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Susanna Piccirillo

Publications and source records attributed to Susanna Piccirillo.

5 recordsLinked to original sources
PubMed2006

Photo-ionization spectroscopy and mass spectrometry of some molecular and supramolecular asymmetric systems in the isolated state.

Asymmetric molecular and supramolecular systems are characterized by: i. the circular dicroism in the angular distribution of valence photoelectrons emitted from randomly oriented chiral molecules by their interaction with circularly polarized VUV light; ii. the different stability and reactivity of diastereomeric aggregates. Both these aspects may have some relationship with the "chiral enrichment mechanism" of chirogenesis, based on the preferential destruction of one enantiomer of a racemate by interaction with a chiral agent, whether a massive species or a circularly polarized photon. The most recent spectroscopic and mass spectrometric studies on this topic are reported in the present mini-review.

Ions↗
PubMed2005

Angle-resolved photoelectron spectroscopy of randomly oriented 3-hydroxytetrahydrofuran enantiomers.

Circular dichroism in the angular distribution of valence photoelectrons emitted from randomly oriented 3-hydroxytetrahydrofuran enantiomers (ThS and ThR) has been observed in gas-phase experiments using circularly polarized vacuum ultraviolet (VUV) light. The measured dichroism for both ThS and ThR, acquired at the single magic angle theta=234.73 degrees and at photon energies of 22, 19, 16, and 14 eV, points to an asymmetric forward-backward scattering of the photoelectrons from their highest occupied molecular orbitals (HOMO) HOMO-1 and HOMO-2, of up to 5%, depending on the photon energy. The asymmetry reverses on exchange of either the helicity of the radiation or the configuration of Th. The photoionization dichroic D parameters of ThS and ThR have been measured and their values discussed in the light of LCAO B-spline density functional theory (DFT) predictions. While an acceptable agreement is found between the dichroic parameter measured and calculated at the highest photon energy for the HOMO and HOMO-2 orbitals of Th, a significant discrepancy is observed for the HOMO-1 state which is attributed to the floppiness of Th, in particular to the comparatively large sensitivity of the size and shape of its HOMO-1 on nuclear vibrational motion.

Circular Dichroism↗
PubMed2005

Excitation, ionization, and fragmentation of chiral molecules in asymmetric microenvironments: a mass-resolved R2PI spectroscopic study.

One- and two-color, mass selected R2PI spectra of the S(1) <-- S(0) transitions in the bare (R)-(+)-1-phenyl-1-propanol and its complexes with bidentate solvent molecules, like the (R)-(-)- and (S)-(+)-3-hydroxytetrahydrofuran enantiomers, have been recorded after a supersonic molecular beam expansion. The one-color R2PI excitation spectra of the diastereomeric complexes are characterized by three main peaks, one red-shifted and the other two blue-shifted relative to the band origin of the most stable anti conformer of the bare chromophore. The opposite direction of these spectral shifts is ascribed to the occurrence of three different hydrogen bonded isomeric structures for each individual complex, while their different magnitude depends on the configuration of the bidentate solvent molecule as well as its specific hydrogen bond interaction center, whether the ethereal oxygen atom or the hydroxyl group. The same factors play a major role in determining the magnitude of the phenomenological activation barriers for the loss of an ethyl radical from the ionized diastereomeric complexes.

Journal Article↗
PubMedDate not supplied

Chiral recognition by mass-resolved laser spectroscopy.

Chiral recognition is a fundamental phenomenon in life sciences, based on the enantioselective complexation of a chiral molecule with a chiral selector. The diastereomeric aggregates, formed by complexation, are held together by a different combination of intermolecular forces and are therefore endowed with different stability and reactivity. Determination of these forces, which are normally affected in the condensed phase by solvent and supramolecular interactions, requires the generation of the diastereomeric complexes in the isolated state and their spectroscopic investigation. This review deals with chiral recognition in the gas phase through the application of laser-resolved mass spectrometric techniques (R2PI-TOF and RET-MS). The measurement of the fragmentation thresholds of diastereomeric clusters by these techniques allows the determination of the nature of the intrinsic interactions, which control their formation and affect their stability and reactivity.

Energy Transfer↗