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Conformation‐Specific Circular Dichroism Spectroscopy of Cold, Isolated Chiral Molecules
Author(s) -
Hong Aram,
Choi Chang Min,
Eun Han Jun,
Jeong Changseop,
Heo Jiyoung,
Kim Nam Joon
Publication year - 2014
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201403916
Subject(s) - circular dichroism , molecule , spectroscopy , chemistry , enantiomer , conformational isomerism , vibrational circular dichroism , chirality (physics) , crystallography , stereochemistry , photochemistry , organic chemistry , physics , nambu–jona lasinio model , chiral symmetry breaking , quantum mechanics , quark
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.