Circularly Polarized Luminescence from an Inverted Singlet-Triplet Chiral Dye

Year: 2025

Authors: Altinier A., Machalska E., Fortunati I., Raulin M., Zonta C., Mazzeo G., Longhi G., Fusi M., Wurst K., Veglianti S., De Vico L., Padula D.

Autors Affiliation: Univ Padua, Dipartimento Sci Chim, I-35131 Padua, Italy; Univ Brescia, Dipartimento Med Mol & Traslazionale, I-25121 Brescia, Italy; Ist Nazl Ott INO, Res Unit Brescia, CNR, CSMT, I-25123 Brescia, Italy; Univ Innsbruck, Dept Gen Inorgan & Theoret Chem, A-6020 Innsbruck, Austria; Univ Siena, Dipartimento Biotecnol Chim & Farm, I-53100 Siena, Italy.

Abstract: Molecules with an inverted singlet-triplet gap (Delta EST = ES1 – ET1 < 0) hold potential for optoelectronic applications as OLEDs and photocatalysis. Despite growing interest, no single-molecule emission from a chiral dye with an inverted gap has been reported, and only one case has shown such emission from supramolecular aggregates. Here, we present the first circularly polarized light emission (CPL) from a chiral molecule exhibiting an inverted singlet-triplet gap. Our design is based on the achiral heptazine core, functionalized with chiral substituents. Computational screening confirmed that the inversion of the singlet-triplet gap is retained upon derivatization. Photophysical characterization, including temperature-dependent optical spectra and photoluminescence decay profiles, supported by computational results, confirms the inverted gap in both achiral and chiral derivatives. Chiroptical properties show dissymmetry factor glum values (approximate to 10-3) comparable to other chromophores functionalized with chiral groups. Combined with promising photoluminescence quantum yields, these findings highlight the potential of such materials for circularly polarized OLED devices. Journal/Review: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY

Volume: 147 (36)      Pages from: 32357  to: 32364

More Information: D.P. thanks Prof. Johannes Gierschner (IMDEA Nanoscience, Spain) for useful discussions and for providing some references. D.P. and L.D.V. thank funding from ICSC – Centro Nazionale di Ricerca in High Performance Computing, Big Data and Quantum Computing, funded by European Union – NextGenerationEU – PNRR, Missione 4 Componente 2 Investimento 1.4, Spoke 7 Materials & Molecular Sciences (Rethinking Organic materials: from Design to Efficient Optoelectronics – RODEO, CUP B93C22000620006), and computational resources kindly provided by Universita di Siena (hpc@dbcf). M.F., G.M., and G.L. acknowledge The Big & Open Data Innovation Laboratory(BODaI-Lab) (University of Brescia) for providing access to CINECA HPC facilities. M.F. thanks CINECA for an award under the ISCRA C project CCESTI – HP10CPAAXL. All authors affiliated with Italian institutions gratefully acknowledge funding from the Italian Ministry of University and Research (MUR, PRIN grant 2022CXHY3A).
KeyWords: Activated Delayed Fluorescence; Light-emitting-diodes; Basis-sets; Molecules; Design; States; Dichroism; Tadf; Gaps
DOI: 10.1021/jacs.5c11353