Conformation-Specific Circular Dichroism Spectroscopy of Cold, Isolated Chiral Molecules

The CD spectroscopy of a chiral compound in solution yields an average CD value derived from all of the conformations of a chiral molecule. By contrast, CD spectroscopy of cold chiral molecules in the gas phase distinguishes specific conformers of a chiral molecule, but the weak CD effect has limite...

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Bibliographic Details
Published in:Angewandte Chemie 2014-07, Vol.126 (30), p.7939-7942
Main Authors: Hong, Aram, Choi, Chang Min, Eun, Han Jun, Jeong, Changseop, Heo, Jiyoung, Kim, Nam Joon
Format: Article
Language:eng ; ger
Subjects:
Cadmium
Chemistry
Chiralität
Circularity
Dichroism
Firing
Gasphasenspektroskopie
Lasers
Laserspektroskopie
Quantum chemistry
Spectra
Spectroscopy
Spectrum analysis
Three dimensional
Ultraschallstrahlen
Zirkulardichroismus
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Summary:The CD spectroscopy of a chiral compound in solution yields an average CD value derived from all of the conformations of a chiral molecule. By contrast, CD spectroscopy of cold chiral molecules in the gas phase distinguishes specific conformers of a chiral molecule, but the weak CD effect has limited the practical application of this technique. Reported herein is the first resonant two‐photon ionization CD spectra of ephedrines in a supersonic jet using circularly polarized laser pulses, which were generated by synchronizing the oscillation of the photoelastic modulator with the laser firing. The spectra exhibited well‐resolved CD bands which were specific for the conformations and vibrational modes of each enantiomer. The CD signs and magnitudes of the jet‐cooled chiral molecules were very sensitive to their conformations and thus offered crucial information for determining the three‐dimensional structures of chiral species, as conducted in combination with quantum chemical calculations. Pulsmessung für Moleküle: Konformationsspezifische Cirkulardichroismusspektren von „kalten“ chiralen Molekülen in einem Ultraschallstrahl wurden mithilfe von circular polarisierten Laserpulsen erhalten, die durch synchronisiertes Abfeuern von Nanosekunden‐Laserpulsen mit der Schwingung des photoelastischen Modulators (PEM) erzeugt wurden. Das Ergebnis waren die ersten CD‐Spektren von Ephedrin mit resonanter Zweiphotonenionisation (R2PI).
ISSN:0044-8249
1521-3757
DOI:10.1002/ange.201403916