Isotropic Three-Dimensional Molecular Conductor Based on the Coronene Radical Cation

0438681 - ÚACH 2015 RIV DE eng J - Journal Article
Yoshida, Y. - Maesato, M. - Kumagai, Y. - Mizuno, M. - Isomura, K. - Kishida, H. - Izumi, M. - Kubozono, Y. - Otsuka, A. - Yamochi, H. - Saito, G. - Kirakci, Kaplan - Cordier, S. - Perrin, Ch.
Isotropic Three-Dimensional Molecular Conductor Based on the Coronene Radical Cation.
European Journal of Inorganic Chemistry. -, č. 24 (2014), s. 3871-3878. ISSN 1434-1948. E-ISSN 1099-0682
R&D Projects: GA ČR GA13-05114S
Institutional support: RVO:61388980
Keywords : Cluster compounds * Magnetic properties * Conducting materials * Charge transfer * Solid-state structures
Subject RIV: CA - Inorganic Chemistry
Impact factor: 2.942, year: 2014

In this study, we obtained the first cation radical solid of a highly symmetric (D-6h) polyaromatic hydrocarbon, coronene, by electrooxidation. The (coronene)(3)Mo6Cl14 salt, which is formed with an O-h-symmetric molybdenum cluster unit Mo6Cl142-, has an isotropic cubic structure with Pm (3) over barm symmetry. The presence of two orientations for the coronene molecules related by an in-plane 90 degrees rotation (merohedral disorder) allows for fourfold symmetry along the 100 direction. The disorder has dynamic features because H-2 NMR spectroscopic 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 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 center dot center dot center dot Cl hydrogen bonds with neighboring Mo6Cl142- cluster units. The electrical conductivity of the salt is rather high but is well-described by a three-dimensional (3D) variable-range hopping mechanism, which is possibly associated with the random charge disproportionation. These results provide a significant step forward in developing an isotropic 3D pi-conducting system composed of planar pi-conjugated molecules.
Permanent Link: http://hdl.handle.net/11104/0242091