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CAS: 575451-86-4
MF: C26H26N2O2Br2
MW: 558.30484
Synonyms:

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Wei Huang

Institute of Chemistry, Chinese Academy of Sciences
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He Tian

East China University of Science and Technology
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Jianli Hua

East China University of Science and Technology
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Jinsang Kim

University of Michigan
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Co-reporter: Kyeongwoon Chung, Min Sang Kwon, Brendan M. Leung, Antek G. Wong-Foy, Min Su Kim, Jeongyong Kim, Shuichi Takayama, Johannes Gierschner, Adam J. Matzger, and Jinsang Kim
pp: 94
Publication Date(Web):May 13, 2015
DOI: 10.1021/acscentsci.5b00091
Thermodynamics drive crystalline organic molecules to be crystallized at temperatures below their melting point. Even though molecules can form supercooled liquids by rapid cooling, crystalline organic materials readily undergo a phase transformation to an energetically favorable crystalline phase upon subsequent heat treatment. Opposite to this general observation, here, we report molecular design of thermally stable supercooled liquid of diketopyrrolopyrrole (DPP) derivatives and their intriguing shear-triggered crystallization with dramatic optical property changes. Molten DPP8, one of the DPP derivatives, remains as stable supercooled liquid without crystallization through subsequent thermal cycles. More interestingly, under shear conditions, this supercooled liquid DPP8 transforms to its crystal phase accompanied by a 25-fold increase in photoluminescence (PL) quantum efficiency and a color change. By systematic investigation on supercooled liquid formation of crystalline DPP derivatives and their correlation with chemical structures, we reveal that the origin of this thermally stable supercooled liquid is a subtle force balance between aromatic interactions among the core units and van der Waals interactions among the aliphatic side chains acting in opposite directions. Moreover, by applying shear force to a supercooled liquid DPP8 film at different temperatures, we demonstrated direct writing of fluorescent patterns and propagating fluorescence amplification, respectively. Shear-triggered crystallization of DPP8 is further achieved even by living cell attachment and spreading, demonstrating the high sensitivity of the shear-triggered crystallization which is about 6 orders of magnitude more sensitive than typical mechanochromism observed in organic materials.

Adam J. Matzger

The University of Michigan
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Xin Li

Institute of Chemistry
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Wei Huang

University of Science and Technology of China
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YongQuan Wu

Shanghai University
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