The application of a mechanical force can distort the potential energy surface of a reactive landscape, leading to new, unexpected, and exciting chemistries. Despite numerous mechanophores being developed in the laboratory, computational tools have lagged behind in their ability to accurately and efficiently simulate these processes. To provide atomistic insight into this emerging area, a force functionality has been developed for the Growing String Method (GSM) and has been demonstrated to be a powerful means to identify reaction paths and transition states on force-modified potential energy surfaces. The use of internal coordinates in GSM is demonstrated to be an effective coordinate system for complicated mechanochemical transformations, leading to efficient and reliable reaction path optimization. Additionally, GSM is able to operate in a single-ended fashion, allowing for its use in discovering nonintuitive mechanochemical products even when the mechanical perturbations to the potential energy surface eliminate intermediates or transition states along a reaction path. The method is applied herein to several challenging mechanochemical transformations with various functions in force-responsive materials. These smart materials include polymers incorporating ring-opening mechanochromes with potential applications as force sensors as well as mechanophores that exploit flex-activation – angular deformation that occurs during elongation of polymer segments. For each of the reactions, mechanistic details that were unavailable using other theoretical methods were readily uncovered using GSM, showing it to be a widely useful tool for studying mechanochemistry.

Computational probing of the force-biased potential energy surface: Uncovering nonintuitive mechanochemical reaction pathways

2019 Fall National Meeting

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