When do molecular bowls encapsulate metal cations

Curved carbon π surfaces have chemical and physical properties suitable for exploitation for chemical microencapsulation and the self-assembly of nanoscale materials. Advances will greatly benefit from more understanding of their host−guest interactions with guests such as metal cations. Here, quantitative predictions are made for the binding of metal cations to three prototypical surfaces using density functional theory calculations: the buckybowls C20H10, C30H10, and C40H10. The focus was on finding the most favorable binding sites, assessing whether binding is more favorable inside or outside the bowl, and exploring factors influencing the binding site preference. Classes of cations studied included small and large monocations and cations with multiple charges: Na+, Cs+, NH4+, Ba+, Ba2+, and La3+. Factors found to favor inside binding were large ion size and high ion charge, suggesting that polarization interactions as well as short-range interactions are important in determining the preferred binding ...