Reconfigurable Mechanically Interlocked Metal-Organic Nanocages for Adaptive Guest Recognition and Allosteric Regulation.

Abstract

Replicating the allosteric regulation of biological systems in synthetic nanostructures remains a fundamental challenge in supramolecular chemistry. Here, we report a reconfigurable Pd₂L₄ nanocage (<b>Ex-MC</b>) that undergoes thermally triggered mechanical interlocking to form a Pd₄L₈ dimer (<b>I-Ex-MC</b>), establishing a versatile platform for stimuli-responsive molecular recognition at the nanoscale. Utilizing electrostatic interactions and the dynamic adaptability of the triphenylamine (TPA) scaffold, <b>Ex-MC</b> achieves exceptional selectivity for sulfonate anions (up to 380-fold) through an induced-fit mechanism reminiscent of enzyme-substrate recognition. Crucially, the monomer-dimer interconversion is fully reversible via temperature modulation or acid/base stimuli, as demonstrated by thermodynamic analysis (Δ<i>H</i> = 36.6 kJ mol^-1, Δ<i>S</i> = 105.5 J mol^-1 K^-1). Furthermore, the encapsulation of ReO₄^- within <b>I-Ex-MC</b> induces a pronounced allosteric response, expanding the central cavity while compressing the peripheral chambers, a behavior reminiscent of cooperative binding in biological receptors. This work establishes mechanical interlocking as a powerful strategy for engineering adaptive nanoarchitectures with potential applications in selective sensing, molecular separation, and intelligent nanomachinery.