Multi-Stimuli-Responsive Fluorescence Switching of a Donor-Acceptor π-Conjugated Compound

An electron donor-acceptor structured pi-conjugated organic compound 1 composed of trifluoromethyl-biphenyl and cyano-stilbene-amine was designed and exhibited multi-stimuli-responsive fluorescence switching behaviors. The synthesized solid exhibited piezochromism in that grinding and heating could change the emission colors between orange-red and yellow. The amorphous 1 also showed interesting vapochromic behavior in that organic vapor could convert the yellow color into orange. The solution of 1 exhibited nearly no fluorescence at room temperature and intensive yellowish green emission at 77 K, while adding CF3COOH (TFA) resulted in green emissive state at room temperature and blue fluorescent state at 77 K.