Where to bind in buckybowls? The dilemma of a metal ion

An exhaustive computational study at the M05-2X/cc-pVDZ level which explores the binding possibilities of cations (Li+, Na+, K+ and Cu+) to the concave and convex sides of the hub and rim rings of prototypical buckybowls, sumanene (C21H12) and corannulene (C20H10), has been carried out. Five distinct minima on the potential energy surface of sumanene and four on the potential energy surface of corannulene were identified. The complex where the metal ion binds to the convex side of the 6-membered rim ring is adjudged as the most stable complex for both the bowls considered. The cation-pi interaction energies of buckybowls are compared with model systems such as benzene, cyclopentadiene, indene and coronene. Energy decomposition analysis has also been performed to delineate the contribution from various components contributing to the cation-pi binding strength.