Observation of Proton Transfer Coupled Spin Transition and Trapping of Photoinduced Metastable Proton Transfer State in an Fe(II) Complex.
Observation of Proton Transfer Coupled Spin Transition and Trapping of Photoinduced Metastable Proton Transfer State in an Fe(II) Complex.
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DOI：
10.1021/jacs.9b07204
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发表时间：
2019-08
影响因子：
15
通讯作者：
Takumi Nakanishi;Y. Hori;Hiroyasu Sato;Shu-Qi Wu;A. Okazawa;N. Kojima;Takashi Yamamoto;Y. Einaga
中科院分区：
文献类型：
--
作者：
Takumi Nakanishi;Y. Hori;Hiroyasu Sato;Shu-Qi Wu;A. Okazawa;N. Kojima;Takashi Yamamoto;Y. Einaga
实现新的基于电子和/或质子的功能的一个重要技术是使用质子-电子耦合机制。当一个质子或电子被激发时，另一个被调制，产生协同作用。然而，尽管已经合成了具有质子耦合电子转移的化合物，但表现出质子转移耦合自旋跃迁(PCST)行为的晶体分子化合物尚未见报道。在这里，我们报道了第一个PCST Fe(II)络合物的例子，其中质子位于高自旋和低自旋Fe(II)的配体中的肼和吡啶部分的N上。当Fe(II)络合物受光照射时，分子内质子从吡啶转移到肼并通过PCST机制发生光致自旋转变。由于光致激发的高自旋态在低温下被捕获在Fe(II)络合物中--这一现象被称为光致激发自旋态陷阱效应--光致质子转移态也被捕获为亚稳态。在190K下，质子转移在50ps内完成。质子位置的双稳态性质，可以通过光照射来切换位置，对于分子器件中基于质子的功能的调制是有用的。
An important technique to realize novel electron- and/or proton-based functionalities is to use a proton-electron coupling mechanism. When either a proton or electron is excited, the other one is modulated, producing synergistic functions. Howev-er, although compounds with proton-coupled electron transfer have been synthesized, crystalline molecular compounds that exhibit proton-transfer-coupled spin-transition (PCST) behavior have not been reported. Here, we report the first example of a PCST Fe(II) complex, wherein the proton lies on the N of hydrazone and pyridine moieties in the ligand at high-spin and low-spin Fe(II), respectively. When the Fe(II) complex is irradiated with light, intramolecular proton transfer occurs from pyridine to hydrazone in conjunction with the photoinduced spin transition via the PCST mechanism. Because the light-induced excited high-spin state is trapped at low temperatures in the Fe(II) complex-a phenomenon known as the light-induced excited-spin-state trapping effect-the light-induced proton-transfer state, wherein the proton lies on the N of hy-drazone, is also trapped as a metastable state. The proton transfer was accomplished within 50 ps at 190 K. The bistable nature of the proton position, where the position can be switched by light irradiation, is useful for modulating proton-based functionalities in molecular devices.