The Z' = 12 superstructure of Λ-cobalt(III) sepulchrate trinitrate governed by C-H...O hydrogen bonds

Somnath Dey, Andreas Schönleber, Swastik Mondal, Siriyara Jagannatha Prathapa, Sander van Smaalen, Finn Krebs Larsen

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

9 Citations (Scopus)
172 Downloads (Pure)

Abstract

Λ-Cobalt(III) sepulchrate trinitrate crystallizes in P6 322 with Z = 2 (Z' = 1/6) at room temperature. Slabs perpendicular to the hexagonal axis comprise molecules Co(sepulchrate) alternating with nitrate groups A and B. Coordinated by six sepulchrate molecules, highly disordered nitrate groups C are accommodated between the slabs. Here we report the fully ordered, low-temperature crystal structure of Co(sep)(NO 3) 3. It is found to be a high-Z' structure with Z' = 12 of the 12-fold superstructure with monoclinic symmetry P2 1 (c unique). Correlations between structural parameters are effectively removed by refinements within the superspace approach. Superstructure formation is governed by a densification of the packing in conjunction with ordering of nitrate group C, the latter assuming different orientations for each of the Z' = 12 independent copies in the superstructure. The Co(sep) moiety exhibits small structural variations over its 12 independent copies, while orientations of nitrate groups A and B vary less than the orientations of the nitrate group C do. Molecular packing in the superstructure is found to be determined by short C-H...H-C contacts, with H...H distances of 2.2-2.3 Å, and by short C-H...O contacts, with H...O distances down to 2.2 Å. These contacts presumably represent weak C-H...O hydrogen bonds, but in any case they prevent further densification of the structure and strengthening of weak N-H...O hydrogen bonds with observed H...O distances of 2.4-2.6 Å.The 12-fold superstructure at T = 95 K is described as a commensurately modulated structure in superspace. Crystal packing in the Z' = 12 superstructure is determined by short C-H...O hydrogen bonds.

Original languageEnglish
JournalActa Crystallographica Section B: Structural Science, Crystal Engineering and Materials
Volume72
Issue3
Pages (from-to)372-380
Number of pages9
ISSN0108-7681
DOIs
Publication statusPublished - 1 Jun 2016

Keywords

  • Z' superstructure
  • commensurately modulated structure
  • hydrogen bonding
  • superspace

Fingerprint

Dive into the research topics of 'The Z' = 12 superstructure of Λ-cobalt(III) sepulchrate trinitrate governed by C-H...O hydrogen bonds'. Together they form a unique fingerprint.

Cite this