The Force Awakens a Dormant Chemiluminescent Pathway in 1,2-Dioxetane.

1,2-Dioxetanes are well-known for their chemiluminescent decomposition initiated by O-O bond scission. Under thermal conditions, this chemiluminescence has been used for molecular imaging, while mechanochemical triggering of chemiluminescence can be a powerful tool for studying stress in materials. It has been widely assumed that mechanochemical activation follows the same O-O scission pathway as the thermal case. However, our first-principles simulations of the mechanochemically triggered decomposition of 1,2-dioxetane show that the traditional O-O scission pathway is largely insensitive to applied force. Instead, a thermally inaccessible C-C bond scission pathway is stabilized by applied force and becomes energetically favored above a critical force (∼1.8-3.0 nN). This force-induced mechanistic switch is robust across various pulling directions and substituents, including the experimentally tested adamantyl derivative. These findings establish a new, fundamentally force-dependent pathway for chemiluminescence. They demonstrate that mechanical force can be used not only to accelerate a reaction, but to fundamentally change its mechanism. This presents significant opportunities for new mechanophore design and mechanochemical sensing applications.