Sep 012010

Presented by:  Dr. Nathan L. Kilah, Matthew D. Wise, Christopher J. Serpell, Nicholas G. White, Dr. Kirsten E. Christensen & Dr. Amber L. Thompson
Research Leader:  Prof. Paul D. Beer
Published:  Journal of the American Chemical Society

This structure represents the first use of solution phase halogen bonding to control and facilitate the anion templated assembly of an interlocked structure.  It  unambiguously confirms the interlocked nature of the system, and the vital role played by halogen bonded anion templation in its assembly.  The crystals were small and diffracted poorly, so data were collected on I19 at Diamond.  Unfortunately, they also suffered severe radiation damage, so data were collected using a single φ scan leading to a paucity of data.  Extensive disorder meant that the final refinement had a data:parameter ratio of 3.6:1 and required 4401 restraints.

Structure of the Month - September 2010

Structure of the Month – September 2010

Aug 012010

Presented by:  Dmitry Kondratiuk, Johannes Sprafke & Dr. Amber L. Thompson.
Research Leader:  Prof. Harry L. Anderson
Published: Journal of the American Chemical Society

Molecules with many strongly coupled π-electrons exhibit unique optical and electronic behaviour because of the way they interact with electric fields, particularly high-frequency optical fields.  The crystals of this material are highly prone to solvent loss as well as giving weak diffraction.  Data were collected on I19 at Diamond and the structure featured on at least four proposals at Diamond and the SRS (Daresbury) before it was finally determined.  Butadiyne linked porphyrin oligomers are generally expected to be rigid, but this structure shows that they are actually quite flexible and can be severely bent to form this highly strained ring.

Structure of the Month - August 2010

Structure of the Month – August 2010


Jul 292010

The ACA was held at the Sheraton Hotel in Chicago, IL.  Contributions from Chem. Cryst. include:

James Haestier, Amber L. Thompson, David J. Watkin, George C. Feast, Jeremy Robertson & Lee Page
Why is P21/n a Standard Non-Standard Space Group? (Poster)

Amber L. Thompson & David J. Watkin
Unpublishable” Data:  Does My R-factor Look Big in This? (Poster)

Amber L. Thompson
Absolute Structure Determination – Interpreting the Flack Parameter  (Presentation)

Apr 152010
Susan Huth presents Kirsten Christensen with the Durward Cruickshank Award

Susan Huth presents Kirsten Christensen with the Durward Cruickshank Award

The final dinner of the British Crystallographic Association Spring Meeting in Warwick was interrupted, as always, with the prize winning awards. Amber Thompson was awarded the International Union of Crystallography Prize (a copy of International Tables) for her explanation of the advantages of choosing non-standard space groups. Kirsten Christensen was awarded the Durward Cruickshank prize for a young crystallographer who had made an outstanding contribution to crystallography.



Other contributions include:

N. David Brown, James Haestier, Mustapha Sadki, Amber L. Thompson & David J. Watkin
matchbOx:  Automatic Structure Matching to Facilitate Crystallographic Refinement (YC Presentation)

Kirsten E. Christensen, Christopher J. Serpell, Nicholas E. Evans & Paul D. Beer
Pushing the Boundaries of Small Molecule Crystallography:  The Challenging Structure of a Macrocyclic Anion Sensor (Poster)

Richard I. Cooper, Amber L. Thompson & David J. Watkin
The Hydrogen Challenge:  Where are we Now? (Poster)

Christopher J. Serpell & Paul D. Beer
Refinement of Large Supramolecular Structures (Presentation)

David J. Watkin
Dealing with Difficult Data (Session Chair)


Aug 212009

The 25th European Crystallographic Meeting was held in the Harbiye Museum and Cultural Centre in the beautiful city of Istanbul.  It was a very eventful week, and contributions to the conference made by Chem. Cryst. include:

N. David Brown, James Haestier, Mustapha Sadki, Amber L. Thompson & David J. Watkin
A Further Improved Structure Matching Algorithm (Poster)

James Haestier
Handling of Cell Errors and their Effect on Derived Parameters (Poster)

Mustapha Sadki
New Modelling for Disordered Atoms in Free-form Based Hybrid Refinement and Visual Representation

Mustapha Sadki
The Application of Novel Modelling and Refinement Strategies to Crystallography

Amber L. Thompson & David J. Watkin
Absolute Configuration Determination – Is there More Information in the Data? (Poster)

David J. Watkin, Richard I. Cooper & Amber L. Thompson
CRYSTALS:  Refinement and Validation Tools (Poster)

David Watkin
The Future of Small Molecule Software (Session Chair)

Feb 162009

Dr. Kirsten E. ChristensenKirsten has been a visiting scientist in the lab since February 2009. She spends one to two days in Oxford doing synthesis of Open-framework germanates and taking a keen interest in difficult structures.  Kirsten’s primary research interest is in “Crystallography on the edge”, studying superstructures, diffuse scattering and modulated structures. As a natural part of being a post doc at Diamond she also takes an enthusiastic interest in collecting data on small and challenging crystals. Kirsten is also local contact when the Oxford BAG goes to Diamond for beamtime on I19.

Jul 011994

Acta Cryst.  (1994), A50, 411-437.    [ doi:10.1107/S0108767393012784 ]

Each year, many single-crystal structure analyses are reported that show evidence of over- or under-refinement. Often, the refinement strategies have been naive or over-complex and alternative strategies might have been more effective. The many descriptions of crystallographic and numerical techniques suitable for assisting with the control of difficult refinements are distributed widely in the literature and so are not always easily accessible. Without being a review of these procedures (which would require a substantial book), this article attempts to list readily available procedures, together with a brief outline of their backgrounds and examples of their applications to organic and organometallic compounds. The analysis of extended-lattice materials (usually inorganic materials) often raises problems in addition to those covered here. The particular aim of this article is to remind the reader that X-ray structure analysis is a modelling process and that, while standard models may be adequate for most analyses, more care and imagination must be applied to the treatment of difficult cases. Principles of methods are described without detailed mathematical derivations, although sufficient references to the literature are provided to permit careful study. Future requirements for refinement processes are outlined, including the use of new machine architectures, applications of sparse-matrix methods and the development of expert systems.

Electronic reprints

  • Oxford University Research Archive [direct pdf]

Publisher’s copy