A Deep Blue B,N-Doped Heptacene Emitter That Shows Both Thermally Activated Delayed Fluorescence and Delayed Fluorescence by Triplet-Triplet Annihilation

Subeesh Madayanad Suresh, Eimantas Duda, David Hall, Zhen Yao, Sergey Bagnich, Alexandra M.Z. Slawin, Heinz Bässler, David Beljonne, Manfred Buck, Yoann Olivier, Anna Köhler, Eli Zysman-Colman

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Résumé

An easy-to-access, near-UV-emitting linearly extended B,N-doped heptacene with high thermal stability is designed and synthesized in good yields. This compound exhibits thermally activated delayed fluorescence (TADF) at ambient temperature from a multiresonant (MR) state and represents a rare example of a non-triangulene-based MR-TADF emitter. At lower temperatures triplet-triplet annihilation dominates. The compound simultaneously possesses narrow, deep-blue emission with CIE coordinates of (0.17, 0.01). While delayed fluorescence results mainly from triplet-triplet annihilation at lower temperatures in THF solution, where aggregates form upon cooling, the TADF mechanism takes over around room temperature in solution when the aggregates dissolve or when the compound is well dispersed in a solid matrix. The potential of our molecular design to trigger TADF in larger acenes is demonstrated through the accurate prediction of ΔEST using correlated wave-function-based calculations. On the basis of these calculations, we predicted dramatically different optoelectronic behavior in terms of both ΔEST and the optical energy gap of two constitutional isomers where only the boron and nitrogen positions change. A comprehensive structural, optoelectronic, and theoretical investigation is presented. In addition, the ability of the achiral molecule to assemble on a Au(111) surface to a highly ordered layer composed of enantiomorphic domains of racemic entities is demonstrated by scanning tunneling microscopy.

langue originaleAnglais
Pages (de - à)6588-6599
Nombre de pages12
journalJournal of the American Chemical Society
Volume142
Numéro de publication14
Les DOIs
Etat de la publicationPublié - 8 avr. 2020

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