title: Conformation-specific circular dichroism spectroscopy of cold, isolated chiral molecules.
abstract: 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.
authors.affiliation: Department of Chemistry, Chungbuk National University, Cheongju, Chungbuk 361-763 (Korea).
authors.forename: Aram
authors.initials: A
authors.lastname: Hong
authors.forename: Chang Min
authors.initials: CM
authors.lastname: Choi
authors.forename: Han Jun
authors.initials: HJ
authors.lastname: Eun
authors.forename: Changseop
authors.initials: C
authors.lastname: Jeong
authors.forename: Jiyoung
authors.initials: J
authors.lastname: Heo
authors.forename: Nam Joon
authors.initials: NJ
authors.lastname: Kim
mesh_terms: D002942:Circular Dichroism / Q000379:methods*; D008958:Models, Molecular; D008968:Molecular Conformation; D013057:Spectrum Analysis / Q000379:methods*; D013237:Stereoisomerism
keywords: chirality; circular dichroism; gas phase; laser spectroscopy; supersonic jet