Nishimura Koki, Yabuki Reiya, Hamachi Tomoyuki, Kimizuka Nobuo, Tateishi Kenichiro, Uesaka Tomohiro, Yanai Nobuhiro
Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka819-0395, Japan.
Cluster for Pioneering Research, RIKEN, RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama351-0198, Japan.
J Phys Chem B. 2023 Feb 9;127(5):1219-1228. doi: 10.1021/acs.jpcb.2c07936. Epub 2023 Jan 30.
Dynamic electron polarization (DEP), induced by quenching of photoexcited species by stable radicals, can hyperpolarize electron spins in solution at room temperature. Recently, development of technologies based on electron spin polarization such as dynamic nuclear polarization (DNP) has been progressing, where it is important to design molecules that achieve long-lasting DEP in addition to high DEP. Hybridization by linking dyes and radicals is a promising approach for efficient DEP, but strong interactions between neighboring dyes and radicals often result in the rapid decay of DEP. In this study, we introduce a flexible linker into the hybrid system of porphyrin and TEMPO to achieve both efficient DEP and long-lasting DEP. The structural flexibility of the linker switches the interaction between the radical and the triplet, which promotes the DEP process by bringing the radical and the triplet into close proximity, while avoiding abrupt relaxation due to strong interactions. As a result, the new hybridized system exhibits a larger DEP than the unlinked system, while at the same time achieving a DEP lasting more than 10 μs.
由稳定自由基猝灭光激发物种所诱导的动态电子极化（DEP），可在室温下使溶液中的电子自旋超极化。最近，基于电子自旋极化的技术如动态核极化（DNP）不断发展，在此过程中，设计出除了具有高DEP之外还能实现持久DEP的分子至关重要。通过连接染料和自由基进行杂交是实现高效DEP的一种有前途的方法，但相邻染料和自由基之间的强相互作用往往会导致DEP迅速衰减。在本研究中，我们将一个柔性连接体引入卟啉与TEMPO的杂交体系中，以实现高效DEP和持久DEP。连接体的结构柔性改变了自由基与三重态之间的相互作用，通过使自由基和三重态紧密靠近来促进DEP过程，同时避免因强相互作用导致的突然弛豫。结果，新的杂交体系比未连接的体系表现出更大的DEP，同时实现了持续超过10微秒的DEP。
