An imine-based molecular cage with distinct binding sites for small and large alkali metal cations
Clément Schouwey1, Rosario Scopelliti, Kay Severin
1Institut des Sciences et Ingénierie Chimiques, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
Abstract:
The synthesis of a cylindrical, imine-based cage composed of two trimeric metallamacrocycles is described. The cage acts as a heterotopic receptor for alkali metal cations. The small cations Li(+), Na(+), and K(+) bind to the outside of the cage with good selectivity for Li(+), whereas the larger cations Rb(+) and Cs(+) are bound inside the cage to form unusual π complexes with a good selectivity for Cs(+). Negative heterotopic cooperativity between the two binding sites is observed. The complexation of Cs(+) is associated with a color change, which enables the cage to be used as a specific sensor for Cs(+).
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