A series of bis(TTF) donors containing aromatic linkers between the two TTF units has been synthesized in order to investigate on the electronic structure of the oxidized species from an experimental and theoretical point of view. A mono(TTF)-pyridine compound has been also prepared and characterized by single-crystal X-ray diffraction analysis. Oxidation of a solution of 2,6-bis(TTF)-pyridine (TTF-Pyr-TTF) or of 1,3-bis(TTF)-benzene (TTF-Bz-TTF) in CH2Cl2 with less than 0.1 equivalent of [Cp2Fe][PF6] gives rise to a seven-line EPR spectrum consistent with the hyperfine structure calculated by DFT for the corresponding radical monocation. Increasing the proportion of oxidant leads to a four-line hyperfine structure, similar to the quartet pattern observed after oxidation of mono(TTF)-pyridine (Pyr-TTF) or mono(TTF)-benzene (Bz-TTF). In good accordance with the very weak value of J calculated by DFT for the dicationic biradicals these four-line spectra are attributed to [2,6-bis(TTF)-pyridine]2+ and [1,3-bis(TTF)-benzene]2+. Similar experimental results are obtained for 1,4-bis(TTF)-benzene. In this case, however, electrochemical oxidation leads to the monoradical at low potential and to the diradical at higher potential, while only the diradical could be observed by electrochemical oxidation of 2,6-bis(TTF)-pyridine or of 1,3-bis(TTF)-benzene.
为了从实验和理论角度研究氧化物的电子结构,我们合成了一系列在两个
TTF 单元之间含有芳香族连接体的双(
TTF)供体。此外,还制备了单(
TTF)-
吡啶化合物,并通过单晶 X 射线衍射分析对其进行了表征。用小于 0.1 等量的[Cp2Fe][PF6]氧化 2,6-双(
TTF)-
吡啶(
TTF-Pyr-
TTF)或 1,3-双(
TTF)-苯(
TTF-Bz-
TTF)在
CH2Cl2 中的溶液,会产生七线 EPR 光谱,与 DFT 计算出的相应自由基一元化超线性结构一致。增加氧化剂的比例会产生四线超正弦结构,这与单(
TTF)-
吡啶(Pyr-
TTF)或单(
TTF)-苯(Bz-
TTF)氧化后观察到的四元组模式相似。根据 DFT 计算得出的双阳离子双鞭烷的极弱 J 值,这些四线光谱可归因于[2,6-双(
TTF)-
吡啶]2+ 和[1,3-双(
TTF)-苯]2+。1,4-双(
TTF)-苯也得到了类似的实验结果。不过,在这种情况下,电
化学氧化在低电位时产生单二极体,在高电位时产生二极体,而 2,6-双(
TTF)-
吡啶或 1,3-双(
TTF)-苯的电
化学氧化只能观察到二极体。