Allosteric Modulation of Substrate Binding within a Tetracationic Molecular Receptor

The synthesis and recognition phenomena of a tetracationic molecular receptor that possesses a nanometer-sized molecular cavity are described. The host guest properties of the molecular receptor can be tuned and modulated allosterically, where the association of a heterotropic effector at the periphery of the molecule serves to modulate its affinity for the globular, electron-rich guest that resides within its molecular cavity. This stimuli-responsive host guest behavior was observed in both the solution phase and the crystalline solid state, and can be reversed with high fidelity by sequestration of the effector molecule.