Figure 3. Schematic of the pattern of groove bound ions participating in cation-pi interactions.

Circles and ovals/rectangles represent cations/FSWs involved in single and double cation-pi interactions respectively. Empty and shaded circles/ovals represent interactions localized to the major and minor grooves respectively. Each circle/oval is positioned adjacent to the base forming hydrogen bonds with the cation/FSW with the π next to the base involved in the cation-pi interaction. Circles/ovals here reflect only the presence of cation-pi interaction and do not distinguish between single cation/FSW interactions and those bases involved in multiple cation-pi interactions with same cations/FSWs. Rectangles reflect FSWs involved in cation-pi interactions with the bases designated with π but without hydrogen bonding to adjacent bases. In 1jgr, the circles represent Tl⁺ ions while in 1sk5 the oval represents FSWs of Ca²⁺. In the remaining structures, circles/ovals represent FSW of Mg²⁺.