Design Guidelines to Elongate Spin-Lattice Relaxation Times of Porphyrins with Large Triplet Electron Polarization
Design Guidelines to Elongate Spin-Lattice Relaxation Times of Porphyrins with Large Triplet Electron Polarization
复制标题
延长具有大三重态电子极化的卟啉自旋晶格弛豫时间的设计指南
DOI：
10.1021/acs.jpca.1c01839
复制
发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Yanai Nobuhiro
中科院分区：
文献类型：
--
作者：
Yamauchi Akio;Fujiwara Saiya;Nishimura Koki;Sasaki Yoichi;Tateishi Kenichiro;Uesaka Tomohiro;Kimizuka Nobuo;Yanai Nobuhiro
光辐照产生的自旋偏振三重态在三重态动态核极化(Triplet-DNP)等方面具有潜在的应用前景。最近，我们报道了游离碱卟啉作为生物相容的多功能偏振剂用于三重态DNP。然而，自由基卟啉的电子极化不是很高，而难题是金属卟啉的高极化伴随着太短的自旋晶格弛豫时间，不能用于三重态DNP。我们在这里报道了在锌卟啉中引入吸电子的氟基团使得在室温下保持较高的极化(Px：Py：Pz=0：0：1)的同时，有足够长的自旋-晶格弛豫时间(>；1μS)。有趣的是，锌卟啉的自旋晶格驰豫时间随着氟取代基的引入而变长，而游离基卟啉的自旋晶格驰豫时间随着氟取代基的引入而变短。理论计算表明，这是因为吸电子氟取代基的引入降低了锌原子的自旋密度，削弱了自旋-轨道相互作用。
The spin-polarized triplet state generated by light irradiation has potential for applications such as triplet dynamic nuclear polarization (triplet-DNP). Recently, we have reported free-base porphyrins as versatile and biocompatible polarizing agents for triplet-DNP. However, the electron polarization of free-base porphyrins is not very high, and the dilemma is that the high polarization of metalloporphyrins is accompanied by a too short spin–lattice relaxation time to be used for triplet-DNP. We report here that the introduction of electron-withdrawing fluorine groups into Zn porphyrins enables a long enough spin–lattice relaxation time (>1 μs) while maintaining a high polarization (Px:Py:Pz= 0:0:1.0) at room temperature. Interestingly, the spin–lattice relaxation time of Zn porphyrin becomes much longer by introducing fluorine substituents, whereas the spin–lattice relaxation time of free-base porphyrin becomes shorter by the fluorine substitution. Theoretical calculations suggest that this is because the introduction of the electron-withdrawing fluorine substituents reduces the spin density on Zn atoms and weakens the spin–orbit interaction.