Sterically Controlled Solid-State Mechanochemistry Under Hydrostatic Pressure

Mechanical stress can modify the energy landscape of chemical reactions and enable new reaction pathways. Mechanochemical mechanisms under tensile stress have been extensively studied in one-dimensional polymers. However, bond activation has not been possible with hydrostatic pressure in three-dimensional solids. Here we show that mechanochemistry through isotropic compression is possible by molecularly engineering structures that translate macroscopic isotropic stress into molecular-level anisotropic strain. We engineer molecules with mechanically heterogeneous components consisting of a compressible mechanophore and incompressible ligands. In these ‘molecular anvils’, isotropic stress leads to anisotropic deformation of the compressible mechanophore and activating bonds. We combine experiments and computations to demonstrate hydrostatic-pressure-driven redox reactions in crystalline metal-organic chalcogenides, where bending of bond angles or shearing of adjacent chains activates the metal-chalcogen bonds. These results reveal an unexplored mechanism and enable new possibilities for high-specificity mechanosynthesis.