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Two piezochromic molecules, (2Z,4E)-2-(4-(Diphenylamino)phenyl)-5-phenylpenta-2,4-dienenitrile (1a) and (2Z,4E)-2-(4-(acridin-10(9H)-yl)phenyl)-5-phenylpenta-2,4-dienenitrile (1b), were synthesized by using Knoevenagel and Buchwald-Hartwig cross-coupling reactions. Their piezochromic fluorescence behavior was tuned by subtle structural change. The system indicates typical intramolecular charge-transfer properties. The luminescence intensity of 1a decreased with increasing pressure with the redshift of the emission wavelength when the hydrostatic pressure in a diamond anvil cell (DAC) was applied on its crystal. However, the emission wavelength of 1b which has a methylene unit more than 1a had no obvious shift and the intensity increased gradually at the pressure range from 0.66 GPa to 5.72 GPa. |
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