Single-Molecule Observation of a Mechanically Activated Cis-to-Trans Cyclopropane Isomerization

摘要

The mechanochemical activation of cis-gemdifluorocyclopropane (cis-gDFC) mechanophore in toluene was characterized with single-molecule force spec-troscopy. Unlike previously reported behavior in methyl benzoate (MB), two transitions are observed in the force vs extension curves of cis-gDFC polymers in toluene. The first transition occurs at the same force of ～1300 pN observed previously in MB, but a second transition is observed at forces of ～1800 pN that reveal the partial formation of the trans-gDFC isomer. The behavior is attributed to competing reactions of the cis-gDFC at the 1300 pN plateau: addition of oxygen to a ring-opened diradicaloid intermediate, and isomerization of cis-gDFC to its trans isomer.