In this study,m echanochromicl uminescencew as induced in acomplex of mechano-inactive compounds. Dye/ acid complexes containing the same p-conjugated backbones were prepared. While the luminophores howedb lue and red shifts in photoluminescence spectra when combined with different acids by grinding, it exhibited slightmechanoresponsiveness itself. Also, compounds with similar molecular backbones to the dye/acid complex were synthesized to clarify the colorc hange mechanism.T he compounds showed both blue and red shifts in photolumines-cence and diffuse reflectance spectra upon grinding, indicating that mechanochromic luminescence in the hydrogenbondedcomplexi slike its monomeric analogue and that aggregations tructure plays an important role in mechanoresponsiveb ehaviorr ather than the p-conjugated structure. It was shown that acolor change can be mechanically induced by imitating the solid-state aggregation structure of other mechanoresponsive compounds without synthetic modification.[a] Dr.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.Recently,C hujo and co-workersd emonstrated switching of the directiono ft he peak shifts of the emission bands by varying the degree of sterich indranceo ft he end group. [14] This result suggested that the MCL behavior enabled switching of the peak shift direction by changing the substituent. Additionally, the hydrogen-bondedM CL complex enabled change in the substituent by changingt he acid species with different chemical structures.H erein, an ovel pyridine-terminated fluorescent dye (luminophore) MX (Figure 1a)i sd escribed, which shows MCL when combined with an acid. Furthermore, the dye showedb oth blue and red shiftc hanges in PL color upon mechanical grinding with different acid species.

Mechanochromic luminescence (MCL) compounds exhibit change of their photoluminescent color in response to mechanical stimuli. The initial molecular alignment of a liquid-crystalline MCL compound was controlled by using an alignment layer. The rubbing method and rubbing direction were successfully determined. Influence of mechanical force on photoluminescent behavior was evaluated.

A pyridine‐terminated fluorescent luminophore has been synthesized that exhibited mechanochromic luminescence (MCL) when combined with an acid. Although the luminophore showed both blue and red shifts in the photoluminescence spectra upon mechanical grinding with different acid species, it exhibited little mechanoresponsiveness itself. Furthermore, compounds with similar molecular backbones to the dye/acid complex were synthesized to clarify the color‐change mechanism. The compounds showed both blue and red shifts in the photoluminescence spectra and diffuse reflectance spectra upon grinding, indicating that the aggregation structure plays an important role in the mechanoresponsive behavior rather than the π‐conjugated structure. More information can be found in the Full Paper by Mizuho Kondo, Nobuhiro Kawatsuki et al. on page 471 in Issue 3, 2019 (DOI: 10.1002/asia.201801647).