Allosteric Interactions in Coordination Cages
Biomolecular receptors can catalyse reactions, alter their geometry, and inhibit their activity in response to molecules binding around their periphery. Synthetic receptors that can mimic this allosteric binding behaviour extend the potential applications of host-guest chemistry to programmable molecular systems. Modulating the degree and magnitude of interaction between components within these systems enables the design of chemical behaviour akin to biological complexity. With a view to developing artificial guest-binding regulation systems, a series of metal-organic cages capable of both the peripheral and internal encapsulation of guests are presented: octahedra capable of accommodating two guests in different locations simultaneously; cuboctahedral receptors that bind fullerenes with all-or-nothing positive cooperativity and assemble supramolecular entities internally; a heteroleptic triangular prism capable of recognising steroids and enantiopure natural products; and a tetrahedron that binds fullerene clusters. Each of these architectures employs one or more binding site to either: a) template specific products; b) regulate the cooperativity of binding of large anionic guests; c) assemble coordination complexes and interlocked species inside their cavities; d) alter their morphology in well-defined ways; or e) form assemblies with new electronic and electrochemical functionality. In all cases, chemical systems that respond to multiple stimuli simultaneously are explored, and new applications for bringing multiple species into proximity are detailed. The allosteric binding motifs described herein can be extended to sort reaction mixtures, generate specific isomeric forms, stabilise labile species and promote tuneable modes of intermolecular cooperativity.
Supramolecular chemistry, Metal-organic cages, Host-guest chemistry, Guest binding, Allostery
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