Colorful variation of tetraphenylethene derivatives in the solid state

Abstract

Stimuli-responsive chromic materials have sensitive responses to mechanical, thermal, chemical vapor, and light stimuli, which exhibited as mechanochromism, mechanoluminesence, thermochromism, vapochromism, photochromism and Ex-De luminescence, etc. Tetraphenylethene (TPE) scaffold as...

Acid–base regulated inclusion complexes of β-cyclodextrin with 1-[2-(4-fluorophenyl)-2-oxoethyl]-4,4′-bipyridinium dichloride displaying multistimuli-responsive chromic behaviors and photomodulable fluorescence

“…Over the past two decades, numerous chromic materials, especially photochromic materials, have been constructed and reported. 27–33 Among the various chromic compounds, viologens (1,1′-disubstituted-4,4′-bipyridinium salts) are particularly attractive due to their thermostability, reversibility, easy synthesis, and novel color-changing properties. 34,35 However, the examples of a chromic material with the capability to respond to multiple stimuli are still limited.…”

Four POM-Viologen Color-Changing Materials with Fast Color Response under Various External Stimuli

“…Stimuli-responsive smart materials can undergo obvious color changes under external stimuli such as heat, light, electricity, pressure, X-rays, and amines. 29 Among these, researchers are drawn to the smart intelligent materials made from viologen derivatives due to their unique properties. 30 The electrons on the N atom of the pyridine ring in viologen derivatives are easily transferable when stimulated externally.…”

Amorphization-Enhanced Emission (AEE) of Tetraphenylethylene

“…MRL materials have received a lot of attention due to their potential applications in fields such as mechanical sensing, anticounterfeit paper, and microphotonic devices. − The alteration of molecular stacking induced by mechanical stimulation is considered the central factor in the appearance of changes in fluorescence emission . In most studies on MRL compounds, the mechanically induced phase can be restored to the initial stacking and the photoluminescence color recovered by heating or vaporization. , Interestingly, some of the materials recover spontaneously without any treatment, a property that, on the one hand, facilitates fast and repetitive switching in some scenarios but, on the other hand, is not conducive to an in-depth study of the photophysical mechanisms behind this mechanically induced phase. − In most of the reported MRL materials with two-color switching, the majority switch back and forth between the crystalline and amorphous states, and most of the amorphous phases have redder and weaker fluorescence emission. , In the study of some aggregation-induced emission (AIE) materials, face-to-face stacking between benzene rings results in weak luminescence, while fluorescence emission was turned on after milling into the amorphous state. − The fluorescence emission of very few AIE materials varies from bright (crystalline) to even brighter (amorphous) under mechanical stimulation. − For the classical AIE material tetraphenylethylene (TPE), a different phenomenon exists, whereby a fluorescence emission that is brighter than the crystalline phase and in a metastable state is clearly observed by modulating the content of the undesirable solvents but has never been observed in mechanical treatments. − This metastable TPE is most likely an amorphous aggregate, and deeply studying this basic scientific question will help to understand further the relationship between the molecular stacking mode and luminescence efficiency and improve the photophysical mechanism behind TPE.…”