title: Structural Collapse of the Hydroquinone-Formic Acid Clathrate: A Pressure-Medium-Dependent Phase Transition.
abstract: The energy landscape governing a new pressure-induced phase transition in the hydroquinone-formic acid clathrate is reported in which the host structure collapses, opening up the cavity channels within which the guest molecules migrate and order. The reversible isosymmetric phase transition causes significant changes in the morphology and the birefringence of the crystal. The subtle intermolecular interaction energies in the clathrate are quantified at varying pressures using novel model energies and energy frameworks. These calculations show that the high-pressure phase forms a more stable host network at the expense of less-stable host-guest interactions. The phase transition can be kinetically hindered using a nonhydrostatic pressure-transmitting medium, enabling the comparison of intermolecular energies in two polymorphic structures in the same pressure range. Overall this study illustrates a need for accurate intermolecular energies when analyzing self-assembly structures and supramolecular aggregates.
authors.affiliation: Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, 8000, Aarhus C, Denmark.
authors.forename: Espen
authors.initials: E
authors.lastname: Eikeland
authors.affiliation: Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, 8000, Aarhus C, Denmark.
authors.forename: Maja K
authors.initials: MK
authors.lastname: Thomsen
authors.affiliation: Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, 8000, Aarhus C, Denmark.
authors.forename: Solveig R
authors.initials: SR
authors.lastname: Madsen
authors.affiliation: Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, 8000, Aarhus C, Denmark.
authors.forename: Jacob
authors.initials: J
authors.lastname: Overgaard
authors.affiliation: School of Chemistry and Biochemistry, M310, University of Western Australia, 35 Stirling Hwy, Crawley, 6009, Australia.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Spackman
authors.affiliation: Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, 8000, Aarhus C, Denmark. bo@chem.au.dk.
authors.forename: Bo B
authors.initials: BB
authors.lastname: Iversen
keywords: crystal engineering; high-pressure crystallography; host-guest interactions; hydroquinone