Richard Cooper

Aug 092013
 

iccossThe 21st International Conference on the Chemistry of the Organic Solid State was held from 5th-9th August 2013 at St Catherine’s College in Oxford. ICCOSS deals with various aspects of the crystalline state and reactivity of organic and hybrid materials from preparation to characterization. It includes the investigation of crystal structures and supramolecular architectures, crystal growth and design, inclusion compounds, topochemical reactions, nanostructures, heterogeneous interfaces.

Amber Thompson presented a talk entitled Modulated structures: a curiosity today, ubiquitous tomorrow? and Richard Cooper presented work carried out with Jerome Wicker: Will it Crystallize?

Jul 242013
 

hawaiiThe Annual Meeting of the American Crytsallographic Association was held from July 20-24 in Honolulu, Hawaii. The programme included a broad range of crystallographic topics on structure validation, materials for a sustainable future, structural enzymology, thin films, data mining, and neutron & synchrotron sources.

Karim Sutton represented Chem Cryst, and was awarded a Margaret C. Etter Student Lecturer Award for his contribution on the application of macromolecular phasing techniques to small molecule crystallography. Andrew Cairns from Oxford also attended and gave a talk on designing new materials with large negative linear compressibility, for which he was also awarded a Student Lecturer Award. Congratualtions to them both!

May 232013
 

botanicThe University of Oxford Botanic Garden has organised a series of guided science walks through the Botanic Garden this summer.

Richard Cooper will be leading the first walk on 30th May entitled “How Do we Know what Molecules Look Like?”  A rich variety of molecules occur naturally in plants and some have incredible properties: from bitter tastes to anti-cancer activity. This walk will take in plants in the Botanic Garden from which interesting molecules have been discovered and describe how we can use analytical techniques to understand their shape and functions.

These guided walks will take place at 6.30pm at the Botanic Garden and will last approximately an hour followed by a glass of wine or soft drink. Tickets are avaliable from the University web site.

May 152013
 

pascalPascal is a senior post-doctoral researcher working on refinement and analysis of diffraction from very short lived excited state chemical species. He obtained a PhD with Dr Mark Murrie at Glasgow University studying the effects of pressure on single molecular magnets, and has since held posts at Utrecht University and University of Nancy working on software development and time-resolved diffraction. Pascal maintains a personal blog on chemical and crystallographic software matters, and in his spare time enjoys hiking and genealogy.

Dec 202012
 

J. Sync. Rad (2013). 20, 200–204. [ doi:10.1107/S0909049512044007 ]

Overlapping absorption edges will occur when an element is present in multiple oxidation states within a material. DetOx is a program for partitioning overlapping X-ray absorption spectra into contributions from individual atomic species and computing the dependence of the anomalous scattering factors on X-ray energy. It is demonstrated how these results can be used in combination with X-ray diffraction data to determine the oxidation state of ions at specific sites in a mixed-valance material, GaCl2 .

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Sep 212012
 

J. Appl. Cryst. (2012). 45, 1057–1060. [ doi:10.1107/S0021889812035790 ]

The traditional Waser distance restraint, the rigid-bond restraint and atomic displacement parameter (ADP) similarity restraints have an equal influence on both atoms involved in the restraint. This may be inappropriate in cases where it can reasonably be expected that the precision of the determination of the positional parameters and ADPs is not equal, e.g. towards the extremities of a librating structure or where one atom is a significantly stronger scatterer than the other. In these cases, the traditional restraint feeds information from the poorly defined atom to the better defined atom, with the possibility that its characteristics become degraded. The modified restraint described here feeds information from the better defined atom to the more poorly defined atom with minimal feedback.

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Aug 022012
 

Congratulations to Karim Sutton, who has been awarded a Margaret C. Etter Student Lecturer Award at the recent American Crystallographic Association annual meeting in Boston.

He presented his recent research determining oxidation states in mixed-valent materials using tunable synchrotron radiation on Diamond beamline I19.

The awards were established to honour the memory of Professor Etter (1943-1992), who was a major contributor to the field of organic solid-state chemistry.

Apr 302012
 

J Appl. Cryst. (2012), 45, 417-429. [ doi:10.1107/S0021889812015191 ]

Leverages measure the influence that observations (intensity data and restraints) have on the fit obtained in crystal structure refinement. Further analysis enables the influence that observations have on specific parameters to be measured. The results of leverage analyses are discussed in the context of the amino acid alanine and an incomplete high-pressure data set of the complex bis(salicylaldoximato)copper(II). Leverage analysis can reveal situations where weak data are influential and allows an assessment of the influence of restraints. Analysis of the high-pressure refinement of the copper complex shows that the influence of the highest-leverage intensity observations increases when completeness is reduced, but low leverages stay low. The influence of restraints, notably those applying the Hirshfeld rigid-bond criterion, also increases dramatically. In alanine the precision of the Flack parameter is determined by medium-resolution data with moderate intensities. The results of a leverage analysis can be incorporated into a weighting scheme designed to optimize the precision of a selected parameter. This was applied to absolute structure refinement of light-atom crystal structures. The standard uncertainty of the Flack parameter could be reduced to around 0.1 even for a hydrocarbon.

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