Revealing resonance effects and intramolecular dipole interactions in the positional isomers of benzonitrile-core thermally activated delayed fluorescence materials
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We report on the properties of the three positional isomers of (2,7-di-tert-butyl-9,9-dimethylacridin-10(9H)-yl)benzonitrile, which are found to have comparable donor steric environments and donor–acceptor dihedral angles. An unexpected intramolecular dipole interaction imparts a unique molecular geometry to the ortho-linked isomer, while comparison of the meta- and para-isomers uncovers how positional differences in acceptor strengths (a consequence of differences in aromatic π-system electron density) lead to very different triplet harvesting and emission properties. These positional-isomer effects on TADF follow the well-known aromatic directing rules from organic synthesis, in keeping with their common origin arising from contributions of multiple electronic resonance structures. Understanding these positional effects and methods of dihedral control is critical to the future design of efficient TADF emitters.
Kukhta , N A , Higginbotham , H F , Matulaitis , T , Danos , A , Bismillah , A N , Haase , N , Etherington , M K , Yufit , D S , McGonigal , P R , Gražulevičius , J V & Monkman , A P 2019 , ' Revealing resonance effects and intramolecular dipole interactions in the positional isomers of benzonitrile-core thermally activated delayed fluorescence materials ' , Journal of Materials Chemistry , vol. 7 , no. 30 , pp. 9184-9194 . https://doi.org/10.1039/C9TC02742D
Journal of Materials Chemistry
Copyright © 2019 The Author(s). Open Access Article. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
DescriptionNAK, HFH, MKE, and APM acknowledge the EU’s Horizon 2020 for funding the PHEBE project under grant no. 641725. NAK, MKE, AD, NH and APM acknowledge the EU’s Horizon 2020 for funding the HyperOLED project under grant no. 641725. APM thanks EPSRC grant EP/L02621X/1 for funding. ANB acknowledges an EPSRC Doctoral Training Grant.
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