Reversible Metastable-State Photoacids

在这个由化学系化学结构、动态和机理B计划资助的项目中，佛罗里达理工学院化学系的廖毅教授和J.Clayton Baum教授正在研究一种在受光照射时可以可逆地改变酸浓度的分子。这些分子被称为亚稳态光酸，可以用光控制各种化学、生物和材料过程。亚稳态光酸的应用包括光导材料、光致机械材料、光致变色材料、抗菌材料和药物释放材料。这种材料还可以用来开发生物传感器、微生物燃料电池和分子开关。它们的反应机理、结构与性质的关系以及这些光酸的潜在应用正在被研究。该项目涉及有机化学、光化学、物理化学、生物化学和材料化学。这项研究非常适合本科生和研究生的教育。针对高中生和中学生的外展活动也是项目活动的一部分。从酸催化的反应到许多酶的活性，许多化学、材料和生物过程对质子浓度都很敏感。光酸在照射后可逆地发生质子解离，有望实现对酸敏感过程的远程、时空控制。这些化合物可以提供一种将光能转化为其他类型的能量的方法。虽然可逆光酸已经被研究，但光诱导的质子浓度变化还不足以驱动或有效地控制酸敏感过程。实现大的质子浓度变化的一个主要问题是高酸度态的寿命受激发态寿命的限制。为了解决这一局限性，研究人员将质子解离与可逆的分子内光反应相结合，从而获得了长寿命的光酸。在这种方法中，高酸度状态不再是激发态，而是光反应产生的亚稳态。亚稳态光酸具有长寿命的高酸度状态，并在光照下产生较大的酸度变化。亚稳态光酸的设计以及这些光酸的光化学行为和机理正在从实验和理论两方面进行研究。

In this project funded by the Chemical Structure, Dynamic & Mechanism B Program of the Chemistry Division, Professors Yi Liao and J. Clayton Baum of the Department of Chemistry at Florida Institute of Technology are investigating a class of molecules that can reversibly change acid concentrations when irradiated with light. These molecules, which are called metastable-state photoacids, allow the control of various chemical, biological and material processes with light. Applications of metastable-state photoacids include photoconductive, photomechanical, photochromic, antibacterial, and drug releasing materials. The materials can also be used to develop biosensors, microbial fuel cells, and molecular switches. The mechanisms by which they react, the structure property relationships, and the potential applications of these photoacids are being studied. The project lies at the interface of organic, photo, physical, biological, and materials chemistry. The research is well suited for the education of undergraduate and graduate students. Outreach activities to high school and middle school students are also part of the project activities. Numerous chemical, material, and biological processes are sensitive to proton concentration, from acid-catalyzed reactions to activities of many enzymes. Photoacids that reversibly undergo proton dissociation upon irradiation promise remote, spatial and temporal control of acid-sensitive processes. These compounds could provide a way to convert photoenergy into other types of energy. Although reversible photoacids have been studied, the photoinduced proton concentration change has not been high enough to drive or effectively control acid sensitive processes. One major problem in achieving large proton concentration changes is that the lifetime of the high-acidity state is limited by the excited-state lifetime. To solve this limitation, the investigators couple proton dissociation with a reversible intramolecular photoreactions so that long-lived photoacids can be obtained. In this approach, the high-acidity state is no longer an excited state, but a metastable state generated from the photoreaction. Metastable-state photoacids can possess a long-lived high-acidity state and produce a large acidity change under irradiation. The design of metastable-state photoacids and the photochemical behaviors and mechanisms of these photoacids are being studied both experimentally and theoretically.