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Homologous critical behaviour in the molecular frameworks Zn(CN)2 and Cd(imidazolate)2

DOI: 10.1021/ja401268g DOI Help

Authors: Ines Collings (University of Oxford) , Andrew Cairns (University of Oxford) , Amber Thompson (University of Oxford) , Julia Parker (Diamond Light Source) , Chiu Tang (Diamond Light Source) , Matthew G. Tucker (ISIS Facility) , Jadna Catafesta (Laboratoire Charles Coulomb, UMR−CNRS 5221, Université Montpellier 2) , Claire Levelut (Laboratoire Charles Coulomb, UMR−CNRS 5221, Université Montpellier 2) , Julien Haines (Institut Charles Gerhardt, Équipe C2M, UMR−CNRS 5253, Université Montpellier 2) , Vladimir Dmitriev (ESRF) , Philip Pattison (École Polytechnique) , Andrew Goodwin (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of The American Chemical Society , VOL 135 (20)

State: Published (Approved)
Published: April 2013

Abstract: Using a combination of single-crystal and powder X-ray diffraction measurements, we study temperature- and pressure-driven structural distortions in zinc(II) cyanide (Zn(CN)2) and cadmium(II) imidazolate (Cd(im)2), two molecular frameworks with the anticuprite topology. Under a hydrostatic pressure of 1.52 GPa, Zn(CN)2 undergoes a first-order displacive phase transition to an orthorhombic phase, with the corresponding atomic displacements characterized by correlated collective tilts of pairs of Zn-centered tetrahedra. This displacement pattern sheds light on the mechanism of negative thermal expansion in ambient-pressure Zn(CN)2. We find that the fundamental mechanical response exhibited by Zn(CN)2 is mirrored in the temperature-dependent behavior of Cd(im)2. Our results suggest that the thermodynamics of molecular frameworks may be governed by considerations of packing efficiency while also depending on dynamic instabilities of the underlying framework topology.

Subject Areas: Chemistry

Instruments: I11-High Resolution Powder Diffraction

Other Facilities: ESRF

Added On: 29/04/2013 08:27

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