Structure Identification for Force-Induced Reaction Using Single-Molecule Conductance Measurement

Spiropyran derivatives are prototype mechanophores with a promising application as molecular sensors because of their changeable structure under external force stimuli. However, the chemical structure evolution under external stimuli remains unclear due to the uncertainty and difficulty in distinguishing the structures of different ring-opened merocyanine isomers generated in the force-induced reaction. Here we identify the structure of isomers produced by the force-induced reaction of spiropyran derivatives using a single-molecule conductance measurement and an unsupervised clustering algorithm. We found that the original data from the single-molecule conductance measurement can be divided into four clusters through unsupervised clustering. By introducing a photoinduced reaction and theoretical calculation, we identified and attributed the four clusters of data to the multiple states of the molecular junctions. Our work demonstrates that a single-molecule break junction measurement can distinguish the isomers in the force-induced reaction, suggesting the great potential of single-molecule conductance measurement and unsupervised clustering approaches for structural analysis. [Graphics] .