Structure and Physical Properties of a New 1:1 Cation-Radical Salt, ζ-(BEDT-TTF)PF6

Hsiang Lin Liu, Liang Kuei Chou, Khalil A. Abboud, Brian H. Ward, Gail E. Fanucci, Garrett E. Granroth, Enric Canadell, Mark W. Meisel, Daniel R. Talham, David B. Tanner

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

The synthesis, structural characterization, electrical transport, optical, and magnetic properties of a new cation-radical salt, bis(ethylenedithio)tetrathiafulvalene hexafluoro-phosphate, ζ-(BEDT-TTF)PF6, are reported. The X-ray structure was determined at 298 K and at 173 K. The primary difference at the two temperatures is that the PF6- anions are disordered at 298 K and ordered at 173 K. At 298 K the salt is in the triclinic space group P1̄ with crystallographic parameters a = 6.2793(1) Å, b = 7.3680(1) Å, c = 9.9006(1) A, α = 92.542(1)°, β= 93.255(1)°, γ = 98.763(1)°, vol = 451.33(1) Å3. At 173 K the salt retains the same space group with parameters a = 6.2293(1) Å, b = 7.2633(2) Å, c = 9.8662(2) Å, α = 92.898(1)°, β= 93.592(1)°, γ = 97.914(1)°, vol = 439.95(2) Å3. Despite a crystal structure with uniform and segregated layers of donors and counterions, the room-temperature dc conductivity is rather low, ∼1.1 × 10-4 Ω-1 cm-1, and decreases rapidly upon cooling. Polarized reflectance measurements along the a axis of ζ-(BEDT-TTF)PF6 provide evidence that the material is a Mott-Hubbard insulator with an effective on-site Coulomb interaction Ueff of 0.82 eV and a transfer matrix element t of 0.21 eV. An analysis of the infrared Ag modes yields a dimensionless electron-molecular-vibration coupling constant λ ∼ 0.1. When the temperature is lowered, the activation energy for transport, the far-infrared phonons, and the magnetic susceptibility χ all exhibit an anomaly at ∼250 K which is related to the order/disorder transition of the PF6- counterions. In the low-temperature phase, the spectral weight of the three lowest Ag modes changes gradually, suggesting that the phase transition is close to second order. Finally, an exponential drop of χ occurs below 40 K, indicating the opening of a gap in the spin excitation spectrum. We suggest that this magnetic phase transition has structural aspects and can probably be associated with a spin-Peierls transition.

Original languageEnglish
Pages (from-to)1865-1877
Number of pages13
JournalChemistry of Materials
Volume9
Issue number8
Publication statusPublished - 1997 Dec 1

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Cations
Physical properties
Salts
Positive ions
Phase transitions
Molecular vibrations
Infrared radiation
Temperature
Order disorder transitions
Reflectometers
Phonons
Coulomb interactions
Magnetic susceptibility
Transport properties
Anions
Magnetic properties
Phosphates
Negative ions
Optical properties
Activation energy

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

Cite this

Liu, H. L., Chou, L. K., Abboud, K. A., Ward, B. H., Fanucci, G. E., Granroth, G. E., ... Tanner, D. B. (1997). Structure and Physical Properties of a New 1:1 Cation-Radical Salt, ζ-(BEDT-TTF)PF6. Chemistry of Materials, 9(8), 1865-1877.

Structure and Physical Properties of a New 1:1 Cation-Radical Salt, ζ-(BEDT-TTF)PF6. / Liu, Hsiang Lin; Chou, Liang Kuei; Abboud, Khalil A.; Ward, Brian H.; Fanucci, Gail E.; Granroth, Garrett E.; Canadell, Enric; Meisel, Mark W.; Talham, Daniel R.; Tanner, David B.

In: Chemistry of Materials, Vol. 9, No. 8, 01.12.1997, p. 1865-1877.

Research output: Contribution to journalArticle

Liu, HL, Chou, LK, Abboud, KA, Ward, BH, Fanucci, GE, Granroth, GE, Canadell, E, Meisel, MW, Talham, DR & Tanner, DB 1997, 'Structure and Physical Properties of a New 1:1 Cation-Radical Salt, ζ-(BEDT-TTF)PF6', Chemistry of Materials, vol. 9, no. 8, pp. 1865-1877.
Liu HL, Chou LK, Abboud KA, Ward BH, Fanucci GE, Granroth GE et al. Structure and Physical Properties of a New 1:1 Cation-Radical Salt, ζ-(BEDT-TTF)PF6. Chemistry of Materials. 1997 Dec 1;9(8):1865-1877.
Liu, Hsiang Lin ; Chou, Liang Kuei ; Abboud, Khalil A. ; Ward, Brian H. ; Fanucci, Gail E. ; Granroth, Garrett E. ; Canadell, Enric ; Meisel, Mark W. ; Talham, Daniel R. ; Tanner, David B. / Structure and Physical Properties of a New 1:1 Cation-Radical Salt, ζ-(BEDT-TTF)PF6. In: Chemistry of Materials. 1997 ; Vol. 9, No. 8. pp. 1865-1877.
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title = "Structure and Physical Properties of a New 1:1 Cation-Radical Salt, ζ-(BEDT-TTF)PF6",
abstract = "The synthesis, structural characterization, electrical transport, optical, and magnetic properties of a new cation-radical salt, bis(ethylenedithio)tetrathiafulvalene hexafluoro-phosphate, ζ-(BEDT-TTF)PF6, are reported. The X-ray structure was determined at 298 K and at 173 K. The primary difference at the two temperatures is that the PF6- anions are disordered at 298 K and ordered at 173 K. At 298 K the salt is in the triclinic space group P1̄ with crystallographic parameters a = 6.2793(1) {\AA}, b = 7.3680(1) {\AA}, c = 9.9006(1) A, α = 92.542(1)°, β= 93.255(1)°, γ = 98.763(1)°, vol = 451.33(1) {\AA}3. At 173 K the salt retains the same space group with parameters a = 6.2293(1) {\AA}, b = 7.2633(2) {\AA}, c = 9.8662(2) {\AA}, α = 92.898(1)°, β= 93.592(1)°, γ = 97.914(1)°, vol = 439.95(2) {\AA}3. Despite a crystal structure with uniform and segregated layers of donors and counterions, the room-temperature dc conductivity is rather low, ∼1.1 × 10-4 Ω-1 cm-1, and decreases rapidly upon cooling. Polarized reflectance measurements along the a axis of ζ-(BEDT-TTF)PF6 provide evidence that the material is a Mott-Hubbard insulator with an effective on-site Coulomb interaction Ueff of 0.82 eV and a transfer matrix element t of 0.21 eV. An analysis of the infrared Ag modes yields a dimensionless electron-molecular-vibration coupling constant λ ∼ 0.1. When the temperature is lowered, the activation energy for transport, the far-infrared phonons, and the magnetic susceptibility χ all exhibit an anomaly at ∼250 K which is related to the order/disorder transition of the PF6- counterions. In the low-temperature phase, the spectral weight of the three lowest Ag modes changes gradually, suggesting that the phase transition is close to second order. Finally, an exponential drop of χ occurs below 40 K, indicating the opening of a gap in the spin excitation spectrum. We suggest that this magnetic phase transition has structural aspects and can probably be associated with a spin-Peierls transition.",
author = "Liu, {Hsiang Lin} and Chou, {Liang Kuei} and Abboud, {Khalil A.} and Ward, {Brian H.} and Fanucci, {Gail E.} and Granroth, {Garrett E.} and Enric Canadell and Meisel, {Mark W.} and Talham, {Daniel R.} and Tanner, {David B.}",
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T1 - Structure and Physical Properties of a New 1:1 Cation-Radical Salt, ζ-(BEDT-TTF)PF6

AU - Liu, Hsiang Lin

AU - Chou, Liang Kuei

AU - Abboud, Khalil A.

AU - Ward, Brian H.

AU - Fanucci, Gail E.

AU - Granroth, Garrett E.

AU - Canadell, Enric

AU - Meisel, Mark W.

AU - Talham, Daniel R.

AU - Tanner, David B.

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N2 - The synthesis, structural characterization, electrical transport, optical, and magnetic properties of a new cation-radical salt, bis(ethylenedithio)tetrathiafulvalene hexafluoro-phosphate, ζ-(BEDT-TTF)PF6, are reported. The X-ray structure was determined at 298 K and at 173 K. The primary difference at the two temperatures is that the PF6- anions are disordered at 298 K and ordered at 173 K. At 298 K the salt is in the triclinic space group P1̄ with crystallographic parameters a = 6.2793(1) Å, b = 7.3680(1) Å, c = 9.9006(1) A, α = 92.542(1)°, β= 93.255(1)°, γ = 98.763(1)°, vol = 451.33(1) Å3. At 173 K the salt retains the same space group with parameters a = 6.2293(1) Å, b = 7.2633(2) Å, c = 9.8662(2) Å, α = 92.898(1)°, β= 93.592(1)°, γ = 97.914(1)°, vol = 439.95(2) Å3. Despite a crystal structure with uniform and segregated layers of donors and counterions, the room-temperature dc conductivity is rather low, ∼1.1 × 10-4 Ω-1 cm-1, and decreases rapidly upon cooling. Polarized reflectance measurements along the a axis of ζ-(BEDT-TTF)PF6 provide evidence that the material is a Mott-Hubbard insulator with an effective on-site Coulomb interaction Ueff of 0.82 eV and a transfer matrix element t of 0.21 eV. An analysis of the infrared Ag modes yields a dimensionless electron-molecular-vibration coupling constant λ ∼ 0.1. When the temperature is lowered, the activation energy for transport, the far-infrared phonons, and the magnetic susceptibility χ all exhibit an anomaly at ∼250 K which is related to the order/disorder transition of the PF6- counterions. In the low-temperature phase, the spectral weight of the three lowest Ag modes changes gradually, suggesting that the phase transition is close to second order. Finally, an exponential drop of χ occurs below 40 K, indicating the opening of a gap in the spin excitation spectrum. We suggest that this magnetic phase transition has structural aspects and can probably be associated with a spin-Peierls transition.

AB - The synthesis, structural characterization, electrical transport, optical, and magnetic properties of a new cation-radical salt, bis(ethylenedithio)tetrathiafulvalene hexafluoro-phosphate, ζ-(BEDT-TTF)PF6, are reported. The X-ray structure was determined at 298 K and at 173 K. The primary difference at the two temperatures is that the PF6- anions are disordered at 298 K and ordered at 173 K. At 298 K the salt is in the triclinic space group P1̄ with crystallographic parameters a = 6.2793(1) Å, b = 7.3680(1) Å, c = 9.9006(1) A, α = 92.542(1)°, β= 93.255(1)°, γ = 98.763(1)°, vol = 451.33(1) Å3. At 173 K the salt retains the same space group with parameters a = 6.2293(1) Å, b = 7.2633(2) Å, c = 9.8662(2) Å, α = 92.898(1)°, β= 93.592(1)°, γ = 97.914(1)°, vol = 439.95(2) Å3. Despite a crystal structure with uniform and segregated layers of donors and counterions, the room-temperature dc conductivity is rather low, ∼1.1 × 10-4 Ω-1 cm-1, and decreases rapidly upon cooling. Polarized reflectance measurements along the a axis of ζ-(BEDT-TTF)PF6 provide evidence that the material is a Mott-Hubbard insulator with an effective on-site Coulomb interaction Ueff of 0.82 eV and a transfer matrix element t of 0.21 eV. An analysis of the infrared Ag modes yields a dimensionless electron-molecular-vibration coupling constant λ ∼ 0.1. When the temperature is lowered, the activation energy for transport, the far-infrared phonons, and the magnetic susceptibility χ all exhibit an anomaly at ∼250 K which is related to the order/disorder transition of the PF6- counterions. In the low-temperature phase, the spectral weight of the three lowest Ag modes changes gradually, suggesting that the phase transition is close to second order. Finally, an exponential drop of χ occurs below 40 K, indicating the opening of a gap in the spin excitation spectrum. We suggest that this magnetic phase transition has structural aspects and can probably be associated with a spin-Peierls transition.

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