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Polymorphic copper iodide clusters: insights into the mechanochromic luminescence properties
Quentin Benito1, Xavier F Le Goff, Sébastien Maron
1Laboratoire de Physique de la Matière Condensée (PMC), CNRS - Ecole Polytechnique, 91128 Palaiseau Cedex, France.
Journal of the American Chemical Society
|July 31, 2014
Summary
Mechanochromic luminescent copper iodide clusters change color when ground. This study reveals that mechanical force alters copper-copper bond distances, explaining the color shift and highlighting cuprophilic interactions.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Photophysics
Background:
- Mechanochromism in metal-based compounds is an area of active research.
- Copper iodide clusters are known for their luminescent properties.
- Structural polymorphism can significantly influence material properties.
Purpose of the Study:
- To investigate the mechanochromic and thermochromic properties of luminescent copper iodide clusters.
- To elucidate the origin of mechanochromic luminescence in these materials.
- To establish a structure-property relationship between Cu-Cu bond distances and luminescence.
Main Methods:
- Synthesis and characterization of copper iodide clusters with structural polymorphism.
- Mechanical grinding experiments to induce mechanochromism.
- Optical spectroscopy (luminescence) and X-ray diffraction for structural analysis.
- (31)P and (65)Cu solid-state Nuclear Magnetic Resonance (NMR) spectroscopy.
Main Results:
- Two crystalline polymorphs of copper iodide clusters exhibit distinct green and yellow luminescence.
- Mechanical grinding of one polymorph induces a color change from green to yellow.
- The photophysical properties of the crushed material resemble those of the yellow polymorph.
- A correlation between Cu-Cu bond distances and luminescence properties was established.
- (31)P and (65)Cu NMR confirmed modifications in the local structure upon grinding.
Conclusions:
- Mechanochromism in these copper iodide clusters is attributed to the disruption of crystal packing and shortening of Cu-Cu bond distances.
- Cuprophilic interactions play a crucial role in the observed mechanochromic phenomenon.
- This study advances the understanding of mechanochromic mechanisms in metal-based luminescent compounds.
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