Reversible Near-Infrared/Blue Mechanofluorochromism of Aminobenzopyranoxanthene

Mechanochromic organic molecules
(MOMs) that exhibit a large difference
of fluorescence wavelength between two states have important potential
applications, but few such compounds are known. Here, we report a
new MOM, cis-ABPX010, which shows switchable
near-IR and blue fluorescence responses. Detailed spectrophotometric
and single-crystal X-ray analyses revealed that the near-IR fluorescence
is attributable to fluorescence from slip-stacked dimeric structures
in crystals, while the blue fluorescence is attributable to fluorescence
from the monomer. Switching between the two is achieved by dynamic
structural interconversion between the two molecular packing arrangements
in response to mechanical grinding and solvent vapor-fuming.