Nuclear Magnetic Resonance Investigation of Possible Molecular Motion in Coronene, Perlene, and Triphenlene in the Solid State

Fyfe, C. A.; Dunell, B. A.; Rimeester, J.

doi:10.1139/v71-554

Cited by 24 publications

(12 citation statements)

References 5 publications

(5 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Activation energy ( E a ) was estimated by using spin‐lattice relaxation time ( T 1 ) data above 273 K, because the magnetization recovery process at these temperatures could be analyzed by assuming a single component. The E a value of 15 kJ mol –1 (155 meV) is smaller than the values for (coronene)(TCNQ) (17–20 kJ mol –1 )5 and pristine coronene (25 kJ mol –1 in ref 30. and 27 kJ mol –1 by our group), and is comparable to that of (coronene) 3 (TCNQ) (14 kJ mol –1 ) 5…”

Section: Resultscontrasting

confidence: 42%

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

et al. 2014

View full text Add to dashboard Cite

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.

show abstract

Section: Resultscontrasting

confidence: 42%

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

et al. 2014

View full text Add to dashboard Cite

show abstract

“…These results indicate that the coronene molecules in crystals of 3 undergo orientational interconversion through in-plane reorientation and that only the energetically favorable orientations (A and B) are present at low temperatures. Similar motions of coronene molecules have been previously reported for single-component crystals and CT crystals with several acceptor molecules. − …”

Section: Resultssupporting

confidence: 84%

Crystals of Charge-Transfer Complexes with Reorienting Polar Molecules: Dielectric Properties and Order–Disorder Phase Transitions

Harada

Yoneyama

Sato

et al. 2018

Crystal Growth & Design

View full text Add to dashboard Cite

Crystals of charge-transfer (CT) complexes were synthesized using the polar molecule tetrachlorophthalonitrile (TCPN) as the electron acceptor and nonpolar aromatic hydrocarbons, such as perylene, coronene, chrysene, and pyrene, as the electron donors. Variable-temperature X-ray crystal structure analyses revealed that the TCPN molecules in all the CT crystals exhibit orientational disorder at room temperature. Some of the CT crystals undergo an order−disorder-type phase transition upon cooling, where the orientation of the TCPN molecules becomes ordered at low temperature. The CT crystals show large dielectric constants at room temperature arising from in-plane reorientation of the polar TCPN molecules. The order−disorder phase transition results in a drastic reduction of the dielectric constant of the CT crystals upon cooling. This study demonstrates that the formation of CT crystals from polar molecules represents a promising method for the development of dielectric crystalline materials, whose properties vary significantly in response to phase transitions.

show abstract

“…The complex [D] 5 b , with a T 1 minimum at 180 K, has an E a of 13.7 kJ mol −1 ( T >180 K), and the reason for [D] 5 b to have a smaller E a value than [D] 5 a must be the same as for the difference in temperatures at which the coronenes start to rotate. Both E a values are significantly lower than that for the in‐plane rotation of coronenes in crystalline coronene;14a namely, the complexation with TCNQ reduces the rotational barrier. This feature is more highlighted when compared with the case of the pyrene system.…”

Section: Resultsmentioning

confidence: 90%

Molecular Rotors of Coronene in Charge‐Transfer Solids

Yoshida

Shimizu

Yajima

et al. 2013

Chemistry A European J

View full text Add to dashboard Cite

Ten types of neutral charge transfer (CT) complexes of coronene (electron donor; D) were obtained with various electron acceptors (A). In addition to the reported 7,7,8,8-tetracyanoquinodimethane (TCNQ) complex of 1:1 stoichiometry with a DA-type alternating π column, TCNQ also afforded a 3:1 complex, in which a face-to-face dimer of parallel coronenes (Cor-As) is sandwiched between TCNQs to construct a DDA-type alternating π column flanked by another coronene (Cor-B). Whereas solid-state (2)H NMR spectra of the 1:1 TCNQ complex formed with deuterated coronene confirmed the single in-plane 6-fold flipping motion of the coronenes, two unsynchronized motions were confirmed for the 3:1 TCNQ complex, which is consistent with a crystallographic study. Neutral [Ni(mnt)2] (mnt: maleonitriledithiolate) as an electron acceptor afforded a 5:2 complex with a DDA-type alternating π column flanked by another coronene, similar to the 3:1 TCNQ complex. The fact that the Cor-As in the [Ni(mnt)2] complex arrange in a non-parallel fashion must cause the fast in-plane rotation of Cor-A relative to that of Cor-B. This is in sharp contrast to the 3:1 TCNQ complex, in which the dimer of parallel Cor-As shows inter-column interactions with neighboring Cor-As. The solid-state (1)H NMR signal of the [Ni(mnt)2] complex suddenly broadens at temperatures below approximately 60 K, indicating that the in-plane rotation of the coronenes undergoes down to approximately 60 K; the rotational rate reaches the gigahertz regime at room temperature. Rotational barriers of these CT complexes, as estimated from variable-temperature spin-lattice relaxation time (T1) experiments, are significantly lower than that of pristine coronene. The investigated structure-property relationships indicate that the complexation not only facilitates the molecular rotation of coronenes but also provides a new solid-state rotor system that involves unsynchronized plural rotators.

show abstract

Nuclear Magnetic Resonance Investigation of Possible Molecular Motion in Coronene, Perlene, and Triphenlene in the Solid State

Cited by 24 publications

References 5 publications

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

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

Crystals of Charge-Transfer Complexes with Reorienting Polar Molecules: Dielectric Properties and Order–Disorder Phase Transitions

Molecular Rotors of Coronene in Charge‐Transfer Solids

Contact Info

Product

Resources

About