Intramolecular Charge Transfer Controls Switching Between Room Temperature Phosphorescence and Thermally Activated Delayed Fluorescence

Chengjian Chen; Rongjuan Huang; Andrei S Batsanov; Piotr Pander; Yu-Ting Hsu; Zhenguo Chi; Fernando B Dias; Martin R Bryce

doi:10.1002/anie.201809945

Intramolecular Charge Transfer Controls Switching Between Room Temperature Phosphorescence and Thermally Activated Delayed Fluorescence

Angew Chem Int Ed Engl. 2018 Dec 10;57(50):16407-16411. doi: 10.1002/anie.201809945. Epub 2018 Nov 15.

Authors

Chengjian Chen^{1

2}, Rongjuan Huang³, Andrei S Batsanov¹, Piotr Pander³, Yu-Ting Hsu¹, Zhenguo Chi², Fernando B Dias³, Martin R Bryce¹

Affiliations

¹ Department of Chemistry, Durham University, Durham, DH1 3LE, UK.
² PCFM Lab, GD HPPC Lab, School of Chemistry, Sun Yat-sen University, Guangzhou, 510275, P. R. China.
³ Department of Physics, Durham University, Durham, DH1 3LE, UK.

PMID: 30339314
DOI: 10.1002/anie.201809945

Abstract

Chemical modification of phenothiazine-benzophenone derivatives tunes the emission behavior from triplet states by selecting the geometry of the intramolecular charge transfer (ICT) state. A fundamental principle of planar ICT (PICT) and twisted ICT (TICT) is demonstrated to obtain selectively either room temperature phosphorescence (RTP) or thermally activated delayed fluorescence (TADF), respectively. Time-resolved spectroscopy and time-dependent density functional theory (TD-DFT) investigations on polymorphic single crystals demonstrate the roles of PICT and TICT states in the underlying photophysics. This has resulted in a RTP molecule OPM, where the triplet states contribute with 89 % of the luminescence, and an isomeric TADF molecule OMP, where the triplet states contribute with 95 % of the luminescence.

Keywords: charge transfer; donor-acceptor systems; polymorphism; room temperature phosphorescence; thermally activated delayed fluorescence.

Grants and funding

EP/L02621X/1/Engineering and Physical Sciences Research Council