Photoinduced crystal melting with luminescence evolution based on conformational isomerisation

Area of Science:

• Materials Science
• Photochemistry
• Crystallography

Background:

• Photo-induced crystal-to-liquid transition (PCLT) offers high spatiotemporal control over material properties.
• Limited compound diversity currently restricts the functionalization and understanding of PCLT-active materials.

Purpose of the Study:

• To introduce heteroaromatic 1,2-diketones as a novel class of PCLT-active compounds.
• To investigate the mechanism of PCLT in these diketones, focusing on conformational isomerization.
• To explore the integration of photofunctionality with PCLT.

Main Methods:

• Synthesis and characterization of heteroaromatic 1,2-diketones.
• Single-crystal X-ray structural analysis.
• Thermal analysis and theoretical calculations.
• UV irradiation studies monitoring luminescence and crystal phase transitions.

Main Results:

• Heteroaromatic 1,2-diketones were identified as a new class of PCLT-active materials.
• PCLT in these compounds is driven by conformational isomerization.
• One diketone exhibited distinct luminescence evolution (color and intensity changes) prior to melting due to sequential crystal loosening and isomerization.
• PCLT-active crystals showed weaker intermolecular interactions and a characteristic layered packing motif.

Conclusions:

• The study expands the molecular design scope for PCLT-active materials beyond traditional photochromic compounds.
• The findings provide fundamental insights into the mechanisms governing light-induced melting in molecular crystals.
• The integration of photofunctionality with PCLT opens avenues for novel light-responsive materials.