Chemists find a new pathway to luminescence through mechanochemical force

Amazing stuff!

"In brief

• Computational modeling revealed an unexpected order of bond breaking in the core molecular structure that causes bioluminescence in nature.
• Mechanical force ruptures the dioxetane molecule’s carbon-carbon bond first, which is contrary to previous understanding of how the break in the molecule’s bonded square of oxygen and carbon atoms leads to light emission.
• The findings suggest the potential to develop improved stress sensors as well as gain insight into some forms of biological luminescence.

...

Chemists have long used molecules called dioxetanes to create light. These molecules have the same core structure that enables biological luminescence: two oxygen atoms and two carbon atoms bonded together in a square. Heat or mechanical force can break those bonds, causing light emission. ...

But when ... researchers modeled force applied to dioxetanes, they found that the bond between the carbon atoms breaks first, then the one between the oxygens."

From the abstract:

"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."

Chemists find a new path to luminescence | Stanford Report "The molecule behind the glow of fireflies and plankton breaks apart in an unexpected order under force – a discovery that could lead to better stress sensors and help illuminate some mysteries of the natural world."

The Force Awakens a Dormant Chemiluminescent Pathway in 1,2-Dioxetane (no public access)

Graphical abstract