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Mechano‐ and Photoresponsive Behavior of a Bis(cyanostyryl)benzene Fluorophore
Author(s) -
Kaneko Ryohei,
Sagara Yoshimitsu,
Katao Shouhei,
Tamaoki Nobuyuki,
Weder Christoph,
Nakano Hideyuki
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201900120
Subject(s) - excimer , photochemistry , amorphous solid , fluorophore , fluorescence , materials science , naked eye , luminescence , dichroic glass , benzene , monomer , chemistry , optics , optoelectronics , polymer , organic chemistry , physics , composite material
The mechanoresponsive behavior and photochemical response of a new bis(cyanostyryl)benzene fluorophore (CSB‐5) were investigated. Green fluorescence with λ em,max of 507 nm was found for CSB‐5 in chloroform solution, mirroring the behavior of a previously reported similar dye (CSB‐6). Alternatively, crystalline samples of CSB‐5 exhibited orange fluorescence with λ em,max of 620 nm, attributable to excimer emission. Although the emission color change was not clearly noticeable by naked eye, CSB‐5 exhibited mechanochromic luminescence, due to transformation into the amorphous state upon grinding the crystalline powder. Interestingly, rubbed films of CSB‐5 prepared on glass substrates exhibited a pronounced emission color change from orange to green when exposed to UV light. This response is the result of a photochemical reaction that occurs in the amorphous state and which causes a decrease of the excimer emission sites so that the emission color changes from excimer to monomer. The crystalline material did not display such a photoinduced emission color change and the difference in photochemical reactivity between crystalline and amorphous states was exploited to pattern the emission color of rubbed films.