Clear piezochromic behaviors of AIE-active organic powders under hydrostatic pressure

• Published in: RSC advances 2016-01, Vol.6 (2), p.1188-1193
• Main Authors: Ouyang, Mi, Zhan, Lingling, Lv, Xiaojing, Cao, Feng, Li, Weijun, Zhang, Yujian, Wang, Kunyan, Zhang, Cheng
• Format: Article
• Language: English
• Subjects: Color; Condensation; Crystal structure; Derivatives; Diamond anvil cells; Fluorescence; Hydrostatic pressure; X ray diffraction
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/c5ra21218a

A novel diphenylacrylonitrile derivative ( Z )-3-(4′-(diphenylamino)-[1,1′-biphenyl]-4-yl)-2-(4-methoxyphenyl)-acrylonitrile ( β-CN-TPA ) containing a twisted triphenylamine and diphenylacetonitrile was synthesized via Knoevenagel condensation and Suzuki coupling reactions. These molecules exhibited aggregation enhanced emission (AIE) effects. Interestingly, their mechano-fluorochromic properties were invisible upon grinding with a pestle. However, when hydrostatic pressure in a diamond anvil cell (DAC) was applied on the crystals of β-CN-TPA , the distinct piezochromic behaviors of the compound were observed. The fluorescence color changed from light green (530 nm) to red (665 nm) with a significant red-shift of 135 nm. The powder X-ray diffraction and high-pressure Raman studies indicated that the as-synthesized and ground samples had the same crystalline structures, while the compressed samples had an evident change in inter-molecular interactions. Comparative tests and theoretical analysis further confirmed that the distinct fluorescence behaviors of the desired dye during the different stress conditions were associated with the various inter-molecular interactions that existed with adjacent molecules. A diphenylacrylonitrile derivative exhibiting the aggregation induced emission and piezochromic behavior with clear wavelength changes under hydrostatic pressure.