Angewandte Chemie International Edition
10.1002/anie.202011770
RESEARCH ARTICLE
T2-p-PyCzBr-C1, the triplet excitons can only diffuse in its own
column; it cannot hop to the neighbor column because of the
inversion of the carbazole short axis orientation between two
adjacent columns and their very small overlap. Because of the
long distance (~ 6Å) between parallel molecules in a column, the
transfer should occur via ‘zig-zag’ diffusion along the herringbone
structure. This process could lead to a short triplet diffusion
distance, which prevents to reach nonradiative traps and leads to
a long-lived phosphorescence as for T3-m-PyCzBr and T2-p-
PyCzBr-C1. The lifetimes are similar for both crystals because
the same crystal structure should lead to the same pathway for
triplet exciton diffusion on the one hand, and similar nonradiative
rates for intramolecular vibrational relaxation and triple quenching
by the surrounding on the other hand. In T2-p-PyCzBr-C2 crystal,
the triplet exciton could hop to the neighbor column of the ‘column
pair’ because of the partial overlap of Cz units with the same
permanent dipole orientation in two adjacent columns. Thus,
triplet diffusion distance increases along with opportunities to find
a trap, which could explain the shorter lifetime.
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Acknowledgements
6
2
This research was supported by the Asian Office of Aerospace
Research and Development (AOARD, FA 2386-17-1-4060). We
are very grateful to Prof. Ha-Jin Lee from the Korea Basic Science
Institute (KBSI, Western Seoul Center) for the single crystal
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AXELERA Pôle de Compétitivité for financial support (PSMN
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thank Dr. Jean-Louis Fave (INSP, Université Sorbonne Université,
Paris) for the very fruitful and friendly discussions.
Keywords: organic room temperature phosphorescence •
molecular crystal • H-bonded directed supramolecular self-
assembly • σ-conjugation • TD-DFT calculations
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