1,721,032 research outputs found
Spin selectivity properties displayed by chiral electrode surfaces under an external magnetic field
No full textThe combination of spintronics with magneto- electrochemistry, particularly involving truly chiral molecular spin selectors, was promoted by the discovery of the Chiral Induced Spin Selectivity (CISS) effect by Ron Naaman and coworkers, observing spin polarization in photo-ejected electrons transmitted through a thin layer of enantiopure material adsorbed on gold, acting as an electron spin filter [1].
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, considering as spin filters four different types of chiral selectors (with different stereogenic elements, i.e. helix, stereogenic axis and chiral pendant). [2,3,4]
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.
References:
[1] O. B Dor, S. Yochelis, S. P. Mathew, R. Naaman, Y. Paltiel, Nat. Commun. 4 (2013), 3256.
[2] T. Benincori, S. Arnaboldi, M. Magni, S. Grecchi, R. Cirilli, C. Fontanesi, P. R. Mussini, Chem. Sci., DOI: 10.1039/C8SC04126A (2019).
[3] S. Arnaboldi, S. Cauteruccio, S. Grecchi, T. Benincori, M. Marcaccio, A. Orbelli Biroli, G. Longhi, E. Licandro P. R. Mussini, Chem. Sci., 10 (2019) 1539-1548.
[4] S. Arnaboldi, T. Benincori, A. Penoni, L. Vaghi, R. Cirilli, S. Abbate, G. Longhi, G. Mazzeo, S. Grecchi, M. Panigati, P. R. Mussini, Chem. Sci., DOI: 10.1039/C8SC04862B (2019)
Enantiomer discrimination in voltammetry in media of high structural order at the electrochemical interphase implemented with chirality
Full text linkEnantiomer discrimination in voltammetry in media of high structural order at the electrochemical interphase implemented with chirality
Patrizia Romana Mussini, Sara Grecchi, Serena Arnaboldi
Università degli Studi di Milano, Dipartimento di Chimica, Via Golgi 19, 20133 Milano
Discrimination of the enantiomers of electroactive chiral molecules in voltammetry is a fascinating frontier target. Of course the necessary condition to achieve it is that the two enantiomers undergo electron transfer in energetically different conditions. Since in an achiral context they would have identical physico chemical properties and thus also identical voltammetry features, this requires the implementation at the electrode|solution interphase of a suitable enantiopure chiral selector.
The so far most popular strategy consists in working on chiral electrode surfaces, and an impressive variety of approaches has been proposed [1,2]. However, working on achiral electrodes with chirality implemented in the medium has also been proposed [1,3], and very recent experiments have highlighted that this approach can yield outstanding discrimination in terms of potential differences for the enantiomers of chiral electroactive probes, when working in media of high structural order at the charged interphase, like ionic liquids ILs [3-7] and deep eutectic solvents DESs [8], implemented with chirality [5,6,9] or, even better, inherent chirality [4,7,8].
Such achievements will be comparatively presented and commented in terms of IL and DES structural order at the interphase (also compared to classical media and to ionic liquids / ionic liquid crystals [9]) as well as of possibility of probe/selector specific interactions.
Support to our chiral electroanalysis research line by Fondazione Cariplo/Regione Lombardia as well as by Università degli Studi di Milano is gratefully acknowledged.
[1] S. Arnaboldi, M. Magni, P.R. Mussini, Curr. Opin. Electrochem. 2018, 8, 60-72. (minireview)
[2] S. Arnaboldi, M. Magni, S. Grecchi, P.R. Mussini, Curr. Opin. Electrochem. 2018, 7, 188-189. (minireview)
[3] S. Grecchi, S. Arnaboldi, P.R. Mussini, Curr. Opin. Electrochem., accepted May 2021. (minireview)
[4] S. Rizzo, S. Arnaboldi, V. Mihali, R. Cirilli, A. Forni, A. Gennaro, A. A. Isse, M. Pierini, P. R. Mussini, F. Sannicolò, Angew. Chem. Int. Ed. 2017, 56, 2079 –2082.
[5] M. Longhi, S. Arnaboldi, E. Husanu, S. Grecchi, I. F. Buzzi, R. Cirilli, S. Rizzo, C. Chiappe, P. R. Mussini, L. Guazzelli, Electrochim. Acta 2019, 298, 194-209.
[6] S. Grecchi, C. Ferdeghini, M. Longhi, A. Mezzetta, L. Guazzelli, S. Khawthong, F. Arduini, C. Chiappe, A. Iuliano, P. R. Mussini, ChemElectroChem 2021.
[7] S. Rizzo, S. Arnaboldi, R. Cirilli, A. Gennaro, A. A. Isse, F. Sannicolò, P. R. Mussini, Electrochem. Commun. 2018, 89 57-61
[8] F. Fontana, G. Carminati, B. Bertolotti, P. R. Mussini, S. Arnaboldi, S. Grecchi, R. Cirilli, L. Micheli, S. Rizzo, Molecules 2021, 26, 311-324.
[9] S. Arnaboldi, A. Mezzetta, S. Grecchi, M. Longhi, E. Emanuele, S. Rizzo, F. Arduini, L. Micheli, L. Guazzelli, P. R. Mussini, Electrochim. Acta 202
Enantiomer discrimination in voltammetry in media of high structural order at the electrochemical interphase implemented with chirality
No full textDiscrimination of the enantiomers of electroactive chiral molecules in voltammetry is a fascinating frontier target. Of course the necessary condition to achieve it is that the two enantiomers undergo electron transfer in energetically different conditions. Since in an achiral context they would have identical physico chemical properties and thus also identical voltammetry features, this requires the implementation at the electrode|solution interphase of a suitable enantiopure chiral selector.
The so far most popular strategy consists in working on chiral electrode surfaces, and an impressive variety of approaches has been proposed [1,2]. However, working on achiral electrodes with chirality implemented in the medium has also been proposed [1], and very recent experiments have highlighted that this approach can yield outstanding discrimination in terms of potential differences for the enantiomers of chiral electroactive probes, when working in media of high structural order at the charged interphase, like ionic liquids ILs [3-7] and deep eutectic solvents DESs [8], implemented with chirality [3,4,8] or, even better, inherent chirality [5-7].
Such achievements will be comparatively presented and commented in terms of IL and DES structural order at the interphase (also compared to classical media and to ionic liquids / ionic liquid crystals [9]) as well as of possibility of probe/selector specific interactions.
Support to our chiral electroanalysis research line by Fondazione Cariplo/Regione Lombardia as well as by Università degli Studi di Milano is gratefully acknowledged.
[1] S. Arnaboldi, M. Magni, P.R. Mussini, Enantioselective selectors for chiral electrochemistry and electroanalysis: Stereogenic elements and enantioselection performance, Curr. Opin. Electrochem. 8 (2018) 60-72. (minireview)
[2] S. Arnaboldi, M. Magni, S. Grecchi, P.R. Mussini, Electroactive chiral oligo- and polymer layers for electrochemical recognition, Curr. Opin. Electrochem. 7 (2018) 188-189. (minireview)
[3] M. Longhi, S. Arnaboldi, E. Husanu, S. Grecchi, I. FrancoBuzzi, R. Cirilli, S. Rizzo, C. Chiappe, P. R. Mussini, L. Guazzelli, A family of chiral ionic liquids from the natural pool: Relationships between structure and functional properties and electrochemical enantiodiscrimination tests, Electrochim. Acta 298 (2019) 194-209.
[4] S. Grecchi, C. Ferdeghini, M. Longhi, A. Mezzetta, L. Guazzelli, S. Khawthong, F. Arduini, C. Chiappe, A. Iuliano, P. R. Mussini, Chiral biobased ionic liquids with cations or anions including bile acid building blocks as chiral selectors in voltammetry, ChemElectroChem accepted March 2021.
[5] S. Rizzo, S. Arnaboldi, V. Mihali, R. Cirilli, A. Forni, A. Gennaro, A. A. Isse, M. Pierini, P. R. Mussini, F. Sannicolò, “Inherently Chiral” Ionic‐Liquid Media: Effective Chiral Electroanalysis on Achiral Electrodes, Angew. Chem. Int. Ed. 56 (2017) 2079 –2082.
[6] S. Rizzo, S. Arnaboldi, R. Cirilli, A. Gennaro, A. A. Isse, F. Sannicolò, P. R. Mussini, An “inherently chiral” 1,1′-bibenzimidazolium additive for enantioselective voltammetry in ionic liquid media, Electrochem. Commun. 89 (2018), 57-61
[7] F. Fontana, G. Carminati, B. Bertolotti, P. R. Mussini, S. Arnaboldi, S. Grecchi, R. Cirilli, L. Micheli, S. Rizzo, Helicity: A Non-Conventional Stereogenic Element for Designing Inherently Chiral Ionic Liquids for Electrochemical Enantiodifferentiation, Molecules 26 (2021) 311-324.
[8] S. Arnaboldi, A. Mezzetta, S. Grecchi, M. Longhi, E. Emanuele, S. Rizzo, F. Arduini, L. Micheli, L. Guazzelli, P. R. Mussini, Natural-based chiral task-specific deep eutectic solvents: a novel, effective tool for enantiodiscrimination in electroanalysis, Electrochim. Acta accepted March 2021.
[9] S. Grecchi, S. Arnaboldi, S. Rizzo, P. R. Mussini Advanced chiral molecular media for enantioselective electrochemistry and electroanalysis (minireview), soon to be submitted.
NOTA: Si tratta di abstract inviato, che è stato in seguito definito "invited lecture" (e così inserito nel programma) dall'organizzatore del simposio in cui è stato presentato
Innovative Chiral Materials and Media for Enantioselection in Chiral Electrochemistry and Advanced Applications in Spintronics
No full textThe 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. Sannicolò, 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
Artificial enantiopure inherently chiral membranes: enantiodiscrimination trough a new “ion-selective like” setup
Full text linkHigh-efficiency resolution technology is fundamental for scaling-up separation of enantiomerically pure substances. Membrane technology fulfils this requisite, in fact it is characterized by i) high efficiency, ii) simplicity and iii) convenience for up- and/or down-scaling. Membrane-based chiral resolution can be achieved using either enantioselective or non-enantioselective membranes. Enantioselective membranes can be used for chiral separation of enantiomers because they contain chiral recognition sites. In this frame we have discovered that the electrooligomerization, in acetonitrile as solvent, for 108 deposition cycles, on an ITO electrode support, of our “inherently chiral” benchmark monomer, leads to self-standing racemic or enantiopure membranes. These ones were obtained by simply peeling off the solid deposit from the ITO immersed in water after the electrodeposition in acetonitrile. We have then characterized inherently chiral membranes by a multivariate technique approach (e.g. electrochemical impedance spectroscopy, scanning electron microscopy, BET for surface area and pore size distribution, and atomic force microscopy) comparing the racemic vs enantiopure deposit properties. Considering i) the outstanding enantioselection ability achieved with our both inherently chiral electrode surfaces and media [1-2] and ii) the perfectly specular CD spectra displayed by the two membrane enantiomers, we have decided to implement enantiopure inherently chiral membranes in a “ion-selective like” set-up in order to study their enantiorecognition capability (as depicted in Figure on the right). First of all we have verified the potential difference was read correctly through the membrane to allow correct determinations of transmembrane potentials. After that we have tested enantiopure membranes in the presence of chiral charged species (in all configurations for both membranes and internal/external electrode solutions) for determining their enantioselective capability. Preliminary results are very promising and encourage us to perform the scaling up of the membrane electrosynthesis to be used for industrial scopes and to extend the study to other probe useful in the analytical and pharmaceutical field.
References:
[1] S. Arnaboldi, M. Magni, P. R. Mussini, Curr. Op. in Electrochemistry 8 (2018) 60-72.
[2] S. Arnaboldi, S. Grecchi, M. Magni, P.R. Mussini, Curr. Op. in Electrochemistry 7 (2018) 188-199
Enantioselective electroanalysis for different chiral active pharmaceutical ingredients and a real matrix, using inherently chiral 2,2’-biindole based oligomer films
No full textChirality and chiral analysis constitute a key aspect of modern chemistry and chemical technologies; the enantiomeric purity of various compounds is important in different fields, especially in the pharmaceutical one [1-3].
A systematic study case is proposed, based on a new 2,2'-biindole series (N-alkyl-IND)2Ph2T4 (alkyl= methyl, propyl or hexyl group), of easy synthesis and modulable functional properties featuring systematic variation of the N alkyl substituents of the pyrrolic rings in the core [4].
The new series shows good performances when applied as selectors in chiral voltammetry for discrimination of the enantiomers of model chiral ferrocenyl probes, either in CH2Cl2, by conversion into enantiopure electroactive electrode surfaces, or in achiral ionic liquid BMIMTf2, as chiral additive (monomer with hexyl chains, hampering electrooligomerization). 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 even observed with the two probe enantiomers concurrently present, either as racemate or with enantiomeric excesses, neatly accounted for by the peak current ratios [4].
Oligo-(N-Me-IND)2Ph2T4 films also result in enantiomer discrimination for quite different chiral probes, active pharmaceutical ingredients: terazosin, lansoprazole, ramosetron and clopidogrel, working in aqueous buffer solution. In addition, the molecule (S)-clopidogrel was also tested in a real matrix, i.e. as the main component of the DuoPlavin®, drug in combination with acetylsalicylic acid (both active substances are antiplatelet medicines).
In all the cases, concentration calibration plots, LOD e LOQ (both on bare and modified chiral electrodes) have also been obtained, by DPV experiments.
This work confirms the wide-scope effectiveness of the new inherently chiral selectors and suggesting application to a wider pool of chiral probes of applicative interest.
[1] S. Arnaboldi, M. Magni, P. R. Mussini, Curr. Opin. Electrochem., 2018, 8, 60.
[2] S. Arnaboldi, S. Grecchi, M. Magni, P. R. Mussini, Curr. Opin. Electrochem., 2018, 7, 188.
[3] S. Arnaboldi, T. Benincori, R. Cirilli, S. Grecchi, L. Santagostini, F. Sannicolò, P. R. Mussini, Anal. Bioanal. Chem., 2016, 408 (26), 7243.
[4] L. Scapinello, S. Grecchi, S. Rossi, F. Arduini, S. Arnaboldi, A. Penoni, R. Cirilli, P. R. Mussini, T. Benincori, Chem. Eur. J., 2021, Accepted Manuscript
A Simultaneous Discrimination of Two Different Probes on Achiral Electrodes
Full text linkA Simultaneous Discrimination of Two Different Probes
on Achiral Electrodes
S. Grecchia, S. Arnaboldia, S. Rizzob, F. Sannicolòa, P.R. Mussinia
a Università degli Studi di Milano, via Golgi 19, 20133 Milano, Italy
b Istituto di Scienze e Tecnologie Molecolari, CNR, Via Golgi 19, 20133, Milano, Italy
[email protected]
In literature few studies have dealt with electrochemistry or electroanalysis on achiral electrodes, the selector being provided by the medium, either having a chiral selector dissolved into it or being itself endowed with chirality. More recently, we have decided to implement the “inherent chirality” concept for the development of media to combine the powerful strategy of inherent chirality with the physico-chemical properties of the ionic liquids.
Ionic liquids, organic salts with low melting points, are increasingly popular media on account of many peculiar advantageous properties respect to volatile organic solvents (low vapor pressure, chemical and thermal stability, high solvating ability, non-flammability ...). They are even more attractive for electrochemical processes, acting as both solvent and supporting electrolyte, and especially featuring an extremely well-ordered structure at the interface with a charged electrode, expanding for many layers, like a semisolid crystal, even in the presence of significant water traces, and modulated by other species possibly present at the interface. Sometimes, they even border with liquid crystals. A high degree of supramolecular organization can induce significant chirality transfer from the medium to the dissolved species. And, analogously to the electrode case, this attitude could be maximized by the “inherent chirality” strategy, that is, working in inherently chiral ionic liquids, ICILs.
To implement inherent chirality in ionic liquids, that are usually based on a heteroaromatic cation with at least one long alkyl chain (to lower the melting point), Sannicolò et al. proposed to start from biheteroaromatic scaffolds, like bipyridine or bibenzimidazole ones. [1] By dialkylation such inherently chiral scaffolds can be converted into the corresponding double salts. With at least one long alkyl chain and a suitable anion, the melting point can be lowered below room temperature; thus, two ICILs have been very recently obtained as enantiopure antipodes, starting from bicollidine, a very convenient scaffold on account of its low-cost synthesis and possibility to be separated into enantiomers by fractional crystallization, without expensive chiral HPLC. Their enantioselectivity was tested as low-concentration additives in achiral commercial ionic liquids on screen-printed electrodes, with chiral probes already used in tests with electrodes modified with inherently chiral surfaces [2]; large, specular enantiomer peak potential differences were observed. Attractively, the same behavior, as chiral additives, was also shown by family terms solid at room temperature, of faster and easier synthesis.
In this context we are studying the effect of the chiral additives on two simultaneously present chiral probes, the first of them giving a chemically reversible ET process. We have to assess the experiments on all possible binary and ternary combinations but evidence of simultaneous discrimination apparently emerges.
The inherent chirality research is currently supported by Regione Lombardia and Fondazione Cariplo (Avviso congiunto per l’incremento dell’attrattività del sistema di ricerca lombardo e della competitività dei ricercatori candidati su strumenti ERC-edizione 2016, Project 2016-0923).
[1] S. Rizzo, S. Arnaboldi, V. Mihali, R. Cirilli, A. Forni, A. Gennaro, A.A. Isse, M. Pierini, P.R. Mussini, F. Sannicolò (2017) Angewandte Chemie. International Edition, 56, 2079-2082; S. Arnaboldi, R. Cirilli, A. Forni, A. Gennaro, A. A. Isse, V. Mihali, P. R. Mussini, M. Pierini, S. Rizzo, F. Sannicolò (2015) Electrochimica Acta, 179, 250-262; S. Rizzo, S. Arnaboldi, R. Cirilli, A. Gennaro, A. A. Isse, F. Sannicolò, P. R. Mussini (2018) Electrochemistry Communications, 89, 57-61
[2] F. Sannicolò, S. Arnaboldi, T. Benincori, V. Bonometti, R. Cirilli, L. Dunsch, W. Kutner, G. Longhi, P.R. Mussini, M. Panigati, M. Pierini, S. Rizzo (2014) Angewandte Chemie. International Edition, 53, 2623-2627; S. Arnaboldi, T. Benincori, R. Cirilli, S. Grecchi, L. Santagostini, F. Sannicolò, P.R. Mussini (2016) Analytical And Bioanalytical Chemistry, 408, 7243-7254. S. Arnaboldi, T. Benincori, R. Cirilli, W. Kutner, M. Magni, P. R. Mussini, K. Noworyta, F. Sannicolò (2015) Chemical Science, 6, 1706-171
Spin Filter Properties of Chiral Thin Film Highlighted by an External Magnetic Field
No full textThe study of the mutual influence between chirality, electron spin and magnetism is a well-documented field of research, in fact implications span from pure fundamental research, to chemical applications of both analytical and synthetic character, to multidisciplinary purposes.1,2 In this context the interrelated disciplines of magnetoelectrochemistry, spintronics and Spin Dependent Electrochemistry (SDE) play a crucial role. In particular, the combination of spintronics with magneto- electrochemistry, involving truly chiral molecular spin selectors, was promoted by the discovery of the Chiral Induced Spin Selectivity (CISS) effect by Ron Naaman and coworkers, observing spin polarization in photo-ejected electrons transmitted through a thin layer of enantiopure material adsorbed on gold, acting as an electron spin filter3.
Our proposed strategy is a variation of the SDE protocol, in fact the innovative set-up involves i) a non-ferromagnetic electrode (ITO as working electrode) covered by thin electroactive chiral films as electron source, ii) achiral redox couples dissolved in aqueous or organic solutions and iii) an external permanent magnet which was placed perpendicular to the electrode surface, considering as spin filters four different types of chiral selectors (with different stereogenic elements, i.e. helix, stereogenic axis and chiral pendant). 4,5,6
A spectacular unforeseen effect was observed performing cyclic voltammetry (CV) experiments under applied magnetic field, in fact the CV peaks of achiral, chemically reversible redox couples undergo impressive potential shifts by flipping the magnet orientation (north vs south), with specular results changing the film 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.
References:
1 G. A. Printz, Science, 1998, 282, 1660-1663.
2 P. L. Popa, N. T. Kemp, H. Majjad, G. Dalmas, V. Faramarzi, C. Andreas, R. Hertel, B. Doudin, Proc. Natl. Acad. Sci., 2014, 111, 10433-10437
3 O. B Dor, S. Yochelis, S. P. Mathew, R. Naaman, Y. Paltiel, Nat. Commun., 2013, 4, 3256-3262.
4 T. Benincori, S. Arnaboldi, M. Magni, S. Grecchi, R. Cirilli, C. Fontanesi, P. R. Mussini, Chem. Sci., 2019, 10, 2750-2757.
5 S. Arnaboldi, S. Cauteruccio, S. Grecchi, T. Benincori, M. Marcaccio, A. Orbelli Biroli, G. Longhi, E. Licandro P. R. Mussini, Chem. Sci., 2019, 10, 1539-1548.
6 . Arnaboldi, T. Benincori, A. Penoni, L. Vaghi, R. Cirilli, S. Abbate, G. Longhi, G. Mazzeo, S. Grecchi, M. Panigati, P. R. Mussini, Chem. Sci., 2019, 10, 2708-2717
Enantiomer discrimination in absorption spectroscopy and in voltammetry: highlighting fascinating similarities and connections
No full textEnantiomer discrimination
in absorption spectroscopy and in voltammetry:
highlighting fascinating
similarities and connections
Patrizia Romana Mussini1, Serena Arnaboldi1, Mirko Magni1,2, Sara Grecchi1 ,
Giovanna Longhi3, Tiziana Benincori4
1 Università degli Studi di Milano, Dipartimento di Chimica
2 present address: Università degli Studi di Milano, Dipartimento di Scienze e Politiche Ambientali;
3Università degli Studi di Brescia, Dipartimento di Medicina Molecolare e Translazionale
4Università degli Studi dell’Insubria, Dipartimento di Scienza e Alta Tecnologia
е-mail: [email protected]
Electronic absorption spectroscopy, involving intramolecular electron transitions triggered by light, and voltammetry, involving electrode-to/from-molecule electron transfers triggered by the electrode potential, have well known analogies and connections, and are usually exploited in synergy for the investigation of electronic properties of advanced molecules and materials.
In our recent investigations of “inherently chiral” electroactive molecules of axial stereogenicity to be exploited as chiral selectors in electroanalysis and electrochemistry, we realized that, fascinatingly, the two techniques also share many connections and analogies at a superior complexity level, when adding chirality to the involved actors, i.e. considering chiral molecules interacting with the left-handed and right-handed helicoidal components of polarized light (in circular dichroism CD spectroscopy) as well as chiral molecules undergoing electron transfer at a chiral electrode surface (in enantioselective voltammetry). [1]
In particular, the following points are indeed worthy of interest:
(i) High performance achieved with inherently chiral molecules: “inherently chiral” molecules of helical or axial stereogenicity usually result in high enantiodiscrimination performances both in chiroptical spectroscopy, in terms of neat differences in absorption of the above left-handed and right-handed polarized light components [2,3] and in enantioselective voltammetry, in terms of neat differences in the electron transfer potentials for (R)- or (S)-molecular probes [4];
(ii) Loss of energy level degeneration for interacting chromophores/redox sites: chiral electroactive molecules of axial stereogenicity, consisting of two equal moieties, behave as equivalent, reciprocally interacting chromophores in CD, and as equivalent, reciprocally interacting redox centres in CV, in both cases resulting in loss of degeneration of energy levels. This implies an absorption wavelength difference with “Davydov splitting” in the CD pattern [3] as well as a twin peak system in the CV pattern [5,6];
(iii) Pseudochiral manifestations with achiral molecular probes + magnetic fields: CD spectra can also be obtained from polarized light absorption by achiral molecules in a magnetic field, and peak potential differences have been observed on chiral electrode surfaces for achiral molecules in a magnetic field [7]; both phenomena are modulated by the magnetic field intensity and orientation.
[1] P.R. Mussini, S. Arnaboldi, M. Magni, S. Grecchi, G. Longhi, T. Benincori, Curr. Opin. Electrochem. 37 (2023) 101128.
[2] N. Berova, L. Di Bari, G. Pescitelli, Chem. Soc. Rev. 36 (2007) 914-931.
[3] J. T. Vázquez, Tetrahedron: Asymmetry, 28 (2017) 1199-1211.
[4] S. Arnaboldi, M. Magni, P. R. Mussini, Curr. Opin. Electrochem. 8 (2018) 60-72.
[5] F. Sannicolò, S. Arnaboldi, T. Benincori, V. Bonometti, R. Cirilli, L. Dunsch, W. Kutner, G. Longhi, P. R. Mussini, M. Panigati, M. Pierini, S. Rizzo, Angew. Chem. Int. Ed., 53 (2014) 2623-2627.
[6] T. Benincori, S. Arnaboldi, M. Magni, S. Grecchi, R. Cirilli, C. Fontanesi, P. R. Mussini, Chem. Sci. 10 (2019) 2750-2757.
[7] S. Arnaboldi, T. Benincori, A. Penoni, L. Vaghi, R. Cirilli, S. Abbate, G. Longhi, G. Mazzeo, S. Grecchi, M. Panigati, P. R. Mussini, Chem. Sci. 10 (2019) 2708-2717
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