The interplay of soft-hard substituents in photochromic diarylethenes

• Diarylethene crystals with substituents of different size and chemical nature were obtained.
• X-ray, FT-IR, DSC were performed to rationalize the thermal transitions processes.
• The role of van der Waals interactions of lateral groups drives the crystal packing formation.
• Different substituents favour either an amorphous or crystalline state after thermal treatment.

A series of diarylethenes with substituents of different size and chemical nature was synthesised showing that beside some intermolecular interactions involving the central diarylethene core, lateral groups clearly play a key role in the crystal packing arrangements. These structural features were further analyzed in relation to the thermal data obtained by differential scanning calorimetry (DSC) and monitored using FT-IR spectroscopy, thus providing a rationalization of the observed thermal transitions processes. The role of van der Waals interactions is crucial in driving crystal packing formation towards loosely packed arrangements characterized by large hydrophobic contact areas. Interestingly, some functional substituents favour an amorphous state after thermal treatment, a peculiar feature that can be exploited to design uniform photochromic layers.

Substituents are crucial in driving the intermolecular packing arrangement in 1,2-dithienylethenes and affecting the physical properties of the solid-state materials.Figure optionsDownload as PowerPoint slide