Enhancing the Room-Temperature Phosphorescence Performance by Salinization of Guests

Although the host–guest doped strategy effectively
improves
the phosphorescence performance of materials and greatly enriches
the variety of materials, most of the guests are organic molecules
with weak luminescence ability, which leads to the need for further
improvement in the phosphorescence performance of doped materials.
Herein, by salinization of organic molecules, the luminescence performance
of the guests was effectively improved, thereby significantly enhancing
the phosphorescence performance of the doped system. A compound 4-(naphthalen-2-yl)quinoline
(QL) containing nitrogen atom was synthesized as initial
guest, then QL was salted to obtain six organic salt
guests containing anions BF4–, PF6–, CF3SO3–, N(CF3SO2)2–,
ClO4–, and C4F9SO3–, respectively. Two doped systems
were constructed using benzophenone and poly(methyl methacrylate)
as the hosts. The phosphorescence quantum yield and phosphorescence
lifetime of doped materials with QL as guest were only
4.1%/5.2% and 131 ms/141 ms, while those of doped materials with salinized
molecules as guests were improved to 32–39% and 534–625
ms, respectively. The single-crystal structures and theoretical calculations
indicated that anions can not only enhance the intermolecular interaction
of guests but also increase the spin–orbit coupling constant.
This work provides an effective strategy for improving the phosphorescence
performance of doped materials.