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<p>Polarized electron spins in photoexcited triplet states enable dynamic nuclear polarization (DNP) to enhance magnetic resonance imaging (MRI) sensitivity. For a practical nuclear polarization of 10%, single crystals must be precisely oriented in a magnetic field to generate narrow electron spin resonance lines, which is not appropriate for actual medical applications. Here, substituted fullerenes as triplet polarizing agents enable <sup>1</sup>H polarizations above 10%, even for random molecular orientations. While they have not been used as polarizing agents for triplet-DNP because of electron spin relaxation via pseudo-rotation, we overcome this by chemical modification of two sites on C<sub>60</sub> fullerenes. Symmetry considerations reveal fullerenes that avoided pseudo-rotations. Di-substituted fullerenes are ideal polarizing agents with sharp linewidths and long relaxation times that enabled 14.2% <sup>1</sup>H polarization in randomly oriented orientations. Optimized polarizing agents represent a promising approach for ultra-sensitive MRI medical diagnostics without the need for DNP under cryogenic temperatures and severe orientation control.</p>

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Substituted Fullerenes for Enhanced Optical Nuclear Hyperpolarization in Random Orientations

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月4日

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  • Keita Sakamoto,
  • Katsuki Miyokawa,
  • Tomoyuki Hamachi,
  • Haoxuan Zhang,
  • Jiarui Song,
  • Kenichiro Tateishi,
  • Tomohiro Uesaka,
  • Hiroshi Imahori,
  • Yasuhiro Kobori,
  • Yuki Kurashige,
  • Nobuhiro Yanai

摘要

Polarized electron spins in photoexcited triplet states enable dynamic nuclear polarization (DNP) to enhance magnetic resonance imaging (MRI) sensitivity. For a practical nuclear polarization of 10%, single crystals must be precisely oriented in a magnetic field to generate narrow electron spin resonance lines, which is not appropriate for actual medical applications. Here, substituted fullerenes as triplet polarizing agents enable 1H polarizations above 10%, even for random molecular orientations. While they have not been used as polarizing agents for triplet-DNP because of electron spin relaxation via pseudo-rotation, we overcome this by chemical modification of two sites on C60 fullerenes. Symmetry considerations reveal fullerenes that avoided pseudo-rotations. Di-substituted fullerenes are ideal polarizing agents with sharp linewidths and long relaxation times that enabled 14.2% 1H polarization in randomly oriented orientations. Optimized polarizing agents represent a promising approach for ultra-sensitive MRI medical diagnostics without the need for DNP under cryogenic temperatures and severe orientation control.