A general strategy towards efficient hyperpolarization in high-field magnetic resonance using mixed-valence compounds

动态核极化(DNP)是一种强有力的方法，它可以极大地增强核磁共振和磁共振成像中的信号强度，使其在生命和材料科学中得到前所未有的应用。最终的科学目标是将DNP的使用扩展到集成了最佳光谱分辨率和灵敏度的超高磁场。虽然在构建在超高磁场下工作的DNP-核磁共振仪器方面已经取得了相当大的进展，但到目前为止，设计在这种条件下最佳工作的偏振剂一直是具有挑战性的。因此，迫切需要研究能够在高场中显著增强DNP的新自由基。最近，所谓的欧豪瑟效应已经成为克服这些挑战的一个有趣的焦点。首先，与之前的预期相反，这种效应被证明发生在玻璃绝缘基质中，这将是核磁共振/核磁共振实际应用所必需的。其次，实验和理论相结合的方法对绝缘固体中的Overhaser效应进行了系统和广泛的研究。在此之前，我已经用从头算方法研究过BDPA自由基。我的发现将这种自由基归入了一大组混合价化合物，也被称为Jahn-Teller系统。在初步计算中，我已经确定了几个新的分子，它们的性质与所研究的自由基相似。合成了一些分子，并在实验上证明了绝缘基质中的Overhaser效应。这些结果为优化它们的分子性质(包括电子转移速率、电荷和周围溶剂)奠定了基础，目标是开发一种在超高磁场下最佳运行的新型强大的DNP试剂。

Dynamic nuclear polarization (DNP) is a powerful method that greatly enhances signal intensities in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) enabling unprecedented applications in life and material science. The ultimate scientific goal is to expand the use of DNP to ultra-high magnetic fields where optimal spectral resolution and sensitivity are integrated. While considerable progress has been made in constructing DNP-NMR instruments operating at ultra-high magnetic fields, designing polarizing agents that optimally perform under such conditions has thus far been challenging. The investigation of new radicals that allow for significant DNP enhancements in high fields is therefore urgently needed. Recently, the so called Overhauser effect has become an interesting focus to overcome these challenges. Firstly, in contrast to previous expectations, the effect was demonstrated to occur in glassy insulating matrices which would be required for practical applications in NMR/MRI. Secondly, the effect was shown to scale favorably with static magnetic field strength.Here I propose to systematically and broadly investigate the Overhauser effect in insulating solids by combination of experimental and theoretical techniques. Previously, I have examined the BDPA radical by ab initio methods. My findings put this radical into a larger group of mixed-valence compounds, also known as Jahn-Teller systems. In preliminary calculations, I have identified several new molecules that have properties similar to the studied radical. Some of the molecules were synthesized, and have experimentally demonstrated Overhauser effect DNP in insulating matrix . These results set the stage for optimization of their molecular properties including the electron transfer rate, charge, and the surrounding solvent with the goal to develop a novel class of powerful DNP agents that optimally perform at ultra-high magnetic fields.