What is it about?
Conventional X-ray structure refinements do usually not allow to distinguish between neighbouring 3d or 4d metal atoms when just relying on diffraction data (i.e. when other spectroscopic information is not available). The situation is better when aspherical scattering factors are used. It had been noticed quite a while ago in 2010 that in some cases the same structure ended up being published twice (in one of our examples even four times with Co2+, Ni2+, Cu2+ or Zn2+ as central atom), where only one structure can is correct --- which one remained elusive until out study. We studied 11 (pairs of) such structures where diffraction data were deposited by the original authors. Claudia identified in retrospect which one is correct, mainly relying on the deposited data, the results of aspherical atom refinements and quantum chemical computations.
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Why is it important?
Aspherical scattering factors improve the analytical capabilities of single-crystal X-ray diffraction. We can now better distinguish between neighbouring 3d or 4d metal atoms.
Perspectives
Coordination compounds can now be modelled with aspherical scattering factors. One aspect we found particularly interesting is that using invarioms for the ligand environment only is enough to make the distinction between elements that differ by only one electron. Diffraction data measured at room temperature and standard resolution already contain this information.
Dr Birger Dittrich
Heinrich-Heine-Universitat Dusseldorf
Read the Original
This page is a summary of: Using invariom modelling to distinguish correct and incorrect central atoms in `duplicate structures' with neighbouring 3delements, Acta Crystallographica Section B Structural Science Crystal Engineering and Materials, September 2017, International Union of Crystallography,
DOI: 10.1107/s2052520617010745.
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