Dark State of the Thiele Hydrocarbon: Efficient Solvatochromic Emission from a Nonpolar Centrosymmetric Singlet Diradicaloid

Punzi A, Dai Y, Dibenedetto CN, Mesto E, Schingaro E, Ullrich T, Striccoli M, Guldi DM, Negri F, Farinola GM, Blasi D (2023)

Publication Type: Journal article

Publication year: 2023

Journal

Journal of the American Chemical Society American Chemical Society

Book Volume: 145

Pages Range: 20229-20241

Journal Issue: 37

DOI: 10.1021/jacs.3c05251

Abstract

In this work, a comprehensive investigation of the photoinduced processes and mechanisms linked to the luminescence of a novel nonperchlorinated Thiele hydrocarbon (TTH) is presented. Despite the comparable diradical character of TTH (y0 = 0.32-0.44) and the unsubstituted Thiele hydrocarbon (TH) (y0 = 0.30), the polyhalogenated species is inert and photostable, showing an intense deep-red/near-infrared (NIR) fluorescence (photoluminescence quantum yield (PLQY) = 0.84 in toluene) even at room temperature and in the solid state (PLQY = 0.19). TTH displays a large Stokes shift (307 nm in benzonitrile) and solvatochromic behavior, which is unusual for a centrosymmetric, nonpolar, and low-conjugated species. These outstanding emission features are interpreted through quantum-chemical calculations, indicating that its fluorescence arises from the low-lying dark doubly excited zwitterionic state, typically found at low excitation energies in diradicaloids, acquiring dipole moment and intensity by state mixing via twisting around the strongly elongated exocyclic CC bonds of the excited p-quinodimethane (pQDM) core, with a mechanism similar to sudden polarization occurring in olefins. Such a mechanism is derived from ns and fs transient absorption measurements.

Authors with CRIS profile

Tobias Ullrich Lehrstuhl für Physikalische Chemie I Dirk Michael Guldi Lehrstuhl für Physikalische Chemie I

Additional Organisation(s)

FAU Profilzentrum Licht.Materie.Quantentechnologien (FAU LMQ)

Involved external institutions

University of Bari Aldo Moro / Università degli Studi di Bari Aldo Moro IT Italy (IT) University of Bologna / Università di Bologna IT Italy (IT) Consiglio Nazionale delle Ricerche (CNR) / National Research Council of Italy IT Italy (IT)

How to cite

APA:

Punzi, A., Dai, Y., Dibenedetto, C.N., Mesto, E., Schingaro, E., Ullrich, T.,... Blasi, D. (2023). Dark State of the Thiele Hydrocarbon: Efficient Solvatochromic Emission from a Nonpolar Centrosymmetric Singlet Diradicaloid. Journal of the American Chemical Society, 145(37), 20229-20241. https://doi.org/10.1021/jacs.3c05251

MLA:

Punzi, Angela, et al. "Dark State of the Thiele Hydrocarbon: Efficient Solvatochromic Emission from a Nonpolar Centrosymmetric Singlet Diradicaloid." Journal of the American Chemical Society 145.37 (2023): 20229-20241.

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