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Azulene revisited: solid-state structure, invariom modeling and lattice-energy minimization of a classical example of disorder.
Journal article

Azulene revisited: solid-state structure, invariom modeling and lattice-energy minimization of a classical example of disorder.

  • Dittrich B Heinrich-Heine Universität Düsseldorf, Institut für Anorganische Chemie und Strukturchemie, Material- und Strukturforschung, Gebäude: 26.42, Universitätsstrasse 1, 40225 Düsseldorf, Germany.
  • Fabbiani FPA GZG der Universität Göttingen, Abt. Kristallographie, Goldschmidtstrasse 1, Göttingen, D-37077, Germany.
  • Henn J Bayreuth, Germany.
  • Schmidt MU Institut für Anorganische u. Analytische Chemie, Johann Wolfgang Goethe-Universität, Max-von-Laue-Strasse 7, Frankfurt Am Main, D-60438, Germany.
  • Macchi P University of Bern, Department of Chemistry and Biochemistry, Freiestrasse 3, Bern, CH-3012, Switzerland.
  • Meindl K Centre for Genomic Regulation (CRG), 08003 Barcelona, Spain.
  • Spackman MA School of Molecular Sciences, University of Western Australia, Perth, WA 6009, Australia.
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  • 2018-10-10
Published in:
  • Acta crystallographica Section B, Structural science, crystal engineering and materials. - 2018
DFT calculations
azulene
disorder
invariom modeling
lattice-energy minimization
English The molecular and solid-state structure of azulene both raise fundamental questions. Therefore, the disordered crystal structure of azulene was re-refined with invariom non-spherical atomic scattering factors from new single-crystal X-ray diffraction data with a resolution of d = 0.45 Å. An unconstrained refinement results in a molecular geometry with Cs symmetry. Refinements constrained to fulfill C2v symmetry, as observed in the gas phase and in high-level ab initio calculations, lead to similar figures of merit and residual densities as unconstrained ones. Such models are consistent with the structures from microwave spectroscopy and electron diffraction, albeit they are not the same. It is shown that for the disorder present in azulene, the invariom model describes valence electron density as successfully as it does for non-disordered structures, although the disorder still leads to high correlations mainly between positional parameters. Lattice-energy minimizations on a variety of ordered model structures using dispersion-corrected DFT calculations reveal that the local deviations from the average structure are small. Despite the molecular dipole moment there is no significant molecular ordering in any spatial direction. A superposition of all ordered model structures leads to a calculated average structure, which explains not only the experimental determined atomic coordinates, but also the apparently unusual experimental anisotropic displacement parameters.
Language
  • English
Open access status
closed
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Persistent URL
https://sonar.ch/global/documents/169863
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