Dipole-bound excess-electron states of adenine tautomers. A theoretical ab initio study

Ab initio calculations performed in this work render a near-zero but positive electron affinity of the major N(9)H tautomer of adenine. However, the electron affinity of the N(7)H tautomer, which has not been detected in the gas phase but coexists with the N(9)H tautomer in the polar solution, is predicted to be equal to 0.12 eV. ln both cases the excess electron is bonded to the dipole field of the molecule. No conventional stable `valence' anionic states have been found. Due to a significant difference between the predicted electron affinities of the N(7)H and N(9)H tautomers, one should expect a noticeable shift in the tautomeric equilibrium when electrons attach to adenine molecules in the gas phase.