Molecular Engineering of Mechanochromic Materials by Programmed C-H Arylation: Making a Counterpoint in the Chromism Trend.
The development of facile methods for screening organic functional molecules through C-H bond activation is a revolutionary trend in materials research. The prediction of mechanochromism as well as mechanochromic trends of luminogens is an appealing yet challenging puzzle. Here, we present a strategy for the design of mechanochromic luminogens based on the dipole moment of donor-acceptor molecules. For this purpose, a highly efficient route to 2,7-diaryl-[1,2,4]triazolo[1,5-a]pyrimidines (2,7-diaryl-TAPs) has been established through programmed C-H arylation, which unlocks a great opportunity to rapidly assemble a library of fluorophores for the discovery of mechanochromic regularity. Molecular dipole moment can be employed to explain and further predict the mechanochromic trends. The 2,7-diaryl-TAPs with electron-donating groups on the 2-aryl and electron-withdrawing groups on the 7-aryl possess a relatively small dipole moment and exhibit a red-shifted mechanochromism. When the two aryls are interchanged, the resulting luminogens have a relatively large dipole moment and display a blue-shifted mechanochromism. Seven pairs of isomers with opposite mechanochromic trends are presented as illustrative examples. The aryl-interchanged congeners with a bidirectional emission shift are structurally similar, which provides an avenue for understanding in-depth the mechanochromic mechanism.
Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry, and State Key Laboratory of Biotherapy, West China Medical School, Sichuan University , 29 Wangjiang Road, Chengdu 610064, P.R. China.
Jie
J
Wu
Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry, and State Key Laboratory of Biotherapy, West China Medical School, Sichuan University , 29 Wangjiang Road, Chengdu 610064, P.R. China.
Yangyang
Y
Cheng
Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry, and State Key Laboratory of Biotherapy, West China Medical School, Sichuan University , 29 Wangjiang Road, Chengdu 610064, P.R. China.
Jingbo
J
Lan
Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry, and State Key Laboratory of Biotherapy, West China Medical School, Sichuan University , 29 Wangjiang Road, Chengdu 610064, P.R. China.
Di
D
Wu
Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry, and State Key Laboratory of Biotherapy, West China Medical School, Sichuan University , 29 Wangjiang Road, Chengdu 610064, P.R. China.
Shengyou
S
Qian
Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry, and State Key Laboratory of Biotherapy, West China Medical School, Sichuan University , 29 Wangjiang Road, Chengdu 610064, P.R. China.
Lipeng
L
Yan
Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry, and State Key Laboratory of Biotherapy, West China Medical School, Sichuan University , 29 Wangjiang Road, Chengdu 610064, P.R. China.
Zhen
Z
He
Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry, and State Key Laboratory of Biotherapy, West China Medical School, Sichuan University , 29 Wangjiang Road, Chengdu 610064, P.R. China.
Xiaoyu
X
Li
State Key Laboratory of Superhard Materials, Jilin University , Changchun 130012, P.R. China.
Kai
K
Wang
State Key Laboratory of Superhard Materials, Jilin University , Changchun 130012, P.R. China.
Bo
B
Zou
Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry, and State Key Laboratory of Biotherapy, West China Medical School, Sichuan University , 29 Wangjiang Road, Chengdu 610064, P.R. China.
Jingsong
J
You