Metal cations switch geometry of β-cyclodextrin complexes

Cationic guests with an adamantylphenyl moiety can form two distinct arrangements with the conical β-cyclodextrin macrocycle. Different metal cations were found to promote the formation of one of the two possible forms, depending on their van der Waals radii. Bulkier ions prefer the wider secondary rim of β-cyclodextrin, pushing the cationic part of the guest towards the narrower primary rim, and vice versa.