Force can induce remarkable non-destructive transformations along a polymer, but we have a limited understanding of the energy transduction and product distribution in tandem mechanochemical reactions. Ladderanes consist of multiple fused cyclobutane rings and have recently been used as monomeric motifs to develop polymers that drastically change their properties in response to force. Here we show that [4]-ladderane always exhibits ‘all-or-none’ cascade mechanoactivations and the same stereochemical distribution of the generated dienes under various conditions and within different polymer backbones. Transition state theory fails to capture the reaction kinetics and explain the observed stereochemical distributions. Ab initio steered molecular dynamics reveals unique non-equilibrium dynamic effects: energy transduction from the first cycloreversion substantially accelerates the second cycloreversion, and bifurcation on the force-modified potential energy surface leads to the product distributions. Our findings illustrate the rich chemistry in closely coupled multi-mechanophores and an exciting potential for effective energy transduction in tandem mechanochemical reactions.

力可以沿着聚合物引起显着的非破坏性转变，但我们对串联机械化学反应中的能量传递和产物分布的了解有限。Ladderanes 由多个稠合的环丁烷环组成，最近已被用作单体基序来开发聚合物，这些聚合物可根据力显着改变其性质。在这里，我们表明 [4]-ladderane 在各种条件下和不同聚合物主链内总是表现出“全有或全无”级联机械活化和生成的二烯的相同立体化学分布。过渡态理论无法捕捉反应动力学并解释观察到的立体化学分布。从头算操纵的分子动力学揭示了独特的非平衡动力学效应：来自第一次循环反转的能量转换大大加速了第二次循环反转，并且在力修改的势能表面上的分叉导致了乘积分布。我们的研究结果说明了紧密耦合的多机械载体中丰富的化学性质以及串联机械化学反应中有效能量转换的令人兴奋的潜力。