A new type of molecular probes for catching reactive radicals

自由基中间体在许多化学和生物过程中起关键作用，并且它们的检测和定量对于燃烧、大气和室内化学、反应机制（包括催化-例如多相催化和最近开发的光氧化还原催化领域）、生物和药物化学（例如，监测氧化应激）。然而，自由基通常是非常短暂的，并且不能直接观察到，特别是在复杂的真实的系统中。自20世纪60年代以来，自旋捕集技术与EPR光谱技术相结合已成为自由基检测的一种有效方法，近年来，质谱技术被认为是一种灵敏度更高、信息量更大的自旋捕集检测方法。然而，由于质谱不需要未成对电子进行检测（与EPR光谱不同），因此传统的自旋陷阱并不适合此目的。令人惊讶的是，这一点被研究界所忽视。我们最近设计了一种不同类型的陷阱用于自由基检测。与传统方法相比，我们的新陷阱在稳定性、灵敏度和检测选择性方面都有了显著的提高，在远低于现有技术检测限的浓度下，提供了以前无法获得的气相自由基中间体的物种结构信息。（迄今为止只用于气相自由基）到液相反应，其中最令人兴奋的应用包括研究生物化学机制（通过氧化应激监测或免疫自旋捕获），探索催化反应的机制，并观察与大气和等离子体化学有关的空气-水界面的反应。我们相信这将导致我们对自由基过程机制的理解发生一步变化，并将为建立新的合作和新的研究领域开辟机会。在这个项目中的挑战包括合成，设计适当的分析方法，和稳定的新探针在真实的系统。然而，由于新方法的可行性已在我们的初步工作中确立，因此整体失败风险较低。

Free radical intermediates play a key role in many chemical and biological processes, and their detection and quantification is critical for combustion, atmospheric and indoor chemistry, reaction mechanisms (including catalysis - such as heterogeneous catalysis and a recently developed area of photoredox catalysis), biological and medicinal chemistry (e.g., monitoring oxidative stress). However, free radicals are often very short lived, and cannot be observed directly, particularly in complex real systems. Free radicals are usually detected using spin trapping technique in conjunction with EPR spectroscopy, a method which has been successfully used since 1960s.In recent years, mass spectrometry was proposed as a more sensitive and informative detection method for spin trapping. However, as mass spectrometry does not require unpaired electrons for detection (unlike EPR spectroscopy), the conventional spin traps are not well-suited for this purpose. This point has surprisingly been overlooked by the research community. We have recently designed a different type of traps for radical detection. Our new traps offer dramatic improvements in stability, sensitivity and selectivity of detection compared to the more conventional methods, providing previously unavailable speciated structural information about radical intermediates in the gas phase at concentrations well below the detection limit of current techniques.In this project, we will expand our new method (which has so far been only used with gas phase radicals) to liquid phase reactions, where the most exciting applications include studying biochemical mechanisms (through oxidative stress monitoring or immuno spin trapping), exploring mechanisms of catalytic reactions and looking at reactions at air-water interface, relevant to atmospheric and plasma chemistry. We believe this will lead to a step change in our understanding of mechanisms of free radical processes and will open up opportunities to establish new collaborations and new areas of research. The challenges in this project include synthesis, design of appropriate analysis method, and stability of the new probes in real systems. However the overall risk of failure is low as the feasibility of the new method has already been established in our preliminary work.