High-pressure reversibility in a plastically flexible coordination polymer crystal

Area of Science:

• Materials Science
• Crystallography
• Solid-State Chemistry

Background:

• Mechanically flexible single crystals are crucial for advanced technologies.
• Understanding deformation mechanisms is essential for material application.
• Coordination polymers offer tunable properties for flexible applications.

Purpose of the Study:

• To investigate the mechanical response of a flexible coordination polymer, [Zn(μ-Cl)2(3,5-dichloropyridine)2]n (1), under quasi-hydrostatic compression and bending.
• To elucidate the atomic-level mechanisms governing the flexibility of this material.
• To compare the effects of compression and bending on crystal lattice integrity.

Main Methods:

• Single crystal X-ray diffraction
• Microfocus Raman spectroscopy
• Density Functional Theory (DFT) calculations
• Microfocus synchrotron X-ray diffraction

Main Results:

• Quasi-hydrostatic compression of crystal (1) up to 9 GPa is fully reversible.
• A structural phase transition occurs around 5 GPa during compression, driven by softening of low-frequency vibrations.
• Bending introduces significant mosaicity into the crystal lattice, unlike compression.
• The observed phase transition during compression is absent during three-point bending.

Conclusions:

• Flexible coordination polymers exhibit disparate mechanical responses to quasi-hydrostatic compression and bending.
• Deformation mechanisms differ significantly between bulk compression and bending in these materials.
• This discrepancy in mechanical response may be a general characteristic of plastically bendable crystalline materials.