High-pressure polymorphism in salicylamide

Russell D L Johnstone, Alistair R. Lennie, Stewart F. Parker, Simon Parsons, Elna Pidcock, Patricia R. Richardson, John E. Warren, Peter A. Wood

    Research output: Contribution to journalArticlepeer-review

    Abstract

    We report the compression of a single crystal of salicylamide to 5.1 GPa. Between ambient pressure and 5.1 GPa the structure remains in a compressed form of the ambient-pressure phase, referred to as salicylamide-I. This phase has been investigated twice previously, but the coordinates appear to have been reported with respect to a non-standard space group origin, though no comment to this effect is made in either of the original reports. Short H⋯H contacts implied by the previously published coordinates are strongly destabilising according to PIXEL packing energy calculations, but are absent in the structure reported here. A new high-pressure polymorph, salicylamide-II, is formed if salicylamide is crystallised in situ from a saturated solution in a 4: 1 mixture of methanol and ethanol at 0.2 GPa. Crystal growth yielded three crystallites within the pressure cell, and combination of single-crystal X-ray diffraction intensity data from all three yielded a dataset which was >90% complete. PIXEL calculations indicate that salicylamide-II exhibits weaker H-bonding but stronger dispersion interactions than phase-I. Harmonic frequencies calculated using periodic DFT (and validated by inelastic neutron scattering data) indicate that phase-II is favoured at high pressure by its lower volume, its lower zero-point energy and higher entropy, and we estimate that at 0.2 GPa the free energy of phase-II is lower than that of phase-I by about 3 kJ mol-1. © 2010 The Royal Society of Chemistry.
    Original languageEnglish
    Pages (from-to)1065-1078
    Number of pages13
    JournalCrystEngComm
    Volume12
    Issue number4
    DOIs
    Publication statusPublished - 2010

    Fingerprint

    Dive into the research topics of 'High-pressure polymorphism in salicylamide'. Together they form a unique fingerprint.

    Cite this