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Dynamic Molecular Triplet Excitons Tune Lanthanide Emission Lifetime
Takuma Nakai1, Kaori Shima1, Mengfei Wang2,3
1Graduate School of Chemical Sciences and Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan.
None:
Optical codes generated from the emission lifetimes of lanthanide complexes have received considerable attention for their potential application in multiplexed bioimaging and anti-counterfeiting. However, such tunable lifetimes are limited to short ranges (0.01-1 ms). Herein, we describe a method that extends the emission lifetime using dynamic molecular triplet excitons in aggregation systems composed of lanthanide complexes. To demonstrate the conceptual method, molecular crystals comprising lutetium (Lu3+) and luminescent lanthanide (europium: Eu3+ or terbium: Tb3+) complexes with two organic ligands (2,2,6,6-tetramethyl-3,5-heptanedionate and 2,7-bis(diphenylphosphoryl)phenanthrene) were prepared. These molecular crystals exhibited persistent emission via slow triplet exciton migration between the phenanthrene units. The extended degree of the lifetime could be controlled between 1 and 152 ms by ligand modifications. This proposed lifetime-tuning method should significantly expand the encoding capacity of lanthanide complexes.
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