D–A–D type high contrast mechanochromic luminescence based on anthracene and pyridinium salt derivatives†

Fluorescent color-changing smart materials based on force stimulus have attracted wide attention due to their multifunctional and reversible characteristics, leading to advanced applications. However, it is still challenging to develop high-contrast mechanochromic luminescent molecules and reveal the relationship between their structure and properties. This article illustrates the high-contrast mechanochromic properties of D–A–D type derivatives. Two pyridine-functionalized anthracene derivatives (MTPA and BTPA) both showed significant photoluminescence shift under mechanical force stimulus. It is worth noting that the unilaterally substituted D–A–D anthracene derivative (MTPA) exhibits a significant wavelength shift of 122 nm when ground, and the luminescence color changes from blue to yellow. Moreover, it can recover to the original luminescent color after steaming with water or ethanol. This study not only elucidates the mechanochromic properties of D–A–D type cationic organic small molecules, but also provides a novel design concept for designing high-contrast mechanochromic materials.