Photo-induced Dissociation of the N1–H Bond in the Imino Tautomers of Isocytosine in Water Medium

The imino tautomers of isocytosine were objects of investigation at the TD-DFT level of theory - TD BLYP/6-311++G(d,p). We studied the mechanisms of the H1-N detachment in these tautomers through excited-state reaction paths. It was proposed that these transformations occur through the [.sup.1][pi][sigma] (*) excited-state reaction paths of the imino tautomers. The mechanisms involve dissociations of the N1-H bonds in the tautomers and lead to crossings between the reaction paths of [.sup.1][pi][sigma] (*) and [S.sub.0] electronic states. One can suppose that such processes would facilitate the tautomerizations of the imino tautomers if further mechanisms have been found. Keywords: conical intersections, TD-DFT calculations, excited states, H-detachments mechanisms, isocytosine.