Sep 262020
 
Howard Flack and the Flack Parameter (D.J. Watkin & R.I. Cooper)

Chemistry 2020, 2(4), 796-804; DOI: 10.3390/chemistry2040052

The Flack Parameter is now almost universally reported for all chiral materials characterized by X-ray crystallography. Its elegant simplicity was an inspired development by Howard Flack, and although the original algorithm for its computation has been strengthened by other workers, it remains an essential outcome for any … Read the rest

Mar 122020
 
Increasing the performance, trustworthiness and practical value of machine learning models: a case study predicting hydrogen bond network dimensionalities from molecular diagrams (A.P. Frade, P. McCabe & R.I. Cooper)

CrystEngComm, 2020, DOI: 10.1039/D0CE00111B

The performance of a model is dependent on the quality and information content of the data used to build it. By applying machine learning approaches to a standard chemical dataset, we developed a 4-class classification algorithm that is able to predict the hydrogen bond network dimensionality that a molecule would … Read the rest

Oct 172019
 
A hexagonal planar transition-metal complex (M. Garçon, C. Bakewell, G. A. Sackman, A. J. P. White, R. I. Cooper, A. J. Edwards & M. R. Crimmin)

Nature 574, 390–393 (2019). [ doi: 10.1038/s41586-019-1616-2 ]

We report the isolation and structural characterization of a simple coordination complex in which six ligands form bonds with a central transition metal in a hexagonal planar arrangement. The structure contains a central palladium atom surrounded by three hydride and three magnesium-based ligands. This finding has … Read the rest

Aug 302018
 
Unexpected Behaviour in Derivatives of Barluenga's Reagent (L. C. F. Morgan, Y. Kim, J. N. Blandy, C. A. Murray, K. E. Christensen & A. L. Thompson)

Chemical Communications 2018, 54, 9849 – 9852 [doi:10.1039/C8CC05430D]

For the collidine analogues of Barluenga’s Reagent (IPy2BF4) reported, a flat cation is necessary for the generation of a modulated phase, in keeping with the “Ratchet Model” theory [Kim et al., Crystal Growth & Design, 2014, Read the rest

Jun 242018
 
An enhanced set of displacement parameter restraints in CRYSTALS (P. Parois, J. Arnold and R.I. Cooper)

Journal of Applied Crystallography, 2018, 51, 1059-1068. [ doi: 10.1107/S1600576718007100 ]

The implementation and use of a set of new displacement parameter restraints is described. Anisotropic displacement parameters account for a large proportion of the parameters in a crystallographic refinement, but very few restraints for conveniently controlling their values have been implemented in … Read the rest

Nov 012017
 
Some Experimental Aspects of Absolute Configuration Determination using Single Crystal X-​Ray Diffraction (A. L. Thompson, S. F. Jenkinson & G. W. J. Fleet)

Tetrahedron Asymmetry 2017, 28(10), 1330-1336 [doi:10.1016/j.tetasy.2017.08.016]

Students of single crystal X-​ray diffraction are often give advice as to how best to collect their data when attempting absolute configuration determination.  These ‘rules’ often have more grounding in gut-​feeling than evidence.  Thus, in an effort to provide advice and evidence that today’s crystallographers can … Read the rest

Oct 232017
 
HUG and SQUEEZE: using CRYSTALS to incorporate resonant-scattering in the SQUEEZE structure factor contributions to determine absolute structure (R.I. Cooper, H.D. Flack and D.J. Watkin)Acta Crystallographica, 2017, C73, 845–853. [ doi:10.1107/S2053229617013304 ] Using an approximate correction to the X-ray scattering from disordered, resonantly scattering regions of crystal structures we have developed and tested a procedure (HUG) to recover the absolute structure using conventional Flack x refi nement or other post-re finement determination methods.
Jul 062017
 
Will They Co-crystallize? (J.G.P. Wicker,  L.M. Crowley,  O. Robshaw,  E.J. Little,  S. Stokes,  R.I. Cooper  and  S.E. Lawrence)

CrystEngComm, 2017, 19, 5336 – 5340 [ doi:10.1039/C7CE00587C ]

A data-driven approach to predicting co-crystal formation reduces the number of experiments required to successfully produce new co-crystals. A machine learning algorithm trained on an in-house set of co-crystallization experiments results in a 2.6-fold enrichment of successful co-crystal formation in a ranked list of … Read the rest

Jun 202017
 
A publicly available crystallisation data set and its application in machine learning (M. Pillong, C. Marx, P. Piechon, J.G.P. Wicker, R.I. Cooper and T. Wagner)

CrystEngComm, 2017,19, 3737-3745 [ doi:10.1039/C7CE00738H ]

We present here the crystallisation outcomes for 319 publicly available compounds in up to 18 different solvents spread over 5710 individual single solvent evaporation trials. The recorded data is part of a much larger, corresponding in-house database and includes both positive as well as negative crystallisation … Read the rest

Nov 242016
 
Beyond Rotatable Bond Counts: Capturing 3D Conformational Flexibility in a Single Descriptor (J.G.P. Wicker and R.I. Cooper)J. Chem. Inf. Model., 2016, 56 (12), 2347–2352 doi: 10.1021/acs.jcim.6b00565 A new molecular descriptor, nConf20, based on chemical connectivity, is presented which captures the accessible conformational space of a molecule. Currently the best available 2-dimensional descriptors for quantifying the flexibility of a particular molecule are the rotatable bond count (RBC) and the Kier flexibility index.