The reactivity of solid rubrene with potassium: competition between intercalation and molecular decomposition,Journal of the American Chemical Society

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The reactivity of solid rubrene with potassium: competition between intercalation and molecular decomposition
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2018-11-30 , DOI: 10.1021/jacs.8b11231
Jiliang Zhang ₁ , George F. S. Whitehead ₁ , Troy D. Manning ₁ , David Stewart ₁ , Craig I. Hiley ₁ , Michael J. Pitcher ₁ , Susanna Jansat ₁ , Kosmas Prassides _{2,

3} , Matthew J. Rosseinsky ₁

Affiliation

We present the synthesis and characterization of the K+-intercalated rubrene (C42H28) phase, K2Rubrene (K2R), and identify the coexistence of amorphous and crystalline materials in samples where the crystalline component is phase-pure. We suggest this is characteristic of many intercalated alkali metal-polyaromatic hydrocarbon (PAH) systems, including those for which superconductivity has been claimed. The systematic investigation of K-rubrene solid-state reactions using both K and KH sources reveals a complex competition between K intercalation and the decomposition of rubrene, producing three K-intercalated compounds, namely, K2R, K(RR*), and K xR' (where R* and R' are rubrene decomposition derivatives C42H26 and C30H20, respectively). K2R is obtained as the major phase over a wide composition range and is accompanied by the formation of amorphous byproducts from the decomposition of rubrene. K(RR*) is synthesized as a single phase, and K xR' is obtained only as a secondary phase to the majority K2R phase. The crystal structure of K2R was determined using high-resolution powder X-ray diffraction, revealing that the structural rearrangement from pristine rubrene creates two large voids per rubrene within the molecular layers in which K+ is incorporated. K+ cations accommodated within the large voids interact strongly with the neighboring rubrene via η6, η3, and η2 binding modes to the tetracene cores and the phenyl groups. This contrasts with other intercalated PAHs, where only a single void per PAH is created and the intercalated K+ weakly interacts with the host. The decomposition products of rubrene are also examined using solution NMR, highlighting the role of the breaking of C-Cphenyl bonds. For the crystalline decomposition derivative products K(RR*) and K xR', a lack of definitive structural information with regard to R* and R' prevents the crystal structures from being determined. The study illustrates the complexity in accessing solvent-free alkali metal salts of reduced PAH of the type claimed to afford superconductivity.

中文翻译：

固体红荧烯与钾的反应性：嵌入与分子分解之间的竞争

我们介绍了 K+ 插层红荧烯 (C42H28) 相 K2Rubrene (K2R) 的合成和表征，并确定了结晶成分为纯相的样品中无定形和结晶材料的共存。我们认为这是许多插层碱金属-多环芳烃 (PAH) 系统的特征，包括那些声称具有超导性的系统。使用 K 和 KH 源对 K-红荧烯固态反应的系统研究揭示了 K 插层和红荧烯分解之间的复杂竞争，产生了三种 K 插层化合物，即 K2R、K(RR*) 和 K xR '（其中 R* 和 R' 分别是红荧烯分解衍生物 C42H26 和 C30H20）。K2R 是在很宽的组成范围内作为主要相获得的，并且伴随着红荧烯分解形成的无定形副产物。K(RR*) 合成为单相，而 K xR' 仅作为主要 K2R 相的次要相获得。K2R 的晶体结构是使用高分辨率粉末 X 射线衍射确定的，这表明原始红荧烯的结构重排在包含 K+ 的分子层内每个红荧烯产生两个大空隙。容纳在大空隙中的 K+ 阳离子通过与并四苯核和苯基的 η6、η3 和 η2 结合模式与相邻的红荧烯强烈相互作用。这与其他嵌入的 PAH 形成对比，其中每个 PAH 只产生一个空洞，并且嵌入的 K+ 与宿主的相互作用很弱。还使用溶液核磁共振检查了红荧烯的分解产物，突出了 C-C苯基键断裂的作用。对于结晶分解衍生产物 K(RR*) 和 K xR'，由于缺乏关于 R* 和 R' 的明确结构信息，因此无法确定晶体结构。该研究说明了获得声称可提供超导性的还原 PAH 类型的无溶剂碱金属盐的复杂性。

更新日期：2018-11-30

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