Aug 012009
 

J. Appl. Cryst. (2009), 42, 798-809.    [ doi:10.1107/S0021889809024376 ]

A new method is presented for handling errors on crystallographic data. In single-crystal diffraction experiments, two variance-covariance matrices are present, one for the cell parameters and the second for the refined parameters (atomic coordinates and anisotropic displacement parameters). These two matrices can be combined so … Read the rest

May 072009
 
X-ray Crystallography and Chirality: Understanding the Limitations (A. L. Thompson & D. J. Watkin)

Tet. Asym. (2009), 20, 712-717.    [ doi:10.1016/j.tetasy.2009.02.025 ]

Advances in hardware and software have made X-ray crystallography even more attractive as the first-option method for structure analysis. For most organic materials containing up to 100 non-hydrogen atoms, getting from the initial visual examination of the sample to producing publication-ready tables and pictures should usually … Read the rest

Apr 212009
 

The 2009 British Crystallographic Association Spring Meeting was held at the University of Loughborough.  Contributions from Chem. Cryst. included:

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

James Haestier
Effects of Cell Errors on Derived Parameters
(YC Presentation)

James Haestier
Computation of
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Apr 012009
 
David Watkin gives the Kathleen Lonsdale Lecture

David Watkin gives the Lonsdale Lecture

Every two years, the Young Crystallographers Group of the British Crystallographic Association nominate a speaker to give the prestigious Kathleen Lonsdale Lecture. Traditionally, they invite well respected scientist who has a good rapport with students. This year the Lonsdale Lecturer was David Watkin who is well known within the … Read the rest

Dec 152008
 

Acta Cryst. (2008), C64, o649-o652.    [ doi:10.1107/S0108270108037086 ]

The absolute and relative configurations of 1-epialexine are established by X-ray crystallographic analysis, giving (1S,2R,3R,7S,7aS)-1,2,7-trihydroxy-3-(hydroxymethyl)pyrrolizidine. The compound crystallizes as the hemihydrate C8H15NO4·0.5H2O, with hydrogen bonds holding the … Read the rest

Jul 172008
 
Discrimination of Chiral Guests by Chiral Channels: Variable Temperature Studies by SXRD and Solid State C-13 NMR of the Deoxycholic Acid Complexes of Camphorquinone and endo-3-Bromocamphor (M. I. M. Tahir, N. H. Rees, S. J. Heyes, A. R. Cowley & K. Prout)

Chirality (2008), 20(7), 863-870.    [ doi:10.1002/chir.20561 ]

3 alpha,12 alpha-Dihydroxy-5 beta-cholan-24-oic acid (deoxycholic acid DCA) is able to discriminate between the R- and S-enantiomers of camphorquinone and endo-(+)-3-bromocamphor and select only the S-enantiomers from a racemic mixture. DCA forms novel well ordered 1:l adducts with (1S)-(+)-camphorquinone and (1S)-endo-(-)-3-bromocamphor, both of which have been characterized … Read the rest

May 152008
 

J. Appl. Cryst. (2008), 41, 491-522.    [ doi:10.1107/S0021889808007279 ]

Most modern small-molecule refinement programs are based on similar algorithms. Details of these methods are scattered through the literature, sometimes in books that are no longer in print and usually in mathematical detail that makes them unattractive to nonprogrammers. This paper aims to discuss these … Read the rest

Apr 082008
 

J. Appl. Cryst. (2008), 41, 531-536.    [ doi:10.1107/S0021889808005463 ]

Librational motion within a crystal structure distorts the measured bond distances and angles from their physical values. TLS analysis of a rigid molecule or a rigid part of a molecule allows the calculation of bond-length and angle corrections. Until now, no estimate of the error … Read the rest

Apr 012008
 

The Annual Meeting of the British Crystallography Association was held in York.  Contributions from Chem. Cryst. included:

Anna Collins, Richard I. Cooper, Andrew R. Cowley, David J. Watkin
2-(1-Hydroxy-2-methyl-propyl)-2,5-dihydro-furan-2-carboxylic acid diisopropylamide:  A study of a phase transition to a pseudosymmetrical Z′=2 structure (Poster)

James Haestier, Mustapha. Sadki, Amber L. Thompson and David J. Watkin
Cell Read the rest

Apr 092007
 

Acta. Cryst. (2007), 63, 303-308. [ doi:10.1107/S0108768106055212 ]

A new polymorph of 2,4-dihydroxybenzoic acid is reported. The structure was characterized by multiple-temperature X-ray diffraction and solid-state DFT computations. The material shows a geometric pattern of hydrogen bonding consistent with cooperativity between the intermolecular carboxylic acid dimer and intramolecular hydrogen bonds. The presence of proton … Read the rest