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ET3(MnCl3)2(EtOH)2: a new organic conductor with a perovskite structure
Synthetic Metals 133–134 (2003) 445–447
ET3(MnCl3)2(EtOH)2: a new organic conductor with a perovskite structure$ T. Naitoa,*, T. Inabea, T. Akutagawab, T. Hasegawab, T. Nakamurab a
Division of Chemistry, Graduate School of Science, Hokkaido University, Hokkaido, Japan b Research Institute for Electronic Science, Hokkaido University, Hokkaido, Japan
Abstract The title salt was obtained as fine black needles from the electrolysis of ET (ET: bis(ethylenedithio)tetrathiafulvalene) with a Mn cluster in 1,1,2-trichloroethane containing 10% of ethanol. The conductivity at room temperature was 25 S cm1 with weakly semiconducting behavior, yet the salt kept a high conductivity down to 4 K (0.1 S cm1). The manganese(II) chloride anion formed an infinite chain made of faceshared MnCl6 octahedrons, and these chains formed insulating sheets with ethanol molecules between the chains. The ET cation radicals formed a0 -type conducting sheets between the insulating sheets. Such crystal structure was characterized as that of a typical hexagonal perovskite ABX3, where A equals to a bulky monocation. The magnetic behavior was reproduced by the Curie–Weiss law, which might be attributable to the face-shared MnCl6 octahedron chains. # 2002 Elsevier Science B.V. All rights reserved. Keywords: ET-based conductors; Hexagonal perovskite lattice; Face-shared MnCl6 chains
1. Introduction
2. Experiment
We have recently reported on the crystal structure and physical properties of b00 -(ET)3(MnCl4)(1,1,2-C3H3Cl3) (ET: bis(ethylenedithio)tetrathiafulvalene) [1], which shows complicated electrical behavior in contrast to its simple magnetic behavior, and the electrical behavior drastically varies with pressure. Such physical properties result from the structural feature; i.e., loosely packed ET molecules. This leads to a marginally metallic band structure. Such crystal and electronic structures can be subjected to transition under the slightest perturbation. Therefore we are now in pursuit of such materials that exhibit complicated physical properties due to the thermodynamical subtle balance among the crystal, electronic and magnetic structures in addition to the interactions among them. We report herein the synthesis and physical properties of the title salt.
In the course of electrolysis with the condition described in the previous paper [1] some batches produced the fibrous thin needles of (ET)3(MnCl3)2(C2H5OH)2 without byproducts. The X-ray structural analysis and measurements of electrical and magnetic properties were carried out as previously described for the related material [1].
$
Yamada Conference LVI, The Fourth International Symposium on Crystalline Organic Metals, Superconductors and Ferromagnets, ISCOM 2001—Abstract Number F20Tue. * Corresponding author. Tel.: þ81-11-706-3534; fax: þ81-11-706-4924. E-mail address: [email protected] (T. Naito).
3. Results and discussion 3.1. Crystal structure 3.1.1. General feature of crystal structure The unit cell is shown in Fig. 1. Crystal data: monoclinic, C2/ ˚ , b ¼ 6:716ð1Þ A ˚ , c ¼ 23:608ð3Þ A ˚, c(#15), a ¼ 38:863ð4Þ A ˚ 3, Z ¼ 4, R, Rw ¼ 0:195, b ¼ 115:007ð3Þ , V ¼ 5584ð1Þ A 0.066 (both for all data). There are many short S–S contacts between the ET molecules and they apparently make twodimensional (2D) sheets in the bc-plane. Assuming that the Mn ion should take þ2 charge and that all the ET species should have equal charges, i.e. þ2/3, which is suggested by the bond lengths, the chemical formula of this salt can be described as AþI BþII XI 3 , where A ¼ ðETÞ3=2 , B ¼ Mn, X ¼ Cl. This is a typical formula shared among the hexagonal perovskite compounds with a bulky monocation A.
0379-6779/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 9 - 6 7 7 9 ( 0 2 ) 0 0 2 6 9 - 2
446
T. Naito et al. / Synthetic Metals 133–134 (2003) 445–447
Fig. 1. Ortep view of (ET)3(MnCl3)2(C2H5OH)2.
Actually the structure has such characteristics that face-shared octahedral MnCl6 ions make infinite chains with the other species packed in the remaining space. Interestingly the ET radicals also make their own columns, which make a nearly right angle to the MnCl6 columns. This means that a Lorentz force from a magnetic field of the MnCl6 columns could exert an action on the conduction electrons on the ET columns in the most effective way, though there are no van der Waals contacts between the ET and MnCl6 species.
opens [2]. In (ET)3(MnCl3)2(C2H5OH)2 the stacking axis ˚ ) as long as the typical (c-axis) is actually three times (24 A ˚ ), well corresponding to the longer periodicity one (8 A (6-fold). In fact a tight-binding band calculation gave a multi-folded but substantially similar Fermi surface to the typical a0 -type ET salts: a scarcely warped 1D band dispersion along the b -axis.
3.1.2. Donor molecular arrangement The ET molecular arrangement of this salt is conventionally called a0 -type [2]. The typical a0 -type ET salts have a commensurate 2-fold periodicity along the stacking axis (a-axis), in which direction a wide energy gap at Fermi level
The resistivity at room temperature was 0.04 O cm. Although the resistivity gradually increased with decreasing temperature, it remained as low as 10 O cm even at 4 K. While all the a0 -type ET salts thus far reported are insulators from room temperature [2], this salt exhibited
3.2. Electrical properties
T. Naito et al. / Synthetic Metals 133–134 (2003) 445–447
447
Fig. 2. Temperature dependence of the magnetic susceptibility of (ET)3(MnCl3)2(C2H5OH)2.
high conductivity along the b-axis. Taking the magnetic properties data discussed below into consideration, the pelectrons can be said in a metallic band. Infrared reflectance spectroscopy may provide clear-cut information whether it actually has a Fermi surface similar to the calculated one.
the conduction electrons and local spins; (iii) 3D magnetic ordering should appear to be suppressed due to the onedimensionality of the MnCl6 networks for lack of enough interaction between them. The last situation could be altered under high pressure.
3.3. Magnetic properties 4. Conclusion The magnetic behavior was reproduced by Curie–Weiss law (Fig. 2; C ¼ 8:75 emu K per formula, Y ¼ 100:7 K). The effective moment well agreed to a spin-only value of Mn(II) (5:92 2mB). Hysteresis loop was not observed down to 1.8 K, probably due to the low dimensionality. Other fitting models are now under consideration. From a preliminary ESR measurement using a single crystal no clear signal was observed down to 3.5 K regardless of the relative orientation of the crystal to the static magnetic field. These results suggest that: (i) a strong antiferromagnetic interaction should occur between the local spins on the Mn(II) ions; (ii) magnetic coupling may occur between
(ET)3(MnCl3)2(C2H5OH)2 is an interesting new molecular conductor with magnetic anions, which is worthy of further examinations.
References [1] T. Naito, T. Inabe, K. Takeda, K. Awaga, T. Akutagawa, T. Hasegawa, T. Nakamura, T. Kakiuchi, H. Sawa, T. Yamamoto, H. Tajima, J. Mater. Chem. 11 (2001) 2221. [2] T. Mori, Bull. Chem. Soc. Jpn. 72 (1999) 2011.
ET3(MnCl3)2(EtOH)2: a new organic conductor with a perovskite structure$ T. Naitoa,*, T. Inabea, T. Akutagawab, T. Hasegawab, T. Nakamurab a
Division of Chemistry, Graduate School of Science, Hokkaido University, Hokkaido, Japan b Research Institute for Electronic Science, Hokkaido University, Hokkaido, Japan
Abstract The title salt was obtained as fine black needles from the electrolysis of ET (ET: bis(ethylenedithio)tetrathiafulvalene) with a Mn cluster in 1,1,2-trichloroethane containing 10% of ethanol. The conductivity at room temperature was 25 S cm1 with weakly semiconducting behavior, yet the salt kept a high conductivity down to 4 K (0.1 S cm1). The manganese(II) chloride anion formed an infinite chain made of faceshared MnCl6 octahedrons, and these chains formed insulating sheets with ethanol molecules between the chains. The ET cation radicals formed a0 -type conducting sheets between the insulating sheets. Such crystal structure was characterized as that of a typical hexagonal perovskite ABX3, where A equals to a bulky monocation. The magnetic behavior was reproduced by the Curie–Weiss law, which might be attributable to the face-shared MnCl6 octahedron chains. # 2002 Elsevier Science B.V. All rights reserved. Keywords: ET-based conductors; Hexagonal perovskite lattice; Face-shared MnCl6 chains
1. Introduction
2. Experiment
We have recently reported on the crystal structure and physical properties of b00 -(ET)3(MnCl4)(1,1,2-C3H3Cl3) (ET: bis(ethylenedithio)tetrathiafulvalene) [1], which shows complicated electrical behavior in contrast to its simple magnetic behavior, and the electrical behavior drastically varies with pressure. Such physical properties result from the structural feature; i.e., loosely packed ET molecules. This leads to a marginally metallic band structure. Such crystal and electronic structures can be subjected to transition under the slightest perturbation. Therefore we are now in pursuit of such materials that exhibit complicated physical properties due to the thermodynamical subtle balance among the crystal, electronic and magnetic structures in addition to the interactions among them. We report herein the synthesis and physical properties of the title salt.
In the course of electrolysis with the condition described in the previous paper [1] some batches produced the fibrous thin needles of (ET)3(MnCl3)2(C2H5OH)2 without byproducts. The X-ray structural analysis and measurements of electrical and magnetic properties were carried out as previously described for the related material [1].
$
Yamada Conference LVI, The Fourth International Symposium on Crystalline Organic Metals, Superconductors and Ferromagnets, ISCOM 2001—Abstract Number F20Tue. * Corresponding author. Tel.: þ81-11-706-3534; fax: þ81-11-706-4924. E-mail address: [email protected] (T. Naito).
3. Results and discussion 3.1. Crystal structure 3.1.1. General feature of crystal structure The unit cell is shown in Fig. 1. Crystal data: monoclinic, C2/ ˚ , b ¼ 6:716ð1Þ A ˚ , c ¼ 23:608ð3Þ A ˚, c(#15), a ¼ 38:863ð4Þ A ˚ 3, Z ¼ 4, R, Rw ¼ 0:195, b ¼ 115:007ð3Þ , V ¼ 5584ð1Þ A 0.066 (both for all data). There are many short S–S contacts between the ET molecules and they apparently make twodimensional (2D) sheets in the bc-plane. Assuming that the Mn ion should take þ2 charge and that all the ET species should have equal charges, i.e. þ2/3, which is suggested by the bond lengths, the chemical formula of this salt can be described as AþI BþII XI 3 , where A ¼ ðETÞ3=2 , B ¼ Mn, X ¼ Cl. This is a typical formula shared among the hexagonal perovskite compounds with a bulky monocation A.
0379-6779/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 9 - 6 7 7 9 ( 0 2 ) 0 0 2 6 9 - 2
446
T. Naito et al. / Synthetic Metals 133–134 (2003) 445–447
Fig. 1. Ortep view of (ET)3(MnCl3)2(C2H5OH)2.
Actually the structure has such characteristics that face-shared octahedral MnCl6 ions make infinite chains with the other species packed in the remaining space. Interestingly the ET radicals also make their own columns, which make a nearly right angle to the MnCl6 columns. This means that a Lorentz force from a magnetic field of the MnCl6 columns could exert an action on the conduction electrons on the ET columns in the most effective way, though there are no van der Waals contacts between the ET and MnCl6 species.
opens [2]. In (ET)3(MnCl3)2(C2H5OH)2 the stacking axis ˚ ) as long as the typical (c-axis) is actually three times (24 A ˚ ), well corresponding to the longer periodicity one (8 A (6-fold). In fact a tight-binding band calculation gave a multi-folded but substantially similar Fermi surface to the typical a0 -type ET salts: a scarcely warped 1D band dispersion along the b -axis.
3.1.2. Donor molecular arrangement The ET molecular arrangement of this salt is conventionally called a0 -type [2]. The typical a0 -type ET salts have a commensurate 2-fold periodicity along the stacking axis (a-axis), in which direction a wide energy gap at Fermi level
The resistivity at room temperature was 0.04 O cm. Although the resistivity gradually increased with decreasing temperature, it remained as low as 10 O cm even at 4 K. While all the a0 -type ET salts thus far reported are insulators from room temperature [2], this salt exhibited
3.2. Electrical properties
T. Naito et al. / Synthetic Metals 133–134 (2003) 445–447
447
Fig. 2. Temperature dependence of the magnetic susceptibility of (ET)3(MnCl3)2(C2H5OH)2.
high conductivity along the b-axis. Taking the magnetic properties data discussed below into consideration, the pelectrons can be said in a metallic band. Infrared reflectance spectroscopy may provide clear-cut information whether it actually has a Fermi surface similar to the calculated one.
the conduction electrons and local spins; (iii) 3D magnetic ordering should appear to be suppressed due to the onedimensionality of the MnCl6 networks for lack of enough interaction between them. The last situation could be altered under high pressure.
3.3. Magnetic properties 4. Conclusion The magnetic behavior was reproduced by Curie–Weiss law (Fig. 2; C ¼ 8:75 emu K per formula, Y ¼ 100:7 K). The effective moment well agreed to a spin-only value of Mn(II) (5:92 2mB). Hysteresis loop was not observed down to 1.8 K, probably due to the low dimensionality. Other fitting models are now under consideration. From a preliminary ESR measurement using a single crystal no clear signal was observed down to 3.5 K regardless of the relative orientation of the crystal to the static magnetic field. These results suggest that: (i) a strong antiferromagnetic interaction should occur between the local spins on the Mn(II) ions; (ii) magnetic coupling may occur between
(ET)3(MnCl3)2(C2H5OH)2 is an interesting new molecular conductor with magnetic anions, which is worthy of further examinations.
References [1] T. Naito, T. Inabe, K. Takeda, K. Awaga, T. Akutagawa, T. Hasegawa, T. Nakamura, T. Kakiuchi, H. Sawa, T. Yamamoto, H. Tajima, J. Mater. Chem. 11 (2001) 2221. [2] T. Mori, Bull. Chem. Soc. Jpn. 72 (1999) 2011.