## Abstract This paper presents some calculations on the monomer and dimer of benzoic acid using optimized molecular geometries. The calculated levels and transition moments are in good agreement with experimental results and they give a good account of some particular features of the absorption an
Electronic absorption and emission spectra of nucleic acids and their components: Some questions of theory and experiment
✍ Scribed by V. I. Danilov; V. I. Pechenaya; N. V. Zheltovsky
- Publisher
- John Wiley and Sons
- Year
- 1980
- Tongue
- English
- Weight
- 716 KB
- Volume
- 17
- Category
- Article
- ISSN
- 0020-7608
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
The results of calculations of the transition energies and polarization in nucleotide bases performed by the CNDO/S CI method are compared with experimental data for long‐wavelength and vacuumabsorption bands. The calculations and the analysis of experimental data testify to the existence of n − π* transitions in the first absorption bands of the bases. The study of double‐stranded polynucleotides and DNA hypochromism based on the theoretical electronic characteristics of the bases and perturbation theory is performed. The role of stacking and complementary interactions within the hypochromic effect is cleared up. Two mechanisms for the shift of the fluorescence band maximum are investigated: two‐proton transfer along H bonds and excimer formation. The study of H‐bond potential curves shows the disadvantage of two‐proton phototautomerism in the nucleotide base pairs in contrast to model systems. The possibility of excimer state formation in stacked homo‐ and heterodimers of nucleotide bases is shown within the extended‐Hückel treatment. The nature of excimer minimum for the excited‐state potential curve is analyzed.
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The electronic absorption spectra of the position isomers nicotinamide and isonicotinamide, nicotinic acid, and isonicotinic acid were investigated, together with the spectra of thionicotinamide, N-methyl nicotinamide and nicotinic acid N oxide. Apparent differences in the spectra of the position is
## Abstract Quantum‐chemical calculation of the energies of the electronic transitions and the electronic structures of the neutral and ionic species of the nucleic acids components in their ground and lower excited singlet and triplet ππ\* and __n__π\* states has been carried out in the all‐valenc