Unexpected Behaviour in Derivatives of Barluenga's Reagent

Aug 302018
 

Chemical Communications 2018, 54, 9849 – 9852 [doi:10.1039/C8CC05430D]

For the collidine analogues of Barluenga’s Reagent (IPy2BF4) reported, a flat cation is necessary for the generation of a modulated phase, in keeping with the “Ratchet Model” theory [Kim et al., Crystal Growth & Design, 2014, 14, 6294]. Attempts to study “diffuse modulation” in Br(Coll)2ClO4 have shown that these non-Bragg features disappear very rapidly on exposure to synchrotron radiation, an effect thought to be caused by the radiation damage disrupting the lattice vibrations that cause the modulation.

 

Radiation Damage

ECM31, Oviedo and ECA Crystallographic Computing School, Mieres

Aug 292018
 

The 31st European Crystallography Meeting was held in Oviedo, Spain from 22-26 August 2018.

During the meeting George Sackman presented a poster (MS10-P05) on recent neutron diffraction work with Richard Cooper and Alison Edwards: Disordered or not: A cautionary tale when inferring proton disorder solely from X-ray and computational data.

Richard Cooper gave a presentation (GI-MS47-O5) in the Saturday afternoon session How to… take your next steps in crystallography, based on experience of a career which despite including several areas of science and organisations rarely strayed outside the OX postcode.

On Sunday afternoon Amber Thompson presented (MS27-O5) Adventures in modulation: derivatives of Barluenga’s reagent, including work from Lewis Morgan, Yejin Kim, Emma McKinley, Jack Blandy, Claire Murray and Kirsten Christensen, in the session Quasicrystals: theory and
experiment.

Prior to the meeting, Richard Cooper was a tutor at the ECA Crystallographic Computing School in Mieres, organised by the ECA SIG 9 and gave a lecture on Programming Crystallographic Symmetry.

Structure of the Month – November 2012

Nov 012012
 

Presented by: Vanessa E. Fairbank & Dr. Amber L. Thompson
Research Leader: Dr. Andrew L. Goodwin
Published: Physical Review B

Cubic Cd(CN)2 shows the strongest known isotropic negative thermal expansion (NTE; volume contraction on heating).  Variable-temperature single-crystal X‑ray diffraction suggests there is temperature-dependent off-centering of Cd2+ ions that has the effect of increasing the cadmium coordination volume at low temperatures, providing an alternate mechanism for NTE in this material. These displacements are evident in the residual electron density and the highly-structured diffuse scattering in the experimental X-ray diffraction patterns.  Using Monte Carlo simulations, we have interpreted these patterns in terms of a basic set of “ice-rules” that establish a mapping between the dynamics of Cd(CN)2and proton ordering in cubic ice VII.

Structure of the Month – November 2012

Structure of the Month – November 2012

 

Dr. Kirsten E. Christensen

Oct 072011
 

Photo of Kirsten ChristensenKirsten’s research is focused on several areas that will establish a fundamental understanding of modulation in molecular materials e.g. their formation and properties. This knowledge can be put to immediate use in Crystal Engineering, and will also affect research in pharmaceuticals, developments in molecular modelling and crystal packing predictions.

See Kirsten’s Departmental web-page for further information.