Matrix isolation studies of nucleic acid constituents. 2. Quantitative ab initio prediction of the infrared spectrum of in-plane modes of uracil

• Published in: Journal of the American Chemical Society 1984-06, Vol.106 (12), p.3415-3422
• Main Authors: Chin, Steven, Scott, Ismael, Szczepani, Krystyna, Person, Willis B
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja00324a006

The dipole moment derivatives (or atomic polar tensors (APTs)) for the atoms in uracil have been calculated in an ab initio quantum mechanical calculation, using the Gaussian 76 program with 4-31G basis functions. The frequencies and normal coordinate transformation matrices have been calculated from the force constants obtained from the ab initio quantum mechanical calculations by Nishimura et al. These are combined with the authors' calculated APTs to predict absolute intensities and to give a prediction from ab initio calculations of the entire infrared spectrum for the in-plane modes of the isolated uracil molecule. This predicted spectrum is in excellent agreement with the experimental spectrum (from Szczesniak et al.) of uracil isolated in a matrix. This result indicates that it is possible at present to make good quantitative predictions that are very useful in assignment and interpretation of vibrational spectra even for molecules that are as complicated as uracil.