Levien Marcel, De Biasi Federico, Karthikeyan Ganesan, Casano Gilles, Visegrádi Máté, Ouari Olivier, Emsley Lyndon
Institut des Sciences et Ingenierie Chimiques, École Polytechnique Fedérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS), Institut de Chimie Radicalaire, 13013 Marseille, France.
J Phys Chem Lett. 2024 Nov 7;15(44):11097-11103. doi: 10.1021/acs.jpclett.4c02805. Epub 2024 Oct 29.
H photochemically induced dynamic nuclear polarization (photo-CIDNP) has recently emerged as a tool to enhance bulk H nuclear magnetic resonance (NMR) signals in solids at magnetic fields ranging from 0.3 to 21.1 T, using synthetic donor-chromophore-acceptor (D-C-A) molecules as optically active polarizing agents (PAs). However, the mechanisms at play for the generation of spin polarization in these systems have not been determined but are essential for an in-depth understanding and further development of the process. Here, we introduce site-selective deuteration to identify the H photo-CIDNP mechanisms at 85 K and 0.3 T in D-C-A molecule PhotoPol. We find that the protons on the acceptor moiety are essential for the generation of polarization, establishing differential relaxation as the main mechanism. These results establish selective deuteration as a tool to identify and suppress polarization transfer mechanisms, which opens up pathways for further optimization of the optical PA at both low and high magnetic fields.
利用合成的供体-发色团-受体（D-C-A）分子作为光学活性极化剂（PA），H光化学诱导动态核极化（光CIDNP）最近已成为一种在0.3至21.1 T磁场范围内增强固体中大量H核磁共振（NMR）信号的工具。然而，这些系统中产生自旋极化的作用机制尚未确定，但对于深入理解该过程并进一步发展至关重要。在这里，我们引入位点选择性氘化，以确定D-C-A分子PhotoPol在85 K和0.3 T下的H光CIDNP机制。我们发现受体部分上的质子对于极化的产生至关重要，确立了差异弛豫作为主要机制。这些结果将选择性氘化确立为一种识别和抑制极化转移机制的工具，这为在低磁场和高磁场下进一步优化光学PA开辟了途径。
