title: Supersonic Jet Spectroscopy and Density Functional Theory Study of Isomeric Diazines: 1,4- and 1,8-Diazatriphenylene. Why Do They Differ So Deeply?
abstract: We report on laser-induced fluorescence excitation and dispersed fluorescence spectra of two isomeric compounds: 1,4- and 1,8-diazatriphenylene (1,4- and 1,8-DAT) isolated in supersonic molecular jets, and their 1:1 complexes with protic solvents. We found that the ground and excited state vibronic patterns of bare 1,4-DAT differ significantly from those of 1,8-DAT, and those of the complexes of both isomers. A marked activity of several out-of-plane vibrations in 1,4-DAT and the symptoms of the distortion of the S1excited molecule were diagnosed from the vibronic spectra, whereas planar structures were predicted for 1,8-DAT in S0and S1states. An anharmonic double-minimum potential along an out-of-plane coordinate has been derived and used to predict higher overtones of the S1state vibration at 113 cm-1. Large enhancement of fluorescence was observed upon formation of 1:1 complexes of 1,4-DAT with water or methanol, which is explained in terms of an increased separation of interacting (n,π*) and (π,π*) electronic states in the H-bonded complexes, and/or a suppression of the intersystem crossing process.
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, PL-01-224 Warsaw, Poland.
authors.forename: Michał
authors.initials: M
authors.lastname: Kijak
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, PL-01-224 Warsaw, Poland.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Peukert
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, PL-01-224 Warsaw, Poland.
authors.forename: Ephriem
authors.initials: E
authors.lastname: Mengesha
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, PL-01-224 Warsaw, Poland.
authors.forename: Jerzy
authors.initials: J
authors.lastname: Sepioł
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, PL-01-224 Warsaw, Poland.
authors.forename: Michał
authors.initials: M
authors.lastname: Gil