Not so Weird and Wonderful?
September 13, 2015
One of the benefits of my role at the CCDC is the chance to look at some of the latest scientific research taking place, as I review structures before they are added to the Cambridge Structural Database (CSD). Occasionally I come across a structure that looks quite unusual at first glance, so much so that it’s hard to resist taking a closer look.
Graph showing a subset of CSD entries listed with Z’ > 4The graph below shows another example of the kinds of checks we can now carry out. The graph shows the measurement of void space in a subset of the CSD containing around 100,000 organic crystal structures. Using the existing search capabilities of ConQuest and the new features of the API makes it simple to choose specific subsets of structures for investigation. Void space calculations are not part of the data we receive from depositors, but by using the API we can harness the tools in Mercury to run these checks for us over this large dataset.
Results of the void space analysis of around 100,000 organic CSD entriesYou can see that the vast majority of this subset of organic structures contain, as you would expect, no solvent-accessible void space. Around 20% of structures contain a small degree of void space, perhaps indicative of non-modelled hydrogen atoms or some disorder in the structure. The graph does have a rather dramatic tail, and this refers to around 200 of the almost 100,000 structures that really do contain significant voids. We can review each of these CSD entries in turn and ensure the comments and remarks we add to CSD entries help make users aware of the issues with these structures. With the new tools we have available it’s much quicker and easier for us to review all aspects of the entries in the CSD. Of course we’re keen to respond to suggestions from our users too; we’d be interested to know how you would like to see the CSD enhanced and improved in the future. These latest API-driven improvements are good news for us, and good news for you too, as it means when you search the CSD you can be confident in the fact that you are receiveing accurate and consistent results from all 50 years of crystal structures. I think that’s a pretty good birthday present for everyone! Seth Wiggin Senior Scientific Editor
CSD System (45)