Non-Phase-Transition Luminescence Mechanochromism of a Copper(I) Coordination Polymer

A copper­(I) coordination polymer,
[Cu2I2L2]n (CP 1), shows luminescence mechanochromism
with a color change from greenish-blue
to yellow upon the application of pressure. Powder X-ray diffraction
and Raman studies reveal that the changes in the bond lengths in crystalline
CP 1 are the main cause of luminescence mechanochromism.
The luminescence mechanochromic process of CP 1 preserves
its crystallinity with a small lattice distortion, despite very high
pressure, and it is a non-phase-transition process. After the addition
of several drops of acetonitrile to the ground and compressed samples,
the original greenish-blue emissive and crystalline states are restored.
Therefore, the luminescence color conversion processes are fully reversible.