International Tomography Center SB RAS, Novosibirsk, 630090, Russia.
Helmholtz-Institut Mainz, Johannes Gutenberg-Universität, 55099, Mainz, Germany.
Sci Rep. 2019 Dec 27;9(1):20161. doi: 10.1038/s41598-019-56734-y.
Long-Lived spin States (LLSs) hold a great promise for sustaining non-thermal spin order and investigating various slow processes by Nuclear Magnetic Resonance (NMR) spectroscopy. Of special interest for such application are molecules containing nearly equivalent magnetic nuclei, which possess LLSs even at high magnetic fields. In this work, we report an LLS in trans-N,N'-azobenzene. The singlet state of the N spin pair exhibits a long-lived character. We solve the challenging problem of generating and detecting this LLS and further increase the LLS population by converting the much higher magnetization of protons into the N singlet spin order. As far as the longevity of this spin order is concerned, various schemes have been tested for sustaining the LLS. Lifetimes of 17 minutes have been achieved at 16.4 T, a value about 250 times longer than the longitudinal relaxation time of N in this magnetic field. We believe that such extended relaxation times, along with the photochromic properties of azobenzene, which changes conformation upon light irradiation and can be hyperpolarized by using parahydrogen, are promising for designing new experiments with photo-switchable long-lived hyperpolarization.
长寿命自旋态 (LLSs) 在通过核磁共振 (NMR) 光谱维持非热自旋有序和研究各种缓慢过程方面具有很大的应用前景。对于此类应用特别感兴趣的是包含几乎等效磁核的分子，即使在强磁场下，这些分子也具有 LLSs。在这项工作中，我们报告了反式-N,N'-偶氮苯中的 LLS。N 自旋对的单重态表现出长寿命的特性。我们解决了生成和检测这种 LLS 的难题，并通过将质子的磁化强度转换为 N 单重自旋有序来进一步增加 LLS 种群。就这种自旋有序的寿命而言，已经测试了各种方案来维持 LLS。在 16.4 T 下实现了 17 分钟的寿命，这比该磁场中 N 的纵向弛豫时间长约 250 倍。我们相信，这种扩展的弛豫时间，以及偶氮苯的光致变色特性，即在光照射下改变构象，并且可以通过使用仲氢进行超极化，对于设计具有光开关长寿命超极化的新实验具有很大的潜力。
