A High-Pressure Single-Crystal to Single-Crystal Phase Transition in DL-Alaninium Semi-Oxalate Mono-Hydrate with Switching-Over Hydrogen Bonds
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials
, E-ISSN: 2052-5206
||High pressure, High-pressure phase, High-pressure phase transitions, Molecular materials, Molecular packings, Pressure-induced phase transition, Single crystal x-ray diffraction, Single-crystal diffraction
Institute of Solid State Chemistry and Mechanochemistry SB RAS, Kutateladze Str. 18, Novosibirsk 630128, Russian Federation
REC-008, Novosibirsk State University, Pirogova Str. 2, Novosibirsk 630090, Russian Federation
A single-crystal to single-crystal transition in dl-alaninium semi-oxalate monohydrate at a pressure between 1.5 and 2.4 GPa was studied by single-crystal X-ray diffraction and Raman spectroscopy. This is the first example of a single-crystal diffraction study of a high-pressure phase transition in a crystalline amino acid salt hydrate. Selected hydrogen bonds switch over and become bifurcated, whereas the others are compressed continuously. The transition is accompanied by pronounced discontinuities in the cell parameters and volume versus pressure, although no radical changes in the molecular packing are induced. Although, in contrast to dl-alanine, in the crystal structure of the salt there are short O - H⋯O hydrogen bonds, the structure of the salt is more compressible. At the same time, the structure of dl-alanine does not undergo pressure-induced phase transitions, whereas the structure of dl-alaninium semi-oxalate monohydrate does, and at a relatively low pressure. The anisotropy of lattice strain for the low-pressure phase differs from that on cooling at ambient pressure; interestingly, the anisotropy of the pressure-induced compression of the high-pressure phase is quite similar to the lattice strain of the low-pressure phase on cooling. © 2013 International Union of Crystallography Printed in Singapore - all rights reserved.