Structural, Thermodynamic, and Spectroscopic Characterization of Diphosgene and Triphosgene

Area of Science:

• Solid-state chemistry
• Molecular spectroscopy
• Computational chemistry

Background:

• Phosgene (COCl2) is a crucial industrial chemical but its hazardous nature restricts laboratory applications.
• Diphosgene and triphosgene serve as safer alternatives, though their solid-state properties are not well-understood.

Purpose of the Study:

• To comprehensively investigate the solid-state structures and vibrational properties of diphosgene and triphosgene.
• To provide a complete solid-state vibrational characterization of these phosgene surrogates.

Main Methods:

• X-ray crystallography
• Differential scanning calorimetry
• Infrared (IR), Raman, and inelastic neutron scattering (INS) spectroscopy
• Density Functional Theory (DFT) calculations

Main Results:

• A new polymorph of diphosgene (β-diphosgene) was identified.
• Rare cold crystallization behavior was observed in diphosgene during differential scanning calorimetry.
• Solid-state DFT calculations successfully reproduced lattice parameters and elucidated the thermodynamic relationships between polymorphs.
• Comprehensive vibrational spectra (IR, Raman, INS) for diphosgene and triphosgene were obtained and assigned using periodic DFT calculations.

Conclusions:

• This study provides the first complete solid-state vibrational characterization of diphosgene and triphosgene.
• The findings enhance the understanding of these important phosgene surrogates, aiding their safer laboratory utilization.