Crystal Structure and Stoichiometric Composition of Potassium-Intercalated Tetracene.

The products of the solid-state reactions between potassium metal and tetracene (K:Tetracene, 1:1, 1.5:1, and 2:1) are fully structurally characterized. Synchrotron X-ray powder diffraction shows that only K ₂ Tetracene forms under the reaction conditions studied, with unreacted tetracene always present for x < 2. Diffraction and ¹³ C MAS NMR show that K ₂ Tetracene has a crystal structure that is analogous to that of K ₂ Pentacene, but with the cations ordered on two sites because of the influence of the length of the hydrocarbon on possible cation positions. K ₂ Tetracene is a nonmagnetic insulator, thus further questioning the nature of reported superconductivity in this class of materials.