Luminescence Mechanochromism Induced by Cluster Isomerization

Area of Science:

• Materials Science
• Solid-State Chemistry
• Luminescence

Background:

• Luminescent mechanochromic materials change emission under mechanical stress, showing promise for stimuli-responsive applications.
• Polynuclear copper iodide clusters are an emerging class of materials with unique structural and optical properties.
• Isomerism in molecular clusters can significantly influence their physical characteristics.

Purpose of the Study:

• To investigate the luminescence mechanochromic properties of a specific chair-geometry copper iodide cluster, [Cu4I4(PPh3)4].
• To understand the mechanism behind the observed mechanochromism by comparing it with related compounds.
• To explore the potential of polynuclear copper iodide compounds in developing advanced mechanochromic materials.

Main Methods:

• Synthesis and characterization of the [Cu4I4(PPh3)4]·2CHCl3 cluster (1) and related compounds (2 and 3).
• Evaluation of luminescence and mechanochromic responses through mechanical stimuli like grinding.
• Comparative analysis of structural and optical properties, supported by electronic structure calculations.

Main Results:

• The [Cu4I4(PPh3)4]·2CHCl3 cluster (1) exhibits a distinct emission change upon manual grinding.
• The optical properties of the ground phase of (1) resemble those of its cubane isomer.
• A solid-state chair-to-cubane isomer conversion is proposed as the mechanism for the observed mechanochromism.

Conclusions:

• Polynuclear copper iodide clusters, particularly those with chair geometries, are highly relevant for developing novel luminescent mechanochromic materials.
• The study demonstrates an unprecedented solid-state isomer conversion mechanism driving mechanochromism.
• Structural isomerism plays a critical role in tuning the mechanochromic behavior of these copper iodide compounds.