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.