Tetrafluoro(aryl)sulfanylated Bicyclopentane Crystals That Self-Destruct upon Cooling

Area of Science:

• Materials Science
• Crystallography
• Organic Chemistry

Background:

• Mechanically responsive crystals are well-studied for heat or light stimuli.
• Crystalline organic compounds exhibiting extreme mechanical responses upon cooling are rare.

Purpose of the Study:

• Investigate the origin of a low-temperature thermosalient effect in a novel tetrafluoro(aryl)sulfanylated bicyclopentane.
• Determine the driving mechanism behind the crystal's jumping and disintegration upon cooling below 193 K.

Main Methods:

• Nuclear Magnetic Resonance (NMR)
• Single-crystal X-ray Diffraction (SC-XRD)
• Powder X-ray Diffraction (PXRD)
• Microscopy
• Differential Scanning Calorimetry (DSC)
• Raman Spectroscopy
• Brillouin Spectroscopy

Main Results:

• The thermosalient effect was observed below ~193 K.
• Experiments indicated the phenomenon is not solely due to a chemical transformation or bulk phase transition.
• Evidence suggests built-up strain release, possibly linked to crystal microstructure or an impurity phase, causes self-destruction.

Conclusions:

• The low-temperature thermosalient effect in the studied organic crystal is not driven by a bulk phase transition.
• Crystal microstructure or impurity phases can significantly influence the mechanical behavior of bulk crystalline materials.
• Microstructure plays a crucial role in mechanically responsive crystals and warrants further investigation.