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Valence band and C 1s core-level photoelectron spectra of S-(+)-2-amino-1-propanol (alaninol) and S-(+)-1-amino-2-propanol (isopropanolamine) have been studied by means of synchrotron radiation photoelectron spectroscopy in gas phase. The alaninol, the reduced derivative of the alanine, is a good test system of amino acid-like structures. The isopropanolamine, presenting the inversion of the two functional groups of the alaninol at the chiral carbon, offers the opportunity to study the effect of -OH and -NH(2) structural position on the photoelectron spectra. The influence of the conformational contribution on the electronic structure and the photoelectron spectra has been interpreted using density functional and ab initio theoretical calculations. Agreement has been achieved by taking into account the presence, in gas phase, of two conformers with different population ratios in both chiral systems. The C 1s core-level spectra of alaninol and isopropanolamine are reported and the peak positions of the three carbon atoms of the molecules are assigned.

The beta angular asymmetry and D dichroic asymmetry parameters of the methyl-oxirane highest occupied molecular orbital (HOMO) band have been experimentally investigated with vibrational resolution using synchrotron radiation. A theoretical calculation of the Franck-Condon factors between vibrational ground state and different ionic vibrational states, in the Born-Oppenheimer harmonic approximation, has been performed in order to gain information on the vibrational states mainly involved in the HOMO photoelectron band. The general good agreement between theoretical and experimental results allows a reliable assignment of the major features. The experimental determination of beta and D shows their dependence on the different final vibrational states. This paper reports, for the first time, experimental evidence of the dependence of the dichroic D parameter on the vibrational excitation of the ion.

We report the results of chemisorption in saturating conditions of D-alaninol on Cu(100) in term of the analysis of low-energy electron diffraction and scanning tunneling microscopy data. A large two-dimensional, single domain, ordered chiral structure of quadrangular tetrameric molecular units is formed. The four molecules interact differently with the surface in the two orthogonal directions.

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.

The dynamical behavior of circular dichroism for valence photoionization processes in pure enantiomers of randomly oriented methyl-oxirane molecules has been studied by circularly polarized synchrotron radiation. Experimental results of the dichroism coefficient obtained for valence photoionization processes as a function of photon energy have been compared with theoretical values predicted by state-of-the-art ab initio density-functional theory. The circular dichroism measured at low electron kinetic energies was as large as 11%. Trends in the experimental dynamical behavior of the dichroism coefficients D(i)(omega) have been observed. Agreement between experimental and theoretical results permits unambiguous identification of the enantiomer and of the individual orbitals.

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.

We have measured for the first time the X-ray natural circular dichroism (XNCD) of a chiral molecule in an isotropic medium. In this condition the only surviving term contributing to CD is the cross product between the electric dipole and the magnetic dipole transition moments. The non-zero value of the magnetic dipole transition moment in a 1s-to-valence electron transition is attributed to contribution of valence states to core molecular orbitals. These results open the way to a "local" chiral molecular analysis and to the study of stereochemically selected photochemical processes.