Organic diradicals are uncommon species that have been intensely studied for their unique properties and potential ap-plicability 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 (TTFtt2-) undergoes a thermally induced Fe-centered spin-crossover which yields significant diradical character on TTFtt2-. 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 TTFtt2- π-manifold from the Fe(II)-centered spin-crossover. The TTFtt2- 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 organ-ic diradical character.

中文翻译：

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通过铁基自旋交叉实现有机双自由基特性的可逆转换

有机双自由基是不常见的物种，因其独特的特性和在各种创新领域的潜在适用性而被深入研究。虽然有越来越多的稳定且特征明确的有机双自由基，但最近人们一直关注如何通过外部刺激来控制或调节双自由基特性。在这里，我们证明了由双氧化配体四硫富瓦烯-2,3,6,7-四硫醇 (TTFTt2-) 桥接的二铁络合物经历了热诱导的以 Fe 为中心的自旋交叉，这在 TTFtt2- 上产生了显着的双自由基特征。UV-vis-Near-IR、Mössbauer、NMR 和 EPR 光谱与磁力测定、晶体学和先进的理论处理表明，这种双自由基特征源于 Fe(II) 中心自旋交叉的 TTFTt2-π 流形收缩。根据理论和可变温度 EPR，以 TTFtt2 为中心的双自由基预计具有单线态基态。这种不寻常的现象表明，无机自旋跃迁可用于调节有机双自由基特性。