Single-molecule force spectroscopy of bimolecular reactions: System homology in the mechanical activation of ligand substitution reactions

The mechanochemistry of the bimolecular nucleophilic substitution of DMSO for substituted pyridines at a square-planar pincer Pd(II) center was investigated using single-molecule force spectroscopy (SMFS). The SMFS data are interpreted in terms of the Bell-Evans model, which gives thermal off-rates for two reactions that agree well with previous, stress-free measurements. The characteristic force dependency of the rupture rate, fβ, is effectively constant for the two reactions examined (22 ± 2 and 24 ± 2 pN), and the system homology in the mechanical response is consistent with expected similarities in the reaction potential energy surfaces. Copyright © 2006 American Chemical Society.