Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA.
J Am Chem Soc. 2013 Aug 28;135(34):12722-9. doi: 10.1021/ja4051108. Epub 2013 Aug 19.
While the field of polymer mechanochemistry has traditionally focused on the use of mechanical forces to accelerate chemical processes, theoretical considerations predict an underexplored alternative: the suppression of reactivity through mechanical perturbation. Here, we use electronic structure calculations to analyze the mechanical reactivity of six mechanophores, or chemical functionalities that respond to mechanical stress in a controlled manner. Our computational results indicate that appropriately directed tensile forces could attenuate (as opposed to facilitate) mechanochemical phenomena. Accompanying experimental studies supported the theoretical predictions and demonstrated that relatively simple computational models may be used to design new classes of mechanically responsive materials. In addition, our computational studies and theoretical considerations revealed the prevalence of the anti-Hammond (as opposed to Hammond) effect (i.e., the increased structural dissimilarity between the reactant and transition state upon lowering of the reaction barrier) in the mechanical activation of polyatomic molecules.
虽然聚合物机械化学领域传统上侧重于利用机械力来加速化学过程，但理论考虑预测了一种尚未充分探索的替代方法：通过机械扰动抑制反应性。在这里，我们使用电子结构计算来分析六个机械试剂（或对机械应力以受控方式做出响应的化学官能团）的机械反应性。我们的计算结果表明，适当定向的拉伸力可能会削弱（而不是促进）机械化学现象。伴随的实验研究支持了理论预测，并表明相对简单的计算模型可用于设计新型机械响应材料。此外，我们的计算研究和理论考虑揭示了在多原子分子的机械活化中反哈蒙德（而非哈蒙德）效应（即在降低反应势垒时反应物和过渡态之间的结构差异增加）的普遍性。
