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Allosterically Regulated Guest Binding Determines Framework Symmetry for an FeII 4 L4 Cage.

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Self-assembly of a flexible tritopic aniline and 3-substituted 2-formylpyridine subcomponents around iron(II) templates gave rise to a low-spin FeII 4 L4 capsule, whereas a high-spin FeII 3 L2 sandwich species formed when a sterically hindered 6-methyl-2-formylpyridine was used. The FeII 4 L4 cage adopted a new structure type with S4 symmetry, having two mer-Δ and two mer-Ʌ metal vertices, as confirmed by NMR and X-ray crystallographic analysis. The flexibility of the face-capping ligand endows the resulting FeII 4 L4 framework with conformational plasticity, enabling it to adapt structurally from S4 to T or C3 symmetry upon guest binding. The cage also displayed negative allosteric cooperativity in simultaneously binding different guests within its cavity and at the apertures between its faces.



Allosteric Regulation, Host-Guest Chemistry, Metal-Organic Cages, Structural Adaptation, Symmetry

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Angew Chem Int Ed Engl

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European Research Council (695009)
Engineering and Physical Sciences Research Council (EP/P027067/1)
EPSRC (EP/T031603/1)