Kawamura Airi, Xie Jiaze, Boyn Jan-Niklas, Jesse Kate A, McNeece Andrew J, Hill Ethan A, Collins Kelsey A, Valdez-Moreira Juan A, Filatov Alexander S, Kurutz Josh W, Mazziotti David A, Anderson John S
Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States.
Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
J Am Chem Soc. 2020 Oct 14;142(41):17670-17680. doi: 10.1021/jacs.0c08307. Epub 2020 Oct 2.
Organic diradicals are uncommon species that have been intensely studied for their unique properties and potential applicability in a diverse range of innovative fields. While there is a growing class of stable and well-characterized organic diradicals, there has been recent focus on how diradical character can be controlled or modulated with external stimuli. Here we demonstrate that a diiron complex bridged by the doubly oxidized ligand tetrathiafulvalene-2,3,6,7-tetrathiolate (TTFtt) undergoes a thermally induced Fe-centered spin-crossover which yields significant diradical character on TTFtt. UV-vis-near-IR, Mössbauer, NMR, and EPR spectroscopies with magnetometry, crystallography, and advanced theoretical treatments suggest that this diradical character arises from a shrinking TTFtt π-manifold from the Fe(II)-centered spin-crossover. The TTFtt-centered diradical is predicted to have a singlet ground state by theory and variable temperature EPR. This unusual phenomenon demonstrates that inorganic spin transitions can be used to modulate organic diradical character.
有机双自由基是一类罕见的物种，因其独特的性质以及在众多创新领域的潜在应用价值而受到广泛深入的研究。尽管目前已经有越来越多稳定且特征明确的有机双自由基，但近期的研究重点在于如何通过外部刺激来控制或调节双自由基的特性。在此，我们证明了一种由双氧化配体四硫富瓦烯 - 2,3,6,7 - 四硫醇盐（TTFtt）桥联的二铁配合物会发生热诱导的以铁为中心的自旋交叉，从而在TTFtt上产生显著的双自由基特性。紫外 - 可见 - 近红外光谱、穆斯堡尔谱、核磁共振谱和电子顺磁共振谱结合磁力测定、晶体学以及先进的理论处理表明，这种双自由基特性源于以Fe(II)为中心的自旋交叉导致TTFtt π - 流形的收缩。理论计算和变温电子顺磁共振预测以TTFtt为中心的双自由基具有单重基态。这一不同寻常的现象表明无机自旋转变可用于调节有机双自由基特性。
