For piezo-, vapo-, and thermochromic materials, it remains a challenge to figure out underlying reason for fluorescence color changes upon external stimulation and determine why only some fluorophores reveal emission switching. A novel triphenylacrylonitrile derivative (TPAN-MeO) with remarkably twisted 10 conformations has been carefully prepared via the Suzuki coupling reaction. The fluorescence of TPAN-MeO in aggregate state depends on the polymorphism forms: three crystalline forms BCrys, SCrys and YCrys are brightly blue, sky-blue and yellow emission, respectively; meanwhile the amorphous powders are also strong fluorescent with green emission. The crystals BCrys and SCrys indicate the mechano-and piezochromism in that grinding and high pressure could alter emission colour, respectively. In addition, 15 the amorphous film reveals vapo-and thermochromic behaviour in that organic vapour and heating could change the green colour into sky-blue. Interestingly, the solvent vapour and heating stimuli can trigger a crystal-to-crystal transformation between SCrys form and YCrys form.

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An efficient mild one-pot synthesis of spiro [indoline-3,4'-pyrano[2,3-c]pyrazole derivatives by a four-component reaction of hydrazine, a β-keto ester, isatin, and malononitrile catalysed by L-proline in water is reported.

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