Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5415512 | Journal of Molecular Spectroscopy | 2008 | 12 Pages |
Abstract
A systematic study of the rotation constants, vibration-rotation constants and quartic centrifugal distortion constants has been performed for furan, pyrrole, thiophene, both oxazoles and thiazoles, 1,2,4- and 1,2,5-oxa- and -thiadiazoles, 1,2,5-selenadiazole, and several 6-membered heterocycles (azines). The main study used cc-pVTZ basis sets. There is a very close correlation between the observed constants above and those calculated, especially using the cc-pVTZÂ +Â B3LYP procedures; some trends in these appear on substitution of HC by N in the azoles. This strong correlation between experimental values and this theoretical procedure is also apparent with vibrational differences in rotation constants, all over large numbers of measured values. However, a small number of calculated values do not correlate well with experiment; this may be a result of some of the experimental values being subject to resonance perturbations not included in the calculations. In general, a TZ2P basis set with B3LYP methodology, and cc-pVTZ results with MP2 methodology, lead to correlations of similar quality, but the latter require markedly more computing power. The present study draws attention to a tetrad in the IR spectrum of 1,2,5-oxadiazole, where further analysis is necessary.
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Authors
Michael H. Palmer, René Wugt Larsen, Flemming Hegelund,