Non-covalent interactions in solid p-C₆F₄Cl₂ and C₆F₅Cl

Area of Science:

• Solid-state chemistry
• Crystallography
• Materials science

Background:

• Organofluorine aromatic compounds are crucial in various chemical applications.
• Understanding their solid-state properties is key to designing new materials.
• Halogen substitution significantly influences molecular interactions and phase behavior.

Purpose of the Study:

• To investigate the crystal structure and solid-state phase transitions of para-dichlorotetrafluorobenzene and chloropentafluorobenzene.
• To analyze the role of non-covalent interactions in their phase behavior.
• To compare the solid-state structures of related halogenated hexafluorobenzenes.

Main Methods:

• Differential scanning calorimetry (DSC) for thermal analysis.
• Variable-temperature powder X-ray diffraction (VT-PXRD) for structural studies.
• Single-crystal X-ray diffraction (SXD) for detailed structural determination.

Main Results:

• Para-dichlorotetrafluorobenzene displayed no solid-state phase transitions.
• Chloropentafluorobenzene exhibited three distinct solid-state phases.
• A reversible solid-solid transition in chloropentafluorobenzene was linked to molecular dipole ordering.

Conclusions:

• Chloropentafluorobenzene's phase transitions are driven by changes in molecular arrangement and dipole ordering.
• Phase II of chloropentafluorobenzene is isomorphous with para-dichlorotetrafluorobenzene.
• The study provides insights into structure-property relationships in organofluorine compounds.