Selected Publications | Crystal Chemistry

Error message

Notice: unserialize(): Error at offset 2 of 23 bytes in variable_initialize() (line 1252 of C:\Apache24\htdocs\Drupal-Sites\crystal\includes\bootstrap.inc).

ζ-Glycine: insight into the mechanism of a polymorphic phase transition. IUCrJ 2017, 4 (5), 569.

Bull, C. L.; Flowitt-Hill, G.; de Gironcoli, S.; Kucukbenli, E.; Parsons, S.; Pham, C. H.; Playford, H. Y.; Tucker, M. G.

Glycine is the simplest and most polymorphic amino acid, with five phases having been structurally characterized at atmospheric or high pressure. A sixth form, the elusive ζ phase, was discovered over a decade ago as a short-lived intermediate which formed as the high-pressure ∊ phase transformed to the γ form on decompression. However, its structure has remained unsolved. We now report the structure of the ζ phase, which was trapped at 100 K enabling neutron powder diffraction data to be obtained. The structure was solved using the results of a crystal structure prediction procedure based on fully ab initio energy calculations combined with a genetic algorithm for searching phase space. We show that the fate of ζ-glycine depends on its thermal history: although at room temperature it transforms back to the γ phase, warming the sample from 100 K to room temperature yielded β-glycine, the least stable of the known ambient-pressure polymorphs.

DOI: 10.1107/s205225251701096x
Reversible Pressure-Controlled Depolymerization of a Copper(II)-Containing Coordination Polymer. Chemistry - A European Journal 2017, 23 (51), 12480.

Clegg, J. K.; Brock, A. J.; Jolliffe, K. A.; Lindoy, L. F.; Parsons, S.; Tasker, P. A.; White, F. J.

A unique pressure‐induced Cu−N bond breaking/bond forming reaction is reported. The variation of pressure on a single crystal of a one‐dimensional copper‐ (II)‐containing coordination polymer (Cu₂L₂(1‐methylpiperazine)₂]_n, where H₂L is 1,1′‐(1,3‐phenylene)‐bis(4,4‐dimethylpentane‐1,3‐dione)), was monitored using single crystal X‐ray diffraction with the aid of a diamond anvil cell. At a very low elevated pressure (≈0.05 GPa) a remarkable reversible phase change was observed. The phase change results in the depolymerization of the material through the cleavage and formation of axial Cu−N bonds as well as “ring flips” of individual axially coordinated 1‐methylpiperazine ligands. Overall, the pressure‐induced phase change is associated with a surprising (and non‐intuitive) shift in structure‐from a 1‐dimensional coordination polymer to a discrete dinuclear complex.

DOI: 10.1002/chem.201703115
Pressure induced enhancement of the magnetic ordering temperature in rhenium(IV) monomers. Nature Communications 2016, 7, 13870.

Woodall, C. H.; Craig, G. A.; Prescimone, A.; Misek, M.; Cano, J.; Faus, J.; Probert, M. R.; Parsons, S.; Moggach, S.; Martinez-Lillo, J.et al.

Materials that demonstrate long-range magnetic order are synonymous with information storage and the electronics industry, with the phenomenon commonly associated with metals, metal alloys or metal oxides and sulfides. A lesser known family of magnetically ordered complexes are the monometallic compounds of highly anisotropic d-block transition metals; the ‘transformation’ from isolated zero-dimensional molecule to ordered, spin-canted, three-dimensional lattice being the result of through-space interactions arising from the combination of large magnetic anisotropy and spin-delocalization from metal to ligand which induces important intermolecular contacts. Here we report the effect of pressure on two such mononuclear rhenium(IV) compounds that exhibit long-range magnetic order under ambient conditions via a spin canting mechanism, with T_c controlled by the strength of the intermolecular interactions. As these are determined by intermolecular distance, ‘squeezing’ the molecules closer together generates remarkable enhancements in ordering temperatures, with a linear dependence of T_c with pressure.

DOI: 10.1038/ncomms13870