Crystal Structure and Stoichiometric Composition of Potassium-Intercalated Tetracene

[Image: see text] 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.