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Conformer-dependent vacuum ultraviolet photodynamics and chiral asymmetries in pure enantiomers of gas phase proline.

Rim HadidiDušan K BožanićHassan GanjitabarGustavo A GarcíaIvan PowisLaurent Nahon
Published in: Communications chemistry (2021)
Proline is a unique amino-acid, with a secondary amine fixed within a pyrrolidine ring providing specific structural properties to proline-rich biopolymers. Gas-phase proline possesses four main H-bond stabilized conformers differing by the ring puckering and carboxylic acid orientation. The latter defines two classes of conformation, whose large ionization energy difference allows a unique conformer-class tagging via electron spectroscopy. Photoelectron circular dichroism (PECD) is an intense chiroptical effect sensitive to molecular structures, hence theorized to be highly conformation-dependent. Here, we present experimental evidence of an intense and striking conformer-specific PECD, measured in the vacuum ultraviolet (VUV) photoionization of proline, as well as a conformer-dependent cation fragmentation behavior. This finding, combined with theoretical modeling, allows a refinement of the conformational landscape and energetic ordering, that proves inaccessible to current molecular electronic structure calculations. Additionally, astrochemical implications regarding a possible link of PECD to the origin of life's homochirality are considered in terms of plausible temperature constraints.
Keyphrases
  • molecular dynamics simulations
  • single molecule
  • amino acid
  • molecular dynamics
  • high resolution
  • ionic liquid
  • single cell
  • crystal structure
  • gas chromatography
  • solar cells