Preparations and photophysical properties of thermally activated delayed fluorescence materials based on N-phenyl-phenothiazine-S,S-dioxide

Four compounds (TM-1 similar to 4) based on N-(4-trifluoromethylphenyl)phenothiazine-S,S-dioxide and N-[3,5-bis(trifluoromethyl)phenyl]phenothiazine-S,S-dioxide are synthesized by Buchwald-Hartwig cross coupling reaction. The effect of different substituents in acceptors on the electronic, photophysical and electrochemical properties are studied by UVVis, fluorescence spectroscopy, cyclic voltammetry curves and theoretical calculations. The energy gaps (Delta E-ST) between singlet excited states (S1) and triplet excited states (T-1) of these compounds decrease by addition of one para-substituted -CF3 or two meta-substituted -CF3 on N-phenyl in order to enhance the electron-withdrawing capability of the acceptors. Small Delta E-ST of these compounds range from 0.09 eV to 0.18 eV. TM-2 similar to 4 exhibit thermally activated delayed fluorescence (TADF) characteristics with short delayed fluorescence lifetimes (tau(d)) within 0.69-1.16 mu s. TM-3 emits blue light with an emission wavelength of 475 nm. (C) 2016 Elsevier Ltd. All rights reserved.