Past exam of the chemistry course of the year 4 of the natural sciences course of the University of Cambridge / 2022 / Paper 3 / Section E / 44 / a

zinc(II) should bind more strongly to 1. The macrocycle presents six amine donors that can chelate the dication in a roughly octahedral environment. Multiple donor contacts, the chelate effect and preorganization favour this binding. lithium is small and strongly prefers an appropriately sized oxygen-rich pocket; it gains less from this large nitrogen-donor cavity. Charge density alone is insufficient to rank the complexes: donor type, geometry, solvation and the strain of wrapping the host around each ion also matter.