Probing and Designing Cascade Reactivity in Consecutive Mechanoactivation of Covalent Bonds

在化学系化学结构、动力学和机理B(CSDM-B)计划的支持下，斯坦福大学化学系的夏燕(音译)和托德·马丁内斯(Todd Martinez)正在设计机械响应分子，机械团，以了解在热或光化学反应流形下无法访问的新的力驱动反应路径。这项研究的目的是通过实验和计算研究连续机械激活事件中的动能传递、非统计动力学效应和级联反应性。该项目位于物理有机、聚合物和计算化学的交界处，因此非常适合于各级下一代科学家的教育。这些小组将以他们的合作研究和教育记录为基础，旨在为科学方面代表性不足的学生提供高水平的教育和培训。计划使用交互式机械变色实验和虚拟现实分子刺激来演示机械力化学，目的是激发K-12学生对科学的兴趣。机械应力几乎普遍存在于所有地面环境和技术应用中。这项研究的目的是了解、探索和发展紧密耦合的梯形多机械载体系统中的级联反应性、非统计动态效应和控制产品分布。在许多多步热化学反应和光化学反应中，反应势垒变得非常小，以至于过渡态理论不能再用来合理地解释反应活性，动力学效应被发现是解释反应活性和产物分布的原因。由于力的应用显著降低了反应势垒，动态效应可能更常见，但在机械力化学中很少被探索。这项拟议的研究试图填补在理解不同的分子参数如何影响共价键的机械力化学反应的程度、动态效应和控制方面的知识空白。了解和设计机械化学级联反应性和强大的动态效应有望使化学系统的设计能够高效地将机械能转化为多方面的化学反应。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，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.