The structure of [18]-annulene: Computed Raman spectra, zero-point level and proton NMR chemical shifts

Bruce S Hudson, Damian G. Allis

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

[18]-Annulene has been of great interest from the structural point of view of its bond alternation. High-level calculations based on structures selected for agreement with NMR spectra lead to a bond-alternate C 2 form over a non-alternating planar D 6h structure deduced from diffraction, infrared (IR) and electronic spectral studies. Here it is shown that computed Raman spectra for the D 6h and C 2 forms are expected to be very different. However, two equivalent non-D 6h bond-alternate minima of D 3h or C 2 geometries are separated by only a small barrier along a motion that involves CC stretching and compression. It is shown here that the zero-point level is above the barrier for this species. In light of that fact, the NMR calculations are reconsidered with inclusion of zero-point level averaging.

Original languageEnglish (US)
Pages (from-to)212-215
Number of pages4
JournalJournal of Molecular Structure
Volume1023
DOIs
StatePublished - Sep 12 2012

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Chemical shift
Protons
Raman scattering
Nuclear magnetic resonance
Stretching
Compaction
Diffraction
Infrared radiation
Geometry

Keywords

  • Bond alternation
  • NMR chemical shifts
  • Raman spectrum
  • Theoretical calculations
  • Zero-point level

ASJC Scopus subject areas

  • Spectroscopy
  • Analytical Chemistry
  • Inorganic Chemistry
  • Organic Chemistry

Cite this

The structure of [18]-annulene : Computed Raman spectra, zero-point level and proton NMR chemical shifts. / Hudson, Bruce S; Allis, Damian G.

In: Journal of Molecular Structure, Vol. 1023, 12.09.2012, p. 212-215.

Research output: Contribution to journalArticle

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