The K-Region in Pyrenes as a Key Position to Activate Aggregation-Induced Emission: Effects of Introducing Highly Twisted N,N-Dimethylamines

Shunsuke Sasaki, Satoshi Suzuki, Kazunobu Igawa, Keiji Morokuma, Gen Ichi Konishi

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Abstract

A new design strategy to activate aggregation-induced emission (AIE) in pyrene chromophores is reported. In a previous report, we demonstrated that highly twisted N,N-dialkylamines of anthracene and naphthalene induce drastic AIE when these donors are introduced at appropriate positions to stabilize the S1/S0 minimum energy conical intersection (MECI). In the present study, this design strategy was applied to pyrene: the introduction of N,N-dimethylamine substituents at the 4,5-positions of pyrene, the so-called K-region, are likely to stabilize MECIs. To examine this hypothesis, four novel pyrene derivatives, which contain highly twisted N,N-dimethylamino groups at the 4- (4-Py), 4,5- (4,5-Py), 1- (1-Py), or 1,6-positions (1,6-Py) were tested. The nonradiative transitions of 4,5-Py are highly efficient (knr = 57.1 × 107 s-1), so that its fluorescence quantum yield in acetonitrile decreases to φfl = 0.04. The solid-state fluorescence of 4,5-Py is efficient (φfl = 0.49). In contrast, 1,6-Py features strong fluorescence (φfl = 0.48) with a slow nonradiative transition (knr = 11.0 × 107 s-1) that is subject to severe quenching (φfl = 0.03) in the solid state. These results underline that the chemistry of the pyrene K-region is intriguing, both from a photophysical perspective and with respect to materials science.

Original languageEnglish
Pages (from-to)6865-6873
Number of pages9
JournalJournal of Organic Chemistry
Volume82
Issue number13
DOIs
Publication statusPublished - Jul 7 2017

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Dimethylamines
Pyrenes
Agglomeration
Fluorescence
Quantum yield
Materials science
Chromophores
Quenching
pyrene
Derivatives

All Science Journal Classification (ASJC) codes

  • Organic Chemistry

Cite this

The K-Region in Pyrenes as a Key Position to Activate Aggregation-Induced Emission : Effects of Introducing Highly Twisted N,N-Dimethylamines. / Sasaki, Shunsuke; Suzuki, Satoshi; Igawa, Kazunobu; Morokuma, Keiji; Konishi, Gen Ichi.

In: Journal of Organic Chemistry, Vol. 82, No. 13, 07.07.2017, p. 6865-6873.

Research output: Contribution to journalArticle

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abstract = "A new design strategy to activate aggregation-induced emission (AIE) in pyrene chromophores is reported. In a previous report, we demonstrated that highly twisted N,N-dialkylamines of anthracene and naphthalene induce drastic AIE when these donors are introduced at appropriate positions to stabilize the S1/S0 minimum energy conical intersection (MECI). In the present study, this design strategy was applied to pyrene: the introduction of N,N-dimethylamine substituents at the 4,5-positions of pyrene, the so-called K-region, are likely to stabilize MECIs. To examine this hypothesis, four novel pyrene derivatives, which contain highly twisted N,N-dimethylamino groups at the 4- (4-Py), 4,5- (4,5-Py), 1- (1-Py), or 1,6-positions (1,6-Py) were tested. The nonradiative transitions of 4,5-Py are highly efficient (knr = 57.1 × 107 s-1), so that its fluorescence quantum yield in acetonitrile decreases to φfl = 0.04. The solid-state fluorescence of 4,5-Py is efficient (φfl = 0.49). In contrast, 1,6-Py features strong fluorescence (φfl = 0.48) with a slow nonradiative transition (knr = 11.0 × 107 s-1) that is subject to severe quenching (φfl = 0.03) in the solid state. These results underline that the chemistry of the pyrene K-region is intriguing, both from a photophysical perspective and with respect to materials science.",
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