Natural and Magnetic Circular Dichroism From the Infrared to the UV of a Hetero[4]helicene Radical Cation

Anno: 2025

Autori: Fusi M., Lupi M., Machalska E., Mazzeo G., Abbate S., Bloino J., Viglianisi C., Menichetti S., Longhi G.

Affiliazione autori: Univ Brescia, Dipartimento Med Mol & Traslaz DMMT, Viale Europa 11, I-25123 Brescia, Italy; Univ Firenze, Dipartimento Chim Ugo Schiff, Via Lastruccia 13, I-50019 Sesto Fiorentino, FI, Italy; CNR, Ist Nazl Ott INO, Res Unit Brescia, CSMT, VIA Branze 45, I-25123 Brescia, Italy; Scuola Normale Super Pisa, Piazza Cavalieri 7, I-56126 Pisa, Italy.

Abstract: Dithiabridged triarylamine hetero[4]helicenes are an interesting class of chiral compounds characterized by a high racemization barrier which makes them an attractive material for several applications. Their rich redox chemistry allows one to obtain radical cations stable at room temperature, that can be isolated in two configurationally stable enantiomers. While several studies have been reported on systems with transition metals possessing low-lying electronic states, the characterization of purely organic open-shell systems by VCD is still scarce. This may be due to the instability of radical-cation species and to the dark color assumed by the solution at the high concentration required by VCD. The oxidation of this molecular system shifts the first electronic transition towards the Near-IR (NIR) region, at approximately 1250 nm. By combining ECD, VCD, MCD, NIR-CD and computational methodologies rooted in density functional theory, we have investigated one molecule of this class of compounds and shed some light on the chiroptical properties accessible via redox-switch.

Giornale/Rivista: CHEMISTRY-AN ASIAN JOURNAL

Maggiori informazioni: Funding was provided by the Italian Ministry of University and Research (MUR) through the PRIN 2022 and PRIN 2020 programs: project Enhancing Circularly Polarised Emitters Quantum Efficiency Exploiting Singlet-Triplet Inversion (INVESTCPE), prot. 2022CXHY3A; project Smart [n]heterohelicenes: enantioselective synthesis, circularly polarized luminescence, redox switching, and functionalized polymers (SMART HELIX), prot. 2022B3EFJH; project Photoreactive Systems upon Irradiation: Modelling and Observation of Vibrational Interactions with the Environment (PSI-MOVIE), prot. 2020HTSXMA).
Parole chiavi: hetero[4]helicenes; VCD; NIR-CD; MCD; computational chiroptical spectroscopy
DOI: 10.1002/asia.202401752