Direct detection of spin polarization in photoinduced charge transfer through a chiral bridge

Alberto Privitera; Emilio Macaluso; Alessandro Chiesa; Alessio Gabbani; Davide Faccio; Demetra Giuri; Matteo Briganti; Niccolò Giaconi; Fabio Santanni; Nabila Jarmouni; Lorenzo Poggini; Matteo Mannini; Mario Chiesa; Claudia Tomasini; Francesco Pineider; Enrico Salvadori; Stefano Carretta; Roberta Sessoli

doi:10.1039/D2SC03712B

Direct detection of spin polarization in photoinduced charge transfer through a chiral bridge†

Alberto Privitera,

^ab Emilio Macaluso,

^cd Alessandro Chiesa,

^cd Alessio Gabbani,

^e Davide Faccio,

^f Demetra Giuri,

^f Matteo Briganti,

^b Niccolò Giaconi,

^bg Fabio Santanni,

^b Nabila Jarmouni,^e Lorenzo Poggini,

^h Matteo Mannini,

^b Mario Chiesa,

^a Claudia Tomasini,

^f Francesco Pineider,

^e Enrico Salvadori,

*^a Stefano Carretta

*^cd and Roberta Sessoli

*^b

Author affiliations

* Corresponding authors

^a Department of Chemistry and NIS Centre, University of Torino, Via Giuria 7, Torino, Italy
E-mail: enrico.salvadori@unito.it

^b Department of Chemistry “U. Schiff” (DICUS), University of Florence & UdR INSTM Firenze, Via della Lastruccia 3-13, Sesto Fiorentino, Italy
E-mail: roberta.sessoli@unifi.it

^c Department of Mathematical, Physical and Computer Sciences, University of Parma & UdR INSTM, Parma, Italy
E-mail: stefano.carretta@unipr.it

^d INFN–Sezione di Milano-Bicocca, gruppo collegato di Parma, I-43124 Parma, Italy

^e Department of Chemistry and Industrial Chemistry, University of Pisa & UdR INSTM Pisa, Via Moruzzi 13, Pisa, Italy

^f Department of Chemistry “Giacomo Ciamician”, University of Bologna, Via Selmi 2, Bologna, Italy

^g Department of Industrial Engineering (DIEF), University of Florence & UdR INSTM Firenze, Via Santa Marta 3, Firenze, Italy

^h CNR-ICCOM, Via Madonna del Piano 10, Sesto Fiorentino, Italy

Abstract

It is well assessed that the charge transport through a chiral potential barrier can result in spin-polarized charges. The possibility of driving this process through visible photons holds tremendous potential for several aspects of quantum information science, e.g., the optical control and readout of qubits. In this context, the direct observation of this phenomenon via spin-sensitive spectroscopies is of utmost importance to establish future guidelines to control photo-driven spin selectivity in chiral structures. Here, we provide direct proof that time-resolved electron paramagnetic resonance (EPR) can be used to detect long-lived spin polarization generated by photoinduced charge transfer through a chiral bridge. We propose a system comprising CdSe quantum dots (QDs), as a donor, and C₆₀, as an acceptor, covalently linked through a saturated oligopeptide helical bridge (χ) with a rigid structure of ∼10 Å. Time-resolved EPR spectroscopy shows that the charge transfer in our system results in a C₆₀ radical anion, whose spin polarization maximum is observed at longer times with respect to that of the photogenerated C₆₀ triplet state. Notably, the theoretical modelling of the EPR spectra reveals that the observed features may be compatible with chirality-induced spin selectivity, but the electronic features of the QD do not allow the unambiguous identification of the CISS effect. Nevertheless, we identify which parameters need optimization for unambiguous detection and quantification of the phenomenon. This work lays the basis for the optical generation and direct manipulation of spin polarization induced by chirality.

Chemical Science

Direct detection of spin polarization in photoinduced charge transfer through a chiral bridge†

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Direct detection of spin polarization in photoinduced charge transfer through a chiral bridge

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