Electronic spectra of gas-phase polycyclic aromatic nitrogen heterocycle cations: Isoquinoline and quinoline

Abstract

Electronic spectra of the gas-phase isoquinoline+-Ar and quinoline+-Ar complexes are recorded using photodissociation spectroscopy by monitoring the Ar loss channel. The D3← 0 and D4←D0 band origins for isoquinoline+-Ar are observed at 15245 ± 15 cm -1 and 21960 ± 15 cm-1, respectively, whereas for quinoline+-Ar they appear at 16050 ± 15 cm-1 and 21955 ± 15 cm-1, respectively. Strong vibronic progressions for the D3←D0 band systems of both isoquinoline +-Ar and quinoline+-Ar are modeled and assigned in terms of ring deformation and carbon-carbon stretch vibrational modes using time-dependent density functional theory calculations in conjunction with Franck-Condon simulations. The properties..