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 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

Dec 172006
 

J. Appl. Cryst. (2006), 39, 842-849.    [ doi:10.1107/S0021889806038489 ]

A sizeable proportion of structures with Z‘ = 2 are thought to exhibit pseudosymmetry, but establishing the extent of the deviation from true symmetry is problematic. By considering both the conformational similarity between the independent molecules and the way in which they are related … Read the rest

Oct 132004
 
Retrieval of Crystallographically-Derived Molecular Geometry Information (I. J. Bruno, J. C. Cole, M. Kessler, Jie Luo, W. D. S. Motherwell, L. H. Purkis, B. R. Smith, R. Taylor, R. I. Cooper, S. E. Harris & A. G. Orpen)

J. Chem. Inf. Comput. Sci. (2004), 44, 2133-2144. [ doi:10.1021/ci049780b ]

The crystallographically determined bond length, valence angle, and torsion angle information in the Cambridge Structural Database (CSD) has been made accessible by development of a new program (Mogul) for automated retrieval of molecular geometry data from the CSD. The program uses a system … Read the rest

Apr 222004
 
CRYSTALS Enhancements: Refinement of Atoms Continuously Disordered Along a Line, on a Ring or on the Surface of a Sphere (L. Schröder, D. J. Watkin, A. Cousson, R. I. Cooper and W. Paulus)

J. Appl. Cryst. (2004), 37, 545-550.    [ doi:10.1107/S0021889804009847 ]

The program CRYSTALS [Betteridge, Carruthers, Cooper, Prout & Watkin (2003). J. Appl. Cryst. 36, 1487] has been extended to include an option for the refinement of a continuous electron density distribution lying along a line, a ring or on the surface of a sphere. … Read the rest

Dec 012003
 

J. Appl. Cryst. (2003), 36, 1487.    [ doi:10.1107/S0021889803021800 ]

CRYSTALS version 12 contains a modern crystallographic user interface, and novel strategies that incorporate chemical knowledge and crystallographic guidance into the crystal structure analysis software.

Electronic reprints

Publisher’s copy

Read the rest
Apr 012002
 

J. Appl. Cryst. (2002), 35, 168-174.    [ doi:10.1107/S0021889802000249 ]

Although non-merohedrally twinned crystal structures can normally be solved without difficulty, problems usually arise during refinement. Careful analysis of poorly fitting data reveals that they belong predominantly to certain distinct zones in which |Fo|2 is systematically larger than |FcRead the rest