A theoretical study on the hydrogen bond and stability of cytosine and thymine dimers

A theoretical examination of homo- and heterodimers of cytosine and thymine was performed at the B3LYP/6-311++G(2d,2p) theory level. The stability of hydrogen-bonded complexes along with their geometrical and energetical properties are presented. The new more stable thymine-thymine and cytosine-thymine dimers were found compared to the previous literature reports. Moreover, the proton affinity of O and N atoms and deprotonation enthalpies of cytosine and thymine are computed at the same level of theory. Findings show that most of the interactions for both CH center dot center dot center dot O/N and NH center dot center dot center dot O/N contacts are red shifted in dimers. In addition, it clearly indicates that NH center dot center dot center dot O contacts has greatest impact on the stability of the nucleobases dimers, as the most stable complexes are characterised by two N-H center dot center dot center dot O bonds. (C) 2017 Elsevier B.V. All rights reserved.