Advanced microcrystallisation techniques for chemical serial X-ray crystallography Sam Lewis 2 , Lauren E. Hatcher 1 , Mark R. Warren 2 , Kenneth D.M. Harris 1 1 Cardiff University & Diamond Light Source, UK and 2 Cardiff University, UK Serial X-ray crystallography (SX) is a method by which structural determination can be achieved through the combination of still images recorded from tens of thousands of individual crystals. This technique is of particular interest to systems that are susceptible to X-ray induced damage at synchrotron or XFEL light sources. This is a problem which will only grow in prevalence with the rise of more intense light sources. Although SX methods have largely seen widespread use in characterizing biological samples, there is now a growing interest in the application of SX for chemical systems. The main bottleneck for SX is the production of microcrystal batches with suitable size and a narrow crystal size distribution. Previously, sample preparation for SX applications has utilized inefficient and wasteful post- processing steps to achieve the required batches, so the control of primary crystallization conditions to produce crystal batches in a single step is the ultimate goal. The system sodium nitroprusside (Na 2 [Fe(CN) 5 (NO)]·H 2 O, SNP) was selected due to its commercial availability and previous usage in photocrystallography studies, which would enable further SX method development opportunities. 1 Unfortunately, SNP tends towards distinctive needle- like habits, thus there is also a need to modify the habit to achieve more desirable block or plate habits. 2 A range of different solvent systems have been screened through a range of classical crystallization techniques for desirable habits. Although only a single polymorph is reported for SNP, novel desirable crystal habits have been observed in drop-casting techniques. These unstable habits undergo a period of growth followed by dissolution and transformation upon further solvent evaporation into the characteristic needle habit. These initial observations have been incorporated into a data-driven approach for obtaining desirable habits of SNP. It is hoped that insights from this work will contribute to a general workflow, which will simplify sample preparation for SX analysis and enable more widespread use of the technique. References 1. M. D. Carducci, M. R. Pressprich and P. Coppens, Journal of the American Chemical Society , 1997, 119 , 2669-2678. 2. P. Manoharan and W. C. Hamilton, Inorganic Chemistry , 1963, 2 , 1043-1047.
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