1. 有機ラジカル固体の物性科学
Solid-state properties of organic radicals
有機物の電気伝導体や磁気的性質などを調べる有機ラジカル固体の物性科学研究は、半世紀以上の歴史をもちます。その中で、もともとは低次元電子系として関心を集めた有機固体が、次元性の向上と分子間相互作用の高まりによって、きわめて多彩な性質を見せることが明らかになりました。我々は、相互作用の高次元化という視点から、有機と無機、分子とポリマーの境界上に位置するような環状チアジルラジカルや関連物質の研究を続けてきましたが、室温磁気双安定性、光誘起相転移、有機強磁性、２重融解、電子移動相転移、非線形電気伝導、電荷移動相転移、巨大過渡光電流など、さまざまな特性を見出しました。さらに最近では、立体的なπ電子系をもつ有機分子によって、３次元的な相互作用をもつ有機ラジカル固体の開発を進めています。

Research into the solid-state properties of organic radical solids has a long history of morethan fifty years, focusing on molecular conductors and magnets. While most organic radicalsolids possess low-dimensional electronic states, improvements in the dimensionality andthe interaction intensity have produced versatile physical properties. We have been working
on the research into cyclic thiazyl radicals and their related compounds, which are quite
unique chemical species, being on the borderlines between organic and inorganic, andbetween molecule and polymer, and, as such, we have observed unique physical properties,
such as room-temperature magnetic bistability, photo-induced phase transitions, organicferromagnetism, double melting, electron-transfer phase transitions, non-linear electricaltransport, anomalous transient current, etc. Very recently, we have started working on 3D
organic radical crystals, formed by polyhedron-shaped π-conjugated organic radicals.

Fig. 1. A thiazyl radical salt, [NT]3[GaCl4], exhibites low-field negative resistance effects ina charge-ordered state on a square, columnar network of NT.

Fig. 2. A disjoint diradical, 4,4‘-bis(1,2,3,5- dithiadiazolyl) (BDTDA), which makes highlyoriented thin films with alternating -stacking perpendicular to the substrates, exhibits aphotocurrent with a high on/off ratio at reverse bias voltages, and photovoltaic behavior atzero bias voltage in ITO/BDTDA/Al sandwich-type cells.

Fig. 3. Amorphous thin-film field-effect transistors of paramagnetic vanadyl tetrakis(thiadiazole)-porphyrazine with ionic liquid gate dielectrics exhibit n-type performance with ahigh mobility of 2.8×10−2 cm2V−1s−1 and an on/off ratio of 104.

Fig. 4. A novel phenanthroline derivative, [1,2,5]thiadiazolo[3,4-f][1,10]phenanthroline(tdapO2) was newly synthesized. Its radical anion, tdapO2, acts as a bridging ligand, andforms multidimensional network structures. Magnetic property measurements reveal thatsuch salts exhibit 1D antiferromagnetic interactions, and magnetic ordering below 15 K.

Fig. 5. We carried out electrochemical crystallization of the radical anion salts ofNDI(naphthalene diimide)-Δ. X-ray crystal analysis revealed the K4 structure, which wasformed by the unique intermolecular π-overlap directed toward three directions from thetriangular-shape NDI-Δ radical anions.

References

1.

“Discovery of the K4 Structure Formed by a Triangular π Radical Anion ”,
A. Mizuno, Y. Shuku, R.Suizu, M. M. Matsushita, M. Tsuchiizu, D R. Mañeru, F. Illas, V. Robert,and K. Awaga,(2015) J. Am. Chem. Soc., 137, pp. 7612−7615.

2.

“Self-assembled honeycomb lattice in the monolayer of cyclic thiazyl diradical BDTDA (=4,4’bis(1,2,3,5-dithiadiazolyl)) on Cu(111) with a zero-bias tunneling spectra anomaly”,
M. Yamamoto, R. Suizu, S. Dutta, P. Mishra, T. Nakayama, K. Sakamoto, K. Wakabayashi, T.
Uchihashi, and K. Awaga,(2015) Sci. Rep., 5, 18359.

3.

“Spatially inhomogeneous, stepwise phase transitions in a thiazyl diradical: a structural mismatch
induced by lattice transformation”,
R. Suizu, A. Iwasaki, Y. Shuku, and K. Awaga,(2015) J. Mater. Chem. C, 3, pp. 7968-7977.

4.

“External-Template-Assisted Formation of Octacyanometalate-Based MV-MnII (M = W, Mo)
Bimetallic Coordination Polymers with Magnetic Properties”,
Q. Jun, Hu. Jingchun, H. Yoshikawa, Z. Jinfang, K. Awaga, Z. Chi,(2015) Euro. J. Inorg. Chem., 2015, pp. 2110-2119

5.

“A Three-Dimensional Hetero-Bimetallic Coordination Polymer with Unusual (4,5)-Connected
Topology and Ferrimagnetic Property Based on Octacyanotungstate and Polydentate Ligand”,
J.Qian, J. Hu, H. Yoshikawa, J. Zhang, K. Awaga, and C. Zhang,(2014) Cryst. Growth Des., 14, pp. 2288-2295

6.

“The key role of vibrational entropy in the phase transitions of dithiazolyl-based bistable
magnetic materials”,
S. Vela, F. Mota, M., Deumal, R. Suizu, Y. Shuku, A. Mizuno, K. Awaga, M. Shiga, J. J Novoa,
J. Ribas-Arino,(2014) Nature Commun., 5, 4411.

7.

“Thiadiazole Dioxide-Fused Picene: Acceptor Ability, Anion Radical Formation, and n-Type
Charge Transport Characteristics”,
Y. Xie, Y. Shuku, M. M. Matsushita, K. Awaga,(2014) Chem. Commun., 50, pp. 4178-4180

8.

“Giant Magnetoresistance in a Molecular Thin Film as an Intrinsic Property”,
L. Pilia, M. Serri, M. M. Matsushita, K. Awaga, S. Heutz, N. Robertson,(2014) Adv. Funct. Mater., 24, pp. 2383-2388

9.

“Molecule-displacive ferroelectricity in organic supramolecular solids”,

H. Ye, Y. Zhang, S. Noro, K. Kubo, M. Yoshitake, Z. Liu, H. Cai, D. Fu, H. Yoshikawa, K. Awaga,
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10. “Synthesis, optical properties and charge transport characteristics of a series of novel thiophenefused phenazine derivatives”
Y. Xie, T. Fujimoto, S. Dalgleish, Y. Shuku, M.M. Matsushita, K. Awaga,(2013) J. Mater. Chem. C, 1, pp. 3467-3481.
11. "Crystal Structure, Spin Polarization, Solid-State Electrochemistry, and High n-Type Carrier
Mobility of a Paramagnetic Semiconductor: Vanadyl Tetrakis(thiadiazole)porphyrazine",
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Kepenekian, V. Robert, M.P. Donzello, C. Ercolani, K. Awaga,(2012) Inorg. Chem., 51, pp. 456-462.
13. "Monovalent and Mixed-Valent Potassium Salts of [1,2,5]Thiadiazolo[3,4f][1,10]phenanthroline 1,1-Dioxide: A Radical Anion for Multidimensional NetworkStructures",Y. Shuku, R. Suizu, K. Awaga,(2011) Inorg. Chem., 50, pp. 11859-11861.
14. “Intermolecular band dispersion in a self-assembled phthalocyanine derivative film: The case oftetrakis(thiadiazole)porhyrazine”,
Y. Tanaka, K. Takahashi, T. Kuzumaki, Y. Yamamoto, K. Hotta, A. Harasawa, Y. Miyoshi, H.
Yoshikawa, Y. Ouchi, N. Ueno, K. Seki, K. Awaga, K. Sakamoto,(2010) Phys. Rev. B, 82, 073408.
15. “Tetrakis(thiadiazole)porphyrazines. 7. Synthesis and structure of mu-oxobis[tetrakis(thiadiazole)porphyrazinato-aluminum(III)]”
M. P. Donzello, M. Fujimori, Y. Miyoshi, H. Yoshikawa, E. Viola, K. Awaga, C. Ercolani,(2010) J. Porphyrazines & Phthalocyanines, 14, pp. 343-348.
16. “Photoconductive Organic Radical Thin Films: Interactive Radical Dimers for Photofunctions”,
A. Iwasaki, L. Hu, R. Suizu, K. Nomura, H. Yoshikawa, K. Awaga, Y. Noda, K. Kanai, Y.
Ouchi, K. Seki, and H. Ito,(2009) Angew. Chem. Int. Ed., 48, pp. 4022-4024.
17. “Ligands bonded to metal ion or through-metal interacting ligands? Analysis of unusual bonds
formation in the (BDTA)2[Co(mnt)2] material”,
M. Kepenekian, B. Le Guennic, Boris, K. Awaga, V. Robert,(2009) Phys. Chem. Chem. Phys., 11, pp. 6066-6071.

18. “Fe(II) spincrossover complex of [1,2,5]thiadiazolo[3,4-f][1,10]phenanthroline”,
Y. Shuku, R. Suizu, K. Awaga, O. Sato,(2009) CrystEngComm. , 11, pp. 2065-2068.
19. “Electronic structure of disjoint diradical 4,4 '-bis(1,2,3,5-dithiadiazolyl) thin films”
K. Kanai, H. Yoshida, Y. Noda, A. Iwasaki, R. Suizu, J. Tsutumi, H. Imabayashi, Y. Ouchi, N.
Sato, K. Seki, K. Awaga,(2009) Phys. Chem. Chem. Phys., 11, pp.11432-11436.
20. “Effects of Hydrostatic Pressure and Uniaxial Strain on Spin-Peierls Transition in an Organic
Radical Magnet, BBDTA•InCl4”
M. Mito, S. Kawagoe, H. Deguchi, S. Takagi, W. Fujita, K. Awaga, R. Kondo, S. Kagoshima,(2009) J. Phys. Soc. Japan, 78, 124705.
21. “Diverse Magnetic and Electrical Properties of Molecular Solids containing the Thiazyl RadicalBDTA”,
K. Awaga, Y. Umezono, W. Fujita, H. Yoshikawa, H.-B. Cui, H. Kobayashi, S. Staniland, N.
Robertson,(2008) Inorg. Chim. Acta, 361, pp. 3761-3770.
22. “Pressure-Induced Ferromagnetic to Nonmagnetic Transition and the Enhancement ofFerromagnetic Interaction in the Thiazyl--BBDTA·GaCl4”,

M. Mito, M. Fujino, Y. Komorida, H. Deguchi, S. Takagi, W. Fujita, K. Awaga,(2008) J. Phys. Soc. Jpn., 77, 124713.
23. “Structural Study of a Dimerization Process in an Organic Radical Magnet, BBDTA InBr4”,
W. Fujita, K. Kikuchi, K. Awaga,(2008) Angew. Chem. Int. Ed., 47, pp. 9480–9483.
24. “Spin, charge and lattice correlation in thiazyl radicals and their molecular compounds”,
K. Awaga, T. Tanaka, T. Shirai, Y. Umezono, W. Fujita,(2007) Comp. Red. Chimie, 10, pp. 52-59.
25. “Charge ordering and nonlinear electrical transport in quasi-1D organic chains with strong
electrostatic interchain interactions”,
K. Okamoto, T. Tanaka, W. Fujita , K. Awaga, T. Inabe,(2007) Phys. Rev. B, 76, No. 075328
26. “Coordination bond formation at charge-transfer phase transition in (BDTA)2[Co(mnt)2]“,
Y. Umezono, W. Fujita, K. Awaga(2006) J. Am. Chem. Soc., 128, pp. 1084-1085.
27. “Multi-dimensional crystal structures and unique solid-state properties of heterocyclic thiazyl
radicals and related materials”,

K. Awaga, T. Tanaka, T. Shirai, M. Fujimori, Y. Suzuki, H. Yoshikawa, W. Fujita,(2006) Bull. Chem. Soc. Japan, 79, pp. 25-34.
28. “A one-dimensional coordination polymer, BBDTA·InCl4: Possible spin-Peierls transition withhigh critical temperature of 108 K”,
W. Fujita, K. Awaga, R. Kondo, and S. Kagoshima,(2006) J. Am. Chem. Soc. 128, pp. 6016-6017.
29. “Low-field negative resistance effect in a charge-ordered state of thiazyl radical crystals”,
K. Okamoto, T. Tanaka, W. Fujita, K. Awaga, and T. Inabe,(2006) Angew. Chem. Int. Ed. 45, pp. 4515-4518.
30. “Ferromagnetic ordering of S=1/2 Heisenberg ferromagnetic chains in organic magnet BBDTA·GaBr4”,
K. Shimizu, T. Gotohda, T. Matsushita, N. Wada, W. Fujita, K. Awaga,Y. Saiga, D. Hirashima,(2006) Phys. Rev. B, 74, No. 172413.
31. “[BDTA]2[Cu(mnt)2]: An almost perfect one-dimensional magnetic material”
S.S. Staniland, W. Fujita, Y. Umezono, K. Awaga K, P.J. Camp, S.J. Clark, N. Robertson,(2005) Inorg. Chem., 44, pp.546-551.
32. “A unique new multiband molecular conductor: [BDTA][Ni(dmit)2]2“S.S. Staniland, W. Fujita, Y. Umezono, K. Awaga, S.J. Clark, H.B. Cui, H. Kobayashi, N.
Robertson,(2005) Chem. Commun., pp. 3204-3206.
33. “Coexistence of ferromagnetic and antiferromagnetic interactions and magnetic ordering in thealternating stacking structure of (BDTA)[Ni(mnt)2]: Possible supramolecular superexchangemechanism”
Y. Umezono, W. Fujita, K. Awaga
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34. “Tetrakis(thiadiazole)porphyrazines. 4. Direct Template Synthesis, Structure, General
Physicochemical Behavior, and Redox Properties of AlIII, GaIII, and InIII Complexes”,
M. P. Donzello, R. Agostinetto, S. S. Ivanova, M. Fujimori, Y. Suzuki, H.Yoshikawa, J. Shen,
K. Awaga, C. Ercolani, K.M. Kadish, and P.A. Stuzhin,(2005) Inorg. Chem., 44 , pp. 8539 -8551.
35. “Crystal structure and magnetic properties of a thiazyl organic ferromagnet, BBDTA·GaCl4
with Tc=7.0 K”
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36. “Pressure effects on magnetic bistability in a heterocyclic thiazyl radical TTTA”
T. Tanaka, W. Fujita, K. Awaga(2004) Chem. Phys. Lett., 393, pp 150-152.
37. “Packing Motifs and Magneto-Structural Correlations in Crystal structures of MetalloTetrakis(1,2,5-thiadiazole)porphyrazine Series, TTDPzM (M = H2, Fe, Co, Ni, Cu, Zn)”
Y. Suzuki, M. Fujimori, H. Yoshikawa, K. Awaga(2004) Chem. Euro. J., 10, pp. 5158-5164.
38. “Packing Motifs in Porphyrazine Macrocycles Carrying Peripherally-Annulated Thiadiazole
Rings: Crystal Growths of Metal-Free and Cobalt Tetrakis(1,2,5-thiadiazole)porphyrazines”
M. Fujimori, Y. Suzuki, H. Yoshikawa, K. Awaga(2003) Angew. Chem. Int. Ed., 42, pp. 5863-5865.
39. “Room-temperature magnetic bistability in organic radical crystals: Paramagnetic-diamagnetic
phase transition in 1,3,5-trithia-2,4,6-triazapentalenyl”
W. Fujita, K. Awaga, H. Matsuzaki, H. Okamoto,(2002) Phys. Rev. B65, 064434.
40. “Complex phase transitions in stable thiazyl radicals: spin-gap, antiferromagnetic ordering anddouble melting”
W. Fujita, K. Awaga, Y. Nakazawa, K. Saito K, M. Sorai,(2002) Chem. Phys. Lett., 352, pp. 348-352.
41. “Organic ferromagnetism of Tc=6.7 K driven by evaporation of crystal solvent”
W. Fujita and K. Awaga,(2002) Chem. Phys. Lett. 357, pp. 385-388.
42. “Spontaneous magnetization below 44 K in (benzo[1,2-d:4,5-d']bis[1,3,2]dithiazole)·FeCl4
driven by evaporation of crystal solvent”,
W. Fujita, K. Awaga, M. Takahashi, M. Takeda, T. Yamazaki,(2002) Chem. Phys. Lett., 362, pp. 97-102.
43.

“Ferromagnetic Coordination Polymer Composed of Heterocyclic Thiazyl Radical, 1,3,5Trithia-2,4,6-triazapentalenyl(TTTA),andBis(hexafluoroacetylacetonato)copper(II)(Cu(hfac)2)”,
W. Fujita and K. Awaga,(2001) J. Am. Chem. Soc. 123, pp. 3601-3602.
44.

“Room-Temperature Magnetic Bistability in Organic Radical Crystals “,
W. Fujita and K. Awaga,(1999) Science, 286, pp. 261-262.