The Adenine and Thymine Molecules. Some Excited Singlet and Triplet Levels of the Normal and Tautomeric Forms

Abstract

The shape of the barrier for the H transfer between the normal and tautomeric forms have been determined for the adenine and thymine molecules. The correlations for several singlet and triplet states has been calculated using the CNDO/2-Cl method. The relative stability between both conformations and the agreement with some experimental values is also discussed.

Polarization, Barriers and Tunneling Times of Some Tautomers of Adenine and Thymine

“…c) The tunneling effect through the barrier reported in our previous work [1] is negligible in the ground state but large enough to be considered in some excited states in both molecules.…”

“…In a previous paper [1] we have reported the correlation between the normal and tautomeric forms for several excited singlet and triplet levels of adenine and thymine. Moreover, we have determined the shape of the barriers between the configurations shown in Fig.…”

“…The relative stability of the normal and tautomeric forms of adenine and thymine has been formerly analysed with semi-empirical and abinitio methods [1][2]. In the same way we have now calculated the charge distribution of several excited states in order to determine the intramolecular charge transfer involved in the tautomerization process.…”

“…Moreover, we have obtained the direction of the polarization of the light emitted during transitions between some excited states and the ground state. From the barriers reported in a preceding paper [1] some characteristic parameters for the tunneling and the equilibria between the tautomers of adenine and thymine were obtained.…”