CAS: Exploiting Pro-Aromaticity for Triplet Photochemistry: Synthesis, Aromaticity, & Photophysics

伊利诺伊大学芝加哥分校（UIC）化学系的Jean-Luc Ayitou在化学系化学结构、动力学机制-B项目的支持下，正在开发新型的前芳香族无重原子有机发色团，即二酮吡咯并吡咯（DPP）和二吡咯并萘二酮（DPND），它们表现出有吸引力的光捕获和光物理特性。本研究的最终目标是利用固有的分子性质，如芳香性来调节所提出的DPP和DPND发色团的光行为和自旋状态，其可以针对诸如三重态光敏化、光动力治疗和太阳能转化为太阳能燃料的应用进行定制。此外，所提出的DPP和DPND发色团可以进一步衍生化以设计用于若干其他应用的下一代光材料。 Ayitou博士将指导和培训学生使用合成有机化学，计算建模和先进光谱学的工具来实现提出的目标，使他们接触多学科科学。拟议研究的其他教育部分包括推广活动，促进伊利诺伊州的STEM（科学，技术，工程和数学）教育。分子芳香性是一个基本特征，通常用于描述π共轭轮烯。经典的芳香族化合物可以在环境条件下容易地制备和处理以用于各种应用。然而，这些化合物在光激发时变得不稳定，这是由于它们的激发态中的局部/全局共振能量稳定性降低。或者，显示（前）芳香性和/或适应性的π-共辄体系在其光激发态中表现出更大的稳定性，导致有效的ISC以填充三重态歧管。因此，在π共轭的有机发色团中截断局部和全局芳香性将产生具有吸引人的物理性质的新型三重态发色团。利用分子的芳香性来调控三重态光化学可以为自旋化学和三重态光化学/光敏化开辟新的途径。此外，Ayitou博士和他的团队正在研究分子芳香性和自旋轨道耦合在影响三重态光动力学和动力学中的协同作用。在基本层面上，使用先进的物理和计算工具，Ayitou团队的目标是确定所提出的发色团系统是否在其光激发态中表现出截断和/或自适应芳香性。此外，研究小组还将评估结构因素、分子拓扑结构和拟议DPP和DPND中各种取代基的电子性质如何影响其相应的三重态光化学。最终，该项目旨在创建一个纯有机三重态发色团和新型光材料的库，这些材料可以在太阳能转换和生物医学应用中进一步探索。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，被认为值得支持。

With support from the Chemical Structure, Dynamic & Mechanism-B Program of the Chemistry Division, Jean-Luc Ayitou of the Department of Chemistry at the University of Illinois Chicago (UIC) is developing novel pro-aromatic heavy-atom-free organic chromophores viz. diketopyrrolopyrroles (DPP) and dipyrrolonaphthyridine-diones (DPND) which exhibit attractive light-harvesting and photophysical properties. The ultimate goal of this research is to exploit the intrinsic molecular properties such as aromaticity to modulate the photo-behavior and the spin state of the proposed DPP and DPND chromophores, which can be tailored for applications such as triplet photosensitization, photodynamic therapy and solar energy conversion into solar fuels. Moreover, the proposed DPP and DPND chromophores can be further derivatized to engineer next-generation photo-materials for several other applications. Dr. Ayitou will mentor and train students to use the tools of synthetic organic chemistry, computational modeling, and advanced spectroscopy to accomplish the proposed goals to give them exposure to multi-disciplinary science. Additional educational components of the proposed research include outreach activities promoting STEM (science, technology, engineering and mathematics) education across Illinois.Molecular aromaticity is a fundamental characteristic often used to describe pi-conjugated annulenes. Classical aromatic compounds can be easily prepared and handled at ambient conditions for various applications. However, these compounds become unstable upon photoexcitation due to reduced local/global resonance energy stabilization in their excited state. Alternatively, pi-conjugated systems that display (pro)aromaticity and/or adaptivity exhibit greater stabilization in their photo-excited state leading to efficient ISC to populate the triplet manifold. Hence, truncating local and global aromaticity in pi-conjugated organic chromophores would create novel triplet chromophores with attractive photophysical properties. Expectedly, exploiting molecular aromaticity to modulate triplet photochemistry can open new avenues in spin chemistry and triplet photochemistry/photosensitization. Also,Dr. Ayitou and his team are investigating the synergistic role of molecular aromaticity and spin-orbit coupling in impacting triplet photo-dynamics and kinetics in the proposed DPP and DPND systems. At the fundamental level, using advanced photophysical and computational tools, the Ayitou team aims to determine whether the proposed chromophoric systems exhibit truncated and/or adaptive aromaticity in their photo-excited state. Furthermore, the team will assess how structural factors, molecular topology, and the electronic nature of various substituents in the proposed DPP and DPND influence their corresponding triplet photochemistry. Ultimately, this project aims to create a library of purely organic triplet chromophores and novel photo-materials that can be further explored in solar energy conversion and biomedical applications.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.