Posts Tagged ‘Adobe’

Data nightmares: B40 and counting its π-electrons

Saturday, July 19th, 2014
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Whilst clusters of carbon atoms are well-known, my eye was caught by a recent article describing the detection of a cluster of boron atoms, B40 to be specific.[1] My interest was in how the σ and π-electrons were partitioned. In a C40, one can reliably predict that each carbon would contribute precisely one π-electron. But boron, being more electropositive, does not always play like that. Having one electron less per atom, one might imagine that a fullerene-like boron cluster would have no π-electrons. But the element has a propensity[2] to promote its σ-electrons into the π-manifold, leaving a σ-hole. So how many π-electrons does B40 have? These sorts of clusters are difficult to build using regular structure editors, and so coordinates are essential. The starting point for a set of coordinates with which to compute a wavefunction was the supporting information. Here is the relevant page: B401 The coordinates are certainly there (that is not always the case), but you have to know a few tricks to make them usable.

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References

  1. H. Zhai, Y. Zhao, W. Li, Q. Chen, H. Bai, H. Hu, Z.A. Piazza, W. Tian, H. Lu, Y. Wu, Y. Mu, G. Wei, Z. Liu, J. Li, S. Li, and L. Wang, "Observation of an all-boron fullerene", Nature Chemistry, 2014. http://dx.doi.org/10.1038/nchem.1999
  2. H.S. Rzepa, "The distortivity of π-electrons in conjugated boron rings", Physical Chemistry Chemical Physics, vol. 11, pp. 10042, 2009. http://dx.doi.org/10.1039/B911817A

Data-round-tripping: moving chemical data around.

Saturday, November 20th, 2010
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For those of us who were around in 1985, an important chemical IT innovation occurred. We could acquire a computer which could be used to draw chemical structures in one application, and via a mysterious and mostly invisible entity called the clipboard, paste it into a word processor (it was called a Macintosh). Perchance even print the result on a laserprinter. Most students of the present age have no idea what we used to do before this innovation! Perhaps not in 1985, but at some stage shortly thereafter, and in effect without most people noticing, the return journey also started working, the so-called round trip. It seemed natural that a chemical structure diagram subjected to this treatment could still be chemically edited, and that it could make the round trip repeatedly. Little did we realise how fragile this round trip might be. Years later, the computer and its clipboard, the chemistry software, and the word processor had all moved on many generations (it is important to flag that three different vendors were involved, all using proprietary formats to weave their magic). And (on a Mac at least) the round-tripping no longer worked. Upon its return to (Chemdraw in this instance), it had been rendered inert, un-editable, and devoid of semantic meaning unless a human intervened. By the way, this process of data-loss is easily demonstrated even on this blog. The chemical diagrams you see here are similarly devoid of data, being merely bit-mapped JPG images. Which is why, on many of these posts, I put in the caption Click for 3D, which gives you access to the chemical data proper (in CML or other formats). And I throw in a digital repository identifier for good measure should you want a full dataset.

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