Local structure in the disordered solid solution of cis- and trans-perinones.

Area of Science:

• Crystallography
• Materials Science
• Organic Chemistry

Background:

• Perinone, a polycyclic aromatic compound, exists as cis- and trans-isomers.
• These isomers form a solid solution known as Vat Red 14.
• The solid solution is isotypic to cis-perinone (Pigment Red 194) and trans-perinone (Pigment Orange 34).

Purpose of the Study:

• To determine the crystal structure of the cis- and trans-perinone solid solution.
• To investigate the combined positional and orientational disorder within the crystal structure.
• To computationally model and validate the observed crystal structure and disorder.

Main Methods:

• Single-crystal X-ray analysis was employed to determine the crystal structure.
• Extensive lattice-energy minimizations using force-field and DFT-D methods were performed.
• Calculations included local structures, preferred arrangements, ordering lengths, and neighbor probabilities.

Main Results:

• The crystal structure of the solid solution exhibits combined positional and orientational disorder.
• Cis-perinone shows twofold orientational disorder, while trans-perinone is ordered.
• Computational models accurately reproduced experimental findings, including atomic positions, site occupancies, and displacement parameters.

Conclusions:

• The study successfully elucidated the complex disordered crystal structure of the perinone solid solution.
• Computational methods provide a powerful tool for understanding and predicting crystal structures with disorder.
• The findings enhance the understanding of pigment behavior and molecular packing in solid solutions.