Mechanochemistry: Fundamentals, applications and future

The influence of external forces on the reaction pathways of cyclobutane systems: a computational study Anne Germann 1 , Robert Strich 1 , Prof. Yun Liu 2 , Prof. Jan Meisner 1 1 Institute of Physical Chemistry, Heinrich Heine University, Germany, 2 College of Chemistry & Molecular Engineering, Peking University, China The mechanochemical behavior of a 2-ladderene system was investigated computationally using the force- modified potential energy surface (FMPES) method. [1] Additionally, ab initio steered molecular dynamics simulations were performed to further analyze the ring opening mechanism. Our calculations revealed the existence of a biradical intermediate, which is highly force dependent (see Fig. 1). Without and at very low pulling forces, the reaction follows an almost concerted one-step mechanism. At very high pulling forces, the reaction proceeds in a one-step mechanism as well, as reaction barriers are lowered to the point where the biradical is no longer a minimum structure. Only in an intermediate force range the mechanism changes to a two-step ring opening with a meta-stable intermediate. It is hypothesized that the biradical intermediate could undergo alternative reactions such as isomerization if the second bond scission was sufficiently suppressed. To analyze the phenomenon of mechanism change further, the FMPES of a model cyclobutane mechanophore was systematically investigated and visualized at different forces.

Figure 1: Qualitative reaction paths calculated for different pulling forces. References 1. M. T. Ong et al. , "First principles dynamics and minimum energy pathways for mechanochemical ring opening of cyclobutene." J. Am. Chem. Soc., 131.18, 6377-6379 (2009). 2. Y. Liu et al. , “Flyby reaction trajectories: Chemical dynamics under extrinsic force.”, Science, 373 (6551), 208-212 (2021).

P23

© The Author(s), 2022

Made with FlippingBook Learn more on our blog