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Observation of a re-entrant phase transition in the molecular complex tris­(μ2-3,5-diiso­propyl-1,2,4-triazolato-κ2N1:N2)trigold(I) under high pressure


Reference:

Raithby, P., Woodall, C., Christensen, J., Skelton, J., Hatcher, L., Parlett, A., Walsh, A., Parker, S., Beavers, C. M., Teat, S., Intissar, M., Reber, C. and Allan, D. R., 2016. Observation of a re-entrant phase transition in the molecular complex tris­(μ2-3,5-diiso­propyl-1,2,4-triazolato-κ2N1:N2)trigold(I) under high pressure. IUCrJ, 3 (5), p. 367.

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    Official URL:

    http://dx.doi.org/10.1107/S2052252516013129

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    Abstract

    We report a molecular crystal that exhibits four successive phase transitions under hydro­static pressure, driven by aurophilic interactions, with the ground-state structure re-emerging at high pressure. The effect of pressure on two polytypes of tris(μ2-3,5-diiso­propyl-1,2,4-triazolato-κ2N1:N2)trigold(I) (denoted Form-I and Form-II) has been analysed using luminescence spectroscopy, single-crystal X-ray diffraction and first-principles computation. A unique phase behaviour was observed in Form-I, with a complex sequence of phase transitions between 1 and 3.5 GPa. The ambient C2/c mother cell transforms to a P21/n phase above 1 GPa, followed by a P21/a phase above 2 GPa and a large-volume C2/c supercell at 2.70 GPa, with the previously observed P21/n phase then reappearing at higher pressure. The observation of crystallographically identical low- and high-pressure P21/n phases makes this a rare example of a re-entrant phase transformation. The phase behaviour has been characterized using detailed crystallographic theory and modelling, and rationalized in terms of molecular structural distortions. The dramatic changes in conformation are correlated with shifts of the luminescence maxima, from a band maximum at 14040 cm−1 at 2.40 GPa, decreasing steeply to 13550 cm−1 at 3 GPa. A similar study of Form-II displays more conventional crystallographic behaviour, indicating that the complex behaviour observed in Form-I is likely to be a direct consequence of the differences in crystal packing between the two polytypes.

    Details

    Item Type Articles
    CreatorsRaithby, P., Woodall, C., Christensen, J., Skelton, J., Hatcher, L., Parlett, A., Walsh, A., Parker, S., Beavers, C. M., Teat, S., Intissar, M., Reber, C. and Allan, D. R.
    DOI10.1107/S2052252516013129
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    URLURL Type
    http://dx.doi.org/10.1107/S2052252516013129Free Full-text
    Uncontrolled Keywordsre-entrant phase transitions; high-pressure crystallography; gold(i); luminescence spectroscopy; dft calculations
    DepartmentsFaculty of Science > Chemistry
    Research CentresCentre for Sustainable Chemical Technologies
    EPSRC Centre for Doctoral Training in Statistical Mathematics (SAMBa)
    Publisher StatementIUCrJ_Woodall_August_2016.pdf: Published as an open access article in September 2016
    RefereedYes
    StatusPublished
    ID Code52311

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