Solid-state supramolecular array through cooperative π-π interactions of 1-(2-methoxyphenyl)-o-carborane

Kiminori Ohta, Hiroto Yamazaki, Fabio Pichierri, Masatoshi Kawahata, Kentaro Yamaguchi, Yasuyuki Endo

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

Dicarba-closo-dodecaborane (carborane) has received much attention as a building block for supramolecular assemblies and bioactive compounds. Among the carborane isomers, 1,2-dicarba-closo-dodecaborane (o-carborane) has unique chemical properties, including the ability of the o-carborane C-H hydrogens to form H-bonds. We have designed and synthesized 1-(2-methoxyphenyl)-o-carborane 1a to study its ability to form an intramolecular H-bond between the o-carborane C-H hydrogen and various H-bond acceptors both in solution and in the solid state. Intramolecular H-bonding ability in solution was evaluated by means of 1H NMR spectroscopic measurements of the C-H hydrogen signal. The signal of the C-H hydrogen of 1a showed a remarkable downfield shift in CDCl3 and various other solvents, i.e., the shift was almost solvent-independent. We suggest that 1a forms an intramolecular H-bond in these solvents. Crystal structure analysis of 1a showed a C-H⋯O distance of 2.05 Å and a nearly planar torsion angle C(2)-C(1)-C(7)-C(8) of 6.5°, indicating intramolecular C-H⋯O H-bond formation in the solid state. The crystal packing of 1a indicates that a supramolecular array is stabilized by cooperative π-π stacking interactions among the methoxyphenyl groups and by hydrophobic interactions of the o-carborane cages. DFT calculations indicate that the strength of the intramolecular H-bond of 1a is about 3.53 kcal/mol. These observations indicate the potential value of o-carborane in supramolecular chemistry and materials chemistry; it should be possible to design novel materials by utilizing both the H-bonding ability of the o-carborane C-H hydrogen and the high hydrophobicity of the o-carborane cage.

Original languageEnglish
Pages (from-to)12160-12165
Number of pages6
JournalTetrahedron
Volume63
Issue number49
DOIs
Publication statusPublished - 2007 Dec 3

Keywords

  • C-H⋯O interaction
  • DFT calculations
  • H NMR study
  • Hydrogen bond
  • Supramolecular array
  • o-Carborane

ASJC Scopus subject areas

  • Biochemistry
  • Drug Discovery
  • Organic Chemistry

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