Structural Evolution of Trimethylacetonitrile under Pressure: A Combined X-ray Diffraction and Computational Study

Rebecca M. Blake, Nicholas D. Stapleton, Isabelle M. Jones, James R. Brookes, Gemma F. Turner, Stephanie A. Bird, Alan Riboldi-Tunnicliffe, Rachel M. Williamson, Rosemary Young, Helen E. Maynard-Casely, Dino Spagnoli, Stephen A. Moggach

Research output: Contribution to journalArticlepeer-review

Abstract

Three high-pressure phases of trimethylacetonitrile, a compound of potential interest in the context of Titan’s atmospheric chemistry, have been investigated using single-crystal X-ray diffraction, periodic density functional theory, and CrystalExplorer intermolecular energy calculations. A disordered tetragonal P4/nmm phase is formed between 0.07 and 0.29 GPa (denoted hp-I). Compression to 0.43 GPa forms an ordered orthorhombic Pnma phase (hp-II), which transforms to a monoclinic P21/m phase (hp-III) at 1.52 GPa. The hp-III phase persists to at least 3.34 GPa. Phase transitions are driven by densification of the crystal and facilitated by rearrangement of the supramolecular hydrogen-bonding network, with 180° reorientation of half the molecules. Compression of each phase is associated with slight shortening of the intermolecular hydrogen bonds, with gradual destabilization of the cohesive energy to 3.34 GPa.

Original languageEnglish
Pages (from-to)1693-1699
Number of pages7
JournalACS Earth and Space Chemistry
Volume8
Issue number9
Early online date20 Aug 2024
DOIs
Publication statusPublished - 19 Sept 2024

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