Multi‐Directional Mechanofluorochromism of Acetyl Pyrenes and Pyrenyl Ynones

A series of acetyl pyrenes and pyrenyl ynones with without tert-butyl groups showed distinct mechanofluorochromism (MFC). Four pairs polymorphic solids were found out six compounds interestingly, each them hypsochromic, bathochromic or off-to-on MFC. The MFC properties rationalized by categorizing the packing schemes into herringbone, sandwich, beta gamma motifs depending on relative contributions C⋅⋅⋅C (or π-π) against C⋅⋅⋅H contacts. bulky trimethylsilyl served not only to reduce number aggregation patterns but also prohibit complete back reactions in solid state. Our results suggest that simple pyrene derivatives may be promising candidates for a novel group mechanically-sensitive materials.