Peel, a modified PPP method, applied on the spectra of some nucleic acid bases
✍ Scribed by Inga Fischer-Hjalmars; Anita Henriksson-Enflo
- Publisher
- John Wiley and Sons
- Year
- 1990
- Tongue
- English
- Weight
- 690 KB
- Volume
- 37
- Category
- Article
- ISSN
- 0020-7608
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✦ Synopsis
Abstract
A comparison between some different modifications of PPP methods is made. It is noticed that each modification may have its advantages but that some may be more suitable for interpretation of electronic spectra than others. It is also pointed out that PPP methods may allow more accurate descriptions of π properties than all‐valence methods, such as CNDO/S.
The Peel method, a PPP method especially adapted to reproduce the lowest π → π* transitions of a few reference molecules, has been applied to studies of the pyrimidine bases cytosine, uracil, and thymine. The obtained frequencies and oscillator strengths compare favorably with experimental evidence. The calculated polarization directions are in general agrreement with measurements. In case of cytosine a reinterpretation of measurements is suggested.