The review focuses on the influence of some important factors on the generation of new and/or high contrast mechanofluorochromic-active organic compounds by the structural modifications of traditional fluorophores.

Three donor (D)-π-acceptor (πA) indene-1,3-dionemethylene-1,4-dihydropyridine (IDM-DHP) derivatives with triphenylamine (TPA)/bis­(diphenylamino)­triphenylamine (BDPA-TPA) end groups were designed and synthesized. These target compounds with highly twisted conformations showed aggregation-induced emission enhancement properties in their THF/water mixtures due to the restriction of intramolecular rotation, and distinct piezofluorochromic (PFC) properties in the solid state. Interestingly, solvent-induced emission changes similar to those resulting from PFC properties can be achieved by a simple dissolution–desolvation process in different solvent systems, such as chloroform, THF, and dichloromethane. X-ray diffraction experiments revealed that the transformations between crystalline and amorphous states were responsible for the PFC properties and solvent-induced emission changes. Moreover, these compounds exhibited remarkable and reversible acid/base-induced fluorescence switching properties in both solution and the solid state. The results indicate that the IDM-DHP derivatives with a TPA/BDPA-TPA unit exhibit intriguing multi-stimulus-responsive fluorescent behaviors. The current study will help researchers to design and synthesize more aggregation-induced emission/aggregation-induced emission enhancement-active multifunctional stimulus-responsive fluorescent materials.

A series ofN-alkylated 1,4-dihydropyridine derivatives were reported to exhibit polymorphic and mechanochromic properties.

A new 1,4-dihydropyridine derivative was reported to display intriguing multifunctional photophysical properties.

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The length and isomerization of the alkyl chains exhibit different effects on the mechanofluorochromic properties of the dicyanomethylene-4H-pyran derivatives when the substitution position of the indole unit is different.

Four twisted 1,4-dihydropyridine derivatives with simple structure were synthesized. N-Substituted groups were found to play a decisive role in determining whether or not these compounds have mechanochromic activities.

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