Mechanochromic Luminescence (MCL) of Purely Organic Two‐Component Dyes: Wide‐Range MCL over 300 nm and Two‐Step MCL by Charge‐Transfer Complexation

Abstract

Despite recent extensive studies on mechanochromic luminescence (MCL), rational control over the magnitude of the emission-wavelength shift in response to mechanical stimuli remains challenging. In the present study, a twocomponent donor-acceptor approach has been applied to create a variety of organic MCL composites that exhibit remarkable emission-wavelength switching. Dibenzofuranbased bis(1-pyrenylmethyl)diamine and typical organic fluorophores have been employed as donor and acceptor dyes, respectively. Outstanding wide-range MCL with an emission-wavelength shift of over 300 nm has been achieved by mixing the diamine with 3,4,9,10-perylenetetracarboxylic diimide. Unprecedented two-step MCL in response to mechanical stimuli of different intensity has also been realized for a twocomponent mixture with 9,10-anthraquinone. Fluorescence microscopy observations at the single-particle level revealed that the segregation and mixing of the two-component dyes contribute to the stimuli-responsive emission-color switching of the MCL composites.

Mechanofluorochromism of 2‐Biarylyl Cinchoninic Acids with High Sensitivity and Large Mechanochromic Shift

“…[17] The general mechanism of this typical two-step MFC materials is based on the transition of crystal-tocrystal during mild grinding, and followed by the transition of crystal-to-amorphous during sufficient grinding. [18] Unlike compound 4, there is no crystal-to-crystal transition.…”

“…Previous reports of stepwise MFC materials have referred to the crystalline dyes that exhibit continuous emission color changes after mild and sufficient grinding [17] . The general mechanism of this typical two‐step MFC materials is based on the transition of crystal‐to‐crystal during mild grinding, and followed by the transition of crystal‐to‐amorphous during sufficient grinding [18] . Unlike compound 4 , there is no crystal‐to‐crystal transition.…”

“…Although stimuli‐responsive material and mechanochromic luminescence materials are being developed, there are many challenges remaining. The maximum mechanochromic shift of single‐component MFC materials reported to date is generally not large [7,18] . In particular, the mechanochromic shifts of most organic MFC materials reported are less than 100 nm.…”

“…The maximum mechanochromic shift of single-component MFC materials reported to date is generally not large. [7,18] In particular, the mechanochromic shifts of most organic MFC materials reported are less than 100 nm. Therefore, utilizing single component fluorophores to acquire a wide range of mechanochromic shift remains a challenging mission.…”

Mechanochromic luminogens with hypsochromically shifted emission switching property: recent advances and perspectives

“…There are few reports on the MLs showing large spectral shifts (4100 nm). [67][68][69][70][71][72][73][74][75][76] Zhu et al reported a benzothiadiazole based luminogen that exhibits a spectral shift of 160 nm on grinding. 77 Larger spectral shift results in high contrast mechanochromism and hence is useful for fabricating strain sensing devices.…”