Job/Unit: I40119 /KAP1 Date: 19-03-14 16:55:37 Pages: 9 FULL PAPER DOI:10.1002/ejic.201400119 Isotropic Three-Dimensional Molecular Conductor Based on the Coronene Radical Cation Yukihiro Yoshida,* [a] Mitsuhiko Maesato, [b] Yoshihide Kumagai, [c] Motohiro Mizuno, [c] Kazuhide Isomura, [d] Hideo Kishida, [d] Masanari Izumi, [e] Yoshihiro Kubozono, [e] Akihiro Otsuka, [f] Hideki Yamochi, [f] Gunzi Saito, [a] Kaplan Kirakci, [g] Stéphane Cordier, [h] and Christiane Perrin [h] Keywords: Cluster compounds / Magnetic conductors / Conducting materials / Charge transfer / Solid-state structures In this study, we obtained the first cation radical solid of a highly symmetric (D 6h ) polyaromatic hydrocarbon, coronene, by electrooxidation. The (coronene) 3 Mo 6 Cl 14 salt, which is formed with an O h -symmetric molybdenum cluster unit Mo 6 Cl 14 2– , has an isotropic cubic structure with Pm3 ¯ m sym- metry. The presence of two orientations for the coronene mo- lecules related by an in-plane 90° rotation (merohedral disor- der) allows for fourfold symmetry along the 100 direction. The disorder has dynamic features because 2 H NMR spectro- scopic studies revealed that the coronene molecules undergo an in-plane flipping motion. The observation of two motional sites with significantly different rotational rates (300 Hz and 5 MHz at 103 K) in an approximate 2:1 ratio appears to be Introduction The construction of three-dimensional (3D) molecular assemblies to generate exotic electronic systems has received considerable attention. [1] 3D networks often inhibit low- temperature transitions to charge- or spin-density wave [a] Faculty of Agriculture, Meijo University, Shiogamaguchi 1-501 Tempaku-ku, Nagoya 468-8502, Japan E-mail: yyoshida@meijo-u.ac.jp http://saitolab.meijo-u.ac.jp [b] Division of Chemistry, Graduate School of Science, Kyoto Uni- versity, Sakyo-ku, Kyoto 606-8502, Japan [c] Department of Chemistry, Graduate School of Natural Science & Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan [d] Department of Applied Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan [e] Research Laboratory for Surface Science, Okayama University, Okayama 700-8530, Japan [f] Research Center for Low Temperature and Materials Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan [g] Institute of Inorganic Chemistry of the AS CR, v.v.i, Husinec-r ˇez ˇ 1001, 25068 R ˇ ez ˇ, Czech Republic [h] Institut des Sciences Chimiques de Rennes, UMR CNRS 6226, Université de Rennes 1, Avenue du Général Leclerc, 35042 Rennes cedex, France Eur. J. Inorg. Chem. 0000, 0–0 © 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1 consistent with the splitting of a Raman-active A 1g mode, confirming a random charge-disproportionated state instead of a uniform partially-charged state. The slower- and faster- rotating species are assigned to charge-rich and charge-poor coronenes, respectively, with respect to C–H···Cl hydrogen bonds with neighboring Mo 6 Cl 14 2– cluster units. The electri- cal conductivity of the salt is rather high but is well-described by a three-dimensional (3D) variable-range hopping mecha- nism, which is possibly associated with the random charge disproportionation. These results provide a significant step forward in developing an isotropic 3D π-conducting system composed of planar π-conjugated molecules. ground states, which eliminate the possibility of supercon- ductivity. In addition, 3D assemblies provide important benefits for the exploration of organic magnets, because magnetic ordering is essentially a 3D property. A note- worthy success in this research is alkali-metal-doped full- erides A 3 C 60 (A: alkali metals), in which π-conjugated net- works of spherical C 60 radical anions are responsible for a wide range of 3D electronic properties such as supercon- ductivity and antiferromagnetic ordering. [1a,2] Of particular importance is the triply degenerate LUMO with t 1u sym- metry arising from the high symmetry of the C 60 molecule (I h symmetry), which is kept in the isotropic (cubic) as- sembly owing to the highly symmetric crystal field. This degeneracy plays a crucial role in the relaxation of the Mott criterion (stabilization of the metallic state), [2a,3] and in the enhancement of the density of states at the Fermi level [sta- bilization of the BCS-type superconducting state, i.e., a high critical temperature (T c )]. However, most radical salts inves- tigated so far consist of planar π-conjugated molecules, and the π···π stacking interactions between such molecules gen- erally result in a stacked 1D or 2D assembly instead of an isotropic 3D assembly. [1b] Thus, it is apparent that the ex- ploration of an isotropic 3D π-conducting network on the