The origin of the unusual red-shifted aggregation-state emission of triphenylamine-imidazole molecules: excimers or a photochemical reaction?,Materials Chemistry Frontiers

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The origin of the unusual red-shifted aggregation-state emission of triphenylamine-imidazole molecules: excimers or a photochemical reaction?
Materials Chemistry Frontiers ( IF 6.0 ) Pub Date : 2020-02-17 , DOI: 10.1039/c9qm00737g
Jin Liu _{1,

2,

3,

4,

5} , Jianai Chen _{1,

2,

3,

4,

5} , Yujie Dong _{1,

2,

3,

4,

5} , Yue Yu _{1,

2,

3,

4,

5} , Shitong Zhang _{5,

6,

7,

8} , Jianli Wang _{1,

2,

3,

4,

5} , Qingbao Song _{1,

2,

3,

4,

5} , Weijun Li _{1,

2,

3,

4,

5} , Cheng Zhang _{1,

2,

3,

4,

5}

Affiliation

At the moment, there is still no consensus regarding the origin of the newly apparent unusual red-shifted aggregation-state emission arising from some triphenylamine-imidazole luminescent materials. One view is that the unusual emission originates from the formation of excimers, but a recently observed photochemical reaction also seems to contribute to it. Herein, a new imidazole molecule, TPDBM, was synthesized to investigate the actual origin of this phenomenon. Compared with a dilute solution of TPDBM, its film obviously exhibits newly apparent high red-shifted emission at around 520 nm in the PL spectrum. According to UV-vis spectra and aggregation-induced emission (AIE) and concentration-dependent emission results, it seems that the red-shifted emission is derived from excimers. However, further studies of excitation spectra, in situ PL spectra and oxygen-free PL spectra entirely overturn this conclusion and ultimately confirm that it seems to come from a photochemical reaction occurring on the imidazole ring of TPDBM. Two photochemical products, TPBMZ and TPDYZ, with excellent AIE effects were obtained through this photochemical reaction, and TPBMZ can be further oxidized to TPDYZ due to the quite fast reaction rate. Furthermore, the photochemical reaction of TPDBM doped into PMMA film was suitably applied as a fluorescent probe for oxygen with a lowest detectable oxygen volume ratio of 0.1%.

中文翻译：

三苯胺-咪唑分子异常红移的聚集态发射的起源：准分子还是光化学反应？

目前，关于由某些三苯胺-咪唑发光材料引起的新出现的异常红移聚集态发射的起源，仍未达成共识。一种观点认为，异常发射源于受激准分子的形成，但最近观察到的光化学反应似乎也对其做出了贡献。本文中，合成了一种新的咪唑分子TPDBM，以研究这种现象的实际来源。与TPDBM的稀溶液比较，它的膜在PL光谱中大约520 nm处明显表现出新的高红移发射。根据紫外可见光谱和聚集诱导发射（AIE）以及浓度相关的发射结果，似乎红移发射源自准分子。然而，对激发光谱，原位PL光谱和无氧PL光谱的进一步研究完全推翻了这一结论，并最终证实它似乎来自TPDBM咪唑环上发生的光化学反应。通过该光化学反应，获得了具有优异的AIE作用的两种光化学产物TPBMZ和TPDYZ，并且TPBMZ可以被进一步氧化为TPDYZ。由于反应速度非常快。此外，掺杂到PMMA膜中的TPDBM的光化学反应适合用作氧的荧光探针，其最低可检测氧体积比为0.1％。

更新日期：2020-02-17

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