Clear piezochromic behaviors of AIE-active organic powders under hydrostatic pressure. Issue 2 (23rd December 2015) - Ouyang, Mi
Abstract : A diphenylacrylonitrile derivative exhibiting the aggregation induced emission and piezochromic behavior with clear wavelength changes under hydrostatic pressure. Abstract : 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 ofβ-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.