Publication Date:
2015-01-06
Description:
The FTIR spectra of isolated 5-ioduracil (5IU) molecules, and its deutero-derivatives, were obtained in low-temperature ( T = 8 K) argon matrices in the frequency range of 3800–200 cm −1 , with a resolution of 0.3 cm −1 . The tautomer population is estimated at the evaporation temperature 395 K, using DFT (functionals B3LYP and B2PLYP) and MP2 quantum-mechanical methods. It is found that the main keto tautomer population in 5IU is above 99.8%. 5IU vibrational spectra are calculated using the DFT/B3LYP method and 6-311++G(df,pd) basis, and the calculated frequencies are corrected using a second order polynomial. It is found that in the region of vCO stretching vibrations of 5IU molecules, a triple Fermi resonance is manifested between the fundamental vC4O mode, and the combinational vibrations with frequencies 1745.3 and 1722.5 cm −1 . Six combination modes in the region of ring stretching vibrations, and in-plane deformational vibrations, of 5IU are found. This classification of the vibrational spectrum bands of 1,3 dideutero-5-ioduracil (D5IU), demonstrates the presence of six combination D5IU modes, in the entire spectral region. It is established that the Fermi resonance causes a split of vND stretching vibrations in pyrimidine base spectra.
Print ISSN:
1063-777X
Electronic ISSN:
1090-6517
Topics:
Physics
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