Reactivity of Solid Rubrene with Potassium: Competition between Intercalation and Molecular Decomposition

Zhang, Jiliang, Whitehead, George FS, Manning, Troy D ORCID: 0000-0002-7624-4306, Stewart, David ORCID: 0000-0001-7281-3850, Hiley, Craig I, Pitcher, Michael J, Jansat, Susanna, Prassides, Kosmas and Rosseinsky, Matthew J ORCID: 0000-0002-1910-2483
(2018) Reactivity of Solid Rubrene with Potassium: Competition between Intercalation and Molecular Decomposition. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 140 (51). pp. 18162-18172.

Access the full-text of this item by clicking on the Open Access link.
[img] Text
K_Rubrene_final_author accepted.DOCX - Author Accepted Manuscript

Download (22MB)


We present the synthesis and characterization of the K<sup>+</sup>-intercalated rubrene (C<sub>42</sub>H<sub>28</sub>) phase, K<sub>2</sub>Rubrene (K<sub>2</sub>R), 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, K<sub>2</sub>R, K(RR*), and K <sub>x</sub>R' (where R* and R' are rubrene decomposition derivatives C<sub>42</sub>H<sub>26</sub> and C<sub>30</sub>H<sub>20</sub>, respectively). K<sub>2</sub>R 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 <sub>x</sub>R' is obtained only as a secondary phase to the majority K<sub>2</sub>R phase. The crystal structure of K<sub>2</sub>R 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<sup>+</sup> is incorporated. K<sup>+</sup> cations accommodated within the large voids interact strongly with the neighboring rubrene via η<sup>6</sup>, η<sup>3</sup>, and η<sup>2</sup> 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<sup>+</sup> weakly interacts with the host. The decomposition products of rubrene are also examined using solution NMR, highlighting the role of the breaking of C-C<sub>phenyl</sub> bonds. For the crystalline decomposition derivative products K(RR*) and K <sub>x</sub>R', 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.

Item Type: Article
Depositing User: Symplectic Admin
Date Deposited: 06 Dec 2018 10:46
Last Modified: 19 Jan 2023 01:09
DOI: 10.1021/jacs.8b11231
Open Access URL:
Related URLs: