Intriguing radical–radical interactions among double-electron oxidized adenine–thymine base pairs

Abstract

We present a theoretical investigation of the structural and electronic properties of double-electron oxidized adenine–thymine base pair as well as its deprotonated Watson–Crick derivatives. Double-electron oxidation can destabilize the AT unit, leading to a barrier-hindered metastable A+T+ state with a dissociation channel featuring negative dissociation energy. This unusual energetic phenomenon originates from the competition of electrostatic repulsion and attractively hydrogen-bonding interaction co-existing between A+ and T+. The associated double-proton-transfer process is also explored, suggesting a possible two-step mechanism. Magnetic coupling interactions of various diradical structures are controlled by both intra- and inter-molecular interactions.