On the Nature of the 5,10-Dimethyl-5,10-dihydrophenazine–Tetracyanoquinodimethane

Fujita, Isao; Matsunaga, Yoshio

doi:10.1246/bcsj.53.267

Cited by 11 publications

(5 citation statements)

References 8 publications

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“…(0.1 Hz) value can be considered to correspond to the dc conductivity of M 2 P-TCNQ, and indeed the value at 150 K, 7 × 10 −12 −1 cm −1 , is consistent with the value reported for a compacted polycrystalline sample, 10 −11 −1 cm −1 [57].…”

Section: B Dielectric Measurementssupporting

confidence: 86%

“…We also recorded the IR and Raman spectra as a function of T , from 430 to 80 K. The T evolution of the spectra in the region of the molecular vibrations shown in Fig. S5 and S6 [45] demonstrate that in this temperature interval there is no phase transition and that the ionicity or the extent of dimerization do not change appreciably, in agreement with X-ray and DSC analysis [57]. New relevant information is instead obtained from the Raman spectra in the lattice (intermolecular) phonon region (30-200 cm −1 ) shown in Figs.…”

Section: Optical Spectrasupporting

confidence: 55%

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Relaxor ferroelectricity in the polar M2P-TCNQ charge-transfer crystal at the neutral-ionic interface

et al. 2021

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We investigated the mixed-stack charge-transfer crystal, N,N'-dimethylphenazine-TCNQ (M 2 P-TCNQ), which is polar at room temperature and just at the neutral-to-ionic interface (ionicity ρ ≈ 0.5). We detect the typical dielectric signature of a relaxor ferroelectric and an asymmetric positive-up-negative-down behavior. While relaxor ferroelectricity is usually ascribed to disorder in the crystal, we find no evidence for structural disorder in the investigated crystals. To elucidate the origin of M 2 P-TCNQ's dielectric properties we perform parallel structural and spectroscopic measurements, associated with theoretical modeling and quantum-mechanical calculations. Our combined effort points to a highly polarizable electronic system that is strongly coupled to lattice vibrations. The found indications for polarization reversal imply flipping of the bent conformation of the M 2 P molecule with an associated energy barrier of a few tens of an eV, broadly consistent with an Arrhenius fit of the dielectric relaxation times. While the polarization is mostly of electronic origin, its possible reversal implies slow collective motions that are affected by solid-state intermolecular interactions.

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Section: B Dielectric Measurementssupporting

confidence: 86%

Section: Optical Spectrasupporting

confidence: 55%

Relaxor ferroelectricity in the polar M2P-TCNQ charge-transfer crystal at the neutral-ionic interface

et al. 2021

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“…The absorption spectra of these films show broad peaks at 1422 nm (0.872 eV) for DHP(8-12)-TCNQ and at 1467 nm (0.845 eV) for DHP(2-6)-TCNQ , respectively ( Figure 2A ). These peaks are reasonably assignable to the ICT absorption bands by reference to that reported for the DHP(Me)-TCNQ crystal (0.84–0.89 eV) (Fujita and Matsunaga, 1980 ; Soo et al, 1981 ). It is to note that additional peaks are observed around at 360 nm (3.44 eV) with a shoulder component around 430 nm (2.88 eV) and at 600 nm (2.07 eV), which are also reported for DHP(Me)-TCNQ (3.41 eV, 2.85 eV and 1.98 eV) (Fujita and Matsunaga, 1980 ).…”

Section: Resultssupporting

confidence: 78%

“…These peaks are reasonably assignable to the ICT absorption bands by reference to that reported for the DHP(Me)-TCNQ crystal (0.84–0.89 eV) (Fujita and Matsunaga, 1980 ; Soo et al, 1981 ). It is to note that additional peaks are observed around at 360 nm (3.44 eV) with a shoulder component around 430 nm (2.88 eV) and at 600 nm (2.07 eV), which are also reported for DHP(Me)-TCNQ (3.41 eV, 2.85 eV and 1.98 eV) (Fujita and Matsunaga, 1980 ). These peaks are assignable to the intramolecular electronic transitions for anion and cation radicals formed in the ICT complexes, as referenced to the previous reports on K-TCNQ (3.17–3.39 eV and 2.00 eV) (Torrance et al, 1980 ; Ikegami et al, 2007 ) and DHP(Me)-PF 6 (3.3 eV and 2.6 eV) (Ohkura et al, 2011 ).…”

Section: Resultssupporting

confidence: 78%

Ionic Charge-Transfer Liquid Crystals Formed by Alternating Supramolecular Copolymerization of Liquid π-Donors and TCNQ

2021

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A new family of liquid π-donors, lipophilic dihydrophenazine (DHP) derivatives, show remarkably high π-electron-donor property which exhibit supramolecular alternating copolymerization with 7,7,8,8-tetracyanoquinodimethane (TCNQ), giving ionic charge-transfer (ICT) complexes. The ICT complexes form distinct columnar liquid crystalline (LC) mesophases with well-defined alternating molecular alignment as demonstrated by UV-Vis-NIR spectra, IR spectra, and X-ray diffraction (XRD) patterns. These liquid crystalline ICT complexes display unique phase transitions in response to mechanical stress: the columnar ICT phase is converted to macroscopically oriented smectic-like mesophases upon applying shear force. Although there exist reports on the formation of ICT in the crystalline state, this study provides the first rational identification of ICT mesophases based on the spectroscopic and structural data. The liquid crystalline ICT phases are generated by strong electronic interactions between the liquid π-donors and solid acceptors. It clearly shows the significance of simultaneous fulfillment of strong π-donating ability and ordered self-assembly of the stable ICT pairs. The flexible, stimuli-responsive structural transformation of the ICT complexes offer a new perspective for designing processable CT systems with controlled hierarchical self-assembly and electronic structures.

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“…At 150 K the conductivity lies between 10 −9 Ω −1 cm −1 and 10 −12 Ω −1 cm −1 . The lowest frequency (0.1 Hz) value can be considered to correspond to the dc conductivity of M 2 P-TCNQ, and indeed the value at 150 K, 7 • 10 −12 Ω −1 cm −1 , is consistent with the value reported for a compacted polycrystalline sample, 10 −11 Ω −1 cm −1 [57].…”

Section: B Dielectric Measurementssupporting

confidence: 84%

Intriguing relaxor ferroelectricity in a polar CT crystal at the neutral-ionic interface

Fischer,

D'Avino,

Masino

et al. 2020

Preprint

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We investigated the mixed-stack charge-transfer crystal, N,N-dimethylphenazine-TCNQ (M2P-TCNQ), which is polar at room temperature and just at the neutral-to-ionic interface (ionicity ρ ≈ 0.5). We detect the typical dielectric signature of a relaxor ferroelectric and an asymmetric positive-up-negative-down behavior. While relaxor ferroelectricity is usually ascribed to disorder in the crystal, we find no evidence for structural disorder in the investigated crystals. To elucidate the origin of M2P-TCNQ's dielectric properties we perform parallel structural and spectroscopic measurements, associated with theoretical modeling and quantum-mechanical calculations. Our combined effort points to a highly polarizable electronic system that is strongly coupled to lattice vibrations. The found indications for polarization reversal imply flipping of the bent conformation of the M2P molecule with an associated energy barrier of a few tens of an eV, broadly consistent with an Arrhenius fit of the dielectric relaxation times. While the polarization is mostly of electronic origin, its possible reversal implies slow collective motions that are affected by solid-state intermolecular interactions.

show abstract

On the Nature of the 5,10-Dimethyl-5,10-dihydrophenazine–Tetracyanoquinodimethane

Abstract: The 5,10-dimethyl-5,10-dihydrophenazine–tetracyanoquinodimethane appears to be largely ionic at room temperature. The results of various physical measurements of this compound can be explained without the reversible nonionic-to-ionic transition proposed by Soos et al.

Cited by 11 publications

References 8 publications

Relaxor ferroelectricity in the polar M2P-TCNQ charge-transfer crystal at the neutral-ionic interface

Relaxor ferroelectricity in the polar M2P-TCNQ charge-transfer crystal at the neutral-ionic interface

Ionic Charge-Transfer Liquid Crystals Formed by Alternating Supramolecular Copolymerization of Liquid π-Donors and TCNQ

Intriguing relaxor ferroelectricity in a polar CT crystal at the neutral-ionic interface

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