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Peel, a modified PPP method, applied on the spectra of some nucleic acid bases
Author(s) -
FischerHjalmars Inga,
HenrikssonEnflo Anita
Publication year - 1990
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560370420
Subject(s) - cndo/2 , cytosine , pyrimidine , uracil , thymine , chemistry , nucleobase , nucleic acid , computational chemistry , spectral line , molecule , tautomer , stereochemistry , quantum mechanics , organic chemistry , physics , dna , biochemistry
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.