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Achieving conformational control in RTP and TADF emitters by functionalization of the central core.

Kukhta, N.A. and Huang, R. and Batsanov, A.S. and Bryce, M.R. and Dias, F.B. (2019) 'Achieving conformational control in RTP and TADF emitters by functionalization of the central core.', The journal of physical chemistry C., 123 (43). pp. 26536-26546.


Three new symmetrical donor–acceptor–donor (D–A–D)-type molecules were prepared with phenothiazine (PTZ) as electron donors and 9,9-dimethylthioxanthene (TX) as the electron acceptor. The PTZ groups are attached at different positions on the acceptor core – ortho or meta to the sulfur of TX. The molecules have been characterized by X-ray crystallography, in-depth photophysical studies and theoretical calculations. This series provides new insights into how molecular functionalization and intramolecular charge transfer determines the singlet-triplet gap ΔEST. Two of the molecules have weak D/A decoupling and a relatively large ΔEST of 0.52 eV which prohibits the upconversion of triplet excitons to the singlet state, showing strong room temperature phosphorescence (RTP). When the TX acceptor strength is enhanced by the attachment of benzoyl substituents a very small ΔEST of <0.01 eV is observed. In this case excitons in the triplet state can be efficiently upconverted to the singlet state via reverse intersystem crossing (RISC) resulting in thermally activated delayed fluorescence (TADF). TADF and RTP are unambiguously assigned by distinctive photophysical data, notably a comparison of degassed and aerated luminescence spectra, temperature-dependent time-resolved fluorescence decays and power dependence of the intensity of delayed emission (for the TADF emitter).

Item Type:Article
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Publisher statement:This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry C: Plasmonics; Optical, Magnetic, and Hybrid Materials, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see
Date accepted:No date available
Date deposited:10 October 2019
Date of first online publication:04 October 2019
Date first made open access:04 October 2020

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