Quantum-mechanical calculations of the intensity distribution in spectra of adenine tautomers: II. Two-photon absorption spectra

Aromaticity from the Viewpoint of Molecular Geometry: Application to Planar Systems

“…The 9 H -amino tautomer is more stable in all phases. In the gas phase, the energy gap between the canonical 9 H -structure and the less preferred 7 H - and 3 H -tautomers is about 7.5 kcal/mol, while this gap is reduced to 2.5 kcal/mol in water, but the order of stability is retained; 7 H - and 3 H -tautomers are energetically very close. − Theoretical results are in agreement with experimental data. − It is also found that the 9 H ,1 H + form of adenine (9 H adenine protonated at the position N1) dominates in water along with the 9 H and 7 H ones. − …”