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Importance of chromophore rigidity on the efficiency of blue thermally activated delayed fluorescence emitters.

Kukhta, Nadzeya A. and Batsanov, Andrei S. and Bryce, Martin R. and Monkman, Andrew P. (2018) 'Importance of chromophore rigidity on the efficiency of blue thermally activated delayed fluorescence emitters.', Journal of physical chemistry C., 122 (50). pp. 28564-28575.


Four new symmetrical donor–acceptor–donor (D–A–D)-type molecules are reported with diphenylamine (DPA) or 10,11-dihydro-5H-dibenz[b,f]azepine (Az) as electron donors and 9,9-dimethylthioxanthene-S,S-dioxide (TXO2) as the electron acceptor. The donors are attached at different positions on the acceptor core: either para or meta to the sulfone unit. This series provides new insights into the effects of chromophore rigidity/flexibility on the efficiency of thermally activated delayed fluorescence (TADF). The molecules have been characterized by X-ray crystallography, by in-depth photophysical studies, and by theoretical calculations. The clear differences observed in the photophysical properties when using DPA or Az as a donor are shown to originate from different geometries of the donor unit which, in turn, influence the geometry of the nitrogen lone pair and the donating strength of the corresponding fragment. Thus, a para-substituted Az derivative demonstrated blue TADF in polar media, while the compounds with more flexible DPA units did not show delayed fluorescence. To obtain deep-blue emitters, weaker donating units are needed. A more flexible donor unit leads to increased local excited state (donor) LE emission and reduced TADF. However, a certain amount of flexibility has to be present to ensure deep-blue TADF.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Publisher statement:This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of physical chemistry C copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see
Date accepted:28 November 2018
Date deposited:10 January 2019
Date of first online publication:07 December 2018
Date first made open access:07 December 2019

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