The effect of molecular symmetry on the mechanofluorochromic properties of 4H-pyran derivatives

Polymorphism and Multicolor Mechanofluorochromism of a D-π-A Asymmetric 4H-Pyran Derivative with Aggregation-Induced Emission Property

“…46−55 Very recently, some asymmetric 4H-pyran derivatives were reported to exhibit higher contrast MFC activities than the corresponding symmetric compounds because the low symmetry was conducive to obtaining crystalline structures, which were easily destroyed by external forces. 56 Although several 4H-pyran derivatives were reported to simultaneously exhibit AIE, polymorphic, and MFC characteristics, 56 as far as we know, these kinds of 4H-pyran derivatives with multiple crystalline polymorphs have not been reported. Herein, a D-π-A-type asymmetric 4H-pyran derivative (AMP, Scheme 1) containing dicyanomethylene, benzene, and 4-hydroxybenzene units was designed and synthesized.…”

“…(1) the aymmetric structure is beneficial for acquiring twisted conformation and loose stacking arrangement to obtain AIE and MFC properties based on our previous work 56 and…”

“…4 H -Pyran derivatives are a class of D-π-A fluorescent compounds where various electron acceptors and electron donors were easily introduced into the parent unit by simple chemical reactions, which are widely used in the fields of fluorescent sensors, organic electroluminescent diodes, molecular logic gates, etc. − Recently, some 4 H -pyran derivatives have been reported to exhibit polymorphic, AIE, and/or solid-state fluorescence stimulus response properties. − Very recently, some asymmetric 4 H -pyran derivatives were reported to exhibit higher contrast MFC activities than the corresponding symmetric compounds because the low symmetry was conducive to obtaining crystalline structures, which were easily destroyed by external forces . Although several 4 H -pyran derivatives were reported to simultaneously exhibit AIE, polymorphic, and MFC characteristics, as far as we know, these kinds of 4 H -pyran derivatives with multiple crystalline polymorphs have not been reported. Herein, a D-π-A-type asymmetric 4 H -pyran derivative ( AMP , Scheme ) containing dicyanomethylene, benzene, and 4-hydroxybenzene units was designed and synthesized.…”

“…Herein, a D-π-A-type asymmetric 4 H -pyran derivative ( AMP , Scheme ) containing dicyanomethylene, benzene, and 4-hydroxybenzene units was designed and synthesized. Our design ideas are as follows: (1) the aymmetric structure is beneficial for acquiring twisted conformation and loose stacking arrangement to obtain AIE and MFC properties based on our previous work and (2) the introduction of dicyanylmethylene is helpful for obtaining ordered self-assemblies and crystalline structures; furthermore, the existence of the cyano group, hydroxyl group, and aromatic rings in a molecular structure is also conducive to increasing the possibility of the generation of the polymorphs by adjusting molecular stacking arrangements through various noncovalent interactions, , such as C–H···N hydrogen bonds, C–H···O hydrogen bonds, C–H···π bonds, and π–π stacking interactions. As a result, this compound was found to exhibit AIE and polymorphic properties with multiple crystalline polymorphs.…”

Deep insights into polymorphism initiated by exploring multicolor conversion materials

“…Taking advantage of aggregation induced emission (AIE) theory 14 and halogen atom effects, 15,16 hydrophilic and hydrophobic interactions, 17 intramolecular charge transfer, [18][19][20] and so forth, twisted molecular configurations and intermolecular weak bond interactions are constructed. Furthermore, the twisted configurations and weak interactions afforded a relatively loose packing, 21 which is prone to be compressed and destroyed by exogenous forces and accompanied by fluorescence changes.…”