Local aromaticity in natural nucleobases and their size-expanded benzo-fused derivatives

The effect of the insertion/addition of a benzene ring to the natural nucleic acid bases on the local aromaticity of the so-called size-expanded (xN, with N being adenine, guanine, cytosine, and thymine) bases is studied. The results reveal notable differences in the aromatic character of the natural and size-expanded bases, which generally are hardly affected upon hydrogen bonding.