Probing and Designing Cascade Reactivity in Consecutive Mechanoactivation of Covalent Bonds

在化学系化学结构、动力学机制-B（CSDM-B）项目的支持下，斯坦福大学化学系的Yan Xia和托德Martinez正在设计机械响应分子，即机械载体，以了解在热或光化学反应歧管下无法实现的新的力驱动反应途径。该研究旨在通过实验和计算研究多个耦合机械载体的连续机械活化事件中的动能转导，非统计动态效应和级联反应。该项目位于物理有机，聚合物和计算化学的接口，因此非常适合各级下一代科学家的教育。 这些团体将建立在他们的合作研究和教育记录的基础上，旨在为科学领域代表性不足的学生提供高水平的教育和培训。使用交互式机械力致变色实验和虚拟现实分子刺激演示机械力化学，旨在激发K-12学生对科学的兴趣。机械应力在几乎所有的陆地环境和技术应用中无处不在。拟议的研究旨在了解，探索和开发级联反应，非统计动态效应，并控制产品分布在紧密耦合的梯形多机械基团系统。动力学效应已经被发现可以解释许多多步热反应和光化学反应中的反应性和产物分布，其中反应势垒变得如此之小，以至于过渡态理论不能再用于合理化反应性。由于力的施加显著降低了反应势垒，动态效应可能更常见，但很少在机械化学中探索。拟议的研究旨在填补知识空白，了解不同的分子参数如何影响共价键的机械化学反应性的程度，动态效应和控制。理解和设计机械化学级联反应性和强动态效应有望使化学系统的设计能够表现出将机械能转换为多方面化学反应的高效率。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估而被认为值得支持。

With support of the Chemical Structure, Dynamics & Mechanisms-B (CSDM-B) Program of the Chemistry Division, Yan Xia and Todd Martinez of the Department of Chemistry at Stanford University are designing mechanically responsive molecules, mechanophores, to understand new force-driven reaction pathways that are inaccessible under thermal or photochemical reaction manifolds. The proposed research aims to experimentally and computationally investigate the kinetic energy transduction, non-statistical dynamic effects, and cascade reactivity in consecutive mechanoactivation events across multiple coupled mechanophores. The project lies at the interface of physical organic, polymer, and computational chemistry, and is therefore well suited to the education of next-generation scientists at all levels. These groups will build on their record of collaborative research and education and aim to provide high level of education and training for students underrepresented in science. Demonstrating mechanochemistry using interactive mechanochromic experiments and virtual reality molecular stimulation is planned with the goal of sparking the interest of K-12 students in science.Mechanical stress is ubiquitous in nearly all terrestrial settings and technological applications. The proposed research aims to understand, explore, and develop cascade reactivity, non-statistical dynamic effects, and control product distribution in closely coupled ladder-type multi-mechanophore systems. Dynamic effects have been found to account for the reactivity and product distribution in many multistep thermal and photochemical reactions, where the reaction barrier becomes so small that transition state theory can no longer be used to rationalize the reactivity. Because the application of force significantly lowers the reaction barrier, dynamic effects are potentially much more common but rarely explored in mechanochemistry. The proposed research seeks to fill a knowledge gap in understanding how different molecular parameters influence the extent dynamic effects and control of mechanochemical reactivity of covalent bonds. Understanding and designing mechanochemical cascade reactivity and strong dynamic effects is expected to enable the design of chemical systems that exhibit a high efficiency of transducing mechanical energy into multifaceted chemical responses.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.