Transforming
Thermally Activated Delayed Fluorescence
to Room-Temperature Phosphorescence through Modulation of the Donor
in Charge-Transfer Cocrystals
posted on 2024-03-01, 16:39authored byYating Wen, Shuaiqiang Zhao, Zhongzhao Yang, Zhe Feng, Zhiqiang Yang, Shi-Tong Zhang, Haichao Liu, Bing Yang
A cocrystallization
strategy is used through incorporation of 1,2,4,5-tetracyanobenzene
(TCNB) as an acceptor with halogen-substituent thioxanthone (TX) derivatives
as donors. The resulting cocrystals TT-R (R = H, F, Cl, Br, or I)
transform the thermally activated delayed fluorescence emission in
the TT-H, TT-F, and TT-Cl cocrystals to room-temperature phosphorescence
in the TT-Br and TT-I cocrystals. Definite crystal packing structures
demonstrate a 1:1 alternative donor–acceptor stacking in the
TT-H cocrystal, a 2:1 alternative donor–acceptor stacking in
the TT-F and TT-Cl cocrystals, and a separate stacking of donor and
acceptor in the TT-Br and TT-I cocrystals. A transformation law can
be revealed that with an increase in atomic number from H, F, Cl,
Br, to I, the cocrystals show the structural transformation of the
number of aggregated TX-R molecules from monomers to dimers and finally
to multimers. This work will facilitate an understanding of the effect
of halogen substituents on the crystal packing structure and luminescence
properties in the cocrystals.