Fourier transform microwave and millimetre wave spectroscopy of quinazoline, quinoxaline, phthalazine

Donald McNaughton, Peter Godfrey, Michaela Jahn, David Dewald, Jens-Uwe Grabow

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The pure rotational spectra of the bicyclic aromatic nitrogen heterocycle molecules, quinazoline, quinoxaline, and phthalazine, have been recorded and assigned in the region 13-87 GHz. An analysis, guided by ab initio molecular orbital predictions, of frequency-scanned Stark modulated, jet-cooled millimeter wave absorption spectra (48-87 GHz) yielded a preliminary set of rotational and centrifugal distortion constants. Subsequent spectral analysis at higher resolution was carried out with Fourier transform microwave (FT-MW) spectroscopy (13-18 GHz) of a supersonic rotationally cold molecular beam. The high spectral resolution of the FT-MW instrument provided an improved set of rotational and centrifugal distortion constants together with nitrogen quadrupole coupling constants for all three species. Density functional theory calculations at the B3LYP/6-311+G** level of theory closely predict rotational constants and are useful in predicting quadrupole coupling constants and dipole moments for such species.
Original languageEnglish
Pages (from-to)1 - 4
Number of pages4
JournalJournal of Chemical Physics
Issue number15
Publication statusPublished - 2011

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