TY - JOUR
T1 - The K-Region in Pyrenes as a Key Position to Activate Aggregation-Induced Emission
T2 - Effects of Introducing Highly Twisted N,N-Dimethylamines
AU - Sasaki, Shunsuke
AU - Suzuki, Satoshi
AU - Igawa, Kazunobu
AU - Morokuma, Keiji
AU - Konishi, Gen Ichi
N1 - Funding Information:
This work was partially supported by a Grant-in-Aid for Scientific Research (Kakenhi) from the MEXT, Japan and S-Innovation from Japan Science and Technology Agency (JST).
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/7/7
Y1 - 2017/7/7
N2 - 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.
AB - 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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U2 - 10.1021/acs.joc.7b00996
DO - 10.1021/acs.joc.7b00996
M3 - Article
C2 - 28656764
AN - SCOPUS:85022331953
VL - 82
SP - 6865
EP - 6873
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
SN - 0022-3263
IS - 13
ER -