Intramolecular electron arrangement with a rotative trigger.
Intramolecular electron arrangement with a rotative trigger.
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DOI：
10.1021/ja906684g
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发表时间：
2009-09
影响因子：
15
通讯作者：
S. Kume;Kuniharu Nomoto;Tetsuro Kusamoto;H. Nishihara
中科院分区：
文献类型：
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作者：
S. Kume;Kuniharu Nomoto;Tetsuro Kusamoto;H. Nishihara
我们构建了一个由二茂铁-铜络合物组成的单分子体系，其中氧化还原中心之间的电子转移是由分子的旋转运动触发的。在该化合物中，一个不对称的甲基取代的2，2‘-吡啶嘧啶配体与二茂铁部分相连，在铜中心周围有两个异构环-反转配位构象。用X-射线单晶衍射法对两种异构体的结构进行了表征。(1)核磁共振氢谱和电化学测量表明，这些异构体在室温下通过嘧啶的旋转相互转化，但在溶液状态下，该过程冻结在233K以下。这两个异构体经历不同的氧化还原过程，第一氧化中心在铜中心和二茂铁之间交替，EPR和UV-Vis吸收光谱监测的化学氧化证实了这一点。化合物的氧化导致嘧啶的自发异构化，这是由于异构体在单价态和二价态的相对稳定性不同。在低温下处于静止状态的氧化从二茂铁中心提取第一电子。当升温释放分子运动时，电子从铜中心移动到二茂铁，导致EPR谱中铜(II)信号的增强。观察到同步运动/电子迁移过程是一步UV-Vis吸收光谱转换过程。
We have constructed a single molecule system, consisting of a ferrocene-tethered copper complex, in which electron transfer between redox centers is triggered by molecular rotational motion. In the compound, an asymmetric methyl-substituted 2,2'-pyridylpyrimidine ligand, tethered to the ferrocene moiety, has two isomeric ring-inversion coordination conformations around the copper center. Both isomeric structures were characterized by X-ray crystallography. (1)H NMR and electrochemical measurements revealed that these isomers interconvert through rotation of the pyrimidine at room temperature, but the process is frozen below 233 K in the solution state. The two isomers undergo different redox processes, and the identity of the first oxidation center alternates between the copper center and ferrocene, as confirmed by chemical oxidation monitored by EPR and UV-vis absorption spectroscopy. Oxidation of the compound causes spontaneous isomerization of the pyrimidine due to the different relative stabilities of the isomers in the monovalent and divalent states. Oxidation in the motionless state at low temperatures extracts the first electron from the ferrocene center. When molecular motion is released by warming, the electron moves from the copper center to the ferrocene, leading to an enhancement of the copper(II) signal in the EPR spectrum. The synchronized motion/electron migration process was observed as a one-step UV-vis absorption spectral conversion.