• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.3039-3044
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• 2009

We report the first electric field dependence IR spectra of three cytosine tautomers solvated in helium nanodroplets. By using an electric field dependence on the three lowest energy tautomers of cytosine and ab initio calculations, we are able to measure the vibrational transition moment angles (VTMAs), specifically for the $NH_2$ symmetric stretch (SS) mode in this study, with more precision; thus we have reassigned the previous $NH_2$ (SS) VTMA of 74$^{\circ}$ for the C1 tautomer to 85$^{\circ}$, which the latter is in excellent agreement with the ab initio value. Nonplanarity of the three lowest energy tautomers of cytosine has been investigated by measuring the VTMA of each vibrational mode for the tautomers.

• Bulletin of the Korean Chemical Society
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• v.29 no.1
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• pp.69-75
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• 2008

Tautomerism of pyrimidine base cytosine has been comparatively examined on nanoparticle and roughened plate surfaces of silver, gold, and copper by surface-enhanced Raman scattering (SERS). The SERS spectrum was found to be different depending on the metals and their substrate conditions suggesting the dissimilar population of various tautomers of cytosine on the surfaces. The ab initio calculations were performed at the levels of B3LYP, HF, and MP2 levels of theory with the LanL2DZ basis set to estimate the energetic stability of the tautomers with the metal complexes as well as the gas phase state. The amino group and N3-coordinated tautomer was predicted to be more favorable for bonding to Au, whereas the hydroxyl and N1-coordinated zwitter ionic form is most stable with Ag and Cu as a bidentate form from the DFT calculation. The binding energy with the Ag atom is calculated to be smaller than those with the Au and Cu atoms in line with the temperature-dependent SERS spectra of cytosine.