Nitrogen Centered Radicals

在这个由化学系化学结构、动力学和机理B计划资助的项目中，内布拉斯加州大学林肯分校化学系的Andrzej博士和S Rajca博士研究了有机自由基，即具有单个未配对电子的分子结构。这些新的自由基化合物与新的磁性、电子和光学技术的发展有关。含有自由基的化合物通常是不稳定的物种，很容易与其他分子反应。本研究的目标是设计、合成和表征具有非常规磁性的稳定的含自由基分子。这些新的结果和见解可能提供对有机分子结构和性质关系的基本理解，同时推动新材料的开发。这种材料可用作磁共振成像(MRI)的造影剂和核磁共振(核磁共振)光谱的弛豫增强剂。该材料还可用作自旋电子学和其他应用的有机自旋滤光器。研究活动包括多步有机合成，有机分子的不同物理/材料表征，以及高水平计算。这项研究为学生提供了获得广泛教育和发展广泛技能的机会。这个项目的具体目标是合成和研究健壮的高自旋氮中心自由基。这些包括：基于四唑基衍生物的二、三自由基和双螺旋pi-体系的二自由基和三自由基。四唑基团具有在超高真空下蒸发制备薄膜的性能。预测了双螺旋氮心高自旋双自由基和三自由基在室温下具有很强的顺磁性，但在室温下是稳定的。这些都可能为高自旋多自由基阳离子提供未来的构建单元。双螺旋pi-体系的氮心高自旋双自由基化合物的手性强度与[n]螺烯相当。由于手性和离域电子自旋的结合，强顺磁性和双螺旋pi系统的结合可能会产生独特的性质。这为开发具有强手性的新型顺磁材料提供了一条途径，可以促进发现新的有机磁光材料和器件，包括用于自旋电子学的高效有机自旋滤光器。这些自由基是用现代有机合成方法制备的，包括最新发展的自由基-自由基交叉偶联，并用电子顺磁共振(EPR)光谱、超导量子干涉装置(SQUID)磁测量以及计算进行了表征。这项研究为学生提供了发展广泛专业技能的机会。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。

In this project funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Drs. Andrzej and S Rajca of the Department of Chemistry at the University of Nebraska-Lincoln investigate organic radicals, molecular structures with a single unpaired electron. These new radical compounds are relevant to the development of novel magnetic, electronic, and optical technologies. Radical-containing compounds usually are unstable species, easily reacting with other molecules. The goal of this research is the design, synthesis, and characterization of stable radical-containing molecules which have unconventional magnetic properties. The new results and insights may provide fundamental understanding of structure and property relationships for organic molecules while advancing the development of new materials. Such materials may serve as contrast agents for magnetic resonance imaging (MRI) and relaxation enhancement agents for nuclear magnetic resonance (NMR) spectroscopy. The materials may also serve as organic spin filters for spintronics, and other applications. The research activities comprise multi-step organic synthesis, diverse physical/materials characterization of organic molecules, and high level computations. This research provides students with opportunities to gain a broad education as well as to develop a wide range of skills. Specific objectives of this project are the synthesis and study of robust high-spin nitrogen-centered radicals. These include: di- and tri-radicals based on tetrazolinyl radical derivatives and diradical dications and triradical trications of double helical pi-systems. The tetrazolinyl radicals possess properties for thin film fabrication by evaporation under ultra-high vacuum. The double helical nitrogen-centered high-spin diradical dications and triradical trications are predicted to be strongly paramagnetic but stable at room temperature. These may provide future building blocks for high-spin polyradical cations. The strength of chiroptical properties of nitrogen-centered high-spin diradical dications of double helical pi-system is comparable to those of [n]helicenes. The combination of strong paramagnetism with double helical pi-systems may render unique properties due to the combination of chirality and delocalized electronic spin. This provides an avenue for development of novel paramagnetic materials with strong chiral properties that could facilitate discovery of new organic magneto-optic materials and devices, including efficient organic spin filters for spintronics. The radicals are prepared by modern organic synthetic methodologies, including newly developed radical-radical cross-couplings, and characterized by electron paramagnetic resonance (EPR) spectroscopy, superconducting quantum interference device (SQUID) magnetometry, as well as computations. This research provides opportunities for students to develop a wide range of professional skills.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.