Figure 7. Terminal Tl+ cation-pi interactions in 1jgr.
TL2112 is perched directly above the centroid of the terminal base C2001. The interaction is optimal since the ion position is sterically unencumbered and in less competition with stacking interactions from flanking bases. For the interaction shown, TL2112 d = 3.56 Å, ƒ = 4.7°.