The physico-chemical mechanism of the tautomerisation via the DPT of the long Hyp∗·Hyp Watson–Crick base pair containing rare tautomer: A QM and QTAIM detailed look

We showed that biologically important planar Hyp∗·Hyp base pair (Cs) formed by the enol and keto tautomers of the hypoxanthine tautomerises via the synchronous concerted mechanism through the TS (C2v). The five key points were detected and completely investigated along the IRC of the Hyp∗·Hyp ↔ Hyp·Hyp∗ tautomerisation via the DPT. It was found that intermolecular antiparallel О6Н…О6 and N1H…N1 H-bonds are cooperative and mutually reinforce each other. It was proved that the Hyp∗·Hyp/Hyp·Hyp∗ base pair is dynamically stable structure with a lifetime 8.2 × 10−12 s and all its six low-frequency intermolecular vibrations are able to develop during this period of time.