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Direct Spectroscopic Evidence for an n→π* Interaction.

Santosh K Singh1, Kamal K Mishra1, Neha Sharma1

  • 1Department of Chemistry, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pune-, 411008, Maharashtra, India.

Angewandte Chemie (International Ed. in English)
|February 17, 2016
PubMed
Summary

Researchers provide the first direct spectroscopic evidence for the n→π* interaction, a weak but crucial noncovalent interaction. This finding explains the cis-conformer preference in phenyl formate, validating its importance in chemistry and biology.

Keywords:
conformational analysiselectronic spectroscopygas-phase IR spectroscopysupersonic jet

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Area of Science:

  • Chemical Physics
  • Molecular Spectroscopy
  • Supramolecular Chemistry

Background:

  • The n→π* interaction is a weak noncovalent interaction.
  • Its presence in biomolecules and materials is significant but debated.
  • Its counterintuitive nature has led to extensive discussion.

Purpose of the Study:

  • To provide direct spectroscopic evidence for the n→π* interaction.
  • To investigate the role of n→π* interaction in the conformational preference of phenyl formate.
  • To resolve the controversy surrounding the existence and importance of n→π* interactions.

Main Methods:

  • Isolated gas-phase infrared (IR) spectroscopy.
  • Probing the carbonyl stretching frequency in phenyl formate.
  • Comparison of cis and trans conformers of phenyl formate.

Main Results:

  • Direct spectroscopic evidence for the n→π* interaction was obtained.
  • The n→π* interaction was identified as the cause for the conformational preference of the cis-conformer in phenyl formate.
  • The carbonyl stretching frequency was shown to be a sensitive probe for this interaction.

Conclusions:

  • The study provides the first direct experimental proof of the n→π* interaction.
  • The n→π* interaction stabilizes the cis-conformer of phenyl formate.
  • This finding is expected to encourage further research into this important noncovalent interaction.