Distinct Responses to Mechanical Grinding and Hydrostatic Pressure in Luminescent Chromism of Tetrathiazolylthiophene

Luminescent
mechanochromism has been intensively studied in the
past few years. However, the difference in the anisotropic grinding
and the isotropic compression is not clearly distinguished in many
cases, in spite of the importance of this discrimination for the application
of such mechanochromic materials. We now report the distinct luminescent
responses of a new organic fluorophore, tetrathiazolylthiophene, to
these stresses. The multichromism is achieved over the entire visible
region using the single fluorophore. The different mechanisms of a
blue shift by grinding crystals and of a red shift under hydrostatic
pressure are fully investigated, which includes a high-pressure single-crystal
X-ray diffraction analysis. The anisotropic and isotropic modes of
mechanical loading suppress and enhance the excimer formation, respectively,
in the 3D hydrogen-bond network.