Abstract
Recently, ligand–metal coordination, stimuli-responsive covalent bonds, and mechanically interlinked molecular constructs have been used to create systems with a large number of accessible structural states. However, accessing a multiplicity of states in sequence from more than one direction and doing so without the need for external energetic inputs remain as unmet challenges, as does the use of relatively weak noncovalent interactions to stabilize the underlying forms. Here we report a system based on a bispyridine-substituted calix[4]pyrrole that allows access to six different discrete states with directional control via the combined use of metal-based self-assembly and molecular recognition. Switching can be induced by the selective addition or removal of appropriately chosen ionic guests. No light or redox changes are required. The tunable nature of the system has been established through a combination of spectroscopic techniques and single crystal X-ray diffraction analyses. The findings illustrate a new approach to creating information-rich functional materials.
Highlights
Ligand–metal coordination, stimuli-responsive covalent bonds, and mechanically interlinked molecular constructs have been used to create systems with a large number of accessible structural states
The relatively greater strength of ligand–metal coordination bonds compared with other noncovalent interactions has permitted the stabilization of a range of elegant structures, including many with properties that are not mimicked in the case of less complex architectures1–6
We postulate that combining weak supramolecular interactions with ligand–metal coordination would allow access to multiple state changes with directional control provided via the simple addition of guest molecules
Summary
Ligand–metal coordination, stimuli-responsive covalent bonds, and mechanically interlinked molecular constructs have been used to create systems with a large number of accessible structural states. From a nonlinear curve fitting of the changes in the UV-vis spectrum as 2 is titrated with 1 in THF, the binding constants, K1 and K2, corresponding to capsule formation were calculated to be 600 ± 100 and 9,000 ± 1,000 l mol −1, respectively (Supplementary Fig. 29).
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