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

Abstract

In this study, we obtained the first cation radical solid of a highly symmetric (D6h) polyaromatic hydrocarbon, coronene, by electrooxidation. The (coronene)3Mo6Cl14 salt, which is formed with an Oh‐symmetric molybdenum cluster unit Mo6Cl142–, has an isotropic cubic structure with Pm$\bar {3}$m symmetry. The presence of two orientations for the coronene molecules related by an in‐plane 90° rotation (merohedral disorder) allows for fourfold symmetry along the <100> direction. The disorder has dynamic features because 2H 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 A1g 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 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 π‐conducting system composed of planar π‐conjugated molecules.

Conducting π Columns of Highly Symmetric Coronene, The Smallest Fragment of Graphene

“…Previously, we reported that the Raman‐active A 1g mode is sensitive to the charge state of coronene molecules, and, therefore, the splitting of the band observed for (coronene) 3 Mo 6 Cl 14 ( 3 ) is indicative of charge disproportionation (Figure ; see Figure S3 in the Supporting Information for spectra over a wider range) . In contrast, the A 1g band at 1373 cm −1 for 2 is well‐fitted by a single Lorentzian function, which strongly indicates uniform charge on A and B .…”

“…To date, structurally refined coronene anion salts formed with Na(dimethoxyethane) 3 + , K(tetrahydrofuran) 2 ( N , N , N ′, N ′‐tetramethylethylenediamine) +[29] and Rb(18‐crown‐6) +[30] have been obtained by alkali‐metal doping in solution, in which the coronene molecules coordinate to the alkali‐metal ions or ligands instead of assembling into π columns. On the other hand, our group recently reported the first coronene cation salts, (coronene) 3 Mo 6 X 14 (X=Cl, Br), obtained by the electro‐oxidation of coronene in the presence of molybdenum halide cluster dianions (Mo 6 X 14 2− ) in solution . However, the salts have a three‐dimensional (3D) anti‐perovskite structure, in which there are no face‐to‐face π–π interactions between adjacent cationic coronene molecules.…”

Improved Dynamic Properties of Charge-Transfer-Type Supramolecular Rotor Composed of Coronene and F4TCNQ

“…It is worth mentioning that investigation of the arrangement patterns of electron-donating/accepting rotator molecules suitable for reducing the rotational barrier would encourage the rational design of CT-type supramolecular rotors. [1][2][3][4][13][14][15][16][17][18][19]36,39 In particular, the present results strongly suggest the possibility of controlling dynamic properties over a wide range by intermolecular interactions. By extrapolating the Arrhenius law to higher temperatures, it is likely that the molecular rotation of coronene in 2 should occur with a frequency as high as ca.…”

“…300 MHz for slower species and ca. 2.6 GHz for faster species at 233 K), 36 were found to be one of the fastest rotators in the coronene-based CT complexes with alternating columns. This confirms the importance of molecular arrangement or intermolecular interactions, i.e., C−H···N and C−H···F hydrogen bonds with adjacent F 4 TCNQ molecules along the side-byside direction and π−π interactions with adjacent coronene and F 4 TCNQ molecules along the stacking direction, in determining dynamic properties.…”

Supramolecular Frameworks Built up from Red‐Phosphor­escent trans‐Re6 Cluster Building Blocks: One Pot Synthesis, Crystal Structures, and DFT Investigations

“…[1][2][3][4] Beyond carrying specific luminescence, sensitization, catalytic and photo-catalytic properties, they could be involved in the material structuration by self-assembling of organic cationic frameworks [5] in charge transfer salts thanks to their ability to form hydrogen bonding. Indeed, many molecular assemblies and nanomaterials built up from M 6 clusters carriers of original chemical and physical properties [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] or as structuring moieties have been reported these last years.…”