.jpg)
](Vibrational Spectroscopy, 2020
Thiophene-based inherently chiral conducting films, under development in our research group, have... more Thiophene-based inherently chiral conducting films, under development in our research group, have very high and stable chiral activity, depending on a tailored torsion of the whole conducting backbone rather than on attached chiral pendants; accordingly, such chirality is modulable by the amount of injected charge (reducing the torsion angle to achieve better system conjugation), a phenomenon which suggested us the image of a breathing system. Perfectly specular electrode surfaces have been prepared by electrodeposition cycles, starting from the corresponding inherently chiral oligomers. To finely discriminate among the racemate and enantiomer film properties, and above all to achieve enantioselective electrode surfaces for applications in the electroanalysis and electrocatalysis domains, reproducibility is a necessary but hard task. In this context, preliminary literature studies [1,2] point to room temperature ionic liquids RTIL, both as such and as co-solvents, significantly improving the regularity and the mechanical and morphological properties of electrodeposited conducting molecular films. In this frame, we have carried out an extensive study aimed to the rationalization of the conducting film features obtained in different conditions (i.e., RTILs vs non polar and polar VOCs, on various electrodes), both on model starting monomers (EDOT and EDOP) and on our newly developed inherently chiral ones. In particular, enantiomer film deposition from RTILs on screen-printed electrodes afforded reproducible and repeatable enantiorecognition ability of the specular electrode surfaces towards specular probes
The highest degree of selectivity in electrochemical recognition is achieved with enantioselectiv... more The highest degree of selectivity in electrochemical recognition is achieved with enantioselective electroanalysis, implying the ability to discriminate specular images of a given electroactive molecule, an issue particularly important in the biological and pharmaceutical fields [1]. In fact the enantiomers of a chiral molecule have identical physico-chemical properties and would have identical electrochemical behaviour excepting when reacting in a diastereomeric context (diastereoisomers are energetically different). Unprecedented enantiorecognition in terms of large potential differences was recently observed in analytical experiments by our research group[2], implementing: 1) enantiopure electrode surfaces based on inherently chiral heterocycle-based electroactive films (with different stereogenic elements, C2 axis vs helix); 2) enantiopure media based on inherently chiral (or simply chiral) ionic liquids or related additives dissolved in an achiral medium [3,4]; 3) Deep Eutectic Solvents (DES), commonly defined as systems composed of a mixture of at least two components, a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD). An even more striking feature implying inherently chiral films was obtained in the frame of the CISS (Chiral Induced Spin Selectivity) effect, recently unveiled by Ron Naaman and co-workers, where spin polarization in photo-ejected electrons transmitted through a thin layer of enantiopure material on gold was observed [5]. In this frame we present an innovative set-up which includes i) a non-ferromagnetic electrode (ITO) modified with a thin electroactive chiral film (the spin filter), ii) achiral redox couples dissolved in aqueous or organic solutions and iii) an external permanent magnet which was placed near the chiral film. A spectacular unforeseen effect was observed by means of cyclovoltammetry (CV), in fact CV peaks recorded in the presence of achiral redox couples reveal an impressive potential shift by flipping the magnet orientation (north vs south). This effect was also specular by changing the spin injector configuration. The importance of these studies includes possible applications in the field of spintronics, electronics, chemical sensoristic and so on and provides a striking evidence of the spin selectivity properties of chiral thin films [6]. References: [1]S. Arnaboldi, T. Benincori, R. Cirilli, S. Grecchi, L. Santagostini, F. Sannicol\uf2, P. R. Mussini, (2016), ABC, 408, 26, 7243. [2]S. Arnaboldi, S. Grecchi, M. Magni, P. Mussini, (2018), Curr. Opinion, 8, 60 [3]S. Arnaboldi, M. Magni, P. Mussini, (2018), Curr. Opinion, 7, 188. [4]M. Longhi, S. Arnaboldi, E. Husanu, S. Grecchi, I. F. Buzzi, R. Cirilli, S. Rizzo, C. Chiappe, P. R. Mussini, L. Guazzelli, (2019), Electrochimica Acta, 298, 194. [5]B Dor, S. Yochelis, S. P. Mathew, R. Naaman, Y. Paltiel, (2013) Nat. Commun. 4, 3256. [6]Benincori, S. Arnaboldi, M. Magni, S. Grecchi, R. Cirilli, C. Fontanesi, P. R. Mussini, (2019), Chem. Sci, 10, 2750
La presente invenzione ha per oggetto composti oligoarenici e oligoeteroarenici macrociclici poli... more La presente invenzione ha per oggetto composti oligoarenici e oligoeteroarenici macrociclici policoniugati, elettroattivi, sia achirali, sia chirali, eventualmente 5 utilizzabili come singoli enantiomeri, e i loro derivati, impiegati nella costruzione di dispositivi per l'elettronica, nel settore della sensoristica, nel settore del fotovoltaico, nel settore delle separazioni cromatografiche o in reazioni di catalisi stereoselettiva
Multithiophene-based semiconductors are a well-known, popular class of organic semiconductors of ... more Multithiophene-based semiconductors are a well-known, popular class of organic semiconductors of very promising potential applications in a wide variety of fields, like electronics, energetics, sensoristics. Starting from our previous exhaustive work on \u201cspider-like\u201d branched oligothiophenes, affording a detailed and reliable rationalization of the relationships between structure and electronic properties1,2, many structure modifications have been recently developed with respect to the original all-thiophene systems, aiming to achieve finer and wider modulation of both the HOMO and LUMO levels. In particular, the \u201ccore\u201d of our oligothiophene systems has been modified by choosing appropriate building blocks of different electron-richness, asymmetrically affecting both the LUMO and HOMO energy levels and localization along the main conjugated backbone, thus achieving one more freedom degree in tuning the electron properties of the molecule. Our voltammetric investigation has been performed on a wide series of \u201cgenetically-modified\u201d spider-like oligothiophenes, exploring both the effect of core modification at constant thiophene side chains, and the effect of increasing length and/or branching in the thiophene side chains at constant modified core. The core modification appears to be much more effective on the HOMO and LUMO energy levels and positions, while effective conjugation in the thiophene side chains is more determining on the oligomerization ability. The exhaustiveness of our investigation affords interpretative and predictive criteria which could usefully exploited in target-oriented molecular design
Thiophene-based inherently chiral conducting films, under development in our research group, have... more Thiophene-based inherently chiral conducting films, under development in our research group, have very high and stable chiral activity, depending on a tailored torsion of the whole conducting backbone rather than on attached chiral pendants; accordingly, such chirality is modulable by the amount of injected charge (reducing the torsion angle to achieve better p system conjugation), a phenomenon which suggested us the image of a breathing system. Perfectly specular electrode surfaces have been prepared by electrodeposition cycles, starting from the corresponding inherently chiral oligomers, and their enantiorecognition ability is currently under study in our group. In order to finely discriminate among the racemate and enantiomer film properties, and above all to achieve optimized enantiomer electrode surfaces for applications as chiral sensors, reproducibility is a necessary but hard task. In this context, preliminary literature studies [1,2] pointed to room temperature ionic liquids RTIL, both as such and as cosolvents, significantly improving the regularity and the mechanical and morphological properties of the conducting films to be employed e.g. in the energetic, optoelectronic, and sensoristic domains (besides other advantages including negligible vapour pressure, high intrinsic conductivity without addition of supporting electrolyte and easy recyclability). In this frame, we will present our recent extensive study aimed to the rationalization of the conducting film features obtained in different conditions (i.e., RTILs vs non polar and polar VOCs, on various electrode), both on model starting monomers (EDOT and EDOP) and on our newly developed inherently chiral ones. References: [1] F. Endres, A.P. Abbott, D.R. MacFarlane, Electrodeposition from Ionic Liquids, 2008, Wiley-VCH, ISBN 978-3-527-31565-9. [2] A.Pietrzyk, W.Kutner, R.Chitta, M. E. Zandler, F. D\u2019Souza, F. Sannicol\uf2, P.R. Mussini, Anal. Chem., 2009, 81(24), 10061-10070
Current Opinion in Electrochemistry, 2021
Abstract An increasing number of strategies and tools have been proposed to endow the electrochem... more Abstract An increasing number of strategies and tools have been proposed to endow the electrochemical interphase with chirality, to achieve enantiodiscrimination in analytical and/or preparative applications. So far, chirality has mostly been implemented not only at the electrode surface side but also on the medium one. Recently, the attractiveness of the latter approach has remarkably increased on account of the increasing availability of advanced chiral molecular media with intrinsic attractive features for electrochemistry applications, such as chiral ionic liquids, chiral ionic liquid crystals, and chiral deep eutectic solvents. With respect to solid layer/fixed chiral networks, advanced chiral media can still offer a reasonably high degree of local structuring, while being less demanding concerning preparation and management protocols, as well as less sensitive to fouling/regeneration issues. Different ways to implement chirality in advanced molecular media, including cases of powerful ‘inherent chirality,’ will be presented and discussed, particularly focusing on recent applications in the electrochemical field.
Angewandte Chemie International Edition, 2017
![Research paper thumbnail of 2,12-Diaza[6]helicene: An Efficient Non-Conventional Stereogenic Scaffold for Enantioselective Electrochemical Interphases](https://attachments.academia-assets.com/89013214/thumbnails/1.jpg)
](Chemosensors
The new configurationally stable, unsymmetrical 2,12-diaza[6]helicene was synthesized as a racema... more The new configurationally stable, unsymmetrical 2,12-diaza[6]helicene was synthesized as a racemate and the enantiomers were separated in an enantiopure state by semi-preparative HPLC on chiral stationary phase. Under selected alkylation conditions it was possible to obtain both the enantiopure 2-N-mono- and di-N-ethyl quaternary iodides. Metathesis with bis(trifluoromethanesulfonyl)imide anion gave low-melting salts which were tested as inherently chiral additives to achiral ionic liquids for the electrochemical enantiodiscrimination of chiral organic probes in voltammetric experiments. Remarkable differences in the oxidation potentials of the enantiomers of two probes, a chiral ferrocenyl amine and an aminoacid, were achieved; the differences increase with increasing additive concentration and number of alkylated nitrogen atoms.
The reductive cleavage of C-Br bonds on Ag electrodes can be regarded as an ideal model of dissoc... more The reductive cleavage of C-Br bonds on Ag electrodes can be regarded as an ideal model of dissociative electron transfer (DET) in electrocatalytic conditions, modulated by many factors, among which the molecular structure is of particular relevance. A detailed mechanistic study based on a large set of compounds with different molecular structures allowed us a full rationalization of the process for the case of aryl bromides in acetonitrile. Now we are extending this research to heteroaromatic halides, in which the heteroatom not only makes the aromatic ring asymmetric from the perspective of the electron density but also can have its own specific interations with the electrode surface, in addition to those of the halide ions. As a first approach, we have selected the mono-, di-, tri- and tetra-bromothiophene series, plus a series of substituted bromothiophenes togeteher with the corresponding bromobenzenes as benchmarks, investigating (by CV supported by EIS in selected cases), the electrochemical reduction of the whole family: (a) on glassy carbon GC, assumed as a non-catalytic reference accounting for intrinsic reactivity; (b) on the highly catalytic silver electrode; (c) on gold electrode, showing in former halide cases lower catalytic effects than silver (on account of its much more positive pzc with respect to the working potentials, hampering halide-surface specific interactions), but having the highest affinity for the sulphur atom in the thiophene ring. While the results on GC and on Ag are fully consistent with the formerly studied aryl bromide case on the same two electrodes (with some enhancement of the catalytic effects on Ag), the catalytic effects of Au appear to be neatly modulated by the relative position of the Br\uf02d leaving group with respect to the sulphur atom. In particular, the catalytic effects for the reduction of C-Br bonds at a positions are significantly higher than those at b, and they even approach the high catalytic effects of Ag. This feature is quite evident and reproducible in the whole series (including polysubstituted cases), and points to the S atom acting as an asymmetrically anchoring group for the molecule on the Au surface, particularly fostering specific interaction of the surface with adjacent halide leaving groups, and thus partially overcoming the electrostatic repulsion connected with the very positive pzc
Azahelicenes are extensively conjugated, intrinsically chiral molecules with interesting optical ... more Azahelicenes are extensively conjugated, intrinsically chiral molecules with interesting optical and optoelectronic properties. They show interesting SERS activity as well as fluorescence. While synthesizing 5-aza[6]helicene (2) we observed concurrent formation of byproduct (3), phenanthreno[2,3-k]phenanthridine in non-negligible amount. Therefore, we decided to characterize it respect to its spectroscopic and emission properties. We recorded UV-Vis absorption and concentration-dependent fluorescence spectra of (3) excited at 314 nm. We observed an excellent linear dependence of the emission maximum (429 nm) vs. concentration in diluted MeOH solutions (5x10-5 - 3x10-4 mM). We studied its IR and Raman spectra and, once assessed its Raman activity, we adsorbed (3) on nanostructured gold substrates produced by PLD with a plasmon resonance close to 785 nm, with the purpose of investigating its SERS response. We also carried out density functional theory calculations, aiming at the inter...
A typical drawback of electrochemical processes consists in the employment of volatile organic so... more A typical drawback of electrochemical processes consists in the employment of volatile organic solvents (VOCs), which imply safety problems and require the addition of high amounts of a supporting electrolyte to obtain the necessary conductivity. Both problems could be overcome by shifting to non-conventional media such as room temperature ionic liquids (RTILs). In fact, RTILs present various desirable advantages over molecular solvents, including negligible vapour pressure, high intrinsic conductivity without addition of supporting electrolyte and easy recyclability. Moreover, specifically dealing with electropolymerizations, preliminary studies[1,2] point to ionic liquids, both as such and as cosolvents, significantly improving the regularity and the mechanical and morphological properties of the conducting films to be employed e.g. in the energetic, optoelectronic, and sensoristic domains. In this context, we present the results obtained in our research work, concerning a class of inherently chiral polymer films[3], studied and characterized as racemates and as separated enantiomers, by means of cyclic voltammetry and electrochemical impedance spectroscopy, together with SEM imaging. In order to finely discriminate among the racemate and enantiomer film properties, and above all to achieve optimized enantiomer electrode surfaces for applications as chiral sensors, reproducibility is a necessary but hard task. In this frame, the present work is aimed to compare the polymer features obtained in different conditions (i.e., RTILs vs VOCs, on various electrode surfaces and for increasing thickness of the electrodeposited films) to select the best working medium for the preparation of the electroactive films. [1] F. Endres, A.P. Abbott, D.R. MacFarlane, Electrodeposition from Ionic Liquids, 2008, Wiley-VCH, ISBN 978-3-527-31565-9 [2] A.Pietrzyk, W.Kutner, R.Chitta, M. E. Zandler, F. D\u2019Souza, F. Sannicol\uf2, P.R. Mussini, Anal. Chem., 2009, 81(24), 10061-10070. [3] F. Sannicol\uf2, S. Rizzo, T. Benincori, W. Kutner, K. Noworita, J.W. Sobczak, V. Bonometti, L. Falciola, P.R. Mussini, M. Pierini, Electrochim. Acta, 2010, 55(27), 8352-8364
Molecules, 2021
Configurationally stable 5-aza[6]helicene (1) was envisaged as a promising scaffold for non-conve... more Configurationally stable 5-aza[6]helicene (1) was envisaged as a promising scaffold for non-conventional ionic liquids (IL)s. It was prepared, purified, and separated into enantiomers by preparative HPLC on a chiral stationary phase. Enantiomerically pure quaternary salts of 1 with appropriate counterions were prepared and fully characterized. N-octyl-5-aza[6]helicenium bis triflimidate (2) was tested in very small quantities as a selector in achiral IL media to perform preliminary electrochemical enantiodifferentiation experiments on the antipodes of two different chiral probes. The new organic salt exhibited outstanding enantioselection performance with respect to these probes, thus opening the way to applications in the enantioselective electroanalysis of relevant bioactive molecules.
Electrochimica Acta, 2021
Abstract Deep Eutectic Solvents (DESs) offer advantages similar to ionic liquid (IL) ones, with e... more Abstract Deep Eutectic Solvents (DESs) offer advantages similar to ionic liquid (IL) ones, with easier and more sustainable synthesis; moreover, bio-based DESs often include chiral components, surprisingly underexploited. A proof of concept is now offered of the impressive potential of enantiopure chiral DESs as chiral media for enantioselective electroanalysis. Three chiral DESs, consisting of a molecular salt with bio-based chiral cation [NopolMIm]+ combined with three natural and/or low-cost partners (levulinic acid, glycerol and urea), are introduced and investigated as chiral voltammetry media. Significant potential differences are observed for the enantiomers of a model chiral probe, with a dramatic tuning depending on the achiral DES component, reaching an impressive ∼0.5 V in the levulinic acid case (while less efficient appears [NopolMIm]+ as chiral additive in IL). With the same medium good enantiodiscrimination is also observed for aminoacid tryptophan, a quite different probe and of applicative interest. These findings can be considered as a remarkable step further in chiral electroanalysis as well as in the development of task-specific enantioselective media.
Electrochemistry Communications, 2018
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Vibrational Spectroscopy, 2020
Thiophene-based inherently chiral conducting films, under development in our research group, have... more Thiophene-based inherently chiral conducting films, under development in our research group, have very high and stable chiral activity, depending on a tailored torsion of the whole conducting backbone rather than on attached chiral pendants; accordingly, such chirality is modulable by the amount of injected charge (reducing the torsion angle to achieve better system conjugation), a phenomenon which suggested us the image of a breathing system. Perfectly specular electrode surfaces have been prepared by electrodeposition cycles, starting from the corresponding inherently chiral oligomers. To finely discriminate among the racemate and enantiomer film properties, and above all to achieve enantioselective electrode surfaces for applications in the electroanalysis and electrocatalysis domains, reproducibility is a necessary but hard task. In this context, preliminary literature studies [1,2] point to room temperature ionic liquids RTIL, both as such and as co-solvents, significantly improving the regularity and the mechanical and morphological properties of electrodeposited conducting molecular films. In this frame, we have carried out an extensive study aimed to the rationalization of the conducting film features obtained in different conditions (i.e., RTILs vs non polar and polar VOCs, on various electrodes), both on model starting monomers (EDOT and EDOP) and on our newly developed inherently chiral ones. In particular, enantiomer film deposition from RTILs on screen-printed electrodes afforded reproducible and repeatable enantiorecognition ability of the specular electrode surfaces towards specular probes
The highest degree of selectivity in electrochemical recognition is achieved with enantioselectiv... more The highest degree of selectivity in electrochemical recognition is achieved with enantioselective electroanalysis, implying the ability to discriminate specular images of a given electroactive molecule, an issue particularly important in the biological and pharmaceutical fields [1]. In fact the enantiomers of a chiral molecule have identical physico-chemical properties and would have identical electrochemical behaviour excepting when reacting in a diastereomeric context (diastereoisomers are energetically different). Unprecedented enantiorecognition in terms of large potential differences was recently observed in analytical experiments by our research group[2], implementing: 1) enantiopure electrode surfaces based on inherently chiral heterocycle-based electroactive films (with different stereogenic elements, C2 axis vs helix); 2) enantiopure media based on inherently chiral (or simply chiral) ionic liquids or related additives dissolved in an achiral medium [3,4]; 3) Deep Eutectic Solvents (DES), commonly defined as systems composed of a mixture of at least two components, a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD). An even more striking feature implying inherently chiral films was obtained in the frame of the CISS (Chiral Induced Spin Selectivity) effect, recently unveiled by Ron Naaman and co-workers, where spin polarization in photo-ejected electrons transmitted through a thin layer of enantiopure material on gold was observed [5]. In this frame we present an innovative set-up which includes i) a non-ferromagnetic electrode (ITO) modified with a thin electroactive chiral film (the spin filter), ii) achiral redox couples dissolved in aqueous or organic solutions and iii) an external permanent magnet which was placed near the chiral film. A spectacular unforeseen effect was observed by means of cyclovoltammetry (CV), in fact CV peaks recorded in the presence of achiral redox couples reveal an impressive potential shift by flipping the magnet orientation (north vs south). This effect was also specular by changing the spin injector configuration. The importance of these studies includes possible applications in the field of spintronics, electronics, chemical sensoristic and so on and provides a striking evidence of the spin selectivity properties of chiral thin films [6]. References: [1]S. Arnaboldi, T. Benincori, R. Cirilli, S. Grecchi, L. Santagostini, F. Sannicol\uf2, P. R. Mussini, (2016), ABC, 408, 26, 7243. [2]S. Arnaboldi, S. Grecchi, M. Magni, P. Mussini, (2018), Curr. Opinion, 8, 60 [3]S. Arnaboldi, M. Magni, P. Mussini, (2018), Curr. Opinion, 7, 188. [4]M. Longhi, S. Arnaboldi, E. Husanu, S. Grecchi, I. F. Buzzi, R. Cirilli, S. Rizzo, C. Chiappe, P. R. Mussini, L. Guazzelli, (2019), Electrochimica Acta, 298, 194. [5]B Dor, S. Yochelis, S. P. Mathew, R. Naaman, Y. Paltiel, (2013) Nat. Commun. 4, 3256. [6]Benincori, S. Arnaboldi, M. Magni, S. Grecchi, R. Cirilli, C. Fontanesi, P. R. Mussini, (2019), Chem. Sci, 10, 2750
La presente invenzione ha per oggetto composti oligoarenici e oligoeteroarenici macrociclici poli... more La presente invenzione ha per oggetto composti oligoarenici e oligoeteroarenici macrociclici policoniugati, elettroattivi, sia achirali, sia chirali, eventualmente 5 utilizzabili come singoli enantiomeri, e i loro derivati, impiegati nella costruzione di dispositivi per l'elettronica, nel settore della sensoristica, nel settore del fotovoltaico, nel settore delle separazioni cromatografiche o in reazioni di catalisi stereoselettiva
Multithiophene-based semiconductors are a well-known, popular class of organic semiconductors of ... more Multithiophene-based semiconductors are a well-known, popular class of organic semiconductors of very promising potential applications in a wide variety of fields, like electronics, energetics, sensoristics. Starting from our previous exhaustive work on \u201cspider-like\u201d branched oligothiophenes, affording a detailed and reliable rationalization of the relationships between structure and electronic properties1,2, many structure modifications have been recently developed with respect to the original all-thiophene systems, aiming to achieve finer and wider modulation of both the HOMO and LUMO levels. In particular, the \u201ccore\u201d of our oligothiophene systems has been modified by choosing appropriate building blocks of different electron-richness, asymmetrically affecting both the LUMO and HOMO energy levels and localization along the main conjugated backbone, thus achieving one more freedom degree in tuning the electron properties of the molecule. Our voltammetric investigation has been performed on a wide series of \u201cgenetically-modified\u201d spider-like oligothiophenes, exploring both the effect of core modification at constant thiophene side chains, and the effect of increasing length and/or branching in the thiophene side chains at constant modified core. The core modification appears to be much more effective on the HOMO and LUMO energy levels and positions, while effective conjugation in the thiophene side chains is more determining on the oligomerization ability. The exhaustiveness of our investigation affords interpretative and predictive criteria which could usefully exploited in target-oriented molecular design
Thiophene-based inherently chiral conducting films, under development in our research group, have... more Thiophene-based inherently chiral conducting films, under development in our research group, have very high and stable chiral activity, depending on a tailored torsion of the whole conducting backbone rather than on attached chiral pendants; accordingly, such chirality is modulable by the amount of injected charge (reducing the torsion angle to achieve better p system conjugation), a phenomenon which suggested us the image of a breathing system. Perfectly specular electrode surfaces have been prepared by electrodeposition cycles, starting from the corresponding inherently chiral oligomers, and their enantiorecognition ability is currently under study in our group. In order to finely discriminate among the racemate and enantiomer film properties, and above all to achieve optimized enantiomer electrode surfaces for applications as chiral sensors, reproducibility is a necessary but hard task. In this context, preliminary literature studies [1,2] pointed to room temperature ionic liquids RTIL, both as such and as cosolvents, significantly improving the regularity and the mechanical and morphological properties of the conducting films to be employed e.g. in the energetic, optoelectronic, and sensoristic domains (besides other advantages including negligible vapour pressure, high intrinsic conductivity without addition of supporting electrolyte and easy recyclability). In this frame, we will present our recent extensive study aimed to the rationalization of the conducting film features obtained in different conditions (i.e., RTILs vs non polar and polar VOCs, on various electrode), both on model starting monomers (EDOT and EDOP) and on our newly developed inherently chiral ones. References: [1] F. Endres, A.P. Abbott, D.R. MacFarlane, Electrodeposition from Ionic Liquids, 2008, Wiley-VCH, ISBN 978-3-527-31565-9. [2] A.Pietrzyk, W.Kutner, R.Chitta, M. E. Zandler, F. D\u2019Souza, F. Sannicol\uf2, P.R. Mussini, Anal. Chem., 2009, 81(24), 10061-10070
Current Opinion in Electrochemistry, 2021
Abstract An increasing number of strategies and tools have been proposed to endow the electrochem... more Abstract An increasing number of strategies and tools have been proposed to endow the electrochemical interphase with chirality, to achieve enantiodiscrimination in analytical and/or preparative applications. So far, chirality has mostly been implemented not only at the electrode surface side but also on the medium one. Recently, the attractiveness of the latter approach has remarkably increased on account of the increasing availability of advanced chiral molecular media with intrinsic attractive features for electrochemistry applications, such as chiral ionic liquids, chiral ionic liquid crystals, and chiral deep eutectic solvents. With respect to solid layer/fixed chiral networks, advanced chiral media can still offer a reasonably high degree of local structuring, while being less demanding concerning preparation and management protocols, as well as less sensitive to fouling/regeneration issues. Different ways to implement chirality in advanced molecular media, including cases of powerful ‘inherent chirality,’ will be presented and discussed, particularly focusing on recent applications in the electrochemical field.
Angewandte Chemie International Edition, 2017
Chemosensors
The new configurationally stable, unsymmetrical 2,12-diaza[6]helicene was synthesized as a racema... more The new configurationally stable, unsymmetrical 2,12-diaza[6]helicene was synthesized as a racemate and the enantiomers were separated in an enantiopure state by semi-preparative HPLC on chiral stationary phase. Under selected alkylation conditions it was possible to obtain both the enantiopure 2-N-mono- and di-N-ethyl quaternary iodides. Metathesis with bis(trifluoromethanesulfonyl)imide anion gave low-melting salts which were tested as inherently chiral additives to achiral ionic liquids for the electrochemical enantiodiscrimination of chiral organic probes in voltammetric experiments. Remarkable differences in the oxidation potentials of the enantiomers of two probes, a chiral ferrocenyl amine and an aminoacid, were achieved; the differences increase with increasing additive concentration and number of alkylated nitrogen atoms.
The reductive cleavage of C-Br bonds on Ag electrodes can be regarded as an ideal model of dissoc... more The reductive cleavage of C-Br bonds on Ag electrodes can be regarded as an ideal model of dissociative electron transfer (DET) in electrocatalytic conditions, modulated by many factors, among which the molecular structure is of particular relevance. A detailed mechanistic study based on a large set of compounds with different molecular structures allowed us a full rationalization of the process for the case of aryl bromides in acetonitrile. Now we are extending this research to heteroaromatic halides, in which the heteroatom not only makes the aromatic ring asymmetric from the perspective of the electron density but also can have its own specific interations with the electrode surface, in addition to those of the halide ions. As a first approach, we have selected the mono-, di-, tri- and tetra-bromothiophene series, plus a series of substituted bromothiophenes togeteher with the corresponding bromobenzenes as benchmarks, investigating (by CV supported by EIS in selected cases), the electrochemical reduction of the whole family: (a) on glassy carbon GC, assumed as a non-catalytic reference accounting for intrinsic reactivity; (b) on the highly catalytic silver electrode; (c) on gold electrode, showing in former halide cases lower catalytic effects than silver (on account of its much more positive pzc with respect to the working potentials, hampering halide-surface specific interactions), but having the highest affinity for the sulphur atom in the thiophene ring. While the results on GC and on Ag are fully consistent with the formerly studied aryl bromide case on the same two electrodes (with some enhancement of the catalytic effects on Ag), the catalytic effects of Au appear to be neatly modulated by the relative position of the Br\uf02d leaving group with respect to the sulphur atom. In particular, the catalytic effects for the reduction of C-Br bonds at a positions are significantly higher than those at b, and they even approach the high catalytic effects of Ag. This feature is quite evident and reproducible in the whole series (including polysubstituted cases), and points to the S atom acting as an asymmetrically anchoring group for the molecule on the Au surface, particularly fostering specific interaction of the surface with adjacent halide leaving groups, and thus partially overcoming the electrostatic repulsion connected with the very positive pzc
Azahelicenes are extensively conjugated, intrinsically chiral molecules with interesting optical ... more Azahelicenes are extensively conjugated, intrinsically chiral molecules with interesting optical and optoelectronic properties. They show interesting SERS activity as well as fluorescence. While synthesizing 5-aza[6]helicene (2) we observed concurrent formation of byproduct (3), phenanthreno[2,3-k]phenanthridine in non-negligible amount. Therefore, we decided to characterize it respect to its spectroscopic and emission properties. We recorded UV-Vis absorption and concentration-dependent fluorescence spectra of (3) excited at 314 nm. We observed an excellent linear dependence of the emission maximum (429 nm) vs. concentration in diluted MeOH solutions (5x10-5 - 3x10-4 mM). We studied its IR and Raman spectra and, once assessed its Raman activity, we adsorbed (3) on nanostructured gold substrates produced by PLD with a plasmon resonance close to 785 nm, with the purpose of investigating its SERS response. We also carried out density functional theory calculations, aiming at the inter...
A typical drawback of electrochemical processes consists in the employment of volatile organic so... more A typical drawback of electrochemical processes consists in the employment of volatile organic solvents (VOCs), which imply safety problems and require the addition of high amounts of a supporting electrolyte to obtain the necessary conductivity. Both problems could be overcome by shifting to non-conventional media such as room temperature ionic liquids (RTILs). In fact, RTILs present various desirable advantages over molecular solvents, including negligible vapour pressure, high intrinsic conductivity without addition of supporting electrolyte and easy recyclability. Moreover, specifically dealing with electropolymerizations, preliminary studies[1,2] point to ionic liquids, both as such and as cosolvents, significantly improving the regularity and the mechanical and morphological properties of the conducting films to be employed e.g. in the energetic, optoelectronic, and sensoristic domains. In this context, we present the results obtained in our research work, concerning a class of inherently chiral polymer films[3], studied and characterized as racemates and as separated enantiomers, by means of cyclic voltammetry and electrochemical impedance spectroscopy, together with SEM imaging. In order to finely discriminate among the racemate and enantiomer film properties, and above all to achieve optimized enantiomer electrode surfaces for applications as chiral sensors, reproducibility is a necessary but hard task. In this frame, the present work is aimed to compare the polymer features obtained in different conditions (i.e., RTILs vs VOCs, on various electrode surfaces and for increasing thickness of the electrodeposited films) to select the best working medium for the preparation of the electroactive films. [1] F. Endres, A.P. Abbott, D.R. MacFarlane, Electrodeposition from Ionic Liquids, 2008, Wiley-VCH, ISBN 978-3-527-31565-9 [2] A.Pietrzyk, W.Kutner, R.Chitta, M. E. Zandler, F. D\u2019Souza, F. Sannicol\uf2, P.R. Mussini, Anal. Chem., 2009, 81(24), 10061-10070. [3] F. Sannicol\uf2, S. Rizzo, T. Benincori, W. Kutner, K. Noworita, J.W. Sobczak, V. Bonometti, L. Falciola, P.R. Mussini, M. Pierini, Electrochim. Acta, 2010, 55(27), 8352-8364
Molecules, 2021
Configurationally stable 5-aza[6]helicene (1) was envisaged as a promising scaffold for non-conve... more Configurationally stable 5-aza[6]helicene (1) was envisaged as a promising scaffold for non-conventional ionic liquids (IL)s. It was prepared, purified, and separated into enantiomers by preparative HPLC on a chiral stationary phase. Enantiomerically pure quaternary salts of 1 with appropriate counterions were prepared and fully characterized. N-octyl-5-aza[6]helicenium bis triflimidate (2) was tested in very small quantities as a selector in achiral IL media to perform preliminary electrochemical enantiodifferentiation experiments on the antipodes of two different chiral probes. The new organic salt exhibited outstanding enantioselection performance with respect to these probes, thus opening the way to applications in the enantioselective electroanalysis of relevant bioactive molecules.
Electrochimica Acta, 2021
Abstract Deep Eutectic Solvents (DESs) offer advantages similar to ionic liquid (IL) ones, with e... more Abstract Deep Eutectic Solvents (DESs) offer advantages similar to ionic liquid (IL) ones, with easier and more sustainable synthesis; moreover, bio-based DESs often include chiral components, surprisingly underexploited. A proof of concept is now offered of the impressive potential of enantiopure chiral DESs as chiral media for enantioselective electroanalysis. Three chiral DESs, consisting of a molecular salt with bio-based chiral cation [NopolMIm]+ combined with three natural and/or low-cost partners (levulinic acid, glycerol and urea), are introduced and investigated as chiral voltammetry media. Significant potential differences are observed for the enantiomers of a model chiral probe, with a dramatic tuning depending on the achiral DES component, reaching an impressive ∼0.5 V in the levulinic acid case (while less efficient appears [NopolMIm]+ as chiral additive in IL). With the same medium good enantiodiscrimination is also observed for aminoacid tryptophan, a quite different probe and of applicative interest. These findings can be considered as a remarkable step further in chiral electroanalysis as well as in the development of task-specific enantioselective media.
Electrochemistry Communications, 2018