Investigation of quinoline derivatives by photoemission spectroscopy and theoretical calculations

The electronic structure of gaseous quinoline and three substituted quinolines, 4-chloroquinoline, 4-aminoquinoline and 4-amino-7-chloroquinoline, have been investigated by valence and core level photoemission spectroscopy. The complete assignment of the spectral features in the valence region has been performed with the aid of the outer valence Green's function (OVGF) method, providing an acceptable description of the measured spectra. The C 1s, N 1s, and Cl 2p core level spectra of quinoline and its derivatives were also measured and compared with theoretical calculations based on density functional theory, which predicted ionization potentials in good agreement with the experimental data. For the case of the Cl 2p ionization the spin-orbit coupling was also included in the calculation. This work provides a full assignment of the relative binding energies of the core level features, and an analysis of the electronic structure of substituted quinolines in comparison with the parent molecule.