Formation of two-dimensional metals by weak intermolecular interactions based on the asymmetric EDO-TTF derivatives

Shao, Xiangfeng; Nakano, Yoshiaki; Yamochi, Hideki; Dubrovskiy, Alexander D.; Otsuka, Akihiro; Murata, Tsuyoshi; Yoshida, Yukihiro; Saito, Gunzi; Koshihara, Shin‐ya

doi:10.1039/b717621j

Cited by 16 publications

(19 citation statements)

References 40 publications

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“…The random distribution of MeEDO-TTF in the conduction column and positional disorder of the methyl group should reduce the Peierls instability of the alloys and play an important role in the low-temperature shift and smearing of the M-I transition. Parameter 2 should not have a large effect on the charge-distribution in the donor stack since the difference of ionization potentials between EDO-TTF and MeEDO-TTF (+0.39 and +0.36 V vs SCE in cyclic voltammetry measurements, respectively) is much smaller than the band widths of the resulting alloys (∼1.3 eV). In fact, the Raman spectra did not exhibit the inhomogeneity of charges on EDO-TTF and MeEDO-TTF molecules (Figure ).…”

Section: Resultsmentioning

confidence: 99%

“…MeEDO-TTF salts formed various types of molecular packing, which strongly affected their electronic structures. The head-to-tail stack of donor molecules provided quasi-one-dimensional systems or localized electronic structures in donor multimers, while the head-to-head stack formed two-dimensional systems with relatively weak donor−donor interactions. , Among the latter cases, (MeEDO-TTF) 2 X (BF 4 and ClO 4 ) showed a metallic behavior down to cryogenic temperature . The slightly bulkier anion, PF 6 provided three kinds of 2:1 salts.…”

Section: Introductionmentioning

confidence: 99%

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Tuning of Multi-Instabilities in Organic Alloy, [(EDO-TTF)_1−x(MeEDO-TTF)_x]₂PF₆

et al. 2010

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Electrocrystallization of a mixture of 4,5-ethylenedioxytetrathiafulvalene (EDO-TTF) and 4,5-ethylenedioxy-4 0 -methyltetrathiafulvalene (MeEDO-TTF) yielded alloyed salts, [(EDO-TTF) 1-x (MeEDO-TTF) x ] 2 PF 6 (x = mole fraction of MeEDO-TTF). EDO-TTF rich alloys (x e 0.5) were isostructural to (EDO-TTF) 2 PF 6 , the metal-insulator transition of which is caused by the cooperation of Peierls, anion-ordering, and charge-ordering mechanisms. Incorporation of MeEDO-TTF into (EDO-TTF) 2 PF 6 extended the donor-anion distance to weaken donor-anion interactions, while donor-donor interactions within the conduction layer remained the same magnitudes to those of (EDO-TTF) 2 PF 6 having a quasi-one-dimensional electronic structure. These alloys showed a metallic behavior or nearly constant resistivity around room temperature, and their transport properties strongly depended on x value. x e 0.13 alloys showed a sharp metal-insulator transition due to Peierls instability and anion-ordering, and transition temperature decreased as x increased. Although charge-ordering in the donor column was also elucidated for the insulator phase of x e 0.05 alloys, uniform þ0.5 charge of donor molecules was preserved in the low-temperature phase of x = 0.13 alloy. In the case of the x ∼0.5 alloy, any abrupt anomalies were not detected down to low temperature, while broad resistivity minimum was observed at 200-270 K. x g 0.9 alloys were isostructural to (MeEDO-TTF) 2 PF 6 , which forms a two-dimensional donor layer. Similar to (MeEDO-TTF) 2 PF 6 , MeEDO-TTF rich alloys exhibited a semiconductor-to-semiconductor phase transition. The transition became gradual, and the transition temperature was suppressed with decreasing x value. Raman spectra indicated that nearly localized and distinct charge-disproportionated states, which are observed in the high-and low-temperature phases of pristine (MeEDO-TTF) 2 PF 6 , respectively, coexist in the high-temperature phase.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tuning of Multi-Instabilities in Organic Alloy, [(EDO-TTF)_1−x(MeEDO-TTF)_x]₂PF₆

et al. 2010

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“…It has been well-defined that a subtle modification of TTF would result in a significant effect on the properties of their complexes [ 5 – 10 ]. For example, the complexes of EDO-TTF (4,5-ethylenedioxy-TTF) [ 11 – 15 ] and MeEDO-TTF (4,5-ethylenedioxy-4’-methyl-TTF) [ 16 – 19 ] show the distinct difference on electrical transport properties. Meanwhile, the modification on TTF, particularly introducing aromatic substituents onto the TTF core, is one of the key strategies to explore functional molecular materials.…”

Section: Introductionmentioning

confidence: 99%

Copper ion salts of arylthiotetrathiafulvalenes: synthesis, structure diversity and magnetic properties

Ma¹,

Sun²,

Lu³

et al. 2015

Beilstein J. Org. Chem.

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SummaryThe combination of CuBr2 and arylthio-substituted tetrathiafulvalene derivatives (1–7) results in a series of charge-transfer (CT) complexes. Crystallographic studies indicate that the anions in the complexes, which are derived from CuBr2, show diverse configurations including linear [Cu(I)Br2]–, tetrahedral [Cu(II)Br4]2–, planar [Cu(II)2Br6]2–, and coexistence of planar [Cu(II)Br4]2– and tetrahedral [Cu(II)Br3]– ions. On the other hand, the TTFs show either radical cation or dication states that depend on their redox potentials. The central TTF framework on most of TTFs is nearly planar despite the charge on them, whereas the two dithiole rings on molecule 4 in complex 4·CuBr4 are significantly twisted with a dihedral angle of 38.3°. The magnetic properties of the complexes were elucidated. The temperature-dependent magnetic susceptibility of complex 5·Cu2Br6 shows the singlet–triplet transition with coupling constant J = −248 K, and that of 3·(CuBr4)0.5·CuBr3·THF shows the abrupt change at 270 K caused by the modulation of intermolecular interactions. The thermo variation of magnetic susceptibility for the other complexes follows the Curie–Weiss law, indicating the weak antiferromagnetic interaction at low temperature.

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“…To achieve the functionalities based on the multistable nature, it is essential to tune the balance of the Coulomb interaction and transfer integrals by using chemical modifications of the donor molecules and the counteranions . As an analogue of (EDO-TTF) 2 PF 6 , (MeEDO-TTF) 2 PF 6 (MeEDO-TTF = monomethyl-EDO-TTF, Chart ) shows a molecular packing motif different from (EDO-TTF) 2 PF 6 with a two-dimensional electronic structure. − This system shows a first-order semiconductor–semiconductor transition associated with charge disproportionation . Fabre and co-workers have reported synthesis and properties of dimethyl-EDO-TTF (DMEDO-TTF) as well as the preparation of its cation radical salts. , (DMEDO-TTF) 2 PF 6 exhibits a first-order structural phase transition at 130 K, but neither the detail of the transport properties, crystal structures at high- and low-temperature phases, nor the mechanism of the phase transition has been investigated probably due to the destructive structural transition.…”

Section: Introductionmentioning

confidence: 99%

Structural Transitions from Triangular to Square Molecular Arrangements in the Quasi-One-Dimensional Molecular Conductors (DMEDO-TTF)₂XF₆ (X = P, As, and Sb)

et al. 2012

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A series of quasi-one-dimensional molecular conductors (DMEDO-TTF)(2)XF(6) (X = P, As, and Sb), where DMEDO-TTF is dimethyl(ethylenedioxy)tetrathiafulvalene, undergo characteristic structural transitions in the range of 130-195 K for the PF(6) salt and 222-242 K for the AsF(6) salt. The dramatic structural transition is induced by the order of the ethylenedioxy moiety, and the resulting anion rotation leads to the reconstruction of the H···F interaction between the methyl groups and the anions. The unique hydrogen bonds play a crucial role in the transition. As a result, the molecular packing is rearranged entirely; the high-temperature molecular stacks with an ordinary quasi-triangular molecular network transforms to a quasi-square-like network, which has never been observed among organic conductors. Nonetheless, the low-temperature phase exhibits a good metallic conductivity as well, so the transition is a metal-metal (MM) transition. The resistivity measured along the perpendicular direction to the conducting ac-plane (ρ(⊥)) and the calculation of the Fermi surface demonstrate that the high-temperature metal phase is a one-dimensional metal, whereas the low-temperature metal phase has considerable interchain interaction. In the SbF(6) salt, a similar structural transition takes place around 370 K, so that the quasi-square-like lattice is realized even at room temperature. Despite the largely different MM transition temperatures, all these salts undergo metal-insulator (MI) transitions approximately at the same temperature of 50 K. The low-temperature insulator phase is nonmagnetic, and the reflectance spectra suggest the presence of charge disproportionation with small charge difference (0.14).

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Formation of two-dimensional metals by weak intermolecular interactions based on the asymmetric EDO-TTF derivatives

Cited by 16 publications

References 40 publications

Tuning of Multi-Instabilities in Organic Alloy, [(EDO-TTF)_1−x(MeEDO-TTF)_x]₂PF₆

Tuning of Multi-Instabilities in Organic Alloy, [(EDO-TTF)_1−x(MeEDO-TTF)_x]₂PF₆

Copper ion salts of arylthiotetrathiafulvalenes: synthesis, structure diversity and magnetic properties

Structural Transitions from Triangular to Square Molecular Arrangements in the Quasi-One-Dimensional Molecular Conductors (DMEDO-TTF)₂XF₆ (X = P, As, and Sb)

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Formation of two-dimensional metals by weak intermolecular interactions based on the asymmetric EDO-TTF derivatives

Cited by 16 publications

References 40 publications

Tuning of Multi-Instabilities in Organic Alloy, [(EDO-TTF)1−x(MeEDO-TTF)x]2PF6

Tuning of Multi-Instabilities in Organic Alloy, [(EDO-TTF)1−x(MeEDO-TTF)x]2PF6

Copper ion salts of arylthiotetrathiafulvalenes: synthesis, structure diversity and magnetic properties

Structural Transitions from Triangular to Square Molecular Arrangements in the Quasi-One-Dimensional Molecular Conductors (DMEDO-TTF)2XF6 (X = P, As, and Sb)

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Tuning of Multi-Instabilities in Organic Alloy, [(EDO-TTF)_1−x(MeEDO-TTF)_x]₂PF₆

Tuning of Multi-Instabilities in Organic Alloy, [(EDO-TTF)_1−x(MeEDO-TTF)_x]₂PF₆

Structural Transitions from Triangular to Square Molecular Arrangements in the Quasi-One-Dimensional Molecular Conductors (DMEDO-TTF)₂XF₆ (X = P, As, and Sb)