J. Appl. Cryst. (2010), 43, 1100-1107. Â Â [ doi:10.1107/S0021889810025598 ]
Because they scatter X-rays weakly, H atoms are often abused or neglected during structure refinement. The reasons why the H atoms should be included in the refinement and some of the consequences of mistreatment are discussed along with selected real examples demonstrating some of the … Read the rest
Cryst. Rev. (2010), 16(2), 133-144. Â Â [ doi:10.1080/08893110903483238 ]
Recent developments in crystallographic error analysis are described. This report provides an introduction to more-formal work, originally published in Ref. (Haestier, J., J. Appl. Cryst. 2009, 42, 798). Prior to the main discussion, a brief overview of the normal distribution and error-propagation is … Read the rest
Acta Cryst. (2009), C65, o635-o638. Â Â [ doi:10.1107/S0108270109046952 ]
The unusual methylene aziridine 6-tert-butyl-3-oxa-2-thia-1-azabicyclo[5.1.0]oct-6-ene 2,2-dioxide, C9H15NO3S, was found to crystallize with two molecules in the asymmetric unit. The structure was solved in both the approximately orthogonal and the oblique settings of space group No. 14, viz. … Read the rest
Inorg. Chim. Acta (2010), 363(6), 1140-1149.   [ doi:10.1016/j.ica.2009.10.020 ]
Four 2-acetylpyridine 4N-alkyl thiosemicarbazones, and their Ga(III) and In(III) complexes have been prepared and characterised by fluorescence, UV–Vis, IR, 1H and 13C NMR spectroscopy, mass spectrometry and X-ray crystallographic analysis. Comparison of the crystal structures gave an insight into the nature of … Read the rest
Acta Cryst. (2009), E65, o2904-o2905. Â Â [ doi:10.1107/S1600536809043827 ]
X-ray crystallographic analysis of the title hydrobromide salt, C10H20N+Br-, of (1R,2S,3R,5R,8aR)-3-hydroxymethyl-5- methyloctahydroindolizine-1,2-diol defines the absolute and relative stereochemistry at the five chiral centres in steviamine, a new class of polyhydroxylated indolizidine alkaloid isolated from Stevia rebaudiana (Asteraceae) leaves.
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… Read the restJ. Appl. Cryst. (2009), 42, 798-809. Â Â [ 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
Tet. Asym. (2009), 20, 712-717. Â Â [ 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
Acta Cryst. (2008), C64, o649-o652. Â Â [ 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
Chirality (2008), 20(7), 863-870. Â Â [ 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
J. Appl. Cryst. (2008), 41, 491-522. Â Â [ 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