Inversion symmetry and local vs. dispersive interactions in the nucleation of hydrogen bonded cyclic n-mer and tape of imidazolecarboxamidines

Sihui Long, Venkatraj Muthusamy, Peter G. Willis, Sean Parkin, Arthur Cammers

Research output: Contribution to journalArticlepeer-review

Abstract

Substitutional changes to imidazolecarboxamidine that preserved intermolecular hydrogen bonding in the solid state were used to study the relationship between packing and the hydrogen bond motif. Various motifs competed, but the most common imidazole-carboxamidine crystalline phase was a Ci symmetric dimer that established inversion centers by associating enantiomeric tautomers. Counter to intuition, the calculated gas-phase energies per molecule of the solid state atomic coordinates of the Ci dimer motifs were higher than those of the C1 dimer, trimer, tetramer and tape motifs, while the packing densities of Ci dimers were found to be higher. This result was interpreted as an enhanced ability of the C i dimers to pack. If other motifs competed, the hydrogen bonds and conformations should be lower in energy than the Ci dimer. The results detail the effect of packing on the conformation in these molecules. The results are interpreted as a rough measure of the energetic compromise between packing and the energies related to the coordinates involving one dihedral angle and hydrogen bonding. The results establish a connection between solution and solid phase conformation.

Original languageEnglish
Article number23
JournalBeilstein Journal of Organic Chemistry
Volume4
DOIs
StatePublished - Jul 7 2008

Keywords

  • Counterpoise
  • Crystal engineering
  • Packing motif
  • Solution conformation
  • Wallach's rule

ASJC Scopus subject areas

  • Organic Chemistry

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